Alafia WMP Update Nov 2010

HilsboroughCounty 

Florida 

November2010 

parson s

ALAFIA RIVER WATERSHED 

MANAGEMENT PLAN UPDATE 

(Known Condition through April 2005) 

Chapters 1 – 6, 13 & 15 

Prepared by 

Tampa, FL 

Prepared for 

Hillsborough County 

Engineering Division 

Department of Public Works 

Stormwater Management Section

Parsons 

This page intentionally left blank.

. 

Table of Contents 

parsons


Alafia River Watershed Management Plan Update 


Executive Summary ....................................................................................... ES-1 

Chapter 1.0 Introduction .............................................................................. 1-1 

1.1 The Watershed Approach .............................................. 1-1 

1.2 Stakeholder Involvement ............................................... 1-3 

1.3 The Alafia River Watershed Management Plant ............ 1-4 

1.4 Previous Studies ........................................................... 1-5 

1.5 Problem Statement ........................................................ 1-6 

1.6 Report Structure ............................................................ 1-6 

1.7 References .................................................................... 1-7 

Chapter 2.0 Watershed Description ............................................................. 2-1 

2.1 Introduction .................................................................... 2-1 

2.2 Climate .......................................................................... 2-1 

2.3 Physiography and Soils ................................................. 2-5 

2.4 Geology and Hydrogeology ........................................... 2-14 

2.5 Land Use ....................................................................... 2-21 

2.6 References .................................................................... 2-31 

Chapter 3.0 Major Conveyance Systems .................................................... 3-1 

3.1 Introduction .................................................................... 3-1 

3.2 Buckhorn Creek Subwatershed ..................................... 3-2 

3.3 Bell Creek Subwatershed .............................................. 3-2 

3.4 Fishhawk Creek Subwatershed ..................................... 3-3 

3.5 Turkey Creek Subwatershed ......................................... 3-4 

3.6 English Creek Subwatershed ........................................ 3-4 

3.7 North Prong Subwatershed ........................................... 3-5 

3.8 South Prong Subwatershed ........................................... 3-5 

3.9 River Subwatershed ...................................................... 3-6 

3.10 Valrico Subwatershed ................................................... 3-6 

Chapter 4.0 Hydrologic/Hydraulic Model Methodology ................................ 4-1 

4.1 Introduction .................................................................... 4-1 

4.2 Hydrologic Model Type .................................................. 4-1 

4.3 Data Sources ................................................................. 4-2 

4.4 Model Resolution ........................................................... 4-3 

4.5 Hydrologic Model ........................................................... 4-4 

4.5.1 Watershed-Subwatershed-Subbasin Definition .. 4-4 

4.5.2 Subbasin Delineation .......................................... 4-5 

4.5.3 Time of Concentration ........................................ 4-6 

4.5.4 Runoff Curve Number ......................................... 4-7 

4.5.5 Existing Land Use Conditions ............................. 4-9 

Parsons i November 2010

Table of Contents (continued) 



4.5.6 Hydrologic Soil Type ........................................... 4-10 

4.5.7 Initial Abstraction Ratio ....................................... 4-11 

4.5.8 Unit Hydrograph Shape Factor ........................... 4-11 

4.6 Hydraulic Model ............................................................. 4-12 

4.6.1 Hydraulic Model Network .................................... 4-12 

4.6.2 Drainage Facility Inventory ................................. 4-14 

4.6.3 Closed Conduits ................................................. 4-15 

4.6.4 Channel Cross-Section and Floodplain 

Definition ............................................................. 4-16 

4.6.5 Overflow Weirs ................................................... 4-17 

4.6.6 Storage Facility Stage-Area Relationships ......... 4-18 

4.6.7 Initial Conditions ................................................. 4-19 

4.6.8 Boundary Conditions .......................................... 4-20 

Chapter 5.0 Hydrologic/Hydraulic Model Development, Calibration and 

Verification ............................................................................... 5-1 


5.1.1 Subwatershed Description .................................. 5-1 

5.1.1.1 Primary Drainage Systems .................... 5-2 

5.1.1.2 Existing Land Use ................................. 5-6 

5.1.1.3 Soils ...................................................... 5-9 

5.1.1.4 Physiography ........................................ 5-10 

5.1.1.5 Previous Studies and Sources of 

Information ............................................ 5-13 

5.1.2 Hydrologic Model Development .......................... 5-15 

5.1.2.1 Subbasin Delineations ........................... 5-15 

5.1.2.2 SCS Runoff Curve Numbers ................. 5-15 

5.1.2.3 Times of Concentration ......................... 5-16 

5.1.3 Hydraulic Model Development ............................ 5-16 

5.1.3.1 Hydraulic Model Network ...................... 5-16 

5.1.3.2 Storage Facilities ................................... 5-16 

5.1.3.3 Closed Conduits .................................... 5-16 

5.1.3.4 Overflow Weirs ...................................... 5-16 

5.1.3.5 Natural Channel Cross Sections ........... 5-17 

5.1.4 Hydrologic/Hydraulic Model Calibration and 

Verification .......................................................... 5-17 





5.2.1.3 Soils ...................................................... 5-25 

5.2.1.4 Physiography ........................................ 5-26 

Parsons ii November 2010















Verification .......................................................... 5-31 





5.3.1.3 Soils ...................................................... 5-39 

5.3.1.4 Physiography ........................................ 5-40 

5.3.1.5 Sources of Information .......................... 5-40 











5.3.4. Hydrologic/Hydraulic Model Calibration and 

Verification .......................................................... 5-45 





5.4.1.3 Soils ...................................................... 5-57 

5.4.1.4 Physiography ........................................ 5-58 






Parsons iii November 2010








5.4.3.4 Weirs ..................................................... 5-63 


5.4.3.6 Subwatershed Boundary Conditions ..... 5-64 


Verification .......................................................... 5-64 

5.4.4.1 Available Streamflow and Precipitation 

Gaging Station Records ........................ 5-64 

5.4.4.2 Calibration and Verification Storm 

Events ................................................... 5-65 

5.4.4.3 Results .................................................. 5-69 


5.5.1 Subwatershed Description ............................... 5-73 

5.5.1.1 Primary Drainage Systems ................ 5-73 

5.5.1.2 Existing Land Use ............................. 5-74 

5.5.1.3 Soils .................................................. 5-78 

5.5.1.4 Physiography .................................... 5-83 

5.5.1.5 Sources of Information ...................... 5-83 

5.5.2 Hydrologic Model Development ....................... 5-84 

5.5.2.1 Subbasin Delineations ....................... 5-84 

5.5.2.2 SCS Runoff Curve Numbers ............. 5-84 

5.5.2.3 Times of Concentration ................. 5-84 

5.5.3 Hydraulic Model Development ......................... 5-84 

5.5.3.1 Hydraulic Model Network ................. 5-84 

5.5.3.2 Closed Conduits ................................ 5-84 

5.5.3.3 Overflow Weirs .................................. 5-85 

5.5.3.4 Natural Channel Cross Sections ....... 5-85 

5.5.3.5 Subwatershed Boundary Conditions . 5-85 

5.5.4 Hydrologic/Hydraulic Model Calibration 

and Verification ................................................ 5-85 

5.6 North Prong Alafia River Subwatershed ........................ 5-86 




5.6.1.3 Soils .................................................. 5-93 

5.6.1.4 Physiography .................................... 5-93 


Parsons iv November 2010







5.6.2.3 Times of Concentration ..................... 5-97 


5.6.3.1 Hydraulic Model Network .................. 5-98 

5.6.3.2 Storage Facilities ............................... 5-98 







Gaging Station Records .................... 5-99 

5.6.4.2 Calibration and Verification 

Storm Events ..................................... 5-100 

5.6.4.3 Results .............................................. 5-102 

5.7 South Prong Alafia River Subwatershed ....................... 5-109 




5.7.1.3 Soils .................................................. 5-118 

5.7.1.4 Physiography .................................... 5-118 












5.7.3.6 Subwatershed Boundary Conditions . 5-126 






Storm Events ..................................... 5-127 

5.7.4.3 Results .............................................. 5-130 

Parsons v November 2010




5.8 Alafia River Main Stem Subwatershed .......................... 5-136 

5.8.1 Basin Description ............................................. 5-136 



5.8.1.3 Soils .................................................. 5-144 

5.8.1.4 Physiography .................................... 5-153 

5.8.1.5 Previous Studies and Sources 

of Information .................................... 5-154 











5.8.3.6 Basin Boundary Conditions ............... 5-157 






Storm Events ..................................... 5-159 

5.8.4.3 Results .............................................. 5-161 





5.9.1.3 Soils ...................................................... 5-173 

5.9.1.4 Physiography ........................................ 5-179 












5.9.3.6 Basin Boundary Conditions ................... 5-182 

Parsons vi November 2010




Chapter 6.0 Existing Conditions Flood Level of Service .............................. 6-1 

6.1 Design Storm Events ..................................................... 6-1 

6.2 Level of Service Designations ....................................... 6-4 

6.3 Level of Service Analysis Methodology ......................... 6-8 


6.4.1 Historical Flooding Problems ........................... 6-10 

6.4-2 Existing Conditions Model Simulation Results . 6-15 

6.4.3 Flooding Level of Service Analysis .................. 6-21 



6.5.2 Existing Conditions Model Simulation Results . 6-31 








6.7.2 Design Storm Simulations ................................ 6-59 






6.9 North Prong Alafia River Subwatershed ........................ 6-91 




6.10 South Prong Alafia River Subwatershed ....................... 6-105 




6.11 Alafia River Main Stem Subwatershed .......................... 6-123 








Parsons vii November 2010




Chapter 13.0 Alternatives Analysis ................................................................ 13-1 

13.1 Flood Control Alternatives Analysis Methodology ......... 13-1 

13.2 Flood Control Alternatives ............................................. 13-6 

13.2.1 Buckhorn Creek Subwatershed .......................... 13-6 

13.2.2 Bell Creek Subwatershed ................................... 13-28 

13.2.3 Fishhawk Creek Subwatershed .......................... 13-32 

13.2.4 Turkey Creek Subwatershed .............................. 13-32 

13.2.5 English Creek Subwatershed ............................. 13-46 

13.2.6 North Prong Alafia River Subwatershed ............. 13-51 

13.2.7 South Prong Alafia River Subwatershed ............ 13-52 

13.2.8 Alafia River Main Stem Subwatershed ............... 13-59 

Chapter 15.0 Proposed Plan and Level of Service ....................................... 15-1 

15.1 Introduction .................................................................... 15-1 

15.2 Proposed Plan and Level of Service ............................. 15-1 

15.2.1 Flood Control Projects ........................................ 15-1 

15.2.2 Water Quality Improvement Projects .................. 15-2 

15.2.3 Natural Systems Enhancement Projects ............ 15-2 

15.3 Prioritized List of Recommended Projects ..................... 15-2 

15.3.1 Flood Control Projects ........................................ 15-2 

15.4 Operation and Maintenance Plan Recommendations ... 15-4 

15.4.1 Routine Maintenance Activities .......................... 15-4 

15.4.2 Identified Maintenance Needs ............................ 15-6 

15.4.3 General Maintenance Recommendations .......... 15-6 

Parsons viii November 2010

List of Figures 



Figure No. Title Page 

2.1-1 Alafia River Watershed Study Area Map............................................. 2-3 

2.3-1 Alafia River Watershed Hydrologic Soil 

Group Classification Map .................................................................... 2-7 

2.4-1 Alafia River Watershed General 

Topographic Relief Map ...................................................................... 2-15 

2.5-1 Alafia River Water Existing (2006) Land Use Map .............................. 2-23 

5.1-1 Buckhorn Creek Subwatershed Drainage System Map ...................... 5-3 

5.1-2 Buckhorn Creek Subwatershed Existing Land Use Map ..................... 5-7 

5.1-3 Buckhorn Creek Subwatershed Soils Map .......................................... 5-11 

5.2-1 Bell Creek Subwatershed Drainage System Map ............................... 5-19 

5.2-2 Bell Creek Subwatershed Existing Land Use Map .............................. 5-23 

5.2-3 Bell Creek Subwatershed Soils Map ................................................... 5-27 

5.3-1 Fishhawk Creek Subwatershed Drainage System Map ...................... 5-33 

5.3-2 Fishhawk Creek Subwatershed Existing Land Use Map ..................... 5-37 

5.3-3 Fishhawk Creek Subwatershed Soils Map .......................................... 5-41 

5.4-1 Turkey Creek Subwatershed Drainage System Map .......................... 5-47 

5.4-2 Turkey Creek Subwatershed Existing Land Use Map ......................... 5-55 

5.4-3 Turkey Creek Subwatershed Soils Map .............................................. 5-59 

5.4-4 Alafia River Watershed Precipitation and 

Streamflow Gage Location Map .......................................................... 5-67 

5.4-5 Turkey Creek Subwatershed Model Calibration, 

September 4 to September 10, 2004 Stage Comparison at 

Edward Medard Reservoir Gage ........................................................ 5-70 

5.4-6 Turkey Creek Subwatershed Model Verification, 

(September 5 to September 15, 1988) Stage Comparison 

at Edward Medard Reservoir Gage .................................................... 5-70 

5.4-7 Turkey Creek Subwatershed Model Verification, 

(December 9-19, 1997) Stage Comparison 

at Edward Medard Reservoir Gage .................................................... 5-71 

5.5-1 English Creek Subwatershed Drainage System Map ......................... 5-75 

5.5-2 English Creek Subwatershed Existing Land Use Map ........................ 5-79 

5.5-3 English Creek Subwatershed Soils Map ............................................. 5-81 

5.6-1 North Prong Alafia River Subwatershed 

Drainage System Map ........................................................................ 5-89 

Parsons ix November 2010

List of Figures (continued) 





Existing Land Use Map ....................................................................... 5-91 


Soils Map ............................................................................................ 5-95 

5.6-4 North Prong Alafia River Subwatershed Model Calibration, 

September 4-10, 2004 Flow Comparison at 

Keysville Road Gage .......................................................................... 5-105 

5.6-5 North Prong Alafia River Subwatershed Model Calibration, 

September 4-10, 2004 Stage Comparison at 


5.6-6 North Prong Alafia River Subwatershed Model Verification, 







December 9-19, 1997 Flow Comparison at 



December 9-19, 1997 Stage Comparison at 


5.6-10 North Prong Alafia River Streamflow Gaging Station 

Rating Curve Comparison ................................................................... 5-108 

5.7-1 South Prong Alafia River Subwatershed Drainage 

System Map ........................................................................................ 5-111 

5.7-2 South Prong Alafia River Subwatershed Existing 

Land Use Map .................................................................................... 5-115 

5.7-3 South Prong Alafia River Subwatershed Soils Map ............................ 5-119 

5.7-4 South Prong Alafia River Subwatershed Model Calibration, 


Jameson Road Gage .......................................................................... 5-132 

5.7-5 South Prong Alafia River Subwatershed Model Calibration, 



5.7-6 South Prong Alafia River Subwatershed Model Verification, 



Parsons x November 2010









December 9-19, 1997 Flow Comparison at 



December 9-19, 1997 Stage Comparison at 


5.7-10 South Prong Alafia River Streamflow Gaging Station 


5.8-1 (East) Alafia River Main Stem Subwatershed Drainage 

System Map ........................................................................................ 5-139 

5.8-1 (West) Alafia River Main Stem Subwatershed Drainage 

System Map ........................................................................................ 5-141 

5.8-2 (East) Alafia River Main Stem Subwatershed Existing 

Land Use Map .................................................................................... 5-145 

5.8-2 (West) Alafia River Main Stem Subwatershed Existing 

Land Use Map .................................................................................... 5-147 

5.8-3 (East) Alafia River Main Stem Subwatershed Soils Map ............................... 5-149 

5.8-3 (West) Alafia River Main Stem Subwatershed Soils Map ............................... 5-151 

5.8-4 Alafia River Main Stem Subwatershed Model Calibration, 


Lithia Pinecrest Road Gage ................................................................ 5-163 






Bell Shoals Road Gage ....................................................................... 5-164 

5.8-7 Alafia River Main Stem Subwatershed Model Verification, 







December 9 to December 19, 1997 Flow Comparison at 


Parsons xi November 2010






December 9 to December 19, 1997 Stage Comparison at 


5.8-11 Alafia River Main Stem Streamflow Gaging Station 


5.9-1 Valrico Subwatershed Drainage System Map ..................................... 5-171 

5.9-2 Valrico Subwatershed Existing Land Use Map ................................... 5-175 

5.9-3 Valrico Subwatershed Soils Map ........................................................ 5-177 

6.4-1 Buckhorn Creek Subwatershed Historical Flooding 

Complaint Locations ........................................................................... 6-13 

6.4-2 Buckhorn Creek Subwatershed Existing Conditions 

Flooding Level of Service Deficiency Locations .................................. 6-25 

6.5-1 Bell Creek Subwatershed Historical Flooding 


6.5-2 Bell Creek Subwatershed Existing Conditions 


6.6-1 Fishhawk Creek Subwatershed Historical 

Flooding Complaint Locations ............................................................. 6-45 

6.6-2 Fishhawk Creek Subwatershed Existing Conditions 


6.7-1 Turkey Creek Subwatershed Historical Flooding 


6.7-2 Turkey Creek Subwatershed Existing Conditions 


6.8-1 English Creek Subwatershed Historical Flooding 


6.8-2 English Creek Subwatershed Existing Conditions 


6.9-1 North Prong Alafia River Subwatershed Historical 


6.9-2 North Prong Alafia River Subwatershed Existing 

Conditions Flooding Level of Service Deficiency 

Locations ............................................................................................ 6-103 

Parsons xii November 2010





6.10-1 South Prong Alafia River Subwatershed Historical 



Conditions Flooding Level of Service Deficiency Locations ................ 6-121 

6.11-1 (East) Alafia River Main Stem Subwatershed Historical 

Flooding Complaint Locations ........................................................... 6-127 

6.11-1 (West) Alafia River Main Stem Subwatershed Historical 

Flooding Complaint Locations ........................................................... 6-129 

6.11-2 (East) Alafia River Main Stem Subwatershed Existing 

Conditions Flooding Level of Service Deficiency Locations ............... 6-147 

6.11-2 (West) Alafia River Main Stem Subwatershed Existing 

Conditions Flooding Level of Service Deficiency Locations ............... 6-149 

6.12-1 Valrico Subwatershed Historical Flooding Complain Locations .......... 6-153 

6.12-2 Valrico Subwatershed Existing 

Conditions Flooding Level of Service Deficiency Locations ................ 6-163 

Chap.15 

Project Fact Sheets/CIP Evaluation Matrix Sheets ............................. End 

of Chapter 

List of Tables 

Table No. Title Page 

ES-1 

ES-2 

Flood Control Project Prioritization Plan ............................................. ES-9 

Project Recommendations .................................................................. ES-11 

2.3-1 Soil Classification ................................................................................ 2-9 

2.4-1 Generalized Geologic and Hydrogeologic Units of the 

Alafia River Basin ............................................................................... 2-19 

2.5-1 Aggregated Land Use ......................................................................... 2-26 

3.1-1 Subwatersheds within the Alafia River Watershed ............................. 3-1 

Parsons xiii November 2010

List of Tables (continued) 




4.5-1 Universal SCS Runoff Curve Numbers for All Subwatersheds ........... 4-8 

4.5-2 Consolidation Land Use Classifications .............................................. 4-9 

5.1-1 Buckhorn Creek Subwatershed Land Use .......................................... 5-9 

5.1-2 Buckhorn Creek Subwatershed Soils ................................................. 5-10 

5.2-1 Bell Creek Subwatershed Land Use .................................................. 5-22 

5.2-2 Bell Creek Subwatershed Soils ........................................................... 5-25 

5.3-1 Fishhawk Creek Subwatershed Land Use .......................................... 5-36 

5.3-2 Fishhawk Creek Subwatershed Hydrologic Model Input Data ............ 5-39 

5.4-1 Turkey Creek Subwatershed Universal SCS 

Runoff Curve Numbers ....................................................................... 5-53 

5.4-2 Turkey Creek Subwatershed Hydrologic Model Input Data ................ 5-57 

5.5-1 English Creek Subwatershed Universal SCS Runoff 

Curve Numbers ................................................................................... 5-77 

5.5-2 English Creek Subwatershed Hydrologic Model Input Data ................ 5-78 

5.6-1 North Prong Alafia River Subwatershed Universal SCS 


5.6-2 North Prong Alafia River Subwatershed Hydrologic Model 

Input Data ........................................................................................... 5-93 

5.7-1 South Prong Alafia River Subwatershed Universal SCS 


5.7-2 South Prong Alafia River Subwatershed Hydrologic Model 

Input Data ........................................................................................... 5-118 

5.8-1 Alafia River Main Stem Subwatershed Universal SCS 


5.8-2 Alafia River Main Stem Subwatershed Hydrologic Model 

Input Data ........................................................................................... 5-153 

5.9-1 Valrico Creek Subwatershed Land Use .............................................. 5-173 

5.9-2 Valrico Creek Subwatershed Soils ..................................................... 5-174 

Parsons xiv November 2010





6.4-1 Buckhorn Creek Subwatershed Reported Flooding 

Problems ............................................................................................. 6-11 

6.4-2 Buckhorn Creek Subwatershed Existing Conditions 

Flood Elevations Summary ................................................................. 6-17 

6.4-3 Buckhorn Creek Subwatershed Peak Flows at 

Selected Locations ............................................................................. 6-15 

6.4-4 Buckhorn Creek Subwatershed Existing Conditions Flooding 

Levels of Service Analysis .................................................................. 6-23 

6.5-1 Bell Creek Subwatershed Reported Flooding Problems ..................... 6-28 

6.5-2 Bell Creek Subwatershed Existing Conditions Flood 

Elevations Summary ........................................................................... 6-33 

6.5-3 Bell Creek Subwatershed Peak Flows at Selected Locations ............. 6-31 

6.5-4 Bell Creek Subwatershed Existing Conditions Flooding 


6.6-1 Fishhawk Creek Subwatershed Reported Flooding Problems ............ 6-43 

6.6-2 Fishhawk Creek Subwatershed Existing Conditions Flood 


6.6-3 Fishhawk Creek Subwatershed Peak Flows at Selected 

Locations ............................................................................................ 6-47 

6.6-4 Fishhawk Creek Subwatershed Existing Conditions Flooding 


6.7-1 Turkey Creek Subwatershed Reported Flooding Problems ................ 6-56 

6.7-2 Turkey Creek Subwatershed Existing Conditions Flood Elevations 

Summary ............................................................................................ 6-61 

6.7-3 Turkey Creek Subwatershed Peak Flows at Selected Locations ........ 6-59 

6.7-4 Turkey Creek Subwatershed Existing Conditions Flooding 


6.8-1 English Creek Subwatershed Reported Flooding Problems ............... 6-72 

6.8-2 English Creek Subwatershed Existing Conditions Flood 


6.8-3 English Creek Subwatershed Peak Flows at 


6.8-4 English Creek Subwatershed Existing Conditions 

Flooding Levels of Service Analysis ................................................... 6-87 

Parsons xv November 2010





6.9-1 North Prong Alafia River Subwatershed Reported 

Flooding Problems .............................................................................. 6-92 

6.9-2 North Prong Alafia River Subwatershed Existing Conditions 


6.9-3 North Prong Alafia River Subwatershed Peak Flows at 


6.9-4 North Prong Alafia River Subwatershed Existing Conditions 


6.10-1 South Prong Alafia River Subwatershed Reported 



Conditions Flood Elevations Summary ............................................... 6-111 

6.10-3 South Prong Alafia River Subwatershed Peak Flows at 


6.10-4 South Prong Alafia River Subwatershed Existing Conditions 


6.11-1 Alafia River Main Stem Subwatershed Reported 


6.11-2 Alafia River Main Stem Subwatershed Existing 

Conditions Flood Elevations Summary ............................................... 6-131 

6.11-3 Alafia River Main Stem Subwatershed Peak Flows at 


6.11-4 Alafia River Main Stem Subwatershed Existing Conditions 


6.12-1 Valrico Subwatershed Reported Flooding Problems .......................... 6-152 

6.12-2 Valrico Subwatershed Existing Conditions 


6.12-3 Valrico Subwatershed Existing Conditions 


15.3.1 Flood Control Project s Prioritization Plan .......................................... 15-3 

15.4-1 Identified Maintenance Needs ........................................................... 15-7 

APPENDICES 

Appendix A DRAFT DETERMINATION OF GREEN-AMPT PARAMETERS FOR 

HYDROLOGY COMPUTATIONS IN ICPR, SWFWMD AUGUST 2008 

Appendix B COST ESTIMATES 

Parsons xvi November 2010

. 

Executive Summary 

parsons



EXECUTIVE SUMMARY 

Introduction 

The original Alafia River Watershed Management Plan (WMP) was completed in 

2001 for Hillsborough County. Since then, changes have occurred within each of the 

watersheds in Hillsborough County which affect the hydrologic and hydraulic 

features. Furthermore, changes to standards and reference elevation datum 

(NAVD88) have been adopted. The combined changes warranted updating the 

existing models used for the WMP development and their associated floodplain 

mapping. The goal of this project was to update the Hillsborough County SWMM 

model and floodplain mapping for the Alafia River Watershed. The update focused 

on resolving inconsistencies between the current conditions within the watershed and 

the information used to develop the original WMP for the watershed. The watershed 

model updates were based on 2006 land use, aerial photography and recent 

development within the watershed. The Alafia River Watershed model was updated 

with the new parameters resulting from the changes introduced. Accordingly, the 

supporting GIS/database was updated to match the updated models. Based on the 

updated watershed model, the Alafia River Watershed Management Plan was 

reevaluated and recommendations for capital improvements to alleviate identified 

flooding level of service deficiencies was developed, along with a revised 

implementation prioritization plan. Only portions of the WMP pertaining to hydraulic 

& hydrologic modeling and flooding conditions assessments was revised and 

updated. Components of the original WMP pertaining to water quality and natural 

systems were not part of this update. 

Significant improvements 

in the quality and quantity 

of available data have 

been made in the last ten 

years. Additionally, the 

use of ArcGIS to facilitate 

the organization and 

computation of these 

available data has 

increased the ability to 

more accurately predict 

model results on a more 

detailed level. These 

advances have warranted 

Hillsborough County, in 

cooperation with the Southwest Florida Water Management District (SWFWMD), to 

update the watershed models throughout the County. These model updates allow for 

the modernization of the FEMA floodplain maps, and County Capital Improvement 

Projects (CIP) and their corresponding project ranking. 

Parsons ES-1 November 2010



Watershed Description 

The Alafia River Watershed is approximately 268,000 acres, or 418 square miles, 

covering approximately one third of Hillsborough County, and extending into the 

western edge of Polk County. Approximately 170 square miles of the Alafia River 

contributing runoff is from Polk County. It is the largest in area of the 17 watersheds 

in Hillsborough County. For the purposes of this WMP the watershed was separated 

into 10 subwatersheds, each large enough to be its own watershed. The headwaters 

of the major flow contributory to the Alafia River originate in a swamp and prairie area 

south of Mulberry in Polk County and then flow 24 miles before entering the 

southeastern corner 

of Hillsborough 

County. There are 

numerous springs 

along the river, but 

surface water runoff 

contributes most of 

the flow. The major 

problems occurring 

within the watershed 

are associated with 

water quality, 

flooding, water 

supply, and natural 

systems. The 

watershed has had a 

history of water 

quality problems, with 

the majority of the 

pollution occurring as 

a result of the mining industry (SWFWMD 1997). Flooding problems have occurred 

throughout the watershed, especially during the El Niño years of 1997 and 1998, and 

the 2004 hurricane season. Open areas and wildlife habitat are rapidly being lost to 

urban sprawl, mining, and expanding agricultural concerns. 

Data Collection 

The purpose for the update of the Alafia River WMP was to update the model to the 

most current conditions using the best and latest available data. This included 

topographic, hydraulic and hydrologic data. Maybe the most significant dataset 

collected for this update was the digital elevation model (DEM) data and 

corresponding aerial photography. In the original 2001 WMP study, the floodplain 

mapping was based primarily on SWFWMD topographic aerial hard copy maps. 

Hillsborough County has collected digital topography for all of the Alafia River 




Watershed. The datasets represent the topography of the watershed varying from 

2001-2007 whereas the previous mapping was based on much older data. These 

digital data allow for more accurate and detailed mapping of the floodplain. The 

Legend 

Subwatersheds 

01 

02 

03 

04 

04_Hanck 

05 

05_POLK 

07 

figure to right shows the 

year of the DEM data for 

each section within the 

watershed. Furthermore, 

the available 2006 aerial 

photography provides the 

ability to more clearly 

identify hydraulic features 

within the watershed 

where no other data is 

available to realize their 

existence and account for 

their function. 

Also, as part of this 

project, areas of new 

No Scale development and/or land 

use changes were 

updated in the model domain. This included residential and commercial 

development, changes due to phosphate mining and the changes due to the 

construction of the new water supply reservoir (C.W. Bill Young Regional Reservoir) 

located within the Fishhawk Creek subwatershed. Data collected for these hydraulic 

and hydrologic updates were collected primarily from the SWFWMD, but also 

collected from the FDOT and DEP as well. Every means possible was extended to 

collect and employ the most recent and current data for the updated model 

compilation. 

Flood Protection 

Watershed Hydrologic and Hydraulic Model Development 

Perhaps the most important aspect of the Watershed Masterplan is the proper 

representation of the hydrologic and hydraulic processes throughout the watershed 

that define flooding conditions. A good understanding of these watershed processes 

is necessary to determine the most effective means of controlling flooding and 

protecting public safety and environmental resources. This understanding comes 

from the compilation of a large amount of data that describe the physical attributes of 

the watershed and its stormwater management infrastructure, including: topographic 

and aerial mapping; land use conditions; soil types; land slope and cover; dimensions 

and elevations of culverts, bridges, pipes, weirs, and control structures; channel and 

floodplain cross sections and roughness coefficients; and storage relationships for 




ponds, lakes, wetlands and depressions. These data are needed to develop a 

computer model of the watershed. 

As a part of the original 2001 WMP study, a field survey plan was executed based on 

the specific needs of the hydraulic model. The emphasis of this survey was placed 

on areas within the basin where there were no available sources of as-built record 

drawings and surveys. This comprehensive field survey program resulted in the 

survey of a total of 533 drainage structures and 1193 channel cross sections 

throughout the Alafia River Watershed (in Hillsborough County). Because of the 

extensive survey data effort during the original study, only 50 additional surveys were 

needed for this model update. 

For the Alafia River Watershed Management Plan update (just as in the original 

study), the Hillsborough County version of the EPA SWMM model (HCSWMM) was 

used. The County has developed this program as a standard for all watershed 

management plans within Hillsborough County. The Alafia River Watershed was 

divided into the following 

ten major subwatersheds, 

as shown: Bell Creek, 

Buckhorn Creek, English 

Creek, Fishhawk and Little 

Fishhawk Creek, North 

Prong Alafia River, South 

Prong Alafia River, Turkey 

Creek, and Alafia River 

Main Stem (east and 

west). The Alafia River 

Main Stem Subwatershed 

includes the drainage 

areas that drain directly to 

the Alafia River or minor 

tributaries to the Alafia 

River. To provide the level 

of detail that was deemed necessary to accurately define and properly analyze the 

primary drainage facilities within the Alafia River Watershed for this update, the 

subbasin discretization was increased from 2092 (in the original study) to 2673 

subbasins. Each of these subbasins was described by its land use and soil type 

distribution using an electronic Geographic Information System (GIS) database. This 

GIS database was also used as a tool to store and retrieve all watershed information 

gathered and generated over the course of the watershed study. 

The hydraulic model (HCSWMM) of the Alafia River Watershed consists of a network 

of open channel segments, culverts, bridges, storm sewers, weirs, lakes, ponds, and 

wetlands that comprise the primary drainage system within the watershed. HCSWMM 

uses a conduit-junction concept to idealize the prototype drainage system. A junction 




is a discrete location in the drainage system, while conduits are the connections 

between junctions that convey water through the system. The entire network of 

junctions and conduits forms the hydraulic model network and serves as the 

computational framework for HCSWMM. The updated Alafia River Watershed 

hydraulic model is quite comprehensive. It now comprises a total of 3800 junctions 

(increased from 3060 junctions) and 6443 linkages in its structure (increased from 

4962 linkages), including 3246 closed conduits and open channels, 3191 weirs and 6 

pump stations. 

The Alafia River Watershed hydrologic and hydraulic model was tested through a 

rigorous process of calibration and verification to ensure that the model was properly 

representing the flooding conditions throughout the watershed. Model calibration 

refers to the adjustment of model parameters within reasonable limitations so that the 

model results (i.e., streamflow and water elevations) are in reasonable agreement 

with a set of measured data. The model is calibrated to several different storm 

events that represent a variety of volumes, intensities, and distributions. The model 

verification process tests the calibration by comparing resulting stage, flow, and 

volume information to data measured or recorded at established gaging stations for a 

set of comparable independent events without any model adjustments. The Alafia 

River Watershed 

hydrologic/hydraulic model 

was calibrated to the 2004 

Hurricane Frances storm 

event and verified to two 

separate historical storm 

events, the September 

1988 and the December 

1997 floods. Model results 

for these events were 

compared to the flows, 

volumes, and water 

elevations recorded at 

several locations in the 

watershed and the model 

was deemed successful in 

its emulation of the 

observed conditions. 

Discharge (cfs) 

12000 

11000 

10000 

9000 

8000 

7000 

6000 

5000 

4000 

3000 

2000 

1000 

0 

North Prong Alafia River at Keysville (USGS 02301000) 

September 4-10, 2004 Calibration Storm Event 

Time (days) 

Flooding Level of Service Deficiencies and Problem Identification 

Recorded 

Simulated 

Upon completion of the development and re-calibration of the hydrologic and 

hydraulic model of the updated Alafia River Watershed, the next step of the flooding 

conditions analysis was to apply the model(s) to assess the performance of the 

basin-wide drainage facilities for a given set of design storm events. Results of these 

simulations were then analyzed with respect to Hillsborough County’s adopted 




flooding level of service (LOS) criteria to identify locations within the watershed where 

the LOS criteria are not being met. These were compared to known flooding problem 

areas which were identified during the recent 1998 and 2004 flood events to prepare 

an assessment of the existing flooding conditions within the watershed, and to target 

the principle areas to be addressed in the update of the watershed management plan 

alternative analysis. 

The LOS definition that has been adopted by the County establishes the assigned 

LOS designation based primarily on the road crown elevation, and relates the 

existence of significant street, yard and/or structure flooding to the depth of flooding 

of the street. The numerical criteria that were adopted as a means of providing 

measurable depth definitions of “significant flooding” are listed in the following table. 

Note the addition of two new LOS designations, D* and O, which were not included 

within the County Comprehensive Plan. 

Flooding 

Level of 

Service 


Comprehensive Plan Definition 

Alafia River Watershed Management 

Plan Definition 

A No significant street flooding Street flooding is less than 3” above the 

crown of road 

B 

No major residential yard flooding 

(Minor street flooding. At least one 

lane drivable) 

Street flooding is more than 3” above the 

crown of road, but less than 6” 

C 

No significant structure flooding 

(Level C - Street flooding. Flooding 

depth above road crown is less than 

one foot.) 

Street flooding is more than 6” above the 

crown of road, but less than 12” 

D No limitation on flooding Street flooding is more than 12” above 

the crown of road 

D* No limitation on flooding* Flood elevation is greater than finished 

floor elevation, and street flooding is less 

than 12” above the crown of road 

O N/A No structure and no street to compare 

with flood elevation 

The Board of County Commissioners, in the Comprehensive Plan, promulgated the 

25-year/24-hour/B flooding level of service as the target level of service for all 

watersheds within the county, including the Alafia River Watershed. Road crown 

elevations were compared with flood elevations generated by the model for the 

hypothetical 25-year/24-hour design storm event to determine the LOS provided. 

Those locations that do not attain the County’s target level of service (‘B’ LOS) were 

identified as flooding level of service violations. 




In addition to the LOS deficiency areas that were identified through the modeling of 

the existing hydrologic and hydraulic conditions, other flooding problem areas were 

identified based on input received during public meetings (during the original 2001 

study), from interviews with Hillsborough County Service Unit staff (during the original 

2001 study), and from the County’s historical flooding complaint database. These 

problem areas were 

investigated where there 

was sufficient information 

provided and alternative 

measures analyzed. In 

some cases, further 

detailed study is needed. 

In many instances, the 

problem was related to a 

maintenance issue and it 

was added to a list of 

recommended 

maintenance needs and 

adopted as a part of the 

watershed management 

plan. 

Plan Recommendations 

The plan contains recommendations aimed at reducing flooding as well as 

recommendations directed at improving the County’s overall stormwater 

management program. Specific project recommendations are provided at the end of 

this chapter. 

Flood Control Recommendations 

Alternatives were developed and evaluated to address the identified flooding problem 

areas. The proposed alternatives were analyzed and evaluated using the design 

storm events to establish a proposed level of service for each subwatershed 

corresponding to the County’s target LOS. Alternatives were compared with respect 

to the Hillsborough County CIP evaluation criteria including; effectiveness in 

alleviating the identified problems, flood frequency, type of flood hazard (school, 

home, yard), and maintenance needs. Based on these ranking criteria a score was 

assigned to each project and a set of flood protection projects was recommended – 

collectively, these projects comprise the flood control element of proposed watershed 

management plan. Table ES-1 presents the Alafia River WMP Update 

recommended CIP prioritization plan with the score each project was assigned. 

Table ES-2 presents a summary of each project. 




Based on the accomplishment of this project some other general stormwater 

recommendations are suggested, these other recommendations include: 

Operation And Maintenance - Comprehensive, regular maintenance of stormwater 

management systems is essential to ensure the efficient function of existing 

stormwater conveyances and that new stormwater facilities, once constructed, 

continue to function within their 

original design parameters for 

many years. Maintenance is also 

often required for prevention of 

water quality degradation, exotic 

species control, aesthetics, and 

safety reasons. The Alafia River 

Watershed Management Plan 

includes recommended practices 

and schedules for mowing and 

clearing, erosion control, and 

stormwater management facility 

maintenance and rehabilitation. 

The plan also lists specific 

locations in the watershed with immediate maintenance requirements and a 

recommended course of action to be taken. These sites were identified over the 

course of this study during field investigations, interviews with County Service Unit 

personnel, and review of field survey records and photographs recorded by survey 

crews. 

Revision of Hillsborough County Flood Level of Service Definitions - The 

current flood level of service definitions contained within the Hillsborough County 

Comprehensive Plan are not clearly defined and subject to a wide range of 

interpretation (e.g. “significant” road flooding, “significant” yard flooding, etc.). 

Stormwater Management Regulations for Closed Drainage Basins - It is 

recommended that Hillsborough County adopt a more strict set of stormwater 

management regulations for development within closed drainage basins. 


. 

Chapter 1 

parsons


Chapter 1 – Introduction 

CHAPTER 1 

INTRODUCTION 

The original report for the Alafia River Watershed Management Plan (WMP) was 

completed in 2001 for Hillsborough County. Since then, changes have occurred 

within each of the watersheds in Hillsborough County which affect the hydrologic and 

hydraulic features. Furthermore, changes to standards and reference elevation 

datum have been adopted. The combined changes warrant updating the existing 

models used for the WMP development and their associated GIS mapping. The goal 

of this project is to update the Hillsborough County SWMM model and GIS mapping 

for the Alafia River Watershed. The update will focus on resolving inconsistencies 

between the current conditions within the watershed and the information used to 

develop the original WMP for the watershed. The watershed model updates will be 

based on latest land use, aerial photography and recent development within the 

watershed. The Alafia River Watershed model will be updated with the new 

parameters resulting from the changes introduced. Accordingly, the supporting 

GIS/database and digital maps will be updated to match the updated models. Based 

on the updated watershed model, the Alafia River Watershed Management Plan will 

be reevaluated and recommendations for capital improvements to alleviate identified 

flooding level of service deficiencies will be developed, along with a revised 

implementation prioritization plan. Those sections of the WMP report dealing with 

modeling and flooding conditions assessments will be revised and updated floodplain 

maps will be created. All other chapters (or discussions within chapters) herein not 

related to flood control have not been updated. 

1.1 THE WATERSHED APPROACH 

Over the past 20 years, significant reductions have been made in the discharge of 

pollutants into the nation’s air and water resources. The majority of these reductions 

have been achieved by controlling point source pollution and preventing 

contamination from hazardous waste sites. However, a national water quality 

inventory revealed that in 1994, nearly 40% of the surveyed waters in the United 

States are still too polluted for fishing or swimming (EPA 1994). The survey also 

determined that the leading sources of water quality problems were pollutants such 

as silt, fertilizers, sewage, toxic metals, oil, and grease being washed into our waters 

with urban and agricultural stormwater runoff. Other causes include riparian habitat 

degradation, reductions in the flow, introduction and proliferation of exotic species, 

over-harvesting of fish and other aquatic organisms, and atmospheric deposition of 

toxins. 

In 1987, the Clean Water Act was amended to require states to expand their water 

quality protection programs to deal with toxic substances, nonpoint sources, 

Parsons 1-1 November 2010



wetlands, water quality standards, and other topics. These water quality protection 

programs led to the development of the Watershed Protection Approach Framework, 

a publication endorsed by senior EPA managers in 1991. This comprehensive 

approach to water resource management is needed to address the myriad water 

quality problems that exist today. The watershed protection approach is based on 

four major features: 

• Targeting Priority Problems – All significant problems within the watershed are 

identified and addressed. For the purpose of this watershed management plan, 

the problems include water quality degradation, flooding, and natural system 

impacts. 

• Identifying and Involving Stakeholders - Creating relationships with the people 

most affected by the management decisions is essential to a successful 

watershed management plan. This ensures that environmental, economic and 

cultural goals are integrated into the planning and implementation activities. 

Those affected by the watershed planning process are known as the 

stakeholders, and include state environmental, public health, agricultural, and 

resource agencies local/regional boards, commissions, and agencies, public 

representatives, private wildlife and conservation organizations, water supply 

providers, the academic community, and private citizens. 

• Integrated Solutions – Because the stakeholders work together, actions are 

based upon shared information and a common understanding of the 

responsibilities of all parties. This approach builds teamwork and improves the 

likelihood of sustaining long-term environmental improvements. The solutions to 

the problems identified during the development of the plan should look at the “big 

picture” of watershed planning, and include benefits to the other facets of the 

study. For example, a project that is constructed for flood abatement should also 

include design considerations that will enhance wildlife habitat and water quality. 

• Measuring Success - Monitoring the progress of the project is important to 

determine the success of measures implemented to address the problems in the 

watershed. One of the easiest parameters to measure to determine the 

effectiveness of the implemented solutions is water quality. Water quality 

sampling programs are essential to tracking the success of the watershed 

management plan. 

The belief that the watershed approach makes a sound basis for resource protection 

goes back to the 1930’s, but we have fallen short in the implementation of the 

integrated concept, likely due to political constraints. Over the last decade, the 

federal government has provided guidance and encouragement to state and local 

entities to develop management plans, with grants available for the implementation of 

approved projects. Tax incentives have also been made available to encourage 

cooperation among stakeholders. 




1.2 STAKEHOLDER INVOLVEMENT 

The Alafia River watershed lies in eastern Hillsborough County and western Polk 

County, portions of which are experiencing rapid population growth. A variety of 

intensive industrial and agricultural activities (e.g., phosphate mining and processing; 

citrus production; truck-farming of fruits and vegetables; concentrated animal feeding 

operations) also occur in the watershed. As a result state, regional, and local 

governments and resident groups are currently addressing a number of public policy 

issues related to the management of land and water resources. 

The Southwest Florida Water Management District (SWFWMD) prepared the 

Comprehensive Watershed Management Plan (CWM) (August 2001) for the Alafia 

River. The purpose of the CWM plan is to coordinate the various projects relating to 

water resources within the watershed. The CWM plan uses existing data and input 

from local governments to form the basis for identifying and prioritizing actions and 

funding strategies for improvements within the watershed. The CWM plan 

establishes a watershed team that includes local governments and other 

stakeholders. The team has established goals that include the following: 

1. Collect, integrate and analyze the existing information pertinent to each 

watershed and create a data base for analytical purposes. 

2. Identify and prioritize existing and future water resource management issues 

relating to water supply, flood protection, water quality and natural systems. 

3. Develop preventative or remedial management actions to address these 

resource management issues. 

4. Identify funding sources and partnerships to support action plan projects. 

5. Implement and monitor the effectiveness of selected actions and the overall 

process and recommend potential revisions. 

Stormwater management goals for the Tampa Bay watershed have also been 

developed by the Tampa Bay National Estuary Program (TBNEP), a partnership of 

federal, state, and local government agencies in which Hillsborough County is an 

active member. Stormwater-related goals adopted by the TBNEP participants 

(TBNEP 1996) include: 

1. Cap nitrogen loadings to Tampa Bay at existing levels (1992-1994 average) to 

encourage the regrowth of an additional 12,350 acres of seagrass. 

2. Protect relatively clean areas of the bay from increases in toxic contamination, 

and minimize risks to marine life and humans associated with toxic 

contaminants in impacted areas. 

3. Reduce bacterial contamination in impacted areas of the bay to levels safe for 

swimming and shellfish harvesting. 




During 1999 a citizens group (the “Alafia River Basin Stewardship Council” [ARBSC]) 

and an interagency team (including representatives of the Hillsborough County 

City/County Planning Commission, several other County departments, and the 

SWFWMD undertook an effort to develop more effective linkages between land and 

water management in the area (SWFWMD 1999). The group developed the 

following series of goals or “visions” for future conditions in the watershed, all of 

which are relevant to future stormwater management activities: 

1. Eliminate flooding. 

2. Employ best management practices (BMPs) for stormwater treatment. 

3. Protect riparian habitat. 

4. Improve water quality by reducing pollutant discharges. 

5. Implement a water quality monitoring program. 

6. Promote restoration of wetlands along the river. 

7. Reduce rate of development and protect wildlife habitat. 

8. Improve maintenance of existing drainage systems. 

9. Exclude development within the 100-year floodplain. 

1.3 THE ALAFIA RIVER WATERSHED MANAGEMENT PLAN 

The 2001 report was prepared for the Stormwater Management Section of the 

Hillsborough County Public Works Department to provide a summary of existing 

environmental conditions within the Alafia River Watershed. To ensure consistency 

with state and regional watershed management efforts (e.g., SWFWMD, February 

2001), the plan addresses four primary topic areas: 1) water quality; 2) natural 

systems; 3) water supply, and 4) flood abatement/protection. 

Policy goals of the Hillsborough County stormwater management program had been 

identified by the Board of County Commissioners through the local government 

comprehensive plan (Hillsborough County 1994). These goals provided County 

residents with a managed system of stormwater infrastructure that would: 

1. Minimize the occurrence of damages due to flooding. 

2. Improve the quality of surface waters. 

3. Re-establish and create wetland habitats. 

4. Improve the recharge of potable water supplies. 

5. Provide opportunities for recreational benefits and water reuse. 

The Stormwater Management Element of the 2008 update to the Comprehensive 

Plan continues to address significant issues related to stormwater quantity, 

stormwater quality, and stormwater management system maintenance. 




1.4 PREVIOUS STUDIES 

The studies listed below were undertaken prior to the 2001 report, and were used in 

the development of the report. A brief description of each report follows: 

• Wolf and Drew (1990) summarized the water quality and biological resources of 

the Tampa Bay watershed, which includes the Alafia River as a tributary. 

• An overview (SWFWMD 1998), provided by the Southwest Florida Water 

Management District’s Eastern Tampa Bay water resource assessment project 

(WRAP), focused on regional hydrogeology, surface-water/ground-water 

relationships, water use and water supply issues. 

• SWFWMD also published a report examining the potential sources of elevated 

and increasing nitrogen concentrations recently observed in Lithia and Buckhorn 

Springs (Jones and Upchurch 1993). 

• The Tampa Bay National Estuary Program (TBNEP) developed a Comprehensive 

Conservation and Management Plan (CCMP) for Tampa Bay and its watershed, 

including long-term goals and strategies for the management of water quality and 

natural systems (TBNEP 1996). 

• The Alafia River Basin Stewardship Council, Inc., a facilitated work group made 

up of citizen volunteers and agency staff, assessed ways and means of linking 

land and water management in the watershed (SWFWMD 1999). 

• A multi-agency task force (Willages et al 1998) investigated the environmental 

impacts caused by an accidental release of approximately 53 million gallons of 

low-pH effluent from a phosphate processing facility owned by Mulberry 

Phosphate, Inc., in the North Prong sub-basin. The accidental release occurred 

on December 7, 1997, producing substantial mortality of fish, other aquatic 

organisms and their habitats in the fresh-water and estuarine portions of the river 

(Polk County 1998). In response to that spill an assessment report and 

restoration plan was developed by the facility’s owner, federal and state 

regulatory agencies, and the affected local governments. 

• A Comprehensive Watershed Management Plan (August 2001), published by the 

SWFWMD coordinated the various water resource related projects within the 

Alafia River Watershed. The potential projects included potable water supply 

assessment, conservation, and development, hydrologic restoration of impacted 

areas, flood protection, land acquisition, habitat preservation and restoration, 

surface and ground water quality monitoring and assessment, flood plain 

mapping, and numerous others. 




• The National Flood Insurance Program published a Flood Insurance Study for 

Hillsborough County in July 1979. The study is revised periodically as recently as 

1992. The study is a flood hazard risk assessment. 

Numerous other reports, documents, studies, and other information were complied 

and used in the preparation of this management plan. These resources are listed at 

the end of each of the chapters for which they provided specific information. 

1.5 PROBLEM STATEMENT 

The Alafia River drains a highly impacted watershed that is currently facing a number 

of public policy concerns related to the management of its surface and ground water 

resources. As noted above, the primary management topics addressed in this report 

include: 

• Water Quality - point and nonpoint source pollutant discharges are impacting 

stream water quality, particularly in the North Prong, Turkey Creek, and the lower 

(tidally-influenced) portion of the watershed. 

• Natural Systems - the spatial extent of riparian, floodplain and other wetland 

areas has been reduced by phosphate mining and other dredge and fill activities, 

eliminating stream buffers and their associated water quality and habitat benefits. 

Upland and transitional habitats have also been fragmented and reduced in 

extent, potentially impacting native plant and wildlife populations. 

• Water Supply – the Alafia River Watershed will play an important part in the future 

potable water supply for the region. This report provides a cursory discussion of 

the existing and future potable water supply projects within the watershed. 

• Flood protection – the main focus of this report is to analyze existing flood 

conditions and levels of service within each of the eight subwatersheds and to 

propose alternatives to achieve a proposed level of service that will provide 

protection from all but the most extreme storm events. 

1.6 REPORT STRUCTURE 

The original report was divided into three volumes; all related to the topic of 

stormwater management within the Alafia River Watershed. The first volume has 

been revised for the 2009 WMP Update and consists of Chapters 1 through 6. It 

discusses existing conditions within the watershed for the following parameters – 

flood protection, natural systems, water quality, and water supply. The first two 

chapters of Volume I provide an overview of the watershed, an introduction to the 

watershed management approach, and a description of the existing conditions within 

the watershed with respect to soils and hydrogeology, climate, hydrology, and land 




use. Chapter 3 provides a brief description of the major conveyance systems that 

are the subject of this plan. 

The next three chapters in Volume I are perhaps the most important chapters in the 

report. Chapter 4 describes in detail the methodology used to complete the 

hydrologic/hydraulic modeling, the most critical part of the report. Chapter 5 provides 

the results of the modeling for each of the eight subwatersheds that comprise the 

Alafia River Watershed. Chapter 6 describes in detail, the existing conditions level of 

service for each of the watersheds. 

Volume II (not any of which has been revised for the 2009 WMP Update) is made 

up of six chapters, the first of which describes the existing water quality conditions 

within the watershed. Chapter 8 describes the existing conditions with respect to the 

natural systems, i.e. wetlands, wildlife habitat, endangered and threatened species, 

and issues that are currently in focus, such as the exponential growth in the area and 

its effect on wildlife habitat. Chapter 9 describes the historical and current issues 

with respect to water supply. Chapter 10 describes the result of the first public 

meeting. Chapters 11 and 12 describe the pollution loading analysis, the modeling 

calibration and results, and the level of service for pollution loading. 

Volume III consists of the final text chapters of the management plan. These 

chapters describe the problems that have been identified and offer alternative 

solutions to the problems. The results of the second public meeting are discussed in 

Chapter 14 (which has not been revised for the 2009 WMP Update). These final 

chapters include the proposed level of service and recommendations which detail the 

steps needed to achieve the proposed levels of service. The final chapter in this 

Volume III provides a prioritized list of the recommended projects along with 

conceptual drawings and projected costs of selected projects. Chapters 13 and 15 

have been revised for the 2009 WMP Update. 

1.7 REFERENCES 

Federal Emergency Management Agency, National Flood Insurance Program, 1992. 

Flood Insurance Study, Hillsborough County, Florida. Washington, D.C. 

Jones, G W. and S. B. Upchurch. 1993. Origin of Nutrients in Ground Water 

Discharging from Lithia and Buckhorn Springs, Ambient Ground-Water Quality 

Monitoring Program, Southwest Florida Water Management District. 

Southwest Florida Water Management District, and Hillsborough County Planning 

and Growth Management Department, 1999. Alafia River Watershed 

Land/Water Linkage Study, A Pre-strategy Report of the Alafia River 

Watershed Task Force, Tampa, Florida 




Southwest Florida Water Management District, 2001. Alafia River Comprehensive 

Watershed Management Plan. Tampa, Florida 

Tampa Bay National Estuary Program, 1996. Charting the Course for Tampa Bay – 

Comprehensive Conservation and Management Plan. Tampa Bay National 

Estuary Program, St. Petersburg, Florida. 

U.S. EPA (Environmental Protection Agency). 1991. The Watershed Protection 

Approach: An Overview. EPA 503/9-92-001. Office of Water. Washington, DC. 

U.S. EPA. 1994. National Water Quality Inventory: 1992 Report to Congress. EPA 

841-R-94-001. Office of Wetlands, Oceans, and Watersheds. Washington, 

DC. 

Willages, Kent, Victor Neugehaur, and Charles Cook, 1998. An Initial Assessment of 

the Impacts to Vegetation Resulting From the Alafia River Acid Spill. Florida 

Department of Environmental Protection, Bureau of Mine Reclamation. 

Wolfe, S. H. and R. D. Drew (eds). 1990. An Ecological Characterization of the 

Tampa Bay Watershed. U. S. Fish and Wildlife Service, Biological Report 

90(20). Washington, D. C. 


. 

Chapter 2 

parsons


Chapter 2 - Watershed Description 

CHAPTER 2 

WATERSHED DESCRIPTION 

2.1 INTRODUCTION 

The Alafia River Watershed is approximately 268,000 acres, or 418 square miles, 

covering approximately one third of Hillsborough County, and extending into the 

western edge of Polk County. Figure 2.1-1 shows the study area as determined for 

this watershed management plan update. It is the largest in area of the 17 

watersheds in Hillsborough County. The headwaters of the major flow contributory to 

the Alafia River originate in a swamp and prairie area south of Mulberry in Polk 

County and then flow 24 miles before entering the southeastern corner of 

Hillsborough County. There are numerous springs along the river, but surface water 

runoff contributes most of the flow. The major problems occurring within the 

watershed are associated with water quality, flooding, water supply, and natural 

systems. The watershed has had a history of water quality problems, with the 

majority of the pollution occurring as a result of the mining industry (SWFWMD 1997). 

Flooding problems have occurred in the past, especially during the El Niño years of 

1997 and 1998, and the 2004 hurricane season. Open areas and wildlife habitat are 

rapidly being lost to urban sprawl, mining, and expanding agricultural concerns. 

Burgeoning population growth has led to water supply shortages. 

The purpose of this section is to provide a general description of the watershed and 

set the stage for the more detailed existing conditions evaluations that are provided 

in the following sections. 

2.2 CLIMATE 

The climate of the area is humid subtropical, with an annual mean temperature of 

72.2 o F and annual average precipitation of about 52 in. During the period between 

1915 and 1997, the extremes in annual rainfall ranged from 37.56 in 1927 to 81.57 

inches in 1959 (SWFWMD 1999). In a typical year approximately 60% of the annual 

precipitation falls during a four-month rainy season that extends from June through 

September. Rainfall in this season comes primarily from convective afternoon and 

evening thunderstorms. Periods of extremely heavy precipitation associated with the 

passage of tropical low pressure systems and storms occur during summer and early 

fall in some years. 

Mean monthly temperatures range from a low of approximately 60 o F in January to a 

high of approximately 82 o F in August. Summer high temperatures typically reach 

95 o F, with occasional highs greater than 100 o F. Annual low temperatures range from 

25-30 o F, and occur following the passage of Arctic cold fronts. Winter 




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MCINTOSH RD 

4 

75 

301 

BUCKHORN 

92 

VALRICO 

S FORBES RD 

TURKEY CREEK RD 

TURKEY 

60 

39 

S PARK RD 

ENGLISH 

HILLSBOROUGH CO 

POLK CO 

Legend 

County Line 

Main Tributaries 

Alafia Subwatersheds 

Major Roads 

General Hydrology 

Alafia River Watershed 

4925 Independence Pkwy 

Suite 120 

Tampa, FL 33634 

41 

75 

RIVER WEST 

301 

BIG BEND RD 

BLOOMINGDALE AVE 

Notes: 

FISHHAWK BLVD 

BELL 

LITHIA PINECREST RD 

BALM BOYETTE RD 

RIVER EAST 

FISHHAWK 

BOYETTE RD 

672 

1:180,000 

39 

0 5,000 10,000 20,000 

Feet 

0 1.25 2.5 5 

Miles 

Filename: 

Fig2_1 

_1.mxd 


Map Date: 

Jan 07, 2010 

Date of Photography: 

N/A 

NORTH 

PRONG 

SOUTH 

PRONG 

Prepared By: 

Yoav 

Rappaport 

37 

60 

Figure: 2.1-1 Alafia River Watershed 

Study Area Map 

Project: Alafia River Model Update 

Alafia River Basin Board 

J:\DATA\260247_Alafia_WMP_Update\GIS\Maps\MXD\Report\Watershed\Fig2_2_1.mxd

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temperatures rarely remain below freezing during daylight hours, and typically rise to 

60-70 o F during periods between the passage of fronts. 

2.3 PHYSIOGRAPHY AND SOILS 

The Alafia River Watershed is located within the Gulf Coastal Lowlands and the Polk 

Upland physiographic regions (SWFWMD 2001). The ground elevations in the 

watershed range from 160 feet at the Polk-Hillsborough County line to sea level at 

the Alafia River’s confluence with Hillsborough Bay. The physiography of the eastern 

portion of the watershed has been altered significantly as a result of strip-mining in 

the ore-bearing Bone Valley Formation areas. 

According to the United States Department of Agriculture/Natural Resource 

Conservation Service (formerly Soil Conservation Service), there are 112 different 

classifications of soils found in the Alafia River Watershed. Figure 2.2-1 shows the 

locations of the hydrological soil groups. The majority of these soils each occupy 

less than 5,000 acres of the 268,000 acres of land area within the watershed. 

Nineteen of the soil types in the table represent more than 5,000 acres each and 

combined over 76% of the total land area. These nineteen soil classifications are 

highlighted in Table 2.3-1 and described in the paragraphs below. 

Arents, Haplaquents, and Hydraquents 

These soil classifications include steep, gently sloping, and nearly level deposits of 

heterogeneous and often clayey soil material. These soils have been excavated, 

reworked, and graded and are found in association primarily with phosphate mines 

and the overburden piles, sludge ponds, gypsum stacks and other features 

associated with the mines. These soils are also found in association with urban 

centers, major highways, and sanitary landfills. Approximately 24% of the surface 

soils in the watershed fit this classification. 

Basinger, Holopaw, and Samsula 

This surface soil type makes up only 3% of the watershed and commonly supports 

wetland species, specifically cypress swamp. This soil complex is usually found in 

depressions within flatwoods and not in large expanses within the watershed. 

Candler 

The Candler soil classification is found in approximately 5% of the watershed and 

historically supported upland vegetation, specifically scrub or xeric oak vegetation 

associations. Most of this has since been converted to pasture or residential areas. 






MCINTOSH RD 

4 

75 

301 

BUCKHORN 

92 

VALRICO 

S FORBES RD 


TURKEY 

60 

39 

S PARK RD 

ENGLISH 


POLK CO 

Hydrologic Soils 

A 

B 

B/D 

C 

D 

Water 

Legend 

County Line 



Major Roads 




Suite 120 


41 

75 

RIVER WEST 

301 

BIG BEND RD 


Notes: 

FISHHAWK BLVD 

BELL 



RIVER EAST 

FISHHAWK 

BOYETTE RD 

672 

1:180,000 

39 

0 5,000 10,000 20,000 

Feet 

0 1.25 2.5 5 

Miles 

Filename: 

Fig2_3 

_1.mxd 


Map Date: 



N/A 

NORTH 

PRONG 

SOUTH 

PRONG 

Prepared By: 

Yoav 

Rappaport 

37 

60 


Hydrologic Soil Group Classification Map 







TABLE 2.3-1 SOIL CLASSIFICATIONS 

SOILS NAME 

AREA (ACRES) 

ADAMSVILLE FINE SAND 1,483.14 

ADAMSVILLE-URBAN LAND COMPLEX 39.73 

ANCLOTE MUCKY FINE SAND/DEPRESSIONAL 21.08 

APOPKA FINE SAND/0 TO 5 PERCENT SLOPES 703.20 

ARCHBOLD FINE SAND 2,423.05 

ARCHBOLD SAND/0 TO 5 PERCENT SLOPES 135.69 

ARENTS/0 TO 5 PERCENT SLOPES 11,997.07 

ARENTS/CLAYEY SUBSTRATUM 843.88 

ARENTS/NEARLY LEVEL 6,757.44 

ARENTS/SANDY 4.73 

ARENTS/VERY STEEP 9,710.09 

ARENTS-URBAN LAND COMPLEX/0 TO 5 PERCENT SLOPES 222.62 

ARENTS-WATER COMPLEX 10,832.87 

ASTATULA SAND/0 TO 8 PERCENT SLOPES 193.49 

BASINGER FINE SAND 261.80 

BASINGER MUCKY FINE SAND/DEPRESSIONAL 607.96 

BASINGER/HOLOPAW/AND SAMSULA SOILS/DEPRESSIONAL 5,603.95 

BRADENTON FINE SAND 6.42 

BROWARD-URBAN LAND COMPLEX 14.37 

CANDLER FINE SAND/0 TO 5 PERCENT SLOPES 10,766.73 

CANDLER FINE SAND/5 TO 12 PERCENT SLOPES 263.26 

CANDLER SAND/0 TO 5 PERCENT SLOPES 633.61 

CANDLER SAND/5 TO 8 PERCENT SLOPES 4.24 

CANDLER-URBAN LAND COMPLEX/0 TO 5 PERCENT SLOPES 503.19 

CHOBEE FINE SANDY LOAM/DEPRESSIONAL 67.77 

CHOBEE FINE SANDY LOAM/FREQUENTLY FLOODED 173.15 

CHOBEE LOAMY FINE SAND 102.02 

CHOBEE SANDY LOAM/FREQUENTLY FLOODED 101.96 

DUETTE FINE SAND 151.05 

EATON FINE SAND 22.85 

EATON MUCKY FINE SAND/DEPRESSIONAL 269.77 

EATON MUCKY SAND/DEPRESSIONAL 25.35 

ELECTRA FINE SAND 30.40 

FELDA FINE SAND 409.38 




TABLE 2.3-1 SOIL CLASSIFICATIONS (continued) 

SOILS NAME 

AREA (ACRES) 

FELDA FINE SAND/DEPRESSIONAL 305.53 

FELDA FINE SAND/FREQUENTLY FLOODED 865.33 

FELDA FINE SAND/OCCASIONALLY FLOODED 480.63 

FLORIDANA FINE SAND 24.58 

FLORIDANA MUCKY FINE SAND/DEPRESSIONAL 229.23 

FORT MEADE LOAMY FINE SAND/0 TO 5 PERCENT SLOPES 3,657.83 

FORT MEADE SAND/0 TO 5 PERCENT SLOPES 1,105.56 

FORT MEADE-URBAN LAND COMPLEX/0 TO 5 PERCENT SLOPES 558.10 

GAINESVILLE LOAMY FINE SAND/0 TO 5 PERCENT SLOPES 759.25 

GYPSUM LAND 3,353.76 

HAPLAQUENTS/CLAYEY 8,825.31 

HOLOPAW FINE SAND/DEPRESSIONAL 300.93 

HONTOON MUCK 2,725.32 

HYDRAQUENTS/CLAYEY 14,684.80 

IMMOKALEE FINE SAND 1,938.40 

IMMOKALEE SAND 478.96 

KALIGA MUCK 38.27 

KENDRICK FINE SAND/0 TO 5 PERCENT SLOPES 239.38 

KENDRICK FINE SAND/2 TO 5 PERCENT SLOPES 65.05 

KESSON MUCK/FREQUENTLY FLOODED 140.05 

LAKE FINE SAND/0 TO 5 PERCENT SLOPES 4,726.99 

LOCHLOOSA FINE SAND 94.17 

LOCHLOOSA-MICANOPY FINE SANDS/0 TO 5 PERCENT SLOPES 58.89 

LYNNE SAND 27.22 

MALABAR FINE SAND 3,111.36 

MILLHOPPER FINE SAND/1 TO 5 PERCENT SLOPES 752.89 

MILLHOPPER-URBAN LAND COMPLEX/0 TO 5 PERCENT SLOPES 4.86 

MYAKKA FINE SAND 28,873.95 

MYAKKA FINE SAND/FREQUENTLY FLOODED 378.66 

MYAKKA-IMMOKALEE-URBAN LAND COMPLEX 3.85 

MYAKKA-URBAN LAND COMPLEX 212.32 

NARCOOSSEE SAND 15.16 

NEILHURST SAND/1 TO 5 PERCENT SLOPES 8,440.89 

NEILHURST-URBAN LAND COMPLEX/1 TO 5 PERCENT SLOPES 455.09 





SOILS NAME 

AREA (ACRES) 

NITTAW SANDY CLAY LOAM/FREQUENTLY FLOODED 940.47 

OLDSMAR FINE SAND 4.69 

ONA FINE SAND 6,590.94 

ORLANDO FINE SAND/0 TO 5 PERCENT SLOPES 1,424.11 

ORSINO FINE SAND/0 TO 5 PERCENT SLOPES 311.18 

PAISLEY FINE SAND/DEPRESSIONAL 139.68 

PLACID AND MYAKKA FINE SANDS/DEPRESSIONAL 458.56 

PLACID FINE SAND/FREQUENTLY FLOODED 257.09 

POMELLO FINE SAND 327.97 

POMELLO FINE SAND/0 TO 5 PERCENT SLOPES 3,538.82 

POMELLO-URBAN LAND COMPLEX/0 TO 5 PERCENT SLOPES 191.17 

POMONA FINE SAND 11,899.24 

POMONA-URBAN LAND COMPLEX 98.50 

POMPANO FINE SAND 45.31 

QUARTZIPSAMMENTS/NEARLY LEVEL 1,939.74 

SAMSULA MUCK 296.77 

SATELLITE SAND 18.50 

SEFFNER FINE SAND 10,112.45 

SLICKENS 1,782.24 

SMYRNA AND MYAKKA FINE SANDS 5,673.65 

SMYRNA FINE SAND 7,122.47 

SPARR SAND/0 TO 5 PERCENT SLOPES 2,834.07 

SPARR-URBAN LAND COMPLEX/0 TO 5 PERCENT SLOPES 39.15 

ST. AUGUSTINE FINE SAND 19.40 

ST. AUGUSTINE-URBAN LAND COMPLEX 45.94 

ST. JOHNS FINE SAND 7,203.70 

ST. JOHNS SAND 53.70 

ST. LUCIE FINE SAND/0 TO 5 PERCENT SLOPES 99.10 

TAVARES FINE SAND/0 TO 5 PERCENT SLOPES 5,154.18 

TAVARES-MILLHOPPER FINE SANDS/0 TO 5 PERCENT SLOPES 2,840.63 

TAVARES-MILLHOPPER FINE SANDS/5 TO 8 PERCENT SLOPES 136.19 

TAVARES-URBAN LAND COMPLEX/0 TO 5 PERCENT SLOPES 274.47 

VALKARIA SAND 10.26 

WABASSO FINE SAND 

50.28 





SOILS NAME 

AREA (ACRES) 

WATER 7,842.29 

WAUCHULA FINE SAND 160.18 

WINDER FINE SAND 38.64 

WINDER FINE SAND/FREQUENTLY FLOODED 16,987.33 

ZOLFO FINE SAND 17,657.28 

TOTAL 268,061.89 

Myakka Fine Sand 

Approximately 11% of the surface soil falls into this classification, making it the most 

prevalent natural soil type within the watershed. This soil type historically supported 

pine flatwoods, but much of this has been converted to residential areas, improved 

pasture, and cropland. 

Neilhurst Sand 

This soil classification comprises approximately 3% of the surface area in the Alafia 

River Watershed. Neilhurst series consists of deep, excessively drained, very rapidly 

permeable soils formed in homogeneous sandy spoil from mining operations 

reworked by wind. Some of these soils have been reworked by earth moving 

equipment during reclamation activities. 

Ona Fine Sand 

Approximately 2% of the surface soils in the watershed are classified as Ona fine 

sand. This soil historically supported pine flatwoods communities, but as with other 

non-hydric soils, the majority of this soil has been cleared and graded for crops, 

pasture, and subdivisions. 

Pomona Fine Sands 

Approximately 4% of the surface soils are classified as Pomono fine sand. No 

information was available regarding the composition of this soil or the vegetation it 

supported. 




Seffner Fine Sand 

This soil type was historically found on broad, low ridges within scrubby pine 

flatwoods communities. Approximately 4% of the surface soils within the watershed 

are classified as Seffner fine sands. Most of the vegetation supported by this soil 

type has been cleared for agriculture or residential development. 

Smyrna Fine Sand and Smyrna and Myakka Fine Sands 

These classifications combined provide almost 5% of the surface soils in the 

watershed. These soils are typically found on broad, low ridges within pine 

flatwoods, but most of this natural vegetation has been cleared for agriculture and 

subdivisions. 

St. Johns Fine Sand 

There is no information available regarding the description of this soil classification. 

The St. Johns soil type makes up nearly 3% of the surface soil in the watershed. 

Winder Fine Sand – Frequently Flooded 

This soil classification is mainly associated with the floodplains of the Alafia River, the 

North and South Prongs and many of the tributaries such as Fishhawk and Little 

Fishhawk Creeks. This soil typically supports an alluvial forest of hydric hardwoods, 

cabbage palm, and herbaceous species tolerant of periodic inundation. This soil 

classification fits approximately 6% of the surface soils within the watershed. The 

majority of this vegetation is intact, protected from development by the frequent 

flooding. 

Zolfo Fine Sand 

This soil classification is appropriate for approximately 7% of the surface soils within 

the watershed. This soil type supports xeric oak, pine, saw palmetto, and other 

species oak scrub vegetative associations. Large areas of this soil type are currently 

being mined in the eastern portion of the county, while others near the McCollough 

and McDonald Branches have been cleared for pasture and citrus. A significant area 

of this soil type is present on Fishhawk Ranch, and is currently intact; however, this 

will eventually be cleared for the construction of a subdivision. Several intact smaller 

tracts will be preserved on land purchased under the ELAP program. 

The remaining 30% of the surface soils within the watershed are those 95 

classifications representing less than 2%, or 5000 acres of the total area, and those 

areas currently and historically covered with water. 




2.4 GEOLOGY AND HYDROGEOLOGY 

Geology 

The elevations within watershed range from 160 feet at the Polk-Hillsborough County 

line to sea level at the Alafia River’s confluence with Tampa Bay. The topography of 

the watershed is relatively flat, except for a few areas along the river where the banks 

are fairly steep. Figure 2.4-1 provides a map of the general topographic relief of the 

watershed. 

The Alafia River basin is underlain by a thick sequence of sedimentary rocks that is 

divided into an upper zone of unconsolidated sediments and a lower zone of 

consolidated carbonate rock. The lower zone was apparently deposited in a shallow 

marine environment. 

At land surface undifferentiated sediments comprised of silt, sand, and clay form 

surficial deposits that vary in thickness from less than 10 feet in coastal areas to over 

100 feet in paleokarst depressions or sand ridges. The typical thickness of these 

sediments varies from 20 to 50 feet. In low-lying areas near lakes and streams, thin 

layers of organic material mix with unconsolidated sediments near the upper part of 

the surficial zone. Pleistocene Series terrace sands, which are fine to very finegrained 

and comprised primarily of quartz, underlie the uppermost sediments. 

Pliocene Series silts and clays underlie the terrace sands, forming the base of the 

undifferentiated surficial deposits. 

Underlying the unconsolidated material is a series of tertiary limestone and dolomite 

units that form the carbonate platform of peninsular Florida. The sequence of 

carbonate rocks includes, in descending order, the following formations: Tampa 

Member of the Hawthorn Group, Suwannee Limestone, Ocala Limestone, and the 

Avon Park, Oldsmar, and Cedar Keys Formations. A lithologic change from 

limestone and dolomite to a sequence of gypsiferous dolomite begins in the lower 

portion of the Avon Park Formation and continues into the Oldsmar and Cedar Key 

Formations. The top of this lithologic change marks the middle confining unit of the 

Floridan aquifer system. The middle confining unit is generally considered the base 

of the freshwater production zone of the Upper Floridan aquifer. 

The entire carbonate series thickens and dips toward the southwest. The total 

thickness of the Upper Floridan aquifer marine sequence varies from 950 to 1200 

feet. Included below, in descending order, are detailed geologic descriptions of each 

of the units that comprise the Upper Floridan aquifer. 

The Tampa Member of the Hawthorn Group is white to light-gray, sand, hard to soft, 

locally clayey, fossiliferous limestone that contains phosphate and chert in places. 

The Tampa Member ranges from 50 to 150 feet in thickness. The Suwannee 

Limestone consists of two rock types; the upper portion is a cream to tan, crystalline, 

highly vuggy limestone containing prominent gastropod and pelecypod molds, and 


MCINTOSH RD 

4 

75 

301 

BUCKHORN 

92 

VALRICO 

S FORBES RD 


TURKEY 

60 

39 

S PARK RD 

ENGLISH 


POLK CO 

Alafia Topography 

Feet NAVD88 

Legend 

High : 380 

Low : -1.7 

County Line 



Major Roads 




Suite 120 


41 

75 

RIVER WEST 

301 

BIG BEND RD 


Notes: 

FISHHAWK BLVD 

BELL 



RIVER EAST 

FISHHAWK 

BOYETTE RD 

672 

1:180,000 

39 

0 5,000 10,000 20,000 

Feet 

0 1.25 2.5 5 

Miles 

Filename: 

Fig2_4 

_1.mxd 


Map Date: 



N/A 

NORTH 

PRONG 

SOUTH 

PRONG 

Prepared By: 

Yoav 

Rappaport 

37 

60 


General Topographic Relief Map 







the lower portion is a white to cream, finely pelletal limestone containing foraminifera 

and pellets of micrite in a finely crystalline limestone matrix. The Suwannee 

Limestone varies from 150 to 300 feet in thickness. 

The upper portion of the Ocala Limestone is a white, generally soft, somewhat friable, 

porous coquina composed of large foraminifera, bryozoan fragments, and partial or 

full echinoid remains, all loosely consolidated in a matrix of micritic limestone. The 

lower portion of the Ocala contains plentiful miliolid remains and scattered 

foraminifera. This unit is late Eocene in age and ranges in thickness from 90 to 300 

feet. 

The Avon Park Formation is comprised of a light to dark brown, highly fossiliferous, 

soft to well-indurated, chalky limestone and a gray to dark brown, very fine to dark 

brown, very fine to microcrystalline dolomite. The Avon Park Formation ranges from 

300 to 500 feet in thickness. 

Hydrogeology 

The Alafia River watershed is underlain by a sequence of sedimentary rocks whose 

lithology, structure, and geologic history control the occurrence and movement of 

fresh and saline groundwater. Fresh groundwater occurs inland from the coastal 

margin of Tampa Bay, whereas saline groundwater occurs in the vicinity of the 

coastal margin of Tampa Bay (SWFWMD, 1994). 

Available data for describing the hydrogeology of the Alafia River watershed are 

sparse. Because of this, the hydrogeologic descriptions in this chapter are 

approximate. However, they should be sufficient for qualitative assessments of the 

potential influence of proposed stormwater management structural projects. 

Table 2.4-1 shows the generalized geologic and hydrogeologic units underlying the 

Alafia River watershed. Geologic units are also known as stratigraphic units. The 

Alafia River watershed is considered to be underlain by three sequences of rocks. 

They are from uppermost to lowermost: 1) a sequence of undifferentiated clastic 

rocks (predominantly sands and clays); 2) a sequence of Miocene carbonate 

(limestone and dolomite) and clastic rocks; and 3) a sequence of Eocene and 

Oligocene carbonate rocks. The correlations between the geologic and 

hydrogeologic units in the vicinity of the Alafia River watershed in this investigation 

are shown in Table 2.4-1. 

The hydrogeologic unit nomenclature used in Table 2.4-1 follows the Southeastern 

Geological Society (1986) and Miller (1986). The Floridan aquifer system (FAS) 

consists of the upper and lower Floridan aquifer systems separated by a middle 

confining unit. The middle confining unit and lower Floridan aquifer generally contain 

highly mineralized water in west-central Florida (Hickey, 1990). The upper Floridan 

aquifer system (UFAS) is defined as the stratigraphic interval in the FAS that, with 

permeable limestone and dolomite rocks, contain fresh groundwater. The UFAS is a 




commonly used hydrogeologic refinement for conceptualizing the major component 

of groundwater flow in the carbonate rocks in west-central Florida. Duer, et al. (1988) 

reported that the UFAS supplied more than ten times the amount of water than either 

the SAS or the IAS in the area of their investigation which included the Alafia River 

watershed. 

Depending upon the geographic location within the Alafia River watershed, the 

hydrogeologic unit that immediately overlies the UFAS may be either the SAS, ICU, 

or IAS (Table 2.4-1). The distribution of the hydrogeologic units and sections 

showing their distribution within the watershed is discussed in greater detail in 

Chapter 9. 




TABLE 2.4-1 GENERALIZED GEOLOGIC AND HYDROGEOLOGIC UNITS 

OF THE ALAFIA RIVER BASIN 

SERIES 

GEOLOGIC 

UNIT 

GENERAL 

LITHOLOGY 

HYDROGEOLOGIC 

UNIT 

UNDIFFERENTIATED 

UNDIFFERENTIATED 

SAND AND CLAY 

PREDOMINANTLY SAND 

WITH SOME INTERBEDDED 

CLAY, SHELL 

SURFICIAL 

AQUIFER SYSTEM 

INTERMEDIATE 

CONFINING 

UNIT 

MIOCENE 

HAWTHORN GROUP 

PEACE RIVER 

FORMATION 

ARCADIA 

FORMATION 

INTERBEDDED SAND, CLAY, 

AND CARBONATE, ALL 

OF WHICH ARE VARIABLY 

PHOSPHATIC 

SANDY AND CLAYEY 

LIMESTONE 

AND DOLOMITE WITH BEDS 

OF SAND AND CLAY, 

ALL OF WHICH ARE 

VARIABLY PHOSPHATIC 

INTERMEDIATE 

AQUIFER 

SYSTEM 

TAMPA 

MEMBER 

SIMILAR TO ARCADIA 

FORMATION BUT WITH LESS 

DOLOMITE, SAND, CLAY 

AND PHOSPHATE 

OLIGOCENE 

EOCENE 

SUWANNEE 

LIMESTONE 

OCALA 

LIMESTONE 

AVON PARK 

FORMATION 

LIMESTONE; SANDY 

LIMESTONE; 

FOSSILIFEROUS 

CHALKY, FORAMINIFERAL 

LIMESTONE; DOLOMITIC 

NEAR BOTTOM 

LIMESTONE AND 

CRYSTALLINE 

BROWN DOLOMITE; 

GYPSUM NODULES 

IN LOWER PART 

UPPER 

FLORIDAN 

AQUIFER 

SYSTEM 

MIDDLE CONFINING 

UNIT 

FLORIDAN AQUIFER SYSTEM 

MODIFIED FROM RYDER, 1985 

AND CAMBELL & ARTHUR, 1993 




The hydrogeologic flow system of the Tampa Bay region contains two distinct 

ground-water reservoirs: the unconfined surficial aquifer and the semi-confined Upper 

Floridan aquifer. In areas where the clay confining layer is discontinuous or absent, 

the Upper Floridan aquifer is under water table conditions. 

Surficial Aquifer: 

The surficial aquifer is comprised primarily of unconsolidated deposits of fine-grained 

sand with an average thickness of 30 feet. Due to the karst geology of the region, 

thickness of the sand is highly variable and ranges from less than 5 feet to over 90 

feet. Water table elevation is primarily influenced by rainfall, with annual highs in 

most years occurring during the end of the wet season (in September-October) and 

annual lows occurring near the end of the dry season (in May-June). The direction of 

groundwater flow varies locally and is significantly influenced by the topography of 

the land surface. The hydraulic gradient (change of elevation per unit length) in the 

area typically ranges from a few feet per mile to about ten feet per mile. The 

permeability of the surficial aquifer is generally low, and water withdrawn from this 

aquifer is used most often for lawn irrigation and watering livestock. Surficial aquifer 

wells typically yield less than 20 gallons per minute. 

Semi-Confining Zone: 

Below the surficial aquifer is a semi-confining unit comprised chiefly of clay, silt, and 

sandy clay that somewhat retards the movement of water between the overlying 

surficial aquifer and the underlying Upper Floridan aquifer. The confining materials 

are comprised of blue-green to gray, waxy, plastic, sandy clay and clay. The upper 

portion of the Arcadia Formation (Hawthorn Group) typically forms the semi-confining 

layer. 

Leakage from the surficial aquifer into the Upper Floridan aquifer occurs by infiltration 

across the semi-confining layer or through fractures or secondary openings in the 

semi-confining unit caused by chemical dissolution of the underlying limestone. Due 

to the highly karstic nature of the geologic system, the clay semi-confining layer can 

be in absent in one area but tens of feet thick a short distance away. These karst 

features—such as the Brandon karst terrain described by Upchurch and Littlefield 

(1987)—in which the clay semi-confining layer is breached or missing, significantly 

increase local hydraulic connections between the surficial and the Upper Floridan 

aquifer (Jones and Upchurch 1993). 

Upper Floridan Aquifer: 

The Upper Floridan aquifer consists of a continuous series of carbonate units that 

include portions of the Tampa Member of the Hawthorn Group, Suwannee 

Limestone, Ocala Limestone, and Avon Park Formation. Groundwater within the 

Upper Floridan aquifer is under artesian conditions at some locations within the 

project area. 




Near the base of the Avon Park Formation lies the middle confining unit of the Florida 

aquifer, an evaporite sequence of very low permeability that is composed of 

gypsiferous dolomite and dolomitic limestone. The middle confining unit generally 

delineates the boundary between the freshwater Upper Floridan aquifer and the 

brine-saturated Lower Floridan aquifer. The evaporites function as a lower confining 

unit and retard vertical flow across the boundary. In general, the permeability of the 

Upper Floridan aquifer is moderate in the Tampa Member and Suwannee Limestone, 

low in the Ocala Limestone, and very high in portions of the Avon Park Formation. 

The limestone and dolomite beds produce significant quantities of water due largely 

to numerous solution openings along bedding planes and fractures. The Ocala 

Limestone yields limited amounts of water and may be considered a semi-confining 

layer within the Upper Floridan aquifer. Overall, the Ocala Limestone tends to act as 

a semiconfining zone between the overlying Tampa/ Suwannee Formations and the 

underlying Avon Park Formation. Transmissivity of the Avon Park Formation is very 

high due to the fractured nature of the dolomite zones. 

Ground water flow in the Floridan aquifer originates as rainfall that percolates 

downward from the surficial aquifer. Recharge can be highly variable throughout the 

area, however, due to the presence or absence of confining units, the region’s karst 

geology, and induced leakage caused by ground-water withdrawals. The regional 

hydraulic gradient and direction of flow in the Upper Floridan aquifer is generally 

toward the south and west. 

2.5 LAND USE 

Land use categorization is necessary to evaluate existing conditions and to plan 

future conditions. If land is developed without planning, conflicts can occur over 

infrastructure, utilities, open space, zoning and many other issues. The 

categorization of land uses can be accomplished in several ways, but the most 

popular and widely used method is the Florida Land Use, cover, and Forms 

Classification System (FDOT, 1999) that was developed in the 1970s. This system 

describes and labels all developed and undeveloped land uses and covers in Florida 

into a simple numbering system. The following paragraphs describe the different 

land uses and their relative importance in this watershed system. The Existing 

Conditions Land Use Map (Figure 2.5-1) depicts the different land uses within the 

Alafia River Watershed. 

Residential (1000-1300) 

Residential land use is usually divided between low, medium, and high density 

residential, depending on the number of housing units per acre. As can be seen from 

Table 2.5-1, the North Prong basin has the highest acreage of residential land use at 

12,243 acres, but this only represents 19% of the total area in this large basin. The 

Buckhorn basin, with only 3,173 acres of residential areas, has the highest 

percentage of area in this land use classification within a basin with 67%. The 




majority of the residential areas within the Buckhorn basin are high density, or greater 

then five housing units per acre. However, the majority of the residential land usage 

areas are medium density, or two to five housing units per acre, in the North Prong 

basin, with 7,276 acres. 

Commercial/Industrial (1400-1500) 

For the purposes of this study, we have combined the commercial and industrial land 

uses, as these two land uses together comprise approximately 2% of the total 

watershed. Commercial land uses include retail and wholesale sales and services 

such as shopping centers, offices, theaters, museums, camping facilities, gas 

stations and storage areas, and cemeteries. 

Industrial land uses include manufacturing, assembly, or processing facilities, 

research and administrative centers, pulp and paper mills, oil refineries, and chemical 

plants. The North Prong basin had the most acreage in industrial land use, with 692 

acres. 

The facility 

in the 

photograph 

to the left is 

an oil 

refinery, an 

example of 

an industrial 

land use. 

Extractive (1600) 

The extractive land use is by far the largest in the watershed, with 84,565 acres 

comprising 32% of the total land area. This land use includes sand, gravel and clay 

pits, phosphate mines, and some reclaimed lands. The North and South Prong 

basins have the most land characterized as extractive with a combined total of 

81,182 acres. The majority of this mined land has been reclaimed or is scheduled for 

reclamation. 


MCINTOSH RD 

4 

Updated Land Use/Cover 

FLUCCS - DESCRIPTION 

1100 - RESIDENTIAL LOW DENSITY 

1200 - RESIDENTIAL MED DENSITY 

1300 - RESIDENTIAL HIGH DENSITY 

1400 - COMMERCIAL 

1500 - INDUSTRIAL 

1600 - EXTRACTIVE 

1700 - INSTITUTIONAL 

1800 - RECREATIONAL 

1900/2600 - OPEN LAND 

1820 - GOLF COURSES 

2000 - AGRICULTURAL 

3000 - RANGELAND 

4000 -UPLAND FOREST 

5000 - WATER 

6000 - WETLANDS 

7000 - BARREN/DISTURBED LANDS 

8000 - TRANS/COM/UTIL 

Legend 

County Line 



Major Roads 




Suite 120 


41 

301 

75 

75 

BUCKHORN 

301 

BIG BEND RD 

Notes: 

92 

VALRICO 

RIVER WEST 


FISHHAWK BLVD 

BELL 



S FORBES RD 

RIVER EAST 

FISHHAWK 

BOYETTE RD 


672 

1:180,000 

TURKEY 

39 

0 5,000 10,000 20,000 

60 

Feet 

0 1.25 2.5 5 

39 

Miles 

S PARK RD 

ENGLISH 

Filename: 

Fig2_5 

_1.mxd 



Map Date: 



N/A 

POLK CO 

NORTH 

PRONG 

SOUTH 

PRONG 

Prepared By: 

Yoav 

Rappaport 

37 

60 


Existing (2006) Land Use Map 







This 

photograph 

was taken in 

a rock 

quarry and 

shows the 

features 

common to 

this land use 

type, such 

as the large 

dragline 

dredge and 

the piles of 

soil 

overburden. 

Institutional (1700) 

The institutional land use includes educational, governmental, military and religious 

facilities and their associated parking lots and grounds. This land use comprises only 

895 acres, or less than one percent of the watershed. The majority of this land use is 

located in the Alafia River Main basin, with approximately 328 acres. 

Recreational (1800) 

Recreational areas comprise 1,764 acres of the total watershed and include parks, 

golf courses, swimming beaches, racetracks, marinas, community recreational 

facilities, historical sites, etc. The basin with the most recreational land is the North 

Prong basin with 618 acres or 35% of the total recreational land use areas. Lands 

managed under the Environmental Lands Acquisition and Protection Program 

(ELAPP) are not included in this category, but are characterized according to the land 

cover. 


Alafia River Watershed Management Plan 


Land Use 

Residential 

(1000-1300) 

Bell 

Creek 

(acres) 

Buckhorn 

Creek 

(acres) 

Turkey 

Creek 

(acres) 

TABLE 2.5-1 AGGREGATED LAND USE 

River 

(acres) 

Fishhawk 

Creek 

(acres) 

South 

Prong 

(acres) 

North 

Prong 

(acres) 

English 

Creek 

(acres) 

Delaney 

Creek* 

(acres) 

Valrico 

(acres) 

Total 

(acres) 

2,978 3,173 5,583 12,468 2,491 2,679 12,243 4,507 22 3,023 49,166 

Commercial/ 

43 164 524 

Ind (14001500) 

Extractive 

(1600) 118 - 1,028 

635 

487 

74 73 

8 53,682 

1,840 

27,500 

1,140 9 163 4,664 

1,741 

- 

- 84,565 

Institutional 

102 67 

38 64 

25 

(1700) 0.4 

328 

247 

- 

24 895 

Recreational 

27 202 138 

65 21 

177 

(1800) 

504 

618 

- 

14 1,764 

Open Land 

307 168 255 

833 147 

(1900) 

755 

1,575 

571 0.016 124 4,734 

Agriculture 

3,636 197 10,681 

5,535 12,906 

8,045 

(2000) 

3,838 

5,673 

- 

151 50,662 

Rangeland 

218 6 67 

486 875 

859 

(3000) 

70 

668 

- 

- 3,249 

Upland Forest 

3,080 136 1,227 

3,375 4,438 3,137 2,321 

(4000) 

3,407 

- 

130 21,251 

Water Bodies 

233 187 1,142 

1,410 531 

685 

(5000) 

1,347 

1,817 

- 

33 7,385 

Wetland Forest 

1,130 247 1,611 

1,447 7,444 

1,831 

(6100-6300) 

3,920 

4,947 

- 

2 22,578 

Wetland Nonforest 

(6400) 

1,465 

402 158 215 575 532 784 

920 0.023 18 5,068 

Barren Land 

- 21 5,146 125 1,475 2,086 

57 

7000 

431 

- 

- 9,341 

Trans./Utilities 

Communication 

(8000) 

- 0.1 279 171 48 22 756 1,296 1 42 2,616 

Total per Basin 12,171 4,769 27,964 

17,817 85,751 

28,629 

62,918 

* Area is within current model domain but actually drains to another the Delaney Creek Watershed. 

24,176 32 3,723 268,061 




Open Land (1900) 

This land use type comprises 4,734 acres or 2% of the entire watershed. This land 

use describes undeveloped urban land that exhibits no indication of what the future 

use may be. Often this land is in a transitional state and will eventually be 

developed, but until that future use is known the area is characterized as open or 

inactive. The basin with the most area described as open land is North Prong, and 

the open land description was applied to lands that have been mined and reclaimed 

but the current use is not known. 

Agriculture (2000) 

The agriculture land use areas are the second largest portion of the watershed, 

occupying 50,662 acres or 19% of the total area. The South Prong basin has the 

most agriculture land with 25% of the agricultural total. The majority of the 

agricultural uses are in crops such as strawberries, summer squash and cucumbers. 

Other agricultural activities include tree crops such as citrus and paper pulp, 

ornamental plant nurseries, fish farms, dairies, and horse farms. 

The 

photograph 

to the left is 

an example 

of improved 

pasture, one 

of the major 

land use 

types in the 

watershed. 

Rangeland (3000) 

The rangeland land cover classification describes lands that are usually dominated 

by grasses, forbs, and shrubs, and are capable of being used as grazing land to raise 

cattle or sheep. This land cover type comprises approximately 1% of the total 

watershed with 3,249 acres. These lands are usually in a semi-natural state and 

have not been graded, cultivated, irrigated, or fertilized. Usually the vegetation and 

hydrology are still somewhat intact. The greatest amount of rangeland is found in the 

largest basin – the South Prong basin – with 875 acres of this land cover type. 




Upland Forests (4000) 

The upland forests within the watershed include those areas with a tree canopy of 

greater than 10%, and with no other land use apparent, such as residential or 

recreational. The upland forests comprise approximately 8% (21,251 acres) of the 

total area within the watershed, ranking this land cover type fifth in area behind 

extractive, agriculture, residential, and wetland forest land uses. Approximately half 

of the upland forest land cover type in the watershed is found in the combined area of 

the North Prong, South Prong, and Fishhawk basins. Typical upland forests found in 

this region include pine flatwoods, xeric oak scrub, sand pine scrub, and upland 

mixed hardwood/conifer forests. The upland mixed hardwood/conifer forests are the 

dominant upland forest found in the watershed (14,130 acres or 66%) and usually 

former pine flatwoods or longleaf pine communities that have been logged out at one 

time. The pines have regenerated, but the hardwoods are usually co-dominant in the 

canopy due to the suppression of the natural fire cycle. This vegetation community 

type is important to the water quality and wildlife of the watershed in that they provide 

habitat and erosion protection. 

This 

photograph 

provides an 

example of 

typical second 

growth in an 

upland 

hardwood - 

conifer mixed 

forest. 

Water Bodies (5000) 

The water body land use classification include ponds, reservoirs, lakes, streams 

springs and sloughs, and usually refer to open waters too deep to support emergent 

aquatic vegetation. The North Prong basin has the most acreage in water bodies 

with 1,817 acres (25% of water bodies for the watershed), but Fishhawk Creek, Alafia 

River Main Stem, and Turkey Creek basins each have over 1,000 acres of water 

bodies. 




The open water 

of the Alafia 

River channel 

comprises a 

majority of the 

water body 

classification. 

Wetland Forests (6100-6300) 

This land cover type comprises 22,578 acres of the watershed or approximately 8% 

of the entire watershed. The North and South Prong basins provide the most 

coverage in wetland forests with a combined area of over 12,391 acres, which is 5% 

of the total land cover. The majority of the wetland forests are characterized as 

stream and lake swamps, also called bottomlands. The bottomlands are 

predominantly associated with the Alafia River floodplain and its tributaries and are 

characterized by a canopy of oak, bay, hickory, maple and other hardwoods and a 

sparse understory of ferns and other shade-tolerant forb species. The bottomlands 

land cover type comprises 95% of the wetland forest classification. The other 

wetland forests making up the remaining 5% of this land cover classification within 

the watershed are cypress swamps, mangroves near the mouth of the Alafia River, 

and wetland mixed hardwood/conifers. 

The 

photograph 

depicts a 

typical view of 

the floodplain 

forest, also 

called 

bottomlands 

along the 

Alafia River. 




Wetland Non-Forested (6400) 

This land cover classification is used to describe vegetated wetlands with no tree 

cover and predominantly herbaceous vegetation. This land cover includes 

freshwater marshes, wet prairies, saltwater marshes, floating aquatic macrophytes, 

and the emergent aquatic vegetation found on the littoral shelf areas of open water 

bodies. In the Alafia River Watershed, the non-forested wetlands comprise only 2% 

of the total land area. The predominant type of non-forested wetland present is the 

freshwater marsh, which make up 65% of this land cover. This figure is skewed, 

however, because the majority of this land cover consists of the large, highly 

disturbed surface water areas that remain after phosphate mining in the South Prong. 

If only natural freshwater marshes were counted, this figure would be much lower. 

This photograph 

depicts a typical 

Florida 

freshwater marsh 

with its concentric 

rings of different 

species of plants 

following the 

hydrological 

gradient. 

Barren Land (7000) 

The barren land classification is usually used to describe lands with little vegetation 

and for which there are no known current or future uses. Barren lands that have 

been disturbed in association with another known land use, such as mined lands and 

agricultural areas that have been tilled but not planted, do not fall into this 

classification. The barren lands within the Alafia River Watershed are disturbed 

lands, and comprise approximately 3% with 9,341 acres. The majority (55%) of 

these acres is found within the Turkey Creek basin. 

Transportation, Utilities, and Communication (8000) 

These three land use categories were combined for discussion because they have 

little impact on the stormwater management of the Alafia River. This land use 

classification includes utility corridors, easements and transmission lines, roads, 

railroads, and highways, water supply facilities, sewage treatment plants, solid waste 

disposal areas, and electrical substations and transformer yards. These land uses 




comprise 1% of the total area within the watershed, and approximately half of this 

area is located within the English Creek Basin. 

2.6 REFERENCES 

Duerr, A. D., Hunn, J.H., Lewelling, B.R., and Trommer, J.T., 1988. Geohydrology 

and 1985 Water Withdrawals of the Aquifer Systems in Southwest Florida, 

with Emphasis on the Intermediate Aquifer System. U.S. Geological Survey 

Water-Resources Investigations 87-4259. 

Florida Department of Transportation, 1999. Florida Land Use, Cover and Forms 

Classification System. Surveying and Mapping Office, Thematic Mapping 

Section, Third Edition. 

Hickey, J. J., 1990. An Assessment of the Flow of Variable-Salinity Ground Water in 

the Middle Confining Unit of the Floridan Aquifer System, West-Central 

Florida. U.S. Geological Survey Water Resources Investigations Report 96- 

4024. 

Jones, G W. and S. B. Upchurch. 1993. Origin of Nutrients in Ground Water 

Discharging from Lithia and Buckhorn Springs, Ambient Ground-Water Quality 

Monitoring Program, Southwest Florida Water Management District. 

Miller, J. A., 1986. Hydrogeologic Framework of the Floridan Aquifer System in 

Florida and in Parts of Georgia, Alabama, and South Carolina. U.S. 

Geological Survey Professional Paper 1903-B. 

Southeastern Geological Society, 1986. 

Publication No. 28. 

Florida Geological Survey Special 

Southwest Florida Water Management District, 1997. 1995 Estimated Water Use. 

Southwest Florida Water Management District, 1994. Aquifer Characteristics Within 

the Southwest Florida Water Management District. 

Southwest Florida Water Management District, 1998. Draft Alafia River 

Comprehensive Watershed Management Plan. Tampa, Florida 

Southwest Florida Water Management District, and Hillsborough County Planning 

and Growth Management Department, 1999. Alafia River Watershed 

Land/Water Linkage Study, A Pre-strategy Report of the Alafia River 

Watershed Task Force, Tampa, Florida 




Upchurch, S. B., and Littlefield, J. R., 1987. Evaluation of data for sinkholedevelopment 

risk models. In Karst Hydrogeology: Engineering and 

Environmental Applications. B. F. Beck and W. L. Wilson, Eds. Pp. 359-364. 

Balkema, Boston, Massachusetts. 


. 

Chapter 3 

parsons


Chapter 3 - Major Conveyance Systems 

CHAPTER 3 

MAJOR CONVEYANCE SYSTEMS 


This chapter provides an overview of the hydrological aspects of the Alafia River 

Watershed and how the extensive area that the watershed encompasses was divided 

and defined for the purposes of this study. The watershed extends over parts of 

west-central Polk County and includes the majority of central Hillsborough County. 

The watershed is bordered on the north by the Hillsborough River Watershed, on the 

east by the Peace River Watershed, on the south by the Little Manatee River 

Watershed, and on the southwest by the Tampa Bay Watershed. 

The Alafia River drains approximately 270,000 acres; over 400 square miles in 

central Hillsborough County. The river is formed by the confluence of several creeks 

that originate in western Polk County and converge in eastern Hillsborough County. 

The river flow is supplemented by additional input from several creeks that flow into 

the river prior to its discharge into lower Hillsborough Bay. These creeks and the 

river itself form nine separate subwatersheds within the Alafia River Watershed. 

These eight subwatersheds comprise the North and South Prongs, Turkey Creek, 

Fishhawk Creek, Buckhorn Creek, Bell Creek, English Creek, Valrico, and the Main 

River Subwatershed. Table 3.1-1 lists the eight subwatersheds and the area each 

one drains. A brief description is provided of each of these subwatersheds in this 

Chapter, with a more detailed description and the modeling results provided in 

Chapter 5 –Hydrologic/Hydraulic Model Development, Calibration and Verification. 

TABLE 3.1-1 

SUBWATERSHEDS WITHIN THE ALAFIA RIVER WATERSHED 

NUMBER SUBWATERSHED NAME AREA (acres) 

1 Buckhorn Creek 4,769 

2 Bell Creek 12,171 

3 Fishhawk Creek 17,773 

4 Turkey Creek 28,039 

5 English Creek 24,176 

6 North Prong 62,918 

7 South Prong 85,916 

8 Alafia River Main Stem 28,535 

9 Valrico 3,723 

parsons 3-1 November 2010



3.2 BUCKHORN CREEK SUBWATERSHED 

Buckhorn Creek originates in the eastern and western headwaters of the 

subwatershed and flows in a generally southwestern direction to its confluence with 

the Alafia River. The subwatershed is approximately 7.4 square miles and is located 

in the southern portion of the community of Brandon, Florida. The subwatershed 

historically was comprised of a system of lakes and wetlands draining through natural 

sloughs and natural channels to the main creek channel. The extensive residential 

and commercial development in the area has significantly altered the subwatershed 

so that the current primary tributaries to the channel are improved urban ditches and 

storm sewers. 

The primary drainage conveyance system of the Buckhorn Creek Subwatershed is 

divided into the four major drainage segments. The nomenclature for these drainage 

segments has been maintained from a 1988 stormwater master plan conducted for 

the SWFWMD, in order to provide continuity. The eleven segments are the Buckhorn 

Main Channel, Tanglewood Ditch, Tributary C, Tributary D, Craft Road Ditch, 

Tributary GG, Bloomingdale West Subdivision, Tributary F, Bloomingdale East 

Subdivision, Northwest Tributary, and the Hurley Ditch. A detailed description of the 

subwatershed and each of the segments is provided in Chapter 5. 

3.3 BELL CREEK SUBWATERSHED 

The Bell Creek Subwatershed is the second smallest of the subwatersheds within the 

Alafia River Watershed, with a drainage area of approximately 20 square miles. The 

creek originates in the southern portion of the subwatershed and flows north to its 

confluence with the Alafia River, approximately 1.2 miles downstream of Bell Shoals 

Road. The subwatershed is bordered on the east by Boyette Road, by Balm 

Riverview Road on the west, County Road 672 on the south and the Alafia River on 

the north. Table 3.1-1 provides the area of the subwatershed with respect to the total 

study area. 

Bell Creek Subwatershed was divided into three major drainage segments; the Bell 

Creek main channel to Lake Grady, Lake Grady, Bell Creek Main Channel from Lake 

Grady to Headwaters, Boggy Branch, Pelleham Branch, Tributary 731402, and 

Tributary 703700. There have been numerous changes and impacts to this drainage 

system due to the significant increase of residential development over the last 20 

years, and the effects of increased agricultural “improvements”. One example is 

Lake Grady, which was created by impounding Pelleham Creek for recreational 

purposes. Other portions of the drainage system are in a relatively natural condition, 

such as the channel between Lake Grady and the main channel of Bell Creek. A 

detailed description and detailed figures of the Bell Creek Subwatershed are 

provided in Chapter 5. 




3.4 FISHHAWK CREEK SUBWATERSHED 

The Fishhawk Creek Subwatershed is a 28-square mile area located in southeastern 

Hillsborough County and is roughly defined by Boyette Road and Balm-Boyette Road 

along the west, CR 39 on the east, SR 672 on the south, and the Alafia River on the 

north. Flow originates in the southern and eastern headwaters of the subwatershed 

and flows in a generally northwestern direction to the subwatershed outfall at the 

confluence with the Alafia River, located approximately 2.2 miles upstream (east) of 

Bell Shoals Road. 

Historically, the Fishhawk Creek Subwatershed consisted of an aggregation of lake 

and wetland systems overflowing through natural sloughs and small channels to 

Fishhawk and Little Fishhawk Creeks. Much of the historic drainage in the northern 

portion of the subwatershed remains semi-natural because until recently the majority 

of the land was under the control of two owners who used the area for cattle 

ranching. The southern portion of the subwatershed has been altered, however, over 

the past half century. Strip mining and agricultural activities have produced many 

changes to the landscape which is evident in the large water-filled borrow pits seen 

on aerial photographs. Although most of the mining activities ceased 20 to 30 years 

ago, their effects still remain. The Hillsborough County Southeast Landfill is about 

700 acres and is located on formerly mined land in the southeastern most corner of 

the subwatershed. 

Until recently, development within the subwatershed has been minimal. Two 250- 

acre portions of the 5000-acre Fishhawk Ranch subdivision are currently being 

constructed. The construction of the Boyette Road Extension (Fishhawk Blvd.) was 

planned to facilitate the development of this area. 

The topography of the Fishhawk Creek Subwatershed is characterized by generally 

flat topography throughout most of the contributing drainage areas, with high water 

tables, and many natural and man-made lakes, depressions, and wetlands. 

For the purpose of discussion in this study, the primary drainage conveyance system 

of the Fishhawk Creek Subwatershed has been segregated into four major drainage 

segments; the main Fishhawk Creek channel, Doe Branch, Long Flat Creek and Little 

Fishhawk Creek. Chapter 5 provides a detailed description of the subwatershed. 




3.5 TURKEY CREEK SUBWATERSHED 

The Turkey Creek Subwatershed is located in the north-central portion of the Alafia 

River Watershed and is bordered by Plant City and Rev. Dr. Martin Luther King, Jr. 

Boulevard to the north, Henry George Road to the southeast, Keysville Road and the 

Alafia River to the south, and Dover Road to the west. Flow in Turkey Creek 

originates in the northern portion of the subwatershed and flows to the south to 

discharge into the Alafia River, two miles upstream of the Lithia-Pinecrest Road 

Bridge. Flow in the Little Alafia River, the major tributary to Turkey Creek, originates 

in the northeast and flows in a southwesterly direction. This subwatershed drains 

approximately 50 square miles. 

The natural hydrologic system in the Turkey Creek Subwatershed probably consisted 

of small lakes, depressions, and wetland systems flowing through sloughs and small 

creeks to Turkey Creek and the Little Alafia River. Anthropogenic land use changes 

from the natural condition to phosphate mining, agriculture, and mixed density 

residential significantly altered the hydrologic system in the basin. 

Ground elevations range from 140 feet in the northeast corner of the basin to 15 feet 

at the confluence of Turkey Creek and the Alafia River. This 125 foot drop in 

elevation occurs over a 7.5-mile linear distance. 

The subwatershed is divided into two major and five minor drainage segments for the 

purpose of this study. The major segments are the Turkey Creek Main Channel and 

the Little Alafia River, and the minor segments are Little Alafia River Tributary A, 

Medard Tributary A, Grassy Creek, Turkey Creek Tributary A, and Turkey Creek 

Tributary B. A detailed description of the Turkey Creek Subwatershed and the seven 

drainage segments is provided in Chapter 5. 

3.6 ENGLISH CREEK SUBWATERSHED 

The English Creek Subwatershed drains 38 square miles and is located in the east 

portion of Hillsborough County. The subwatershed is roughly defined by Interstate 4 

to the north, Coronet Road to the west, and the Lakeland Regional Airport to the 

northeast. Flow originates in the eastern and northern headwater of the 

subwatershed and flows in a generally southwestern direction to its outfall at the 

confluence with the North Prong of the Alafia River. The outfall is located 

approximately 6.0 miles upstream of the crossing at County Road 39. 

A majority of the land use within the watershed has been modified for agriculture, 

phosphate mining and residential development. Historically the upper watershed 

consisted of a series of lakes, isolated wetlands and depressions that over flowed 

from one to the other and eventually discharging to the main channel segment. The 

majority of these natural streams and drainage ways have been channelized over the 

years in an effort to improve drainage. 




For the purpose of this discussion, the primary drainage conveyance system of the 

English Creek Basin has been segregated into five major drainage segments. These 

segments are the English Creek Main Channel, Horton Branch, Howell Branch, 

Howell Creek, and the Lakeland Airport Tributary. 

3.7 NORTH PRONG SUBWATERSHED 

The North Prong Subwatershed consists of 98 square miles and is located east of 

English Creek; south of Interstate 4; west of State Road 37; and north of Porter 

Road. Of the 98 square mile watershed, approximately 93.6 square miles is located 

within Polk County. Flow originates in the eastern headwaters of the watershed and 

flows in a generally western direction. The watershed outfalls at the confluence with 

the South Prong of the Alafia River, approximately 0.5 miles east of County Road 39. 

Historically this subwatershed consisted of a series of hydrologically interconnected 

wetlands and depressions that over flowed from one to the other and eventually 

discharged to the main channel segment. Within the last 50 years the majority of the 

land use within the watershed has been modified for agricultural and residential 

development, and the majority of the streams and drainage ways have been 

channelized or otherwise “improved” for drainage. Active and unreclaimed 

phosphate mine areas have significantly altered the topography and hydrology of the 

subwatershed. 


North Prong Basin has been segregated into six major drainage segments. These 

segments are the North Prong Main Channel, Sloman Branch, Poley Creek, Lake 

Drain, Thirty-Mile Creek, and North Prong Tributary. A detailed description of these 

segments and detailed figures of the subwatershed are provided in Chapter 5. 

3.8 SOUTH PRONG SUBWATERSHED 

The South Prong Subwatershed drains 134 square miles and is located within the 

southeast portion of Hillsborough County. The subwatershed boundaries are 

approximately defined by County Road 39 to the east; the Hillsborough / Manatee 

line to the south; and State Road 37 to the west. Flow originates in the eastern and 

southern headwaters of the subwatershed and continues in a generally northwest 

direction, to it confluence with the Alafia River approximately 0.5 miles upstream of 

the crossing at County Road 39. 

The majority of the land use within this subwatershed has been modified for 

phosphate mining and agricultural development. Historically, the headwaters 

consisted of isolated wetlands, swamps and high groundwater depressional areas 

that were hydraulically connected only during large storm events. Due to 

development in the watershed, many of these systems have either been channelized 

or mined. 





South Prong subwatershed has been segregated into six major drainage segments; 

the South Prong Main Channel, West Branch, Mizelle Creek, Chito Branch, Owens 

Branch, and Halls Branch. Chapter 5 provides a detailed discussion of these 

segments. 

3.9 RIVER SUBWATERSHED 

The subwatershed referred to as the River Subwatershed includes the main stem of 

the Alafia River and the lower portion of the North Prong. The main stem of the river 

extends from the confluence of the North and South Prongs of the river westward to 

the point of outfall into Hillsborough Bay. Rice Creek, approximately 2.3 miles in 

length and joining the river near McMullen Road from south, is the only major natural 

conveyance system in this subwatershed. The geographic boundary of the Alafia 

River main Stem Subwatershed is defined by Hillsborough Bay to the east, County 

Road 39 to the west, Gibsonton City to the northeast, and the cities of Riverview and 

Bloomingdale to the south. 

The lower North Prong extends from the point of confluence eastward to the Keysville 

Road Gage located 300 feet downstream of the Keysville Road Bridge. The 

remaining, upper portion of the North Prong is discussed in a separate section. The 

combined subwatersheds drain an area of approximately 45 square miles. 

The historic natural hydrologic system in the River Subwatershed consisted of an 

aggregation of small lakes, natural depression, and wetland systems overflowing 

through numerous natural sloughs and small springs to the river. The north central 

portion of the subwatershed contains a number of natural depressions (sinkholes) 

with no defined drainage outlets. These sinkholes act as closed basins except in 

extreme storm events. 

3.10 VALRICO SUBWATERSHED 

The subwatershed referred to as the Valrico subwatershed includes an area that 

does not actually drain to the Alafia River Watershed but is included in the study 

area. This subwatershed is located in the unincorporated area of Hillsborough 

County called Valrico. Generally, its center is approximately located where St. Cloud 

Ave. and Miller Rd. intersect SR 60. The area was included as part of the Turkey 

Creek subwatershed in the original 2001 Alafia River Watershed study. This area 

consists of a number of internally draining subbasins which do not discharge or 

outfall naturally to any other watershed. It is bounded by the Pemberton-Baker Creek 

Watershed to the north and the Delaney Creek Watershed to east. 


. 

Chapter 4 

parsons


Chapter 4 – Hydrologic/Hydraulic Model Methodology 

CHAPTER 4 

HYDROLOGIC/HYDRAULIC MODEL METHODOLOGY 


This chapter details assumptions and methodologies used to develop the hydrologic 

and hydraulic models of the Alafia River Watershed. For the purpose of this study, 

Parsons utilized the Hillsborough County version of the EPA SWMM (v.4.31) model 

(HCSWMM). The County has developed this program as a standard for all 

stormwater management planning within Hillsborough County as it provides a direct 

interface between a hydrologic package based on the SCS Curve Number method 

and the EPA SWMM EXTRAN Block. This was preferred over other SWMM model 

packages as it utilizes the SCS Curve Number method which is recommended for 

Hillsborough County stormwater system analyses, per the County’s Stormwater 

Management Technical Manual (SMTM). The hydrologic model output is delivered to 

EXTRAN, which is the hydraulic model. EXTRAN provides dynamic flood routing of 

flow through channels, lakes, and control structures such as bridges, culverts, storm 

sewers, weirs, pumps, and orifices. EXTRAN accounts for conservation of mass, 

energy, and momentum in its hydraulic algorithms, thereby representing looping, 

splits, flow reversals, etc. in the hydraulic system network should they occur. 

4.2 HYDROLOGIC MODEL TYPE 

Hydrologic modeling is an attempt to represent 

the hydrologic cycle to predict the reaction of a 

prototype watershed’s response to a dynamic 

set of meteorological conditions. There are two 

general types of hydrologic models that are in 

use for this purpose: event models and 

continuous simulation models. Event models 

describe the wet portion of the hydrologic 

cycle: precipitation, runoff, surface-water 

transport, and storage. They are used 

extensively and are considered to accurately 

describe the hydrologic cycle during extreme 

conditions. However, event models provide no 

means by which to numerically model the 

recovery of surface storage during the dry 

portion of the hydrologic cycle. Continuous 

simulation models describe both the wet and 

dry portions of the hydrologic cycle, whereas 

event models describe a smaller portion of the 

hydrologic cycle than continuous simulation 

HYDROLOGIC CYCLE 

Water cycles within our environment. 

Rainwater might soak into the ground 

or run off across the ground surface. 

Rainwater that runs off across the 

ground surface may flow into a ditch, 

then into a creek, a river, and 

eventually the ocean. Runoff may 

also be collected in impoundments 

such as ponds, lakes, wetlands, or 

depressional areas. Water in an 

impoundment or river may evaporate 

or seep into the ground. 

This example describes some of the 

ways that water cycles through our 

environment. This example is by no 

means a complete description. We 

collectively refer to all the possible 

ways that water moves through our 

environment as the hydrologic cycle. 




models. 

The Hillsborough County Stormwater Management Section modified Version 4.31 of 

EPA SWMM to allow hydrographs to be generated by the Soil Conservation Service 

Method, which differs significantly from the EPA SWMM RUNOFF Block method. 

The County also made minor modifications-of-convenience to the EXTRAN Block. 

These modifications increase the utility of the EXTRAN block. This model, referred to 

as HCSWMM, is a one-dimensional, junction-conduit, hydrodynamic event model. 

HCSWMM was utilized, as required by contract with Hillsborough County, to model 

the hydrologic response to extreme storm events within the Alafia River Watershed. 

This model describes flood hazards within the watershed. These data were 

generated using highly variable factors determined by a study of the watershed, as it 

existed in 2006. Many judgements and assumptions are required to establish these 

factors. The resultant data are sensitive to changes, particularly of antecedent 

conditions, urbanization, channelization, and land use. Users of these data are 

cautioned against assumptions of precision that cannot be attained; and that flood 

hazards within the watershed will change with anthropogenic and natural influences 

on the watershed. 

4.3 DATA SOURCES 

Data from numerous sources are incorporated into this model. Specific citations are 

made throughout this report. In general, the following data were utilized in the 

development of the original 2001 WMP study model or the 2009 WMP study update: 

• Lake Atlas Database at the University of South Florida’s Center for 

Community Design and Research 

• Geographic Information System Database at the Southwest Florida Water 

Management District 

• Geographic Information System Database at the University of Florida 

• Geographic Information System Database at Polk County 

• Hillsborough County Soil Survey by the U.S. Department of Agriculture, 

Natural Resources Conservation Service 

• Streamflow and lake gaging station records from the U.S. Geological 

Survey 

• Rainfall records by the National Oceanic and Atmospheric Administration 

and Southwest Florida Water Management District 

• Aerial photography at 1”=200’ scale by Hillsborough County 

• Aerial photography at 1”=200’ scale with 1-foot and 2-foot topographic 

contours, respectively, by the Southwest Florida Water Management 

District 

• Quadrangle maps at 1”=2000’ scale with 5-foot topographic contours by 

the U.S. Geological Survey 




• Digital Ortho Quarter Quadrangles by the U.S. Department of the Interior, 

Geological Survey 

• Environmental Resource Permits at the Southwest Florida Water 


• Environmental Resource Permits for mine lands at the State of Florida, 

Department of Environmental Protection 

• Stormwater management master plans, comprehensive plans, and 

Development of Regional Impact plans at Hillsborough County 

• Cross section geometry and flood hazard risk assessment maps from the 

Federal Emergency Management Agency 

• Drainage plans at the Florida Department of Transportation 

• Interviews with residents 

• Interviews with Hillsborough County maintenance personnel 

• Future land use data from the Hillsborough County Planning Commission 

• Future land use data from Polk County 

• Future land use data from the City of Plant City 

• Conventional field survey by Edgemon Land Surveying, Wilson Miller, 

Tomasino and Associates, Strayer Surveying and Mapping and Northwest 

Engineering Inc. 

• Hydrologic reconnaissance survey by Parsons 

• Hillsborough County digital elevation model (DEM) data 

• Hillsborough County Capital Improvement Projects (CIP) data 

4.4 MODEL RESOLUTION 

Hydrologic and hydraulic model development requires the abstraction or 

generalization of an infinitely complex natural system into a finite network. Onedimensional 

hydrodynamic models are built on a network of conduits and junctions. 

Clearly, a challenge of resolution exists. A balance must be struck between a 

prohibitively expensive high resolution, and a non-descriptive low resolution. It is 

model use that dictates resolution. The Alafia River Watershed covers portions of 

Hillsborough and Polk Counties, but this is a planning model intended for use in 

Hillsborough County. The resolution programmed into this model is sufficient to 

assess level of service and general risk associated with flood hazards within the 

primary drainage system and portions of the secondary drainage system. The level 

of resolution in the portions of the watershed within Polk County is sufficient to make 

estimates within Hillsborough County, but the level of resolution within Polk County 

may not be sufficient to make estimates there. 

This model may not be sufficiently detailed to study complex, localized hydraulic 

phenomena nor design hydrologic or hydraulic structures at any given location within 

the watershed. Future design users of these data are cautioned to carefully examine 

the level of resolution within the area-of-concern, and independently ascertain the 

sufficiency of these data for design purposes. Future design users of these data are 




also cautioned to determine the effect that anthropogenic and natural change in the 

watershed since the late 2006 may have on model assumptions. 

4.5 HYDROLOGIC MODEL 

The hydrologic modeling of the Alafia River 

Watershed was conducted using 

Hillsborough County’s modified version of 

the U.S. Army Corps of Engineers 

Hydrologic Engineering Center Program 1 

(HEC-1) code. This model uses the U.S. 

Soil Conservation Service (SCS) Runoff 

Curve Number (CN) method to estimate 

runoff volume as the result of rainfall. The 

SCS Method conceptually separates 

rainfall into three components: runoff, an 

initial abstraction, which represents rainfall 

lost at the beginning of a storm, and 

losses. The computation of runoff depth 

within any given time step is based on an 

accounting of precipitation components, 

and two empirical relationships. 

The code generates subbasin runoff 

hydrographs with the Dimensionless Unit 

Hydrograph Method. The model assigns 

subbasin hydrographs to the routing model 

WHAT IS A WATERSHED? 

A watershed is an area of land, which 

contributes runoff to a point on the 

surface of the earth. The point can be 

somewhat arbitrary, such as a location in 

a river; or specific, such as a lake, the 

confluence of two rivers, or the outfall of a 

river into a bay or the ocean. 

Watersheds are separated from other 

watersheds by ridges of land, or by 

elevated barriers such as roads or fill 

associated with development. The area 

that contributes runoff to the point is said 

to be a watershed to the point. 

Hydrologically, the terms watershed, 

subwatershed, and subbasin all share the 

same definition, with one important 

difference: scale. It is the convention of 

this report that watersheds are divided 

into subwatersheds, and subwatersheds 

are further broken down into subbasins. 

at junction locations in the model network. Hillsborough County modified the code to 

observe a unit hydrograph shape factor of 256, which accounts for flat terrain. The 

County adopts this standard to be consistent with the guidance provided in the 

Hillsborough County Stormwater Management Technical Manual. In addition, the 

County observes a standard initial-abstraction ratio of 0.2. 

The following hydrologic variables are required by the HCSWMM model: rainfall data, 

rainfall distribution, subbasin number, junction number, time of concentration, curve 

number, subbasin area, initial abstraction, and shape factor. The SCS Hydrograph 

Method generates subbasin runoff hydrographs with these variables using the 

Dimensionless Unit Hydrograph Method. These runoff hydrographs are assigned to 

the hydraulic routing model at specified junction locations in the hydraulic model 

network. 

4.5.1 Watershed-Subwatershed-Subbasin Definition 

Hydrologists sometimes use the terms watershed, basin, catchment, subwatershed, 

subbasin, and subcatchment interchangeably. By convention, within this document 

and the accompanying model, the term watershed describes the area that drains to 




the outfall of the Alafia River at Hillsborough Bay. The term subwatershed describes 

the areas that drain to the major tributaries of the Alafia River, at the confluence of 

the major tributaries and the Alafia River. The term subbasin describes further aerial 

subdivision within the subwatersheds. 

The Alafia River Watershed is divided into the following nine subwatersheds: Bell 

Creek, Buckhorn Creek, English Creek, Fishhawk and Little Fishhawk Creek, North 

Prong Alafia River, South Prong Alafia River, Turkey Creek, Alafia River Main Stem 

and Valrico. The Alafia River Main Stem Subwatershed includes the drainage areas 

that drain directly to the Alafia River or minor tributaries to the Alafia River. 

Each subwatershed is divided into a number of subbasins (i.e. a basin consists of a 

set of subbasins). Each subbasin is numbered with the junction number to which the 

subbasin drains. A subbasin is not always delineated for every junction. 

4.5.2 Subbasin Delineation 

To provide the level of detail that was deemed necessary to accurately define and 

properly analyze the primary drainage facilities within the Alafia River Watershed, the 

watershed was divided into discrete subbasins. The delineation of individual 

subbasins was dictated to a large extent by the primary drainage network itself and 

the need to properly define the contributing drainage area to individual elements of 

the conveyance system and storage facilities. Subbasin designations were also 

selected to segregate drainage areas of homogeneous land use and/or define the 

complete contributing drainage area of a secondary drainage system at its outfall to 

the modeled primary network. 

The means of defining subbasin boundaries employed a number of sources of 

information and methods. The principle source was the County-supplied DEM 

dataset. This mapping shows overland topography, thus indicating direction of 

overland flow. In addition, various reports describing hydrologic studies conducted in 

the basin were reviewed and the information was incorporated into this study. 

However, much of the watershed drainage patterns have been modified due to 

mining activities, agriculture, and development with a variety of residential, 

commercial, industrial, and institutional developments. As a result of these activities, 

man-made drainage systems comprising swales, gutters, storm sewer systems, 

ditches, and detention ponds have interrupted the natural overland flow patterns 

within the watershed and, in many cases, diverted storm runoff in directions that are 

not readily apparent from inspection of the topographic mapping. Such activities 

have resulted in the alteration of the original drainage patterns, including the 

complete severance of drainage through creation of closed impoundments, or 

through integration of previously existing closed basins to the creek system. 

To assist in the delineation of subbasin boundaries, available record drawings of 

county roads within the basin were also used to define the drainage facilities and 

contributing drainage areas that are served by these systems. Parsons also 




conducted a thorough review of record drawings of permitted stormwater 

management facilities within the basin on file with SWFWMD as a means of defining 

the drainage systems and contributing drainage areas for new development that did 

not show up on any of the other information sources. Additionally, development 

plans and Capital Improvement Project plans were used define subbasin boundaries. 

The final check of subbasin delineations was field reconnaissance of the watershed 

to; (1) confirm the initial boundaries and to inspect the drainage facilities and 

conditions in the basin firsthand, (2) investigate areas where there was no 

information available from the previously listed sources, and (3) resolve 

discrepancies where there were conflicts between different sources of information 

regarding drainage facilities. 

4.5.3 Time of Concentration 

A necessary input parameter for the unit hydrograph method that is used by the 

County’s version of the SWMM model is the subbasin time of concentration. The 

time of concentration (Tc) represents the amount of time it takes for a particle of 

water to travel from the hydraulically most distant point in the drainage basin to its 

outlet. As more thoroughly documented in detail in previous discussion, the County 

has adopted a standard method for Tc calculation that is documented in its 

Stormwater Management Technical Manual (SMTM). In this method, the Tc is 

computed by summing all the travel times for consecutive flow components of the 

subbasin conveyance system. The SMTM provides methods for computing flow 

times for overland flow (sheetflow), shallow concentrated flow, and open channel flow 

as a function of slope and the type of flow path. 

As detailed in the SMTM, the overland flow component was calculated based on the 

kinematic wave solution applied to overland flow. The following formula was applied: 

L 0.6 N 0.6 

t 1 = 0.093 ------------ 

I 0.4 S 0.3 

Where: 

t 1 = Travel time (min) 

L = Length of overland flow (feet) 

N = Manning’s roughness coefficient for overland flow 

S= Average overland flow Slope (feet/feet) 

I = Rainfall intensity (inches/hour) 

For the Alafia River Watershed, the subbasin length of overland flow and slope data 

were obtained from the topographic maps. Surface roughness, represented by the 

Manning’s coefficient (n), was determined using literature values expressed as a 

function of land cover. A maximum overland flow length of 300 feet was used for 

computations. The type of land cover for the subbasin overland flow path was 

identified from aerial mapping. The shallow concentrated and channel flow 

components of the time of concentration were calculated based on length and 




velocity. Again, the method outlined in the SMTM for shallow concentrated flow was 

used to calculate this component. Tc values from the original 2001 WMP study were 

utilized for the updated model if the subbasin delineation represented the same 

drainage area and no developments of impact were observed. New Tc calculations 

were made for the rest of the subbasins in the watershed. The same methods were 

used for the new Tc calculations. The entire method of Tc calculation was automated 

within a spreadsheet designed for this purpose, and the new individual Tc data are in 

ArcGIS geodatabase submittal (Alafia_Update_TCs). It should be noted that, in 

many cases, the studies and design plans for the residential and commercial 

developments, along with the road improvement projects, included time of 

concentration calculations. Where such information was available, these data were 

used in lieu of any new calculations and referenced within the time of concentration 

spreadsheet. Also, a minimum subbasin Tc of 10 minutes was assumed for the 

purpose of this study. 

4.5.4 Runoff Curve Number 

Hydrologic modeling with the Hillsborough County version of the SWMM model was 

performed using the U.S. Soil Conservation Service (SCS) Runoff Curve Number 

Method to compute a runoff volume from rainfall. This method uses a family of curves 

to relate direct runoff depth to rainfall depth. Numbers between 0 and 100, which are 

referred to as curve numbers (CN), describe the family of curves. Recall that the 

SCS Method conceptually separates rainfall into three components: runoff, initial 

abstraction, and losses. The CN is a lumped representation of the initial abstraction 

and loss components and is an index that represents the combined hydrologic effect 

of hydrologic soil group, cover type, land use, hydrologic condition, and antecedent 

soil moisture condition. Curve numbers were determined over the course of this 

study for each subbasin by an area-weighted averaging procedure that assigned a 

universal CN value to each combination of land use category and hydrologic soil 

group classification, and then calculated the subbasin average based on the relative 

percentages of each combination within it. The universal CN values were selected 

based on values provided by Hillsborough County (antecedent moisture condition 

(AMC) II) and is shown in Table 4.5-1. 




Table 4.5-1 


Universal SCS Runoff Curve Numbers for All Subwatersheds 

LAND USE 

CLASSIFICATION 

FLUCCS CODES 

HYDROLOGIC SOIL GROUP 

CLASSIFICATION 

A B B/D C D Water 

Low Density Residential 1100 50 68 82 79 84 100 

Medium Density Residential 1200 57 72 84 81 86 100 

High Density Residential 1300 77 85 91 90 92 100 

Commercial 1400 89 92 95 94 95 100 

Industrial 1500 81 88 92 91 93 100 

Transportation, 

8100,8200,8300 81 88 92 91 93 100 

Communications, and Utilities 

Mining (active) 1600 77 86 93 91 94 100 

Institutional 1700 69 81 89 87 90 100 

Open Land and Rangeland 1800 49 69 82 79 84 100 

1820 44 65 80 77 82 100 

1900 39 61 77 74 80 100 

2600 30 58 75 71 78 100 

3100 63 71 85 81 89 100 

3200 35 56 74 70 77 100 

3300 49 69 82 79 84 100 

7100,7400 77 86 93 91 94 100 

Cropland and Pastureland 2100,2140 49 69 82 79 84 100 

2200 44 65 80 77 82 100 

Specialty Farms 2300 73 83 91 89 92 100 

2400 57 73 84 82 86 100 

2500,2550 59 74 84 82 86 100 

Forest 4100 45 66 80 77 83 100 

4110 43 65 79 76 82 100 

4120 43 65 79 76 82 100 

4200,4340,4400 36 60 76 73 79 100 

Wetland 6100,6110,6120,6150,6200, 98 98 98 98 98 98 

6210,6300,6400,6410,6420, 

6430,6440,6500,6510,6520, 

6530,6600 

Water 5100,5200,5300,5400 100 100 100 100 100 100 




4.5.5 Existing Land Use Conditions 

Derivation of subbasin runoff curve numbers is dependent on the type of land use 

conditions within the subbasin. Existing land use conditions in the Alafia River 

Watershed were defined by use of digital coverages obtained from the Southwest 

Florida Water Management District (SWFWMD) Geographic Information System 

(GIS) database. The 2006 GIS dataset is based on the Florida Land Use and Cover 

Classification System (FLUCCS). For the purpose of calculating subbasin weightedaverage 

curve numbers, the original set of SWFWMD land use classifications was 

aggregated into the following set of fifteen in accordance with Table 4.5-2. 

Table 4.5-2 


Consolidated Land Use Classifications 

LAND USE CLASSIFICATIONS 

FLUCCS CODES 

INCLUDED 

Low Density Residential 1100 

Medium Density Residential 1200 

High Density Residential 1300 

Commercial 1400 

Industrial 1500 

Open Land and Rangeland 1401,1701,1800,1900,2600, 

3100,3200,3300,7100,7400 

Cropland and Pastureland 2100,2140,2200 

Forest 4100,4110,4120,4200,4340, 

4400 

Institutional 1700 

Transportation, Communications and Utilities 8100,8200,8300 

Specialty Farms 2300,2400,2500,2550 

Mined Lands (active) 1600 

Mined Lands (reclaimed) 1650,1660 

Water 5100,5200,5300,5400 

Wetland 6100,6110,6120,6150,6200, 

6210,6300,6400,6410,6420, 

6430,6440,6510,6530 

A great deal of effort was exerted as a part of this study to verify and update the 

original SWFWMD land use database to reflect a consistent and up-to-date set of 

hydrologically valid land use coverages. This was deemed especially important for 

the more highly developed areas of the watershed, as the SWFWMD land use 

database did not reflect a number of the significant developments that have been 

constructed in the past ten years. In addition to adding these new developments to 

the land use coverage database, it was deemed necessary by visual examination of 




aerial mapping to reclassify some of the residential areas to a different density to 

maintain a consistency throughout the basin and watershed. Also, large areas of 

open, undeveloped land that were observed to be contained within the confines of 

the commercial, industrial, institutional, and the transportation, communications, and 

utilities parcels were segregated from these parcels digitally and reclassified as open 

land. In the mined areas of the watershed, areas were digitally reclassified according 

to current status of activity. This was deemed necessary since these areas act 

differently hydrologically. The resultant individual subwatershed existing land use 

maps of the Alafia River Watershed that were used for model development purposes 

are contained in Chapter 5. This land use coverage was intersected with the 

digitized subbasin delineations using GIS overlay techniques to develop an accurate 

measurement of the distribution of the various land use classifications within each of 

the defined subbasins in the watershed. 

4.5.6 Hydrologic Soil Type 

The standard method of soils classification used for hydrologic modeling is the 

hydrologic soils group. By this method, soils are grouped into four hydrologic soil 

groups A through D. These hydrologic soil groups are commonly used in hydrologic 

analyses to estimate infiltration rates and soil moisture capacities. Soils within the 

Alafia River Watershed were categorized according to this hydrologic soil group 

classification system, as defined by the Natural Resource Conservation Service. 

There are six different soil groups that the basin soils fall into: A, B, B/D, C, D, and 

Water: 

• Hydrologic Soil Group A (low runoff potential): Soils with high infiltration rates 

even when thoroughly wetted and a high rate of water transmission. Typical 

maximum infiltration rate of 10 inches per hour when dry and 0.5 inch per hour 

when saturated. 

• Hydrologic Soil Group B (moderately low runoff potential): Soils with moderate 

infiltration rates when thoroughly wetted and a moderate rate of water 

transmission. Typical maximum infiltration rate of 8 inches per hour when dry 

and 0.4 inch per hour when saturated. 

• Hydrologic Soil Group C (moderately high runoff potential): Soils with low 

infiltration rate when thoroughly wetted and a slow rate of water transmission. 

Typical maximum infiltration rate of 5 inches per hour when dry and 0.25 inch 

per hour when saturated. 

• Hydrologic Soil Group D (high runoff potential): Soils with very low infiltration 

rates when thoroughly wetted and a very low rate of water transmission. 

Typical infiltration rate of 3 inches per hour when dry and 0.10 inch per hour 

when saturated. 

In many locations in Florida, dual hydrologic soil group classifications (A/D or B/D) 

are assigned to soils that are saturated throughout much of the soil column during 

the wet season, due to a high surficial water table. During the wet season, infiltration 




is impeded and the soil acts as a Type D soil. During the rest of the year, when the 

water table is lower, the soil acts as an A-type or B-type soil. 

The modeling approach utilized for this study uses an intermediate curve-number 

assignment for areas with dual hydrologic soil type. The assigned curve number is 

greater than if the area were made up with Type A or B soils, and less than if the 

area were made up with Type D soils. This approach is appropriate due to the 

planning nature of the model and size of the watershed. This approach is realistic as 

opposed to conservative. Where conservatism is appropriate, users may wish to recalculate 

subbasin curve number with a Type D assignment in areas with dual 

hydrologic soil group classifications and re-run the watershed model. 

A hydrologic soils classification map of the Alafia River Watershed that was 

developed for this study was previously presented in Chapter 2. Individual 

subwatershed soils maps are contained in Chapter 5. Similar to the calculation of 

land use acreages, the distribution of hydrologic soil types within each subbasin was 

determined by intersection of the soils coverage in the GIS database with the 

digitized subbasin delineations. 

4.5.7 Initial Abstraction Ratio 

The computation of runoff depth in the SCS Hydrograph Method is based on two 

empirical relationships: one between runoff curve number and losses, and the 

second between losses and initial abstraction. The initial abstraction ratio drives the 

second relationship. The HCSWMM model dictates that a standard initial abstraction 

ratio of 0.2 be used throughout the watershed. 

4.5.8 Unit Hydrograph Shape Factor 

Analyses of large volumes of measured data form the basis of the SCS Hydrograph 

Method. An observation that three-eighths of the total volume of a hydrograph 

occurs before the peak and five-eighths after the peak is one generalization born 

from these analyses. This generalization is largely a function of watershed 

geography and topology. Where watersheds are steep and mountainous, a larger 

fraction of the total hydrograph volume occurs before the peak; where watersheds 

are more shallow and flat, a smaller fraction of the total hydrograph volume occurs 

before the peak. 

The SCS recommends use of a hydrograph shape factor of 484 in typical 

applications. Where watersheds are flat, such as in Florida, the hydrograph shape 

factor is smaller. Because of the flat terrain within Hillsborough County, the HEC-1 

hydrologic model was modified to use a unit hydrograph shape factor of 256. This 

was a standard adopted to be consistent with the guidance provided in the 

Hillsborough County Stormwater Management Technical Manual (SMTM). This 

standard equates to an assumption that one-fifth of the total subbasin hydrograph 

volume occurs before the peak, and four-fifths occurs after the peak. 




4.6 HYDRAULIC MODEL 

The hydraulic model used for this study was a version of the EXTRAN block of the 

U.S. Environmental Protection Agency Stormwater Management Model, Version 

4.31b (SWMM) Extended Transport Block (EXTRAN) that was modified by 

Hillsborough County for use in its watershed management planning program. This 

program (HCSWMM) is a hydraulic flow routing model for open channel and/or 

closed conduit conveyance systems that conduit-junction representation of the 

drainage system. HCSWMM receives hydrograph input at specific junctions by file 

transfer from the hydrologic model and performs dynamic routing of stormwater flows 

through the defined storm drainage system. Simulation output takes the form of 

water surface elevations and discharges at each junction and conduit within the 

model network, respectively. 

4.6.1 Hydraulic Model Network 

The hydraulic model (HCSWMM) of the Alafia River Watershed consists of a network 

of open channel segments, culverts, bridges, storm sewers, weirs, lakes, ponds, and 

wetlands that comprise the primary drainage system within the watershed. 

HCSWMM uses a conduit-junction concept to idealize the prototype drainage system. 

A junction is a discrete location in the drainage system where conservation of mass 

(continuity) is maintained. Conduits are the connections between junctions and are 

used to convey water through the system. The entire network of junctions and 

conduits forms the hydraulic model network and serves as the computational 

framework for HCSWMM. 

The first step in development of a model schematic was to identify the primary 

drainage system and all drainage facilities within it. This task was accomplished 

through the research and review of all available sources of information that have 

been previously described, and through field reconnaissance of the watershed. All 

such information was compiled and a watershed drainage map developed which 

depicts the primary drainage system. To achieve the required planning level of 

resolution, junction locations are established at most primary and some secondary 

drainage structures, surface water outfall points, storage areas, and other locations 

with significant hydrologic control. Junction locations are also established at the 

confluence of most primary and some secondary drainage system conveyances, and 

at locations of interest with respect to flood hazard risk assessment, level of service 

analysis, and pollutant analyses. Finally, junctions are established at some locations 

to ensure numerical stability within the primary drainage system. 




Junction Numbering Scheme 

Hillsborough County employs a junction-conduit numbering convention: six digits for 

junctions, seven digits for conduits. All junction numbers must be unique and 

generally, junction numbers increase from downstream to upstream. It is not 

required that junction numbers increment by one. More often than not, junction 

numbers increment by no specific increment or by fives or tens. The following figure 

illustrates the Hillsborough County numbering convention that was utilized for model 

development: 

7 X X X X X 

Watershed Identifier 

Major Conveyance or Tributary to Major Conveyance 

Minor Tributary 

Lesser Tributaries or Junctions within Parent System 

By convention, all junctions within the Alafia River Watershed begin with the number 

“7”. The following table defines the major conveyance numbering scheme. These 

codes represent the first two register locations in the six-digit junction number. 

Code 

Conveyance 

70 Alafia River 

71 Rice Creek 

72 Buckhorn Creek 

73 Bell Creek 

74 Fishhawk Creek and Little Fishhawk Creek 

75 Turkey Creek (Valrico) 

76 Little Alafia River 

77 South Prong Alafia River 

78 North Prong Alafia River 

79 English Creek 

The task of observing the junction numbering convention within a model that contains 

a few thousand junctions is complicated and challenging. The junction numbering 

convention is an ideal; it is not possible to observe the convention everywhere. 

Violations of the convention are rare, but manageable. The reader is cautioned to 

check the conduit connection network and invert elevations to ascertain direction of 

flow. 




Conduit Numbering Scheme 

The root of the seven-digit conduit number is equivalent to the upstream junction 

number. A single-digit prefix is attached to the root to denote conduit type. The 

following table presents the Hillsborough County conduit prefix convention: 

Prefix 

Conduit Type 

1, 2, 3, 4, or 5 Closed Conduit 

6 Overland Flow Weir 

7 Roadway Overtop Weir 

8, 4 or 5 Sharp-Crested or Broad-Crested Weir 

9 Open Channel 

The first closed conduit in a pair of parallel closed conduits takes the prefix “1”; the 

second takes the prefix “2”, etc. The Hillsborough County conduit numbering 

convention allows up to five closed conduits to be modeled in parallel. Where more 

than five closed conduits exist in parallel, the existing set of closed conduits is 

represented as a hydraulically equivalent set of five closed conduits in parallel. In 

some cases the Hillsborough County numbering convention was violated to account 

for multiple weir connections and the number of different hydraulic connections to a 

specific junction. 

To complete the naming conventions, subbasins are also assigned the same 6- 

character name as the receiving (load) junction for subbasin inflows. 

4.6.2 Drainage Facility Inventory 

The initial and most important step in the development of the hydraulic model of the 

Alafia River Watershed was the inventory of the drainage structures along the 

designated primary drainage system. This information provides the foundation for 

the model representation of the hydraulic system. The drainage facility inventory of 

the study area was compiled from an array of sources and methods. Hydraulic data 

for channels, culverts, storm sewers, bridges, and control structures were obtained 

from previous studies, development plans, roadway plans, field survey, and field 

identification. Data collected included elevations, lengths, dimensions, construction 

materials, channel vegetation, structure entrance and exit conditions, and any other 

pertinent features. This task required a considerable amount of effort, but it was 

necessary to develop the appropriate level of detail to accurately define the 

hydrologic and hydraulic conditions of the study area. Detailed discussions of the 

sources and methods used to collect this information are presented in Chapter 5 for 

each of the subwatersheds. 

As a part of this investigation, Parsons developed a field survey plan to establish the 

size, location, dimensions and inverts of drainage structures, and to define current 

stream channel and floodplain cross sections within the Alafia River Watershed 

based on the specific needs of the hydraulic model. The emphasis of this survey was 

placed on areas within the basin where there were no available sources of as-built 




record drawings and surveys. Conventional field survey was performed by Edgemon 

Land Surveying, Wilson Miller, Tomasino and Associates, and Strayer Surveying and 

Mapping for the original WMP study and Northwest Engineering, Inc. for the WMP 

update survey. The comprehensive field survey program for the original 2001 WMP 

study resulted in the survey of a total of 533 drainage structures and 1193 channel 

cross sections throughout the Alafia River Watershed (in Hillsborough County). 51 

additional survey locations were added to the model for the 2009 model update. 

To augment the collection of available information and field survey activities, limited 

field reconnaissance of the watershed was conducted. This consisted of driving and 

walking the basin to record drainage patterns, map drainage facilities, measure 

facility dimensions inspect the condition of the drainage facilities in the field, 

assemble a photographic log of drainage facilities, and confirm information collected 

from the previously discussed sources and/or resolve differences between different 

sources. In some instances, field measurements were used as model input where 

there were no other available sources of information for that particular drainage 

structure, or where surveys and other data sources were incomplete for proper 

representation in the HCSWMM model. 

4.6.3 Closed Conduits 

Eight different types of conduits can be modeled in HCSWMM. The following table 

lists conduit types, the corresponding model code, and a graphical representation of 

the conduit shape: 

Conduit Type Model Code (NKLASS) Shape 

Circle 1 

Rectangle 2 

Ellipse 3 

Arch 3 

Baskethandle 5 

Trapezoid 6 

Parabola/power function 7 

Irregular 8 

HCSWMM has internally automated the procedure by which hydraulic head losses 

are computed for closed conduits. The original EPA EXTRAN version had an input 

requirement for the friction loss coefficient (Manning’s n) that was the sole basis for 

the calculation of the total head loss in a closed conduit. It was necessary to adjust 

this coefficient to account for the other minor losses of the conduit such as entrance, 

exit, and transition losses. In addition, equivalent conduits or pipes were created to 

ensure model stability and simplify the total number of conduits in the model. 

Conduits were lengthened, had slope adjusted and/or combined as necessary for 

model stability and Manning’s n roughness coefficients were adjusted to maintain 




equal flow for an equal head loss. It should be noted that, for this model update, 

Arch-shaped pipes were entered into the model as model code 3. This was due to 

the concern that type 4 pipe areas were not correctly calculated by the model 

(according to model input echo). 

The Hillsborough County version of EXTRAN has additional data fields that allow the 

user to directly include the entrance, exit, and transition loss coefficients, and an 

elongation factor to lengthen a short conduit segment for model stability. This allows 

for the internal computation and creation of an equivalent conduit that includes the 

minor losses, while the roughness coefficient that is input by the user represents just 

the friction loss component. Standard engineering references were utilized to assign 

the various entrance, exit, transition and friction loss coefficients based on 

observations of the site-specific physical conditions of drainage conveyances. 

It is necessary within the framework of the EXTRAN model to represent bridge 

structures as either an open channel or some combination of equivalent closed 

conduits. In the Alafia River Watershed model application, some bridge spans were 

modeled as their respective surveyed cross-section, with roughness for the piers, 

unless it was determined that, during expected flooding conditions, the bridge would 

be in a full flow condition (i.e. water would reach the low chord of the structure, 

creating a surcharge or pressure flow condition). In such cases, the bridge structures 

were entered into the model using the guidelines for an equivalent combination of 

box culverts with different dimensions and/or inverts. The procedure that was 

followed was to: 

• Plot the bridge cross section, including piers and bridge low chord elevations; 

• Estimate a parallel set of box culverts which appear to fit the approximate 

flow area of the bridge opening at respective depths across the crosssection; 

and 

• Calculate the hydraulic conveyance for the prototype bridge section and for 

the equivalent set of box culverts and adjust the parallel culvert dimensions 

(width, inverts, and/or depths) until the terms reasonably match. 

4.6.4 Channel Cross-Section and Floodplain Definition 

The HCSWMM model data requirements for definition of the open channel reaches of 

the primary drainage system of the Alafia River Watershed included channel cross 

section information that is of sufficient detail to define not only the shape of the 

channel within the confines of its banks, but for a sufficient distance outward from the 

banks into the floodplain. For the original Alafia River Watershed Management Plan 

modeling efforts, it was judged important that the natural floodplain be included 

explicitly in the definition of the channel cross sections so that both the floodplain 

storage and conveyance functions are represented as accurately as possible. For 

this Update of the Alafia WMP, channel cross section storage and static (or 

overbank) storage were distinguished and accounted for separately (this process is 




described in detail in section 4.6.6). Parsons used what was judged to be the most 

current, detailed, and representative source of information available for any particular 

reach of the open channel system. In many cases, channel cross sections were 

extended by the addition of endpoints that defined the full extent of the natural 

floodplain. If no developmental changes within the channel floodplain area were 

observed since the original study or if no static overbank storage was considered to 

be separated out from the channel storage, the original cross section was used. If 

any developmental changes or significant overbank storage were observed within the 

original channel cross section the cross section was augmented accordingly. 

One of the most overlooked, but extremely important, needs of the HCSWMM model 

representation of open channel reaches is the selection of an appropriate channel 

roughness coefficient, or Manning’s n value. This value is a measure of the relative 

degree of hydraulic efficiency (retardance) of a channel and is dependent upon 

factors such as the extent and type of channel vegetation, channel bottom material, 

channel irregularity, channel alignment, obstructions, and depth of flow. Selection of 

an appropriate Manning’s n value for a particular channel reach is a highly subjective 

procedure and requires a certain level of experience. Parsons personnel relied 

primarily upon published guides and past modeling experience in the selection of 

channel and floodplain Manning’s n values for the EXTRAN model representation of 

the Alafia River Watershed open channel segments. These values were either 

confirmed or adjusted during the model calibration process. For the most part, the 

channel roughness coefficients ranged from a low of 0.030 for the “cleanest” channel 

reaches to 0.100 for the most highly vegetated. The floodplain roughness 

coefficients generally ranged from 0.080 to 0.160. 

4.6.5 Overflow Weirs 

The proper definition of overflow weirs in the HCSWMM model representation of the 

Alafia River Watershed was an important element of the hydraulic model 

development. These flowpaths are necessary to represent pond control structures, 

pond banks, overtopping of roadways at channel crossings, and overland flow. The 

data for weir crest elevations and widths for pond control structures were obtained 

from the structure surveys, construction plans, and/or field measurements conducted 

by Parsons staff. All pond representations included a top of bank weir that allowed 

for overtopping during extreme flood events. 

Roadway overtopping was simulated using broad-crested weirs as the conveyance 

mechanism. The weir crest elevation was obtained from the structure surveys or asbuilt 

construction drawings, if available, or from the SWFWMD topographic mapping. 

In certain cases within the basin, overland flow provides a conduit for floodwater that 

circumvents the normal flowpath or drainage system. Again, broad-crested weirs 

were used to simulate these drainage paths, with the weir crest elevations and weir 

lengths obtained from the SWFWMD topographic mapping. 

The following table summarizes the range of weir coefficients for various weir flow 

situations as used in the Alafia River Watershed model application, and the general 




prefix required by the Hillsborough County conduit numbering convention. Because 

of model naming limitations the model prefix numbers could not always be strictly 

adhered to. 

Weir Type Coefficient 

Range 

Model 

Prefix 

Overland Flow 1.0 6 

Roadway Overtop 2.3 to 2.8 7 

Broad-Crested 2.6 to 2.8 8 

Sharp-Crested 3.1 to 3.4 8,4,5 

4.6.6 Storage Facility Stage-Area Relationships 

To properly represent the hydrologic and hydraulic processes of stormwater runoff 

within a watershed, it is important that all significant storage facilities and their 

hydraulic functions be defined. This is especially important in the Alafia River 

Watershed, where much of the drainage throughout the basin is controlled by manmade 

reservoirs, stormwater detention and retention ponds, natural lakes, and 

wetlands. 

The EXTRAN model allows the user to specify a variable stage-area relationship at 

any model junction (node) that defines the storage properties at that point, be it a 

pond, lake, wetland, depression, or other such open surface waterbody. The DEM 

dataset which was supplied by the County and compiled by Parsons was utilized 

extensively for this purpose. For areas where topographic voids exist, available 

record drawings and permits were utilized as a means of establishing stage-area 

relationships of constructed stormwater management facilities. All stage-area 

relationships were defined to an elevation such that the 100-year peak stages did not 

exceed the highest stage in the data entry. This avoided extrapolation of the storage 

curves. 

To avoid duplication of storage in the model network it was important to “separate” 

the channel storage from the overbank or static storage (which is assigned to the 

node in the stage-area data in the E1, E2 cards). This was accomplished by creating 

exclusion polygons for the modeled channels. These polygons were created using 

the extent of the cross section (for the polygon width), the length of the channel (for 

the polygon length) and the shape/configuration of the channel itself (using the GIS 

database channel line segment as the channel “centerline”). The resulting polygon 

areas were excluded from the DEM datasets before stage-area data was extracted 

from it. 

The initial (starting) water surface elevations for these variable storage facilities were 

established through several methods. For storage facilities where a control structure 

exists, the starting elevation was assumed to be the crest elevation of the control 

weir, or the invert elevation of the bleeddown orifice. The exception to this was for 

dry retention ponds, where the starting elevation was the pond bottom. For natural 




ponds, lakes and wetlands, the initial elevation was assumed to be the normal high 

water elevation, as could best be determined from topographic mapping and/or other 

collected data. 

4.6.7 Initial Conditions 

Initial Conditions 

Initial water surface elevations for the Alafia River Watershed model update were 

determined using various sources of data. It is common practice to assume “average 

wet season conditions” for the model design storm events. This produces 

conservative (but not over-conservative) the model results. The idea is to simulate 

hydraulic conditions in the watershed that would mimic typical conditions during the 

Florida “wet” season (typically June – November). To accomplish this many sources 

of data were used and the assumption is that natural storage features and designed 

ponds would be full and major rivers and streams would have some baseflow within 

channel banks. The type of hydraulic element modeled determined the most 

appropriate data source to be used for the initial stage. The major types of elements 

and their initial condition (stage) data source are as follows; 

ERP Permitted ponds, wetlands and the Edward Medard Reservoir 

• Wet pond – All permitted wet ponds/wetlands were assigned the weir overflow 

elevation (no orifices were modeled) 

• Dry ponds – All permitted dry pond were assigned the pond bottom as the 

starting elevation 

The unpermitted ponds, wetlands 

Natural unpermitted ponds, ungaged lakes and wetlands were either assigned the 

outfall elevation (i.e. outfall pipe invert) or, if no structural outfall existed, the aerial 

and DTM data was used to determine the “wet” season elevation by aerial 

interpretation (i.e. wetland tree lines) 

Free flowing channel and culvert reaches 

In the Florida wet season, groundwater elevations rise from large rainfall quantities 

and groundwater recharge, this produces natural flow in major wetland rivers and 

streams. This means that streamflow exists most of the time in the wet season. 

Determining the magnitude of these flows is an inexact science as the flow rates are 

always in flux and are not the same from year to year. During the original Alafia 

River WMP study, the streamflows at the onset of the calibration and verification 

events were considered for use as typical wet season conditions. Using the recorded 

data from the Alafia River at Lithia (USGS gage 02301500), it was determined the 

1988 tropical event (September 5) base streamflow of ~400 cfs was a appropriate 

initial condition. This was corroborated by a cursory review of daily streamflow 

records over the last 20 to 30 years. This initial streamflow condition for design storm 

events was still considered appropriate by this author. Hurricane Frances in 2004 had 




~1200 cfs of streamflow at the Lithia gage which was too conservative to use as 

typical baseflow conditions, even during the wet season. 

To emulate the design event baseflow condition inflows were added to model 

junctions (D1 cards) and distributed throughout the watershed in the major creek 

tributaries (i.e Fishhawk Creek, Bell Creek, etc.) and the Alafia River main channel. 

After the baseflow (junction inflows) was assigned to the nodes the model was ran for 

several thousand hours to attain a flowing hydraulic equilibrium. A HCSWMM “hot 

start” file was then created for use as the model initial conditions. 

Modeled tertiary systems such as small creeks, minor streams, drainage ditches, and 

outfall channels were started “dry” meaning initial elevations were assigned at the 

channel invert. 

4.6.7 Boundary Conditions 

The HCSWMM model requires specification of hydraulic boundary conditions at all 

outfall points of the model schematic. In the Alafia River Watershed application, the 

primary watershed outlet is located at the downstream end of the river itself where it 

discharges to Hillsborough Bay. A constant tailwater boundary condition 

representing the water elevation of the bay, a tidal waterbody, was specified at 1.09 ft 

NAVD88 for all model simulations. This elevation represents a high tide condition. 

Additional boundary connections were specified at locations around the watershed 

perimeter wherever it was anticipated that flood elevations might reach the point at 

which the Alafia River Watershed might interconnect with an adjacent watershed 

such as the Hillsborough River Watershed, the Little Manatee River Watershed, the 

Delaney Creek Watershed, and the Bullfrog Creek Watershed. The nature of these 

possible interconnections was quantified through coordination with the other 

engineering consultant firms engaged in similar studies of these watersheds for 

Hillsborough County. In most cases adjacent watershed boundary conditions were 

minor relative to the magnitude of the volume of water during flood events. These 

connections to adjacent watersheds were modeled as weirs. 


. 

Chapter 5 

parsons


Chapter 5 – Hydrologic/Hydraulic Model Development, 

Calibration and Verification 

CHAPTER 5 

HYDROLOGIC/HYDRAULIC MODEL DEVELOPMENT, 

CALIBRATION AND VERIFICATION 

Perhaps the most important aspect of any watershed master plan is the proper 

representation of the current flooding conditions throughout the watershed. A good 

understanding of the watershed hydrologic and hydraulic processes is necessary to 

determine the most effective means of controlling flooding and protecting public safety 

and environmental resources. The previous chapter has detailed the methods and 

procedures used to develop the hydrologic and hydraulic models of the Alafia River 

Watershed. Within this chapter, documentation is provided of model development, 

calibration and verification that are specific to each of the major subwatersheds within 

the Alafia River Watershed. These models provide the main tools used to assess 

flooding conditions and expected levels of service (LOS), and to evaluate stormwater 

management options in the watershed. 


5.1.1 Subwatershed Description 

The Buckhorn Creek Subwatershed is a 7.4 square mile watershed located in the 

south Brandon community of Hillsborough County in an area roughly defined by 

Providence Road on the west, Lithia Pinecrest Road on the east, Brooker Road on 

the north, and centrally bisected by Bloomingdale Avenue. The drainage basin, as 

defined for this study, is shown in Figure 5.1-1. Flow originates in the eastern and 

northern headwaters of the basin and flows in a generally southwestern direction to 

the basin outfall at the confluence with the Alafia River, located approximately onemile 

downstream (south) of Bloomingdale Avenue near Watson Road. 

Historically, the Buckhorn Creek Subwatershed consisted of an aggregation of lake 


Buckhorn Creek. However, due to extensive development activities that have 

transformed the basin since the early 1980’s, the system has been drastically altered, 

and a continuously defined natural channel is now evident only between Bell Shoals 

Road and the mouth of the creek. Currently, the primary tributary drainage systems 

that drain to Buckhorn Creek consist of improved channel systems fed by a manmade 

network of urban ditches and storm sewer systems. The basin is extensively 

developed, with most of it occurring over the last 20 years and consisting of singlefamily 

residential land use (over 50% of the basin). Some commercial development is 

clustered along the major road corridors of Bloomingdale Avenue, Bell Shoals Road, 

and Kings Avenue. As with most urbanized watersheds, much of the main channel 

system and floodplain have been artificially altered and encroached by 





man-made development, and ditches, control structures and pipes interconnect most 

of the lakes and wetland systems. 

Typical of southern Florida conditions, the Buckhorn Creek drainage basin is 

characterized by generally flat topography throughout most of the contributing 

drainage areas, with high water tables, and many natural and man-made lakes and 

depressions, and a few remaining isolated wetlands. The exception is the 

northernmost portions of the basin where high sand ridges drain southward at 

relatively steep slopes from some of the highest natural elevations in the county. This 

northern portion of the basin contains a number of natural depressions (sinkholes) 

with no defined drainage outlets that act as closed basins for all but the most extreme 

flooding events. 

5.1.1.1 Primary Drainage Systems 


of the Buckhorn Creek Subwatershed has been segregated into four major drainage 

segments. To provide continuity, these drainage segments and their naming 

nomenclature have been designated consistent with a stormwater management 

master plan study of Buckhorn Creek conducted in 1988 for the Southwest Florida 

Water Management District (SWFWMD) and Hillsborough County by Singhofen & 

Associates, Inc. Refer to Figure 5.1-1 to determine the locations of these primary 

drainage systems. 

Buckhorn Creek Main Channel 

The Buckhorn Creek main channel originates immediately west of Bell Shoals Road 

at the convergence of the Bloomingdale East Subdivision and the Northeast Tributary 

drainage system. The stream channel profile starts at elevation 39 ft NAVD and has 

been previously channelized to a certain extent from this point westward to Kings 

Avenue. It remains in a relatively natural condition downstream of Kings Avenue to its 

outfall to the Alafia River. The lower reaches of Buckhorn Creek, between 

Bloomingdale Avenue (west of Kings Avenue) and the Alafia River, are in an 

undisturbed state as the creek flows through a hardwood swamp. The creek falls 

from an elevation of 11 ft NAVD at Bloomingdale Avenue to –3.5 ft NAVD at the Alafia 

River, and a number of natural springs contribute flow to the creek along this reach. 

There are a total of ten bridges or culvert crossings of Buckhorn Creek along the main 

channel segment, including two Bloomingdale Avenue crossings, Creek Bridge Road, 

Kings Avenue, John Moore Road, Bloomingdale Plaza Entrance, a private drive, 

Holland Drive, Forest Bridge Road, and Brookside Manor Road. Of these, four road 

crossing structures have been replaced with new structures since the time of the 1988 

Buckhorn Creek Subwatershed study as a part of the County’s road improvement 

projects for Bloomingdale Avenue and Kings Avenue. None of these new structures 

were recommended improvements of the 1988 study. 


Legend 

County Line 

Subwatershed Boundary 

Subbasin Boundary 


Roads 


Watershed Boundary 


Suite 120 


S US HIGHWAY 301 

Notes: 

BUCKHORN CREEK 

ALAFIA RIVER 

S KINGS AVE 

W BLOOMINGDALE AVE 

1:24,000 

JOHN MOORE RD 

0 600 1,200 2,400 

Feet 

0 0.125 0.25 0.5 

CRAFT ROAD DITCH 

Miles 

E BLOOMINGDALE AVE 


Filename: 

Fig5_1_ 

1.mxd 

Map Date: 

BELL SHOALS RD 



N/A 

NE TRIBUTARY SYSTEM 

Prepared By: 

Yoav 

Rappaport 

GUILES RD 

HURLEY DITCH 


Figure: 5.1-1 - Drainage System Map 

Buckhorn Creek Subwatershed 



J:\DATA\260247_Alafia_WMP_Update\GIS\Maps\MXD\Report\Subwatersheds\BUCKHORN\Fig5_1_3.mxd 

AL





Craft Road Ditch 

The Craft Road Ditch system is a major tributary of Buckhorn Creek that drains most 

of that portion of the basin north of Bloomingdale Avenue, east of John Moore Road, 

and west of Bracken Road. The ditch has been excavated for virtually all of its length, 

beginning at Bell Shoals Road on the east and flowing westward until taking a turn to 

the south just east of John Moore Road and discharging to Buckhorn Creek. Along 

this track, there are four road crossings, including Craft Road, a private road, Bryan 

Road, and Bell Shoals Road. 

This part of the Buckhorn Creek Subwatershed has experienced extensive 

development in the last 20 years, but large tracts of rural and undeveloped land still 

remain. Significant development within the Craft Road Ditch contributing drainage 

area include Bloomingdale Villas, Bloomingdale Village, Bryan Manor, Bryan Estates, 

Belle Timber, Burns Middle School, Bell Shoals Baptist Church, and Highland Ridge. 

Much of the northernmost parts of the Craft Road Ditch contributing drainage basin 

actually contribute little or no flow to the ditch except during perhaps the most 

extreme storm events. Highly permeable sands and deep water table characterize 

this region of the Buckhorn Creek Subwatershed, located roughly north of Guiles 

Road. Natural depressions (i.e. sinkholes) with no positive outfalls collect runoff and 

rarely, if ever, discharge. In addition, most of the residential and institutional 

stormwater ponds in this region are dry retention ponds that retain and percolate the 

runoff from all but the largest storm events. Many of these ponds have no formal 

outfall structures. 

The Craft Road Ditch traverses along the foot of this northern sand ridge at a flat 

slope. There is only 15 feet of fall along its length, starting at elevation 40 ft NAVD at 

Bell Shoals Road and ending at 25 ft NAVD at Buckhorn Creek. 

Northeast Tributary 

The Northeast Tributary system originates on the north side of Bloomingdale Avenue 

just east of Bell Shoals Road. It effectively drains areas both north and south of 

Bloomingdale Avenue, east of Bell Shoals Road, and west of Springvale Drive. At 

one time, this system was connected to the Hurley Ditch along the north side of 

Bloomingdale Avenue, but the County’s current Bloomingdale Avenue road 

improvement project has severed this connection. Now, discharge from the Colonial 

Oaks subdivision stormwater pond, along with overland flow from undeveloped rural 

land, flow southward into a closed pipe system that crosses Bloomingdale Avenue 

and traverses the Bloomingdale/Bell Shoals Shopping Center. It joins with discharge 

from the shopping center stormwater pond(s) and passes under Bell Shoals Road 

and thence southward to discharge to the upstream end of the Buckhorn Creek Main 

Channel, after passing through two sets of culverts at the entrances to Bloomingdale 

Square. 





Hurley Ditch 

The Hurley Ditch system, upon completion of the County’s current Bloomingdale 

Avenue road improvements project, will discharge through a culvert from the north 

side of the road directly into the large 50-acre natural wetland at the head of the 

Bloomingdale East Subdivision system. This ditch collects local drainage from the 

Hurley property, discharge from the Avalon Terrace, Rolling Hills, and Ridgevale 

stormwater ponds on the north, and flows from the Bloomingdale High School 

drainage system to the northeast. 

The Bloomingdale High School has enclosed portions of the Hurley Ditch system in a 

closed pipe network and receives discharge from north of Guiles Road as well as flow 

from the Buckhorn Springs Manor Subdivision stormwater pond to the east. The 

County has recently constructed a drainage improvement project that has enlarged 

the capacity of the east culvert crossing of Guiles Road to enhance drainage from 

areas north of Guiles Road and east of Lithia Pinecrest Road. There are two 

locations where culverts under Lithia Pinecrest Road convey drainage collected in the 

eastern roadside ditch to Guiles Road from the most extreme northeastern region of 

the basin. Several residential development ponds also discharge to Guiles Road from 

the north, including Brooker Trace, Manor Oaks, and Timber Knoll. In addition, a 

large orange grove drains eastward from Bracken Road to the Guiles Road ditch and 

thence into the high school drainage system. 

Despite the number of small residential developments, much of the Hurley Ditch 

drainage basin remains undeveloped at this time. The northernmost portions of the 

basin (north of Guiles Road) exhibit very steep slopes, but the terrain becomes quite 

flat in the southern end as flows converge into the high school and flow towards 

Bloomingdale Avenue. 

5.1.1.2 Existing Land Use 

As discussed in Chapter 4, existing land use conditions in the Buckhorn Creek 

Subwatershed were defined by use of digital coverages obtained from the Southwest 

Florida Water Management District (SWFWMD) Geographic Information System 

(GIS) database. A great deal of effort was exerted as a part of this study to verify and 

update the original SWFWMD land use database to reflect a consistent and up-todate 

set of hydrologically valid land use coverages. This was deemed especially 

important for the Buckhorn Creek Subwatershed, as the SWFWMD land use 

database did not reflect a number of the significant developments that have been 

constructed in the past ten years. 

The resultant existing land use map of the Buckhorn Creek Subwatershed that was 

used for model development purposes is shown in Figure 5.1-2. This land use 

coverage was intersected with the subbasin delineations using GIS overlay 

techniques to develop an accurate measurement of the distribution of the various land 

use classifications within each of the defined subbasins in the watershed. 












1900/2600 - OPEN LAND 





5000 - WATER 




Legend 

County Line 



Roads 




Suite 120 



Notes: 


ALAFIA RIVER 

S KINGS AVE 


1:24,000 

0 600 1,200 2,400 

Feet 

0 0.125 0.25 0.5 

JOHN MOORE RD 

Miles 



Filename: 

Fig5_1_ 

2.mxd 


Map Date: 



N/A 


Prepared By: 

Yoav 

Rappaport 


GUILES RD 

HURLEY DITCH 


Figure: 5.1-2 - Existing Land Use Map 




J:\DATA\260247_Alafia_WMP_Update\GIS\Maps\MXD\Report\Subwatersheds\BUCKHORN\Fig5_1_2.mxd





The following table presents a composite breakdown of land use acreages and 

percentages in the Buckhorn Creek Subwatershed: 

TABLE 5.1-1 BUCKHORN CREEK SUBWATERSHED LAND USE 

LAND USE CLASSIFICATION 

TOTAL 

AREA 

(acres) 

PERCENTAGE OF 

SUBWATERSHED 

(%) 

Low Density Residential 586 12.3% 

Medium Density Residential 1,118 23.5% 

High Density Residential 1,469 30.9% 

Commercial 164 3.4% 

Industrial 0 0.0% 

Open Land and Rangeland 403 8.5% 

Cropland and Pastureland 178 3.7% 

Forest 136 2.9% 

Institutional 102 2.1% 

Transportation, Communications and Utilities 0.1 0.0% 

Specialty Farms 12 0.3% 

Mined Lands (active) 0 0.0% 

Mined Lands (reclaimed) 0 0.0% 

Water 184 3.9% 

Wetland 407 8.6% 

TOTAL: 4,758 100.0% 

According to the existing land use mapping database, 24% of the Buckhorn Creek 

Subwatershed is classified as medium density residential. High-density residential 

development comprises another 31% of the basin. This classification includes areas 

of both multiple family and high-density single-family residential development. 

Another 12% of the basin is classified as low density residential. Less than 16% of 

the watershed remains as undeveloped land. The majority of the remaining 

developable land, excluding golf courses and parks, is located in the upper 

(northeastern) regions of the watershed. 

5.1.1.3 Soils 

As was discussed in Chapter 4, the standard method of soils classification used for 

hydrologic modeling is the hydrologic soils group. Soils within the Buckhorn Creek 

Subwatershed were categorized according to this hydrologic soil group classification 

system, as defined by the Natural Resource Conservation Service. 

Figure 5.1-3 presents the hydrologic soils classification map of the Buckhorn Creek 

Subwatershed that was developed for this study. 





Similar to the calculation of land use acreages, the distribution of hydrologic soil types 

within each subbasin was determined by intersection of the soils coverage in the GIS 

database with the subbasin delineations. The following table lists a composite 

breakdown of the distribution of the hydrologic soil types within the Buckhorn Creek 

Subwatershed. It can be seen that nearly 41% of the watershed is comprised of soils 

that are classified as hydrologic soil group B/D. 29% of the basin is classified as 

hydrologic soil group A soils, with most of these occurring in the northern regions of 

the basin. There are very few hydrologic soil group D soils, which generally include 

wetlands that occur in the watershed. Soils in the basin, as categorized by the Natural 

Resources Conservation Service (NRCS), consist predominantly of fine sands of the 

Candler (A), Lake (A), Fort Meade (A), Orlando (A), Tavares-Millhopper (A), Myakka 

(B/D), Ona (B/D), Smyrna (B/D), St. Johns (B/D), Malabar (B/D), Seffner (C), and 

Zolfo (C) series. 

TABLE 5.1-2 BUCKHORN CREEK SUBWATERSHED SOILS 

HYDROLOGIC 

SOIL GROUP 

TOTAL AREA 

(acres) 

PERCENTAGE OF 

SUBWATERSHED 

(%) 

A 1,379 29.0% 

B 0 0.0% 

B/D 1,935 40.7% 

C 1,032 21.7% 

D 377 7.9% 

Water 35 0.7% 

TOTAL: 4,758 100.0% 

5.1.1.4 Physiography 

While the lower (western) portion of the Alafia River Watershed is characterized as 

sandy and poorly drained coastal lowlands, with a flat plain sloping gently upward for 

several miles eastward from Hillsborough Bay, there is a distinct change in the 

general physiography beginning approximately with the Buckhorn Creek 

Subwatershed. A scarp rims the low-lying areas, resulting from the advance of the 

sea during Pleistocene time to approximately elevation 30 to 35 ft NAVD. Located 

above this scarp, Buckhorn Creek is characterized by upland areas consisting of 

rolling hills and features associated with older marine terraces including sinkholes, 

depressions, ponds and swamps. 

At its confluence with the Alafia River, the Buckhorn Creek lower reach is a hardwood 

swamp at an elevation of 9 ft NAVD or lower. The creek slopes sharply upstream 

from this swamp, and upland elevations exceed 24 ft NAVD by the time the first 

Bloomingdale Avenue bridge crossing is reached. Through the lower reaches of the 



A 

B 

B/D 

C 

D 

Water 

Legend 

County Line 


Suite 120 





Roads 



Notes: 


ALAFIA RIVER 

S KINGS AVE 


1:24,000 

JOHN MOORE RD 

0 600 1,200 2,400 

Feet 

0 0.125 0.25 0.5 


Miles 



Filename: 

Fig5_1_ 

3.mxd 

Map Date: 




N/A 


Prepared By: 

Yoav 

Rappaport 

GUILES RD 

HURLEY DITCH 


Figure: 5.1-3 - Soils Map 





AL





main creek, the channel is very incised, with steep slopes and depths of 8 to 10 feet 

typical from Bloomingdale Avenue to John Moore Road. The upland regions that 

drain to the creek along this reach are very flat and range in elevation from 24 to 34 ft 

NAVD. 

Proceeding upstream, the creek traverses a flat and swampy floodplain from John 

Moore Road to Bell Shoals Road. The channel has been excavated for most of this 

stretch and is typically 5 to 10 feet deep. The fall of the creek is only 16 feet, from 

elevation 39 ft NAVD to 23 ft NAVD, over this 5700’ length of channel (i.e. 0.28% 

slope). The southern ridgeline of the Buckhorn Creek Subwatershed is roughly 

defined by a 55 to 65 ft NAVD contour along this reach. 

The northeastern portion of the Buckhorn Creek Subwatershed, which drains via the 

Tanglewood Ditch system, is an area of very flat terrain with upland elevations that 

range from mostly 29 to 32 ft NAVD. This man-made ditch is constructed at an 

extremely flat slope of approximately 0.03%, cutting through this region of what was 

formerly wet pasture and wetland. 

The northern region of the Buckhorn Creek Subwatershed is comprised of sand 

ridges that exhibit a relatively steep gradient in a southward direction towards the 

creek and its tributary systems. The northern ridgeline of the basin, roughly defined 

along Brooker Road, has elevations that range from roughly 55 ft NAVD in the 

northeast, to over 130 ft NAVD in the northwest portions of the basin. 

The southeastern quadrant of the basin, east of Bell Shoals Road and south of Guiles 

Road, is a very flat and wet region with numerous natural wetlands and little 

topographic relief. Upland elevations here range for the most part from roughly 50 to 

65 ft NAVD. 

5.1.1.5 Previous Studies and Sources of Information 

Previous Studies 

Before the original Alafia River WMP study (2001), there were three previous flood 

studies conducted for all or portions of the Buckhorn Creek Subwatershed. The first 

of these studies was the “Flood Study of Portions of Buckhorn Creek and Delaney 

Creek Watersheds” (1984) by the Nelson Consulting Group. The purpose of this 

study was to update flood insurance rate maps in the Tanglewood Ditch drainage 

system, and the results were officially adopted as revisions to the FEMA Flood 

Insurance Study for Hillsborough County in 1987. The main stem of Buckhorn Creek 

from its mouth to Kings Avenue was included. Hydrologic analyses were conducted 

using regional regression equations, and the HEC-2 backwater model was used to 

compute flood profiles of the channels. 

The second study of Buckhorn Creek, published by the Southwest Florida Water 

Management District in 1984, was the “Floodplain Information on Buckhorn Creek, 





Hillsborough County, Florida”. In this study, the hydrologic analyses were conducted 

using the Soil Conservation Service program TR-20, and the U.S. Geological Survey 

model E-431 was used for hydraulic backwater computations. Only the main channel 

of Buckhorn Creek was included in the floodplain analysis. 

In the last study, the Buckhorn Creek Subwatershed was the subject of a stormwater 

management master plan study conducted in 1988 for the Southwest Florida Water 

Management District (SWFWMD) and Hillsborough County by Singhofen & 

Associates, Inc. (SAI). This study was by far the most detailed and comprehensive of 

the three. The SCSUNIT program was used for hydrologic modeling computations, 

and a unit hydrograph peak rate factor of 323 was used in conjunction with a design 

storm distribution derived specifically for the area from data at the Tampa 

International Airport. The EXPLC model was then used to perform dynamic hydraulic 

routing calculations to simulate flows and flood stages on a time-dependent basis. 

Sources of Information 

The initial and most important step in the development of the hydraulic model of the 

Buckhorn Creek Subwatershed was the accurate definition of the channels and 

structures along the primary drainage system. This information provides the 

foundation for the model representation of the hydraulic system. Information 

describing the drainage facilities of the study area was compiled from a variety of 

sources and methods. Hydraulic data for culverts, bridges, control structures, and 

channel cross sections were obtained from as-built construction plans, previous 

studies, development plans, roadway plans, and field measurements. Data collected 

included elevations, lengths, dimensions, construction materials, channel vegetation, 

structure entrance and exit conditions, and any other pertinent features. This task 

required a considerable amount of effort, but it was deemed necessary to develop the 

appropriate level of detail to accurately define the hydrologic and hydraulic conditions 

of the study area. The following is a discussion of the sources and methods used to 

collect this information. Sources of data for individual elements of the hydraulic 

network are referenced in the model input file as comments and documented in the 

project files. 

Buckhorn Creek Stormwater Management Master Plan (SAI, 1988) 

As a part of the 1988 study for the SWFWMD and Hillsborough County, an extensive 

survey of the primary drainage facilities was conducted throughout the Buckhorn 

Creek Subwatershed at that time. For the purposes of this updated study, it was 

judged that the information from this study should be reasonably accurate for the 

hydraulic conveyances (i.e. structures, channels) that serve those portions of the 

basin that have not changed over the last 20 years. Therefore, this information 

provided a major portion of the data that were used to describe the conveyance 

system of the basin within the hydraulic model representation, and no additional field 

survey was conducted within this basin for the Alafia River Watershed Management 

Plan. 





Hillsborough County converted the original SAI model files of Buckhorn Creek to a 

HCSWMM model format in 1995. These model data files were provided to Parsons at 

the initiation of this study for subsequent conversion to the County’s current model 

version. While this provided the basic framework for the Buckhorn Creek 

Subwatershed model development, there was an extensive amount of effort 

expended in the confirmation, modification, correction, and update of the original SAI 

model data to reflect the current drainage conditions within the basin. 

Subdivision and Commercial Development Plans 

Available plans for residential and commercial developments within the Buckhorn 

Creek were obtained from Hillsborough County and the Southwest Florida Water 

Management District (SWFWMD) and used extensively for this effort. These sources 

for subdivision and commercial development grading and drainage plans provided the 

much of the hydraulic model information and are commented appropriately in 

comment lines in the SWMM model input file. 

Roadway Plans 

Public roadway drainage systems (i.e. Hillsborough County roads) comprise a 

significant percentage of the drainage systems and conveyance structures within the 

Buckhorn Creek Subwatershed. Available record drawings of county roads were 

collected as a means of defining these elements of the primary drainage system of 

the basin. These sources of data provided part of the hydraulic model information 

and are commented appropriately in comment lines in the SWMM model input file. 

5.1.2 Hydrologic Model Development 

The methodology employed in the hydrologic model development of the Buckhorn 

Creek Subwatershed has been described in Chapter 4. Parameters used to develop 

the hydrologic model with information unique to Buckhorn Creek Subwatershed are 

discussed. 

5.1.2.1 Subbasin Delineations 


properly analyze the primary drainage facilities within the Buckhorn Creek 

Subwatershed, the basin was divided into a total of 223 discrete subbasins that range 

in size from 1 to 170 acres. The average subbasin size is approximately 21 acres. 

The delineation of individual subbasins was dictated to a large extent by the primary 

drainage network itself and the need to properly define the contributing drainage area 

to individual elements of the conveyance system and storage facilities. 

5.1.2.2 SCS Runoff Curve Numbers 

As described in Chapter 4, runoff curve numbers were calculated over the course of 

this study for each subbasin in the Buckhorn Creek Subwatershed by an areaweighted 

averaging procedure that assigned a universal CN value to each 

combination of land use category and hydrologic soil group classification. Weighted 

runoff curve numbers were generated based on Table 4.5-1 values (See Chapter 4). 





The resulting final subbasin runoff curve numbers for the Buckhorn Creek 

Subwatershed are presented in the updated Alafia River ArcGIS geodatabase 

5.1.2.3 Times of Concentration 

As documented in detail in Chapter 4, the County has adopted a standard method for 

Tc calculation. 

5.1.3 Hydraulic Model Development 

5.1.3.1 Hydraulic Model Network 

The Buckhorn Creek Subwatershed hydraulic model follows the methods outlined in 

the Chapter 4 description. It is a comprehensive model, comprised of a total of 351 

junctions and 620 links in its structure, including 211 closed conduits, 57 irregular 

open channels, and 341 weirs. 

5.1.3.2 Storage Facilities 


within the Buckhorn Creek Subwatershed, it was important that all significant storage 

facilities and their hydraulic functions be defined. As described in Chapter 4, the 

initial (starting) water surface elevations for these variable storage facilities were 



weir, or the invert elevation of the bleed-down orifice. The exception to this was for 



water elevation. Stage–area data was obtained from the DEM dataset or available 

record plans where DEM data did not match existing conditions of the model domain 

(i.e. topographic void area). 

5.1.3.3 Closed Conduits 

The Buckhorn Creek Subwatershed model includes a total of 211 closed conduits that 

take the various forms of circular, rectangular, elliptical, and/or arch pipes that is 

allowed by the HCSWMM model formulation. Also, in the Buckhorn Creek model 

application, some bridge spans were modeled as their respective surveyed crosssection, 

with additional roughness for any piers. If it was determined that, during 

expected flooding conditions, the bridge would be in a full flow condition (i.e. water 

would reach the low chord of the structure, creating a surcharge or pressure flow 

condition), the depth of the channel cross section was limited to the elevation of the 

low chord to reproduce the surcharge condition within the model representation. In 

some cases, the bridge structures were entered into the model using the guidelines 

for an equivalent combination of box culverts with different dimensions and/or inverts. 

5.1.3.4 Overflow Weirs 

As discussed in Chapter 4, the proper definition of overflow weirs in the HCSWMM 

model representation of the Buckhorn Creek Subwatershed was an important element 





of the hydraulic model development. These flowpaths are necessary to represent 

pond control structures, pond banks, overtopping of roadways at channel crossings, 

and overland flow. 

5.1.3.5 Natural Channel Cross Sections 

The HCSWMM model data requirements for definition of the open channel reaches of 

the primary drainage system of the Buckhorn Creek Subwatershed included channel 

cross section information that is of sufficient detail to define not only the shape of the 

channel within the confines of its banks, but for a sufficient distance outward from the 

banks into the floodplain. As has been previously noted, the Buckhorn Creek 

Subwatershed model was formulated using available information from the 1988 study 

and other sources of channel cross section and drainage structure data. Parsons 

used what was judged to be the most current, detailed, and representative source of 

information available for any particular reach of the open channel system. There are 

a total of 69 irregular channel cross sections that are used to define the open channel 

systems and natural floodplains of the basin. 

Parsons personnel relied primarily upon published guides and past modeling 

experience in the selection of channel and floodplain Manning’s n values for the 

HCSWMM model representation of the Buckhorn Creek open channel segments. 

These values were either confirmed or adjusted during the model calibration process. 

For the most part, the channel roughness coefficients ranged from a low of 0.040 for 

the “cleanest” channel reaches to 0.090 for the most highly vegetated. The floodplain 

roughness coefficients ranged from 0.080 to 0.120. 

5.1.4 Hydrologic/Hydraulic Model Calibration and Verification 

Model calibration refers to the adjustment of model parameters within reasonable 

limitations so that the model results (i.e., streamflow and water elevations) are in 

reasonable agreement with a set of measured data. A reasonable range of values for 

the adjustment of model parameters is established through the review of literature 

references, and adjustments outside of those ranges are made only if some unusual 

hydrologic or hydraulic condition exists. The model is considered well-calibrated 

when the resulting stage, flow, and volume information is in reasonable agreement 

with the recorded data. No model calibration was performed for the Buckhorn Creek 

subwatershed portion of the Alafia River watershed. Hurricane Frances is the 

preferred calibration event for this WMP update and the only streamflow gage for the 

creek was no longer in service at the time of Frances. The USGS gaging station 

(02301695) for Buckhorn Creek near Brandon only has an October 1985 through 

September 1991 period of record. 







The Bell Creek Subwatershed, located in the southwest portion of the Alafia River 

Watershed, drains 19.0-square miles in south-central Hillsborough County. The 

drainage basin is roughly defined by Boyette Road on the east, County Road 672 on 

the south, Balm Riverview Road on the west, and the Alafia River on the north. The 

drainage basin, as defined for this study, is shown in Figure 5.2-1. Flow originates in 

the southern headwaters of the basin and flows in a generally northern direction to the 

basin outfall at the confluence with the Alafia River, located approximately 1.2 miles 

downstream (west) of Bell Shoals Road. 



of the Bell Creek Subwatershed has been segregated into five major drainage 

segments. Figure 5.2-1 depicts the locations of these primary drainage systems. 

Bell Creek Main Channel to Lake Grady 

This segment of the Bell Creek main channel originates immediately downstream of 

the outlet control structure of Lake Grady. The stream channel profile starts at 

elevation 19 ft NAVD and meanders for 2.25 miles in a relatively natural condition to 

its confluence with the Alafia River. The creek falls from an elevation of 7.8 ft NAVD 

at Boyette Road to –4.4 ft NAVD at the Alafia River. 

Lake Grady 

Lake Grady was created in 1969 as a recreational and irrigation supply facility to 

serve the adjacent landowners of the Shadow Run Subdivision. Lake Grady is owned 

and maintained by the residents of the Shadow Run Subdivision. The lake was 

formed by the impoundment of Pelleham Branch and a portion of Bell Creek, and 

Lake Grady has been the topic of much discussion and investigation since 1983 when 

one of the seven, six-foot diameter corrugated metal pipes (CMP) collapsed. This 

failure resulted in erosion and sloughing of the existing bank surface on the upstream 

side. Following inspection of the dam by SWFWMD, the impoundment structure was 

deemed an “endangerment to human life” in its present state. Lake Grady was then 

drained and its outlet control structure was locked open. The lake remained in its 

drained condition while investigations were conducted. In 2000, the dam structure 

was rehabilitated. The existing concrete control structure was replaced, reinforced 

box culverts (RBC’s) were added under Shadow Run Boulevard, a slurry wall was 

constructed under Shadow Run Boulevard, and Lake Grady was once again filled. 


BOYETTE RD 

FISHHAWK BLVD 

301 

BELL CREEK 

75 

BALM RIVERVIEW RD 

Lake Grady 

PELLEHAM BRANCH 

BELL CREEK 

BOGGY CREEK 

Legend 

County Line 




Roads 




Suite 120 


BIG BEND RD 

Notes: 

BOGGY CREEK 

1:52,000 

BELL CREEK 

BALM WIMAUMA RD 

0 1,250 2,500 5,000 


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0 0.25 0.5 1 

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Bell Creek Subwatershed 



J:\DATA\260247_Alafia_WMP_Update\GIS\Maps\MXD\Report\Subwatersheds\BELL\Fig5_2_1.mxd





Bell Creek Main Channel from Lake Grady to Headwaters 

This segment of the Bell Creek main channel originates at the Jay Mar Farm #2 

property located due north of the intersection of County Road 672 and Dupree Road. 

The stream channel profile starts at elevation 106.7 ft NAVD and meanders for 3.8- 

miles in a relatively natural condition through cropland and pastureland until its 

impoundment by Lake Grady. The creek falls from an elevation of 99.3 ft NAVD at 

Balm-Boyette Road to 26.8 ft NAVD at its impoundment with Lake Grady. 

There are a total of seven culvert crossings of Bell Creek along this segment of Bell 

Creek: Balm-Boyette Road, Rhodine Road, and five dirt road crossings. This 

segment of Bell Creek remains undeveloped and conveys runoff from primarily 

agricultural and open-land land uses. 

Boggy Branch 

Boggy Branch is a major tributary to the segment of Bell Creek south of Lake Grady. 

Flow originates in the extreme southern portion of the basin and receives runoff from 

the eastern portion of the Goodson Farm, Inc. property located at the northeast corner 

of the intersection of County Road 672 and Balm Riverview Road. Runoff from this 

portion of the property travels through a wetland system and discharges to both 

Boggy Branch and Pelleham Branch at the same relative elevation of 121.6 ft NAVD. 

The stream channel profile meanders for approximately 4.25 miles in its natural 

condition through more or less undeveloped open-land to its outfall at the confluence 

of Bell Creek, located 0.47 miles downstream (south) of Rhodine Road. The creek 

falls from an elevation of 60.8 ft NAVD at Big Bend Road to 38.3 ft NAVD at its 

confluence with Bell Creek. 

There are a total of three culvert crossings of Boggy Branch along the main channel: 

a dirt road, a dam outfall, and Big Bend Road. The creek passes through two manmade 

lakes; the most upstream lake is controlled by an outlet control structure at an 

elevation of 83.6 ft NAVD and the lake downstream is controlled by an outfall channel 

at an elevation of 47.8 ft NAVD. Ample storage exists in these lakes to provide 

attenuation for extreme storm events. 

Pelleham Branch 

Pelleham Branch is a major tributary to Lake Grady. The stream channel profile 

starts at 76.4 ft NAVD and flows 0.75 miles in its natural state to its confluence with 

Lake Grady and Bell Creek. The creek falls from an elevation of 58.1 ft NAVD at 

Rhodine Road to 29.1 ft NAVD at Lake Grady. Additionally, Pelleham Branch 

conveys runoff from a 0.8-mile long roadside ditch along Balm Riverview Road, which 

includes runoff from the Goodson Farm, Inc. property. The majority of the Tropical 

Acres Subdivision and portions of the Shadow Run Subdivision discharge to this 

system. 

There are a total of seven major culvert crossings of Pelleham Branch along the main 

channel including Shelby Drive, Entrance Way, Lenwood Lane, Edgeknoll Drive, 





Rhodine Road, and Donneymoor Drive. 


Chapter 4, Section 4.5.5 describes in detail the methodology used to determine the 

existing land use map of the Bell Creek Subwatershed. The land use map used for 

model development is shown in Figure 5.2-2. The land use coverage was intersected 

with the subbasin to develop an accurate measurement of the distribution of the 

various land use classifications within each of the subbasins in the subwatershed. 


percentages in the Bell Creek Subwatershed: 

TABLE 5.2-1 BELL CREEK SUBWATERSHED LAND USE 


TOTAL 

AREA 

(acres) 

PERCENTAGE OF 

SUBWATERSHED 

(%) 



High Density Residential 315 2.6% 


Industrial 11.2 0.1% 

Open Land and Rangeland 1,027 8.4% 

Cropland and Pastureland 3,050 25.1% 

Forest 3,080 25.3% 

Institutional 0.4 0.0% 

Transportation/Communications/Utilities 0 0.0% 




Water 225 1.8% 

Wetland 1,541 12.7% 

Total: 12,171 100.0% 


BOYETTE RD 

FISHHAWK BLVD 

301 

BELL CREEK 

75 


Lake Grady 











1900/2600 - OPEN LAND 





5000 - WATER 




Legend 

County Line 



Roads 




Suite 120 


BIG BEND RD 

Notes: 


1:52,000 

0 1,250 2,500 5,000 

Feet 

0 0.25 0.5 1 

Miles 

BOGGY CREEK 

BELL CREEK 

BOGGY CREEK 

Filename: 

Fig5_2_ 

2.mxd 

BELL CREEK 



Map Date: 



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Prepared By: 

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According to the existing land use mapping database, 5.6% of the Bell Creek 

Subwatershed is classified as low density residential. Medium density residential 

comprises another 16.3% of the basin. 8.4% of the basin remains as open land, 

however, 26% of the basin consists of cropland, pastureland, specialty farms, and 

forest land uses. Approximately 14.5% of the basin is comprised of waterbodies and 

wetlands that serve to store and attenuate stormwater runoff during extreme flooding 

events. 

5.2.1.3 Soils 

Figure 5.2-3 presents the hydrologic soils classification map of the Bell Creek 

Subwatershed that was developed for this study. Similar to the calculation of land 

use acreages, the distribution of hydrologic soil types within each subbasin was 

determined by the intersection of the soils coverage in the GIS database with the 

subbasin delineations. The following table lists a composite breakdown of the 

distribution of the hydrologic soil types within the Bell Creek Subwatershed. It can be 

seen that nearly 65% of the watershed is comprised of soils that are classified as 

hydrologic soil group B/D. Over 16% of the basin is classified as hydrologic soil group 

A soils, with most of these occurring in the northern half of the basin, north of Rhodine 

Road. There are very few hydrologic soil group D soils, which generally include 

wetlands that occur in the watershed. Soils in the basin, as categorized by the Natural 

Resources Conservation Service (NRCS), consist predominantly of fine sands of the 

Archbold (A), Candler (A), Orlando (A), Lake (A), Tavares (A), Immokalee (B\D), 

Malabar (B/D), Myakka (B/D), Ona (B/D), Smyrna (B/D), St. Johns (B/D), Winder 

(B/D), Arrents (C), Pomello (C), Seffner (C), Zolfo (C), and Basinger (D) series. 

TABLE 5.2-2 BELL CREEK SUBWATERSHED SOILS 

Hydrologic Soil Group 

Total Area 

(acres) 

Percentage of 

Subwatershed 

(%) 

A 1,993 16.4% 

B 0 0.0% 

B/D 7,899 64.9% 

C 1,595 13.1% 

D 462 3.8% 

Water 224 1.8% 

Total: 12,171 100.0% 






The Bell Creek Subwatershed is located in the lower portion of the Alafia River 

Watershed and as such can be described as lying in the Gulf Coastal Lowlands 

province. This is a relatively flat plain extending eastward with a gentle slope upward 

to the border of the Polk Upland physiographic province. The western edge of the 

Polk Upland is defined by the presence of the first of several paleo-shoreline scarps 

associated with the Pleistocene Ice-Age sea level fluctuations. This physiographic 

feature is known as the Pamlico Scarp or shoreline. Elevations in this part of the Gulf 

Coast Lowlands province range from sea level to 25 feet NAVD. The Polk Uplands 

typically ranges in elevation from 100 to 130 feet NAVD. 

The lower reach of Bell Creek meets the Alafia River at an elevation of –4.6 feet 

NAVD. The creek meanders for more than 2 miles until it meets Lake Grady at an 

elevation of roughly 39 feet. Along this reach the flood plains are wide and full of 

hardwoods and the banks of the creek are relatively steep. 

Lake Grady is one of the more prominent physiographic features of the Bell Creek 

Subwatershed. It is formed by the impoundment of Pelleham Branch and a portion of 

Bell Creek. It is interesting to note that Lake Grady exemplifies an important point 

concerning southwest Florida’s geology and that is the close interrelatedness 

between surface and ground waters. The karst topography of the region means that 

water-soluble limestone below the earth’s surface can dissolve and cause the land to 

sink or collapse. A sinkhole in the bed of Lake Grady has been traced as the source 

of fecal coli form bacteria in nearby private wells causing some consternation for the 

County and local residents. 

The topography south of Lake Grady is generally open with very flat terrain although 

hardwood forests cluster along the floodplains of the primary drainage systems. In the 

most southern portion of the subwatershed, along the basin ridgeline are areas of 

agriculture, which are bordered on the north by an undeveloped, large forested region 

drained by both Boggy Branch and the uppermost reaches of Bell Creek. The 

ridgeline elevation is nearly 120 feet NAVD. 

Sources of Information 

Survey Data 

Professional survey services were required to provide the necessary information to 

accurately develop the hydraulic model for the basin since only about 25% of the Bell 

Creek Subwatershed is comprised of residential, commercial, or institutional land 

uses. For the original 2001 Alafia River WMP study, Wilson, Miller, Barton, and Peek, 

Inc. were hired by Parsons to conduct survey in the Bell Creek Subwatershed. A total 

of 50 survey structure locations and 31 survey cross-section locations were obtained. 

At each survey structure location, structure invert elevations, lengths, construction 

materials, overtop elevations, and pictures were obtained. Typically cross-sections 

were taken upstream and downstream of each of the surveyed structures. Cross 


BOYETTE RD 

FISHHAWK BLVD 

301 

BELL CREEK 

75 


Lake Grady 


BELL CREEK 

BOGGY CREEK 


A 

B 

B/D 

C 

D 

Water 

Legend 

County Line 



Roads 




Suite 120 


BIG BEND RD 

Notes: 

BOGGY CREEK 

1:52,000 

BELL CREEK 


0 1,250 2,500 5,000 


Feet 

0 0.25 0.5 1 

Miles 

Filename: 

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sections were also taken at 31 other locations along the main channel segments. 

Information obtained included channel invert elevations, toe of slope, top of bank, 

natural ground elevations, and pictures. It was necessary to extend the channel 

cross-sections using the SWFWMD one-foot contour aerial topographic maps 

(1”=200’ scale) to account for channel storage in the floodplain. 


The Bell Creek Subwatershed has only a small percentage of subdivisions and/or 

commercial development. Available plans for residential and commercial 

developments within the Bell Creek Subwatershed were obtained from Hillsborough 

County and the Southwest Florida Water Management District (SWFWMD) and 

hydraulic information from the plans were used in the model inputs. These sources 

for subdivision and commercial development grading and drainage plans provided the 

bulk of the hydraulic model information and are commented appropriately in comment 

lines in the SWMM model input file. 

Field Measurements 

Where plans, as-built construction drawings, and survey information for drainage 

facility data were not readily available, hydraulic model deficiencies were resolved, in 

a preliminary measure, through field measurements of existing drainage facilities by 

Parsons staff. Model input data were estimated from field measurements for those 

areas where adequate existing survey or as-built data were not available and noted 

accordingly in comment lines in the SWMM model input file. 


The methodology employed in the hydrologic model development of the Bell Creek 

Subwatershed has been described in Chapter 4. Parameters used to develop the 

hydrologic model with information unique to Bell Creek Subwatershed are discussed. 



properly analyze the primary drainage facilities within the Bell Creek Subwatershed, 

the basin was divided into 166 discrete subbasins that range in size from 2 to 408 

acres. The average subbasin size is approximately 73 acres. In accordance with the 

subbasin nomenclature previously discussed, “73” will be used as the first two digits 

referring to the Bell Creek Subwatershed for model junctions (nodes) and subbasins. 

Methods used in subbasin delineation are discussed in Chapter 4. 



this study for each subbasin in the Bell Creek Subwatershed by an area-weighted 

averaging procedure that assigned a universal CN value to each combination of land 

use category and hydrologic soil group classification. Weighted runoff curve numbers 

were generated based on Table 4.5-1 values (See Chapter 4) for the Bell Creek 





Subwatershed. The resulting final subbasin runoff curve numbers for the Bell Creek 

Subwatershed are presented in the Alafia River ArcGIS geodatabase. 






The Bell Creek Subwatershed hydraulic model follows the methods outlined in the 

Chapter 4 description. It is a comprehensive model, comprised of a total of 246 

junctions and 442 links in its structure, including 134 closed conduits, 104 irregular 

open channels, and 204 weirs. 



within the Bell Creek Subwatershed, it was important that all significant storage 

facilities and their hydraulic functions be defined. As described in Chapter 4, the 

initial (starting) water surface elevations for these variable storage facilities were 










The Bell Creek Subwatershed model includes a total of 134 closed conduits that take 

the various forms of circular, rectangular, elliptical, and/or arch pipes that is allowed 

by the EXTRAN model formulation. 

Bridge structures can be represented within the framework of the EXTRAN model as 

either an open channel or some combination of equivalent closed conduits. In the 

Bell Creek model application, some bridge spans were modeled as trapezoidal 

channels, with additional roughness for any piers. A more detailed discussion of the 

methodology involved is presented in Chapter 4. 


Overflow weirs are an important element of the hydraulic model development and are 

necessary to represent pond control structures, pond banks, overtopping of roadways 

at channel crossings, and overland flow 






The majority of the channel cross sections in the Bell Creek Subwatershed were 

obtained from survey data. In most cases, channel cross sections were extended by 

the addition of endpoints that defined the full extent of the natural floodplain. Within 

the Bell Creek Subwatershed model representation, there are a total of 104 irregular 

channel cross sections that are used to define the open channel systems and natural 

floodplains of the basin. 

Appropriate selections of Manning’s n values as described in Chapter 4, were either 

confirmed or adjusted during the model calibration process. In the Bell Creek 

Subwatershed, for the most part, the channel roughness coefficients ranged from a 

low of 0.040 for the “cleanest” channel reaches to 0.090 for the most highly 

vegetated. The floodplain roughness coefficients ranged from 0.080 to 0.140. 


No existing streamflow gage data is available in the Bell Creek subwatershed so no 

calibration and verification could be performed for this portion of the Alafia River 

watershed. 







The Fishhawk Creek Subwatershed (including the Little Fishhawk Creek 

Subwatershed) is a 27.8-square mile watershed located in southeastern Hillsborough 

County in an area roughly defined by Boyette Road and Balm-Boyette Road along the 

west, CR 39 on the east, and SR 672 on the south. The subwatershed location and 

boundaries, as defined for this study, are shown in Figure 5.3-1. Flow originates in 

the southern and eastern headwaters of the subwatershed and flows in a generally 

northwestern direction to the subwatershed outfall at the confluence with the Alafia 

River, located approximately 2.15 miles upstream (east) of Bell Shoals Road. 

Historically, the Fishhawk Creek Subwatershed consisted of an aggregation of lake 


Fishhawk Creek. With the exception of the southern portion of the subwatershed, the 

creek channel remains fairly natural. Strip-mining for phosphate and agricultural 

“improvements” has significantly altered the hydrologic/hydrologic system in the 

southern portion of the subwatershed over the past half-century. Although most of 

the mining activities ceased 20 to 30 years ago, their effects are still obvious on aerial 

photography in the linear pits and reclaimed overburden soils. The Hillsborough 

County Southeast Landfill is in the most southeastern corner of the Subwatershed 

and is roughly 700 acres. 

Residential development within the subwatershed has been minimal until recently. 

Construction of the 5000-acre Fishhawk Ranch development has been nearly 

completed within the northern portion of the subwatershed. The Boyette Road 

Extension (or Fishhawk Boulevard) was constructed to facilitate the development of 

this portion of the Fishhawk Creek Subwatershed. 

Typical of southern Florida conditions, the Fishhawk Creek drainage basin is 

characterized by generally flat topography throughout most of the contributing 

drainage areas, with high water tables, and many natural and man-made lakes, 

depressions, and wetlands. 



of the Fishhawk Creek Subwatershed has been segregated into four major drainage 

segments, the main Fishhawk Creek channel, Doe Branch, Long Flat Creek and Little 

Fishhawk Creek. Figure 5.3-1 depicts the location of these primary drainage 

systems. 


ALAFIA RIVER 

ALAFIA RIVER 

ALAFIA RIVER 

BOYETTE RD 

FISHHAWK BLVD 

LITTLE FISHHAWK CREEK 


RICE CREEK 

FISHHAWK CREEK 

BOYETTE RD 

Legend 

County Line 




Roads 




Suite 120 



Notes: 


1:60,000 

LONG FLAT CREEK 

0 1,500 3,000 6,000 

Feet 

0 0.25 0.5 1 

Miles 

DOE BRANCH 

CW Bill 

Young 

Regional 

Reservoir 

Filename: 

Fig5_3_ 

1.mxd 

672 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 

39 


Fishhawk Creek Subwatershed 



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Fishhawk Creek Main Channel 

The Fishhawk Creek main channel originates in an agricultural area immediately 

north of CR 672 and a mile east of Balm-Boyette Road. The stream channel profile 

starts at elevation 119.4 ft NAVD and remains in a relatively natural condition 

downstream of the agricultural area at its headwaters to its outfall to the Alafia River. 

The creek falls from an elevation of 47.3 ft NAVD at the confluence with Doe Branch 

to 1.9 ft NAVD at the Alafia River. 

There are a total of 7 bridges or culvert crossings of Fishhawk Creek along the main 

channel segment, including the bridges at the TECO easement, Fishhawk Boulevard, 

and Boyette Road as well as two crossings at unpaved, unnamed private roads, 

Hobson-Simmons Road, and the unpaved entrance to Balm-Boyette Scrub Preserve. 

Of these, Fishhawk Boulevard Bridge (also known as Boyette Road, Extension) was 

constructed in 1995 to facilitate lateral traffic flows into Tampa as the area develops. 

Doe Branch 

Doe Branch is a major tributary to Fishhawk Creek. The natural channel provides 

drainage to very flat and wet contributing areas. Doe Branch originates just south of 

Wendell Ave, east of CR 39 (Picnic Road) and flows in a northwesterly direction 

through very flat terrain, dropping only 5 feet in the first 1½ mile of channel. The 

contributing drainage subwatershed remains basically undeveloped and drains 

primarily agricultural and open-land uses. Doe Branch discharges to Fishhawk Creek 

approximately 2860’ southeast (upstream) of Boyette Road where Boyette Road 

crosses Fishhawk Creek. 

Long Flat Creek 

Long Flat Creek diverges from the Fishhawk Creek 0.6 mile upstream (south) of the 

Doe Branch confluence. Long Flat Creek meanders through old phosphate strip mine 

areas (now considered as open land or reclaimed mine land areas), eventually 

reaching its headwaters in an agricultural zone on the north side of State Road 672 at 

the entrance to the Hillsborough County Southeast Landfill. 

Little Fishhawk 

Little Fishhawk does not contribute to Fishhawk Creek flow but outfalls directly to the 

Alafia River 0.86 miles upstream of the Fishhawk Creek outfall and 2.3 miles 

downstream of Lithia-Pinecrest Road. Little Fishhawk Creek is unique to the 

Fishhawk Creek Subwatershed in that it contains within its watershed the only area of 

significant recent development and urbanization (Fishhawk Ranch). 


Existing land use conditions in the Fishhawk Creek Subwatershed were defined by 

use of digital coverages obtained from the SWFWMD GIS database. The resultant 

existing land use map of the Fishhawk Creek Subwatershed that was used for model 

development purposes is shown in Figure 5.3-2. Using GIS techniques, the subbasin 

delineations were intersected with the land use coverage to develop the distribution of 





the various land use classifications within each of the defined subbasins in the 

watershed. The following table presents a composite breakdown of land use acreages 

and percentages in the Fishhawk Creek Subwatershed: 

TABLE 5.3-1 FISHHAWK CREEK SUBWATERSHED LAND USE 


TOTAL 

AREA 

(acres) 

PERCENTAGE OF 

SUBWATERSHED 

(%) 

Low Density Residential 1,141 6.4% 

Medium Density Residential 804 4.5% 






Forest 3,375 18.9% 


Transportation, Communications and 

48 0.3% 

Utilities 


Mined Lands (active) 8.1 0.0% 


Water 1,407 7.9% 

Wetland 1,983 11.1% 

Total: 17,817 100.0% 

According to the existing land use mapping database, 46% of the Fishhawk Creek 

Subwatershed is classified as openland/rangeland or cropland/pastureland. Forested 

areas comprise another 19% of the subwatershed. Only 14% of the subwatershed is 

classified as residential development. The majority of the development is located in 

the northern third of the subwatershed. Much of Fishhawk Creek has the potential for 

urbanization, which has thus far been kept to a minimum. Approximately 19% of the 

subwatershed is comprised of waterbodies and wetlands that serve to store 

stormwater runoff during extreme flooding events. 


ALAFIA RIVER 

ALAFIA RIVER 

ALAFIA RIVER 

BOYETTE RD 

FISHHAWK BLVD 


Suite 120 


RICE CREEK 

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1900/2600 - OPEN LAND 





5000 - WATER 




Legend 

County Line 



Roads 




BOYETTE RD 


Filename: 

Fig5_3_ 

2.mxd 

Map Date: 


DOE BRANCH 

CW Bill 

Young 

Regional 

Reservoir 


N/A 

672 

Prepared By: 

Yoav 

Rappaport 

39 










A 15 billion gallon surface water storage facility, the C.W. Bill Young Regional 

Reservoir, was fully constructed in early 2005 in the southeast portion of the 

subwatershed. It is a 1,100 acre reservoir located on 5,200 acres of land south of 

Lithia-Pinecrest Road between Boyette Road and County Road 39. It encompasses 

approximately 6% of the subwatershed. The facility is an earthen structure, with an 

embankment as wide as a football field at its base and that averages 50 feet in 

height. Armored with 16 inches of soil cement, including a stair step design that rings 

the top, the reservoir is built to withstand hurricane force wind and rain. 

5.3.1.3 Soils 

Soils within the Fishhawk Creek Subwatershed were categorized according to the 

hydrologic soil group classification system, as defined by the Natural Resource 

Conservation Service (NRCS). Figure 5.3-3 presents the hydrologic soils 

classification map of the Fishhawk Creek Subwatershed that was developed for this 

study. Using a methodology similar to that described above for the land use 

classifications, the distribution of hydrologic soil types within each subbasin was 

determined by intersection of the soils coverage in the GIS database with the 

subbasin delineations. The following table lists a composite breakdown of the 

distribution of the hydrologic soil types within the Fishhawk Creek Subwatershed. It 

can be seen that 58% of the watershed is comprised of soils that are classified as 

hydrologic soil group B/D. Nearly 20% of the subwatershed is classified as hydrologic 

soil group C soils, mostly occurring in the extreme southern portion of the 

subwatershed. A large portion of this soil type is classified as Arents or man-made 

soil. These are the remnants of past mining activity. Fifteen percent of the 

subwatershed is classified as hydrologic soil group A soils. There are very few 

hydrologic soil group D soils, which generally includes wetlands that occur in the 

watershed. Soils in the subwatershed, as categorized by the (NRCS), consist 

predominantly of fine sands of the Candler (A), Archbold (A), Malibar (B/D), Myakka 

(B/D), Smyrna (B/D), St. Johns (B/D), Ona (B/D), Pomello (C), Arents (C), Zolfo (C) 

and Basinger/Holopaw/Samsula (D) series. 

TABLE 5.3-2 FISHHAWK CREEK SUBWATERSHED 

HYDROLOGIC MODEL INPUT DATA 

HYDROLOGIC 

SOIL GROUP 

TOTAL AREA 

(acres) 

PERCENTAGE OF 

SUBWATERSHED 

(%) 

A 2,617 14.7% 

B 0 0.0% 

B/D 10,399 58.4% 

C 3,517 19.7% 

D 955 5.4% 

Water 327 1.8% 

Total: 17,817 100.0% 






The Alafia River Watershed lies within two physiographic provinces; the Gulf Coastal 

Lowlands, and the Polk Upland (White 1970). The lower portion of the watershed 

flows over the Gulf Lowlands province, a relatively flat plain extending eastward with a 

gentle slope upward to the border with the Polk upland physiographic province. The 

western edge of the Polk Upland is defined by the presence of the first of several 

paleo-shoreline scarps associated with the Pleistocene Ice-Age sea level fluctuations. 

This physiographic feature is known as the Pamlico Scarp or shoreline. Elevations in 

this part of the Gulf Coast lowlands province range from sea level to 25 feet. 

The remainder of the Alafia River watershed (including the Fishhawk Creek 

Subwatershed) is situated in the Polk Upland Province. Elevations in the extensive 

Polk Upland range up to between 100 and 130 feet, however, in this area of the 

province the elevations are mostly between 25 and 75 feet within the watershed. 

The Fishhawk Creek Subwatershed and its tributaries drain an area of the Polk 

Upland where the Pleistocene marine sands (overburden), and the underlying 

materials of the ore-bearing Bone Valley Formation and underlying Hawthorn Group 

rock have been disturbed for phosphate strip-mining in many areas. Much of this 

area has had its physiography and associated surface water drainage systems 

modified by this mining activity. This process generally strips the overburden 

sediments and stores the soil in huge spoil areas. Then the ore layer is mined and 

removed. The overburden sediments are then redistributed and graded and the 

mining activity is then described as “reclaimed.” Outstanding physiographic features 

in this region include many water filled, former mine pits and large bermed claysettling 

areas of various rectilinear configurations easily observable on maps and 

aerial photos. Most of the areas identified as “Open Water” natural systems in the 

Fishhawk Creek Subwatershed are of phosphate mining origin. 

The northeastern region of the Fishhawk Creek Subwatershed, particularly within the 

Little Fishhawk Creek Subwatershed, is currently experiencing large-scale 

development. The area drains to the west and upland elevations here range for the 

most part from roughly 75 feet to 110 feet NAVD at the ridgeline. 

The eastern central portion of Fishhawk Creek Subwatershed, which drains via Doe 

Branch, is an area of very flat terrain and little topographic relief. Doe Branch falls 

only 13 feet in over two miles of reach in this region as it cuts through wet pasture and 

what was formerly wetland in its upper most reach. 

5.3.1.5 Sources of Information 

As discussed in Chapter 4, survey data, subdivision/commercial development plans 

and field measurements provided the necessary information required for model 

development. In the Fishhawk Creek Subwatershed approximately 15% of the entire 

basin is comprised of developed land use, placing a tremendous need for 

professional survey services to accurately develop the hydraulic model for the 


ALAFIA RIVER 

ALAFIA RIVER 

ALAFIA RIVER 

BOYETTE RD 

FISHHAWK BLVD 



RICE CREEK 


BOYETTE RD 


A 

B 

B/D 

C 

D 

Water 

Legend 

County Line 



Roads 




Suite 120 



Notes: 


1:60,000 


0 1,500 3,000 6,000 

Feet 

0 0.25 0.5 1 

Miles 

DOE BRANCH 

CW Bill 

Young 

Regional 

Reservoir 

Filename: 

Fig5_3_ 

3.mxd 

672 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 

39 










subwatershed. A total of 61 structure locations and 17 cross section locations were 

surveyed for the original 2001 WMP study by the firm of Wilson, Miller, Barton and 

Peek, while 5 additional structure locations were surveyed by Edgeman and Sons. 

Subdivision grading and drainage development plans and as-built plans for 

developments were accessed through the Southwest Florida Water Management 

District permit records. The information culled from the plans was the source of the 

hydraulic data used to model these developments. Sources of data for individual 

elements of the hydraulic network are referenced in the model input file as comments 

and documented in the project files. 

Any remaining hydraulic model deficiencies were resolved, in a preliminary measure, 

through field measurements of existing drainage facilities by Parsons staff. Model 

input data for those areas where adequate existing survey or as-built data were not 

available were estimated from the field measurements and noted as such in comment 



The methods used to develop the hydrologic model for the Fishhawk Creek 

Subwatershed are consistent with the other subwatersheds being modeled in the 

Alafia River Watershed. These methods are discussed in detail in Chapter 4. 

Hydrologic parameters specific to the Fishhawk Creek Subwatershed are presented 

in the following sections. 


The Fishhawk Creek Subwatershed was divided into a total of 295 discrete subbasins 

that range in size from 0.6 to 950 acres, with the average subbasin size of 

approximately 60 acres. As discussed in Chapter 4, the nomenclature convention for 

the SWMM model representation assigns the subbasin name corresponding to the 

model junction (node) that serves as the outfall for the subbasin. For the Fishhawk 

Creek and Little Fishhawk Creek drainage basins, the first two digits of the 6- 

character numerical code nomenclature are “74”. 


Hydrologic modeling with the Hillsborough County version of the SWMM model 

requires using the SCS Runoff Curve Number Method to compute a runoff volume 

from rainfall. As described in Chapter 4, runoff curve numbers were calculated over 

the course of this study for each subbasin in the Fishhawk Creek Subwatershed by an 

area-weighted averaging procedure that assigned a universal CN value to each 


runoff curve numbers were generated based on Table 4.5-1 values (See Chapter 4) 

for the Fishhawk Creek Subwatershed. The resulting final subbasin runoff curve 

numbers for the Fishhawk Creek Subwatershed are presented in the updated Alafia 

River ArcGIS geodatabase. 










As discussed in Chapter 4, the hydraulic model mathematically describes the 

Fishhawk Creek Subwatershed as a network of open channel segments, culverts, 

bridges, storm sewers, weirs, lakes, ponds, and wetlands that comprise the primary 

drainage system within the subwatershed. Identification of this primary drainage 

system was performed as previously described and is depicted in Figure 5.3-1 as the 

map of the Fishhawk Creek Subwatershed. 

The Fishhawk Creek Subwatershed hydraulic model is quite comprehensive. It 

comprises a total of 417 junctions and 321 reaches in its structure, including 187 

closed conduits, 134 irregular open channels, and 437 weirs. 


It is important that all significant storage facilities and their hydraulic functions be 

defined in order to properly represent the hydrologic and hydraulic processes of 

stormwater runoff within the watershed. In the Fishhawk Creek Subwatershed much 

of the storage is either natural storage in the form of wetlands or man-made storage 

on undeveloped land that was created from past phosphate mining activities. Stagearea 

data was obtained from the DEM dataset or available record plans where DEM 

data did not match existing conditions of the model domain (i.e. topographic void 

area). 

5.3.3.3. Closed Conduits 

As discussed in detail in Chapter 4, the Hillsborough County version of EXTRAN 

permits the user to directly include the entrance, exit, and transition loss coefficients 

for closed conduits. This allows the model to represent friction losses within those 

conduits. The Fishhawk Creek Subwatershed model includes a total of 187 closed 

conduits that take the various forms of circular, rectangular, elliptical, and/or arch 

pipes that is allowed by the EXTRAN model formulation. 


Overflow weirs are an important element of the hydraulic model development 

particularly in the Fishhawk Creek Subwatershed. As mentioned previously, these 

flowpaths can represent pond control structures, pond banks, overtopping of 

roadways at channel crossings, and overland flow. 

Due to the remains of past mining activities, there are a significant number of 

anthropogenic water storage areas acting almost as small, closed basins which would 





spill over via a broad-crested weir during large storm events. Within the Fishhawk 

Creek Subwatershed hydraulic model, there are a total of 437 weir connections that 

are specified to represent the various components of the basin-wide drainage system. 


To properly represent the primary drainage system in the Fishhawk Creek 

Subwatershed, the model requirements necessitate channel cross section information 

of sufficient detail to define the shape of the channel within the banks and also a 

portion of the floodplain. In the Fishhawk Creek Subwatershed, many channel cross 

sections were extended by the addition of endpoints that defined the full extent of the 

natural floodplain. Within the Fishhawk Creek Subwatershed model representation, 

there are a total of 134 irregular channel cross sections that are used to define the 

open channel systems and natural floodplains of the drainage basin. 

Hydraulic efficiency is measured by the channel roughness coefficient, or the 

Manning’s n value, which is selected as a model input. These values were either 

confirmed or adjusted during the model calibration process. For the most part, the 

channel roughness coefficients ranged from a low of 0.040 for the “cleanest” channel 

reaches to 0.095 for the most highly vegetated. The floodplain roughness coefficients 

ranged from 0.080 to 0.140. 


No existing streamflow gage data is available in the Fishhawk Creek subwatershed so 

no calibration and verification could be performed for this portion of the Alafia River 

watershed. 







The Turkey Creek Subwatershed is located in the north-central portion of the Alafia 

River Watershed. The subwatershed, shown in Figure 5.4-1, drains 43.7 square 

miles. The subwatershed is roughly bounded by the following landmarks: Plant City 

to the northeast, Rev. Dr. Martin Luther King, Jr. Boulevard to the north, Henry 

George Road to the southeast, Keysville Road to the south, and Dover Road to the 

west. Turkey Creek Road bisects the subwatershed into approximately equal east 

and west halves; State Road 60 bisects the subwatershed into approximately equal 

north and south halves. The subwatershed is approximately eight miles along the 

central north-south axis, and seven miles along the central east-west axis. Flow in 

Turkey Creek originates in the north and flows to the south. Flow in the Little Alafia 

River, the major tributary to Turkey Creek, originates in the northeast and flows in a 

southwesterly direction. Turkey Creek discharges to the Alafia River, two miles 

upstream of the Lithia-Pinecrest Road Bridge. 

The natural hydrologic system in the Turkey Creek Subwatershed probably consisted 

of small lake, depression, and wetland systems flowing through sloughs and small 

creeks to the Little Alafia River and Turkey Creek. Anthropogenic land use changes 

from the natural condition to phosphate mining, agriculture, and mixed density 

residential significantly altered the hydrologic system in the subwatershed. 

Ground elevations range from 140 feet NAVD in the northeast corner of the 

subwatershed to 15 feet NAVD at the confluence of Turkey Creek and the Alafia 

River. This 125-foot drop in elevation occurs over a 7.5-mile linear distance. 

Subwatershed slope is approximately 17 feet per mile, or 0.3 percent. 

Soils are generally sandy. Myakka and Seffner are the predominant fine-sand 

species. Basinger, Holopaw, and Samsula depressional soils, and various Arents are 

also common. Hydrologic soil type B/D and C dominant. 


Two major reaches -- Turkey Creek and the Little Alafia River -- and five minor 

reaches define the primary conveyance system in the Turkey Creek Subwatershed. 

Figure 5.4-1 shows major and minor reaches. 


S ALEXANDER ST 

4 

92 

S COLLINS ST 

MARTIN LUTHER KING BLVD 

S FORBES RD 

Hillsborough Co 

Polk Co 

JAMES L REDMAN PKWY 

TURKEY CREEK 

Legend 

County Line 




Roads 




Suite 120 


E LUMSDEN RD 


Notes: 

ALAFIA RIVER 

LITTLE ALAFIA RIVER 

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60 60 


Medard 

Reservoir 

Filename: 

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N/A 

S COUNTY ROAD 39 

Prepared By: 

Yoav 

Rappaport 


Turkey Creek Subwatershed 



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Turkey Creek 

Turkey Creek originates upstream of Rev. Dr. Martin Luther King, Jr. Boulevard. The 

channel profile ranges from 12.8 ft NAVD at the Alafia River - Turkey Creek 

confluence to 101.9 ft NAVD just upstream of Rev. Dr. Martin Luther King, Jr. 

Boulevard. The Turkey Creek outfall to the Alafia River is located two miles upstream 

of the Lithia-Pinecrest Road Bridge. Turkey Creek is 9.6 miles long. Channel slope is 

9.3 feet per mile or 0.18 percent. 

Turkey Creek flows through 14 hydraulic structures. The following six roads cross 

Turkey Creek: Durant Road, East State Road 60, Garland Branch Road, Sydney 

Road, Caruthers Road, Downing Street, Rev. Dr. Martin Luther King, Jr. Boulevard. 

Two railroads also cross Turkey Creek. Turkey Creek drains 27,964 acres, or 43.7 

square miles, at the Alafia River - Turkey Creek confluence. 

Turkey Creek flows under Rev. Dr. Martin Luther King, Jr. Boulevard south to 

Downing Street. South of Downing Street, Turkey Creek flows through the 

Williamson Berry Farms to Caruthers Road, and Sydney Road. A railroad crosses 

Turkey Creek just downstream of Sydney Road. The creek takes ditched and natural 

forms through this reach. Channel vegetation is thick. Agricultural and open land 

uses dominate the area that drains to this reach. 

Turkey Creek flows through more agriculture land south of Sydney Road, and then 

flows under Garland Branch Road into a wetland area upstream of State Road 60. 

Runoff from State Road 60 between Dover Road and Turkey Creek Road drains to 

Turkey Creek. Abandoned Sydney Mine units are located west of the creek upstream 

of East State Road 60. The Hillsborough County Environmental Lands Acquisition 

and Protection Program own these units. Crop and pastureland, and residential land 

uses along Jerry Smith Road are located to the east of this reach of the creek. 

Turkey Creek Tributary A and Turkey Creek Tributary B join Turkey Creek along this 

reach. 

Downstream of State Road 60, Turkey Creek flows through the abandoned Sydney 

Mine to Durant Road. Steep mine embankments dominant channel overbanks. 

Channel vegetation is thick. The channel might be described as a series of cascading 

pools in this reach. A major abandoned phosphate-mine ring ditch discharges to 

Turkey Creek from the west. A major abandoned phosphate mine ring ditch to the 

east might overtop to Turkey Creek during very rare, extreme storm events: this ditch 

primarily discharges to the Little Alafia River. A railroad crosses Turkey Creek 

approximately 1,000 feet upstream of Durant Road. 

Downstream of Durant Road, Turkey Creek flows through open lands and parallel to 

residential land uses along Blount Road. Turkey Creek then joins the Little Alafia 

River and flows through a forested wetland owned by the Hillsborough County 

Environmental Lands Acquisition and Protection Program. A small percentage of the 

River Hills development discharges from the west to this reach of Turkey Creek. The 





remainder of the River Hills development discharges to the Alafia River. The Turkey 

Creek channel is less vegetated along this reach than the upstream reaches. 

Little Alafia River 

The Little Alafia River originates at the confluence of two small creeks, 1,000 feet 

west of Pippin Road. The point of origination is near the Dumont Subdivision. The 

channel profile ranges from19.5 ft NAVD at the Turkey Creek - Little Alafia River 

confluence to 90.5 ft NAVD at the upstream end. The Little Alafia River outfall to 

Turkey Creek is located 4,000 feet upstream of the Turkey Creek - Alafia River 

confluence. The Little Alafia River is 6.2 miles long. Channel slope is 11.4 feet per 

mile or 0.22 percent. 

The Little Alafia River flows through 15 hydraulic structures. The following five roads 

cross the Little Alafia River: Holloway Road, Mud Lake Road, West State Road 60, 

Turkey Creek Road, Durant Road. One railroad also crosses Turkey Creek. The Little 

Alafia River discharges into and drains the Edward Medard Reservoir, also known as 

the Pleasant Grove Reservoir. The Little Alafia River drains 16,025 acres, or 25.0 

square miles, at the outfall to Turkey Creek and approximately 12,900 acres or 20.2 

square miles drains to the Medard Reservoir. 

The Little Alafia River originates in a wetland at the west end of Turtle River Court. 

The wetland is the outfall of two small tributaries: an unnamed creek east of Trapnell 

School and an unnamed creek north of Berea Church. The Little Alafia River flows in 

a southwesterly direction through the wetland, to an open pasture. The reach 

downstream of the wetland is bounded on all sides by cropland and pastureland. 

Channel vegetation is relatively light, with instances of channel bank sloughing where 

the channel meanders through open pastures. The Little Alafia then flows under a 

two-span bridge at Holloway Road. 

Downstream of Holloway Road, the Little Alafia River enters a 55-acre forested 

wetland. Channel vegetation is moderate to heavy in this reach. The wetland is 

bounded on most sides by cropland and pastureland. The Little Alafia River 

continues in a southwesterly direction to Mud Lake Road. A small low-density 

residential area borders the channel to the north, just upstream of Mud Lake Road. 

Downstream of Mud Lake Road, the Little Alafia River flows through the southern 

portion of a 150-acre wetland, bisected by a utility easement. Channel vegetation in 

this reach is dense. Grassy Creek joins the Little Alafia River within the 150-acre 

wetland. The channel meanders south, past a high-density residential manufactured 

home development, toward State Road 60. The channel in the southern portion of 

this reach is adverse, at some locations. This may cause ponding in the low flow 

channel of the Little Alafia River. The Little Alafia River flows through three ten-foot 

by ten-foot reinforced concrete box culverts at West State Road 60. Runoff from 

State Road 60, between Turkey Creek Road to the west and State Road 39 to the 

east, discharge to the Little Alafia River. 





Downstream of State Road 60, the Little Alafia River enters the grounds of 

Hillsborough County's Edward Medard Park. The 750-acre Edward Medard Reservoir 

is the focus of the park. The water body is also referred to as the Pleasant Grove 

Reservoir in some government documents and by some local residents. Operations 

of the reservoir are under the direction of the Southwest Florida Water Management 

District. The reservoir and park are on reclaimed mine lands: formerly the Sydney 

Mine. Medard Tributary A also outfalls to the Medard Reservoir. 

A structure at the southwest corner of the water body controls the water-surface 

elevation in the reservoir. The structure consists of three six-foot long by two-foot 

deep orifices at elevation 59.1 ft NAVD; and one six-foot long orifice with an 

adjustable weir crest. The District can raise or lower the crest between elevation 58.1 

and 59.1; adjustable orifice depth varies between two and three feet. An earthen 

emergency overtop weir at elevation 65.1 feet is located on the northwest corner of 

the reservoir. Two drawdown orifices exist at elevation 51.1 and 43.6. If necessary, 

the District could open these orifices to draw down the reservoir water surface. An 

elevation and rain gage exist at the reservoir. Section 5.4.1 contains a description of 

the historic record at these gages. 

The Little Alafia River discharges from the reservoir, through a six-foot deep by fourfoot 

wide reinforced concrete box, into a rip-rap lined trapezoidal channel. The 

channel flows southwesterly toward a three-span bridge at Turkey Creek Road. 

Downstream of Turkey Creek Road, the channel flows through a forested wetland. 

The 150-acre unincorporated community of Pleasant Grove is located to the south; a 

1,000-acre abandoned mine unit on the old Sydney Mine is to the north. The ring 

ditch from the mine unit discharges to the Little Alafia River in this reach. The Little 

Alafia River then flows under Durant Road and toward a railroad bridge. 


Existing land use in the Turkey Creek Subwatershed is defined with update to the 

Southwest Florida Water Management District's 1995 Geographic Information System 

coverage. This District coverage is based on the Florida Department of 

Transportation's Florida Land Use and Cover Classification System, or FLUCCS. The 

methods used to update the District's coverage are outlined in Chapters 2 and 4. 

It is important to note that this update is done for hydrologic modeling purposes only. 

Hillsborough County's Stormwater Management Model is based on the Soil 

Conservation Service Curve Number method. This method is described in Chapter 4. 

Calibration of the Turkey Creek Subwatershed with the Curve Number method is 

sensitive to the infiltration capacity and percent impervious cover. Changes to the 

District's land use coverage are done purely to increase the accuracy of the 

hydrodynamic model. 





It is appropriate for governments to promulgate multiple land use designations: 

political, zoning, and hydrologic land uses might be defensible and different for the 

same parcel of land. It is not appropriate for governments to require that the same 

political, zoning, and hydrologic land use exist on a parcel of land. The District's 

coverage is updated, for hydrologic modeling reasons, to observe the following 

changes: 

• Where construction occurred since 1995, other land uses are replaced with a 

residential land use. 

• Where existing land use density is inconsistently identified, density is changed. 

For example, some areas in the Turkey Creek Subwatershed, which are identified 

as low or high density, might be more consistently described as medium density 

with respect to other identified medium density land uses. This is done to 

accurately describe impervious surface area within and between residential land 

use polygons. 

• Where commercial, industrial, and institutional land uses, and the transportationcommunications-utilities 

land use contain large tracts of open land, the area is 

segregated and reclassified with the open land use. 

• Where mine lands are reclaimed to a quasi-natural state, land use is changed 

from mine land to an appropriate designation: usually open land or rangeland. 

• Where cropland and pastureland are inconsistently identified, designation is 

changed. For example, some areas in the Turkey Creek Subwatershed, which are 

identified as cropland and pastureland, might be more consistently described as 

open land and rangeland with respect to other identified open land and rangeland 

areas. 

Figure 5.4-2 is the hydrologic land use map for the Turkey Creek Subwatershed. 

These data are combined with Southwest Florida Water Management District soils 

data to develop subbasin curve numbers. Land use in the Turkey Creek 

Subwatershed is broken down in the following table. 





TABLE 5.4-1 TURKEY CREEK SUBWATERSHED 

UNIVERSAL SCS RUNOFF CURVE NUMBERS 


TOTAL 

AREA 

(acres) 

PERCENTAGE OF 

SUBWATERSHED 

(%) 








Forest 1,227 4.4% 


Transportation, Communications and Utilities 279 1.0% 


Mined Lands (active) 1,028 3.7% 


Water 1,142 4.1% 

Wetland 1,827 6.5% 

Total 27,964 100.0% 

Agricultural land uses, which include cropland, pastureland, and row and tree crops, 

are the largest single land use in the Turkey Creek Subwatershed, comprising over 34 

percent of the subwatershed. Residential development comprises 20 percent of the 

subwatershed. Nearly 27 percent of the subwatershed remains as natural landforms. 

Approximately 11 percent of the subwatershed is comprised of waterbodies and 

wetlands. These landforms store or attenuate runoff during extreme flooding events. 








4 

92 

S COLLINS ST 











1900/2600 - OPEN LAND 





5000 - WATER 




Legend 

County Line 



Roads 




Suite 120 




Notes: 

ALAFIA RIVER 

S FORBES RD 

TURKEY CREEK 

1:72,000 


0 1,500 3,000 6,000 


60 60 

Feet 

0 0.25 0.5 1 

Miles 


Medard 

Reservoir 

Filename: 

Fig5_4_ 

2.mxd 

Map Date: 



N/A 



Prepared By: 

Yoav 

Rappaport 


Polk Co 










5.4.1.3 Soils 

The U.S. Natural Resource Conservation Service classifies soils into hydrologic soil 

groups A through D, as a function of infiltration rates and soil moisture capacities. A 

dual hydrologic soil group classification -- B/D -- is assigned to undrained soils: 

saturated throughout much of the soil column due to a high surficial water table during 

the wet season. Infiltration is impeded and the soil acts as a D soil. When the water 

table is lower the soil acts as a B soil: a well drained soil. 

Figure 5.4-3 shows hydrologic soil classifications for the Turkey Creek Subwatershed. 

The following table lists a composite breakdown of the distribution of the hydrologic 

soil types within the Turkey Creek Subwatershed. Approximately one third of the 

subwatershed is comprised of Type B/D soils, and one third of Type C soils. Type 

B/D soils are assumed to act as a composite of Type B and Type D soils for 

hydrodynamic model calibration purposes. For the Turkey Creek Subwatershed 

model calibration, it was necessary to assume that Type B/D soils act closer to Type 

B than Type D under normal conditions in the subwatershed. 

TABLE 5.4-2 TURKEY CREEK SUBWATERSHED 


Hydrologic Soil Group 

Total Area 

(acres) 

Percentage of 

Subwatershed 

(%) 

A 5,274 18.9% 

B 0 0.0% 

B/D 9,720 34.8% 

C 7,483 26.8% 

D 4,462 16.0% 

Water 1,025 3.7% 

Total 27,964 100.0% 

The U.S. Natural Resource Conservation Service identifies 31 unique soils in the 

Turkey Creek Subwatershed. Arents, Basinger Holopaw Samsula Depressional, 

Haplaquents Clayey, Myakka Fine Sand, Ona Fine Sand, Seffner Fine Sand, and 

Zolfo Fine Sand are the dominant soil species in the Turkey Creek Subwatershed. 






A line that extends from the unincorporated town of Sydney to the State Road 60 

bridge over Turkey Creek and then east along State Road 60 to the subwatershed 

divide roughly divides the Turkey Creek Subwatershed into two homogenous 

sections. Abandoned and reclaimed phosphate mine lands dominate the area 

southwest and south of the polyline. Agriculture lands dominate the area northeast 

and north of the polyline. The northern area covers roughly twice the aerial extent of 

the southern area. 

Turkey Creek and the Little Alafia River flow south and southwest, respectively, 

through agricultural lands and wetlands in the northern portion of the subwatershed to 

abandoned mine lands. Channels in the northern portion take two general forms. The 

first form is a natural compound cross-section, which consists of a low flow channel 

and a wider overbank section. Flows in this channel type are through wetlands and 

forested wetlands. This channel type is generally overgrown and thick with 

vegetation. The second form is a partially or fully altered trapezoidal ditch through 

agriculture lands. In the southern portion, cascading pools are the dominant channel 

form. Surface water is significantly impounded by constructed earthen structures and 

linear depressions associated with abandoned mine lands. 

A Y-shaped dendritic flow pattern defines the broad drainage trend in the Turkey 

Creek Subwatershed. Turkey Creek forms the west arm of the Y-shape; the Little 

Alafia River forms the east arm. A very shallow ridge running from the Walden Lake 

development in the north to the intersection of State Road 60 and Turkey Creek Road 

separates the arms of the Y-shape, and defines the general drainage divide between 

Turkey Creek and the Little Alafia River. 

The most prominent ridge in the subwatershed extends from the Valrico Lookout 

Tower near the intersection of Dover Road and State Road 60 to the Diamond Hills 

Golf Course, just east of the Valrico Wastewater Treatment Plant. The ridge is along 

the western edge of the Turkey Creek Subwatershed, with elevations above 130 feet. 

Enormous closed basins, some in excess of 1,000 acres, make up the abandoned 

mine lands. Stormwater that falls within these basins typically collects in depressed 

areas and evaporates or infiltrates; if these areas were reclaimed to a pre-mine 

condition, stormwater that falls within these areas would enter the surface water 

drainage system. Flood hazards would increase. Large embankments, some more 

than 30 feet in height, create the divides that form the closed basins. Wetland and 

forest landforms exist within these closed basins. Soil types tend to be Arents and 

clayey. 



4 

92 

S COLLINS ST 


S FORBES RD 


Polk Co 


TURKEY CREEK 


A 

B 

B/D 

C 

D 

Water 

Legend 

County Line 



Roads 




Suite 120 


E LUMSDEN RD 


Notes: 

ALAFIA RIVER 

1:72,000 


0 1,500 3,000 6,000 


60 60 

Feet 

0 0.25 0.5 1 

Miles 


Medard 

Reservoir 

Filename: 

Fig5_4_ 

3.mxd 

Map Date: 



N/A 


Prepared By: 

Yoav 

Rappaport 













development. Tomasino and Associates surveyed approximately 165 structures and 

approximately 370 cross sections in the Turkey Creek Subwatershed for the original 

2001 study. Data from almost all of these surveys are incorporated into the 

hydrodynamic model. For hydrologic structures, such as culverts or bridges, 

Tomasino collected location, orientation, invert and weir overtop elevations, 

dimensions, material type, water surface elevations, and cross sections at the 

upstream and downstream ends of the structure. Tomasino collected location, 

orientation, ground and water surface elevations for cross sections. In addition, 

Tomasino photographed most locations. 14 new structure locations were surveyed 

as part of this model update. Survey data is in digital format as x,y,z points and is 

included in the updated Alafia River ArcGIS geodatabase submittal. 













The methods used to develop the hydrologic model for the Turkey Creek 

Subwatershed are consistent with the other subwatersheds being modeled in the 

Alafia River Watershed. These methods are discussed in detail in Chapter 4. 

Hydrologic parameters specific to the Turkey Creek Subwatershed are presented in 

the following sections. 


The Turkey Creek Subwatershed is divided into 431 discrete subbasins, to provide 

the level of detail necessary to define and the primary and portions of the secondary 

drainage system. Subbasins range in area from 1 to 1153 acres, and the average 

subbasin area is 65 acres. Hillsborough County’s naming convention derives 

subbasin name from the junction to which the subbasin drains. The convention 

dictates a six-character numerical code for each subbasin. The first two digits refer to 

subwatershed. “75xxxx” refers to the Turkey Creek Subwatershed. 





The Pemberton-Baker Creek Closed Subwatershed observes a "759xxx" series, 

although this subwatershed does not drain to the Turkey Creek Subwatershed, as 

implied by the digit five in the second register from the left. The "759xxx" series is not 

used in the Turkey Creek Subwatershed model. 

Junction and subbasin numbers in the Delaney Creek Closed Subwatershed fall 

between 706860 and 706880, although this subwatershed does not drain to the Alafia 

River Main Stem Subwatershed, as implied by the digit zero in the second register 

from the left. These numbers are not used in the Alafia River Main Stem 

Subwatershed model. 



this study for each subbasin in the Turkey Creek Subwatershed by an area-weighted 



were generated based on Table 4.5-1 values (See Chapter 4) for the Turkey Creek 

Subwatershed. The resulting final subbasin runoff curve numbers for the Turkey 

Creek Subwatershed are presented in the updated Alafia River ArcGIS geodatabase. 






The Turkey Creek Subwatershed hydraulic model is quite comprehensive. It 

comprises a total of 599 junctions and 1081 linkages in its structure, including 260 

channels, 348 closed conduits and 473 weirs. 


Stormwater management facilities, lakes, natural depressions, and wetlands control 

drainage at some locations. The Extended Transport Block allows the user to specify 

a variable stage-area relationship at junctions. Hillsborough County DEM data and 

other backup data are used to develop these relationships. 

The initial water-surface elevations at these junctions are from three methods. On 

wet stormwater-management facilities, where a control structure exists to discharge 

stormwater into the surface-water drainage system, the starting water-surface 

elevation is the crest elevation of the control weir, or the invert elevation of the bleeddown 

orifice. On dry stormwater-management facilities, where stormwater seeps into 

the ground or evaporates, the starting water-surface elevation is the pond bottom. 

For natural ponds, lakes, and wetlands, the starting water-surface elevation is the 

normal high water elevation. If normal high water elevations do not exist in backup 





data, the starting water-surface elevation is some gross approximation of the normal 

high water elevation. Stage–area data was obtained from the DEM dataset or 

available record plans where DEM data did not match existing conditions of the model 

domain (i.e. topographic void area). 


The model details approximately 348 closed conduits, for the Turkey Creek 

Subwatershed. Closed conduits take the form of circular, rectangular, elliptical, or 

arch pipes. Data are from surveys and other backup data. 

It is necessary within the framework of the Extended Transport Block to represent a 

bridge structure as either an open channel or some combination of equivalent closed 

conduits. In the Turkey Creek Subwatershed model, a small number of bridge spans 

are modeled as the respective surveyed cross-section, with additional roughness 

coded to represent friction loss associated with piers. Where bridges experience fullflow 

conditions, the depth of the channel cross section is limited to the elevation of the 

low chord. This strategy allows the surcharge condition to be modeled. In most 

cases, bridge structures are modeled using the guidelines described in Section 4 for 

abstraction of an equivalent combination of box culverts, with different dimensions 

and inverts. The model includes numerous equivalent sections for bridges. 

5.4.3.4 Weirs 

The model includes 473 weir connections for the Turkey Creek Subwatershed. Weirs 

model the overtopping of control structures, pond banks, roadways at channel 

crossings, and overland flow. Data for crest elevations and widths are form structure 

surveys, construction plans, and field measurements. All stormwater management 

ponds include a top-of-bank weir to allow overtopping of the pond bank during 

extreme flood events. All road crossings include a top-of-road weir to allow 

overtopping of the road during extreme flood events. Roadway overtopping is 

simulated with broad-crested weirs. Weir crest elevations are from structure surveys, 

construction plans, or topographic maps. Overland flow provides a conduit for 

floodwater to circumvent the normal flowpath in the drainage system. Weirs simulate 

these drainage paths, with weir crest elevations and lengths from DEM data. 


The model details 260 channels, for the Turkey Creek Subwatershed. Irregular cross 

section data define the low flow channel and overbank floodplain of natural cross 

sections. It is necessary to code the natural overbank floodplain explicitly so that both 

floodplain storage and conveyance functions are modeled. The most current, 

detailed, and representative data for any particular reach of the open channel system 

are coded. In many cases, channel cross section data from surveys are extended 

with data from topographic maps to define the full extent of the natural floodplain. 

Manning’s roughness coefficients represent hydraulic efficiency. Manning’s 

roughness coefficient is a function of the extent and type of vegetation, bottom 





material, irregularity, alignment, obstructions, and depth of flow in a channel. 

Selection of an appropriate Manning’s roughness coefficient for any particular reach is 

highly subjective. The procedure requires experience. Specification in this model is 

supported by published guides and past modeling experience. These values are 

confirmed or adjusted during model calibration. Channel roughness coefficients 

range from 0.040 for the cleanest channel reaches to 0.100 for the most vegetated. 

Floodplain roughness coefficients range from 0.090 to 0.200. 

5.4.3.6 Subwatershed Boundary Conditions 

The Extended Transport Block requires a boundary condition at all model outfalls. A 

strict boundary does not exist in the Turkey Creek Subwatershed: all subwatershed 

models are combined into one single Alafia River Watershed model. The Turkey 

Creek Subwatershed boundary condition is the dynamic elevation in the Alafia River 

at the outfall of Turkey Creek into the Alafia River. 



limitations so that predicted results are in approximate agreement with measured 

data. A reasonable range of values for the adjustment of model parameters is 

established through the review of literature; adjustments outside these ranges are 

made only if unusual hydrologic or hydraulic conditions exist. Ideally, a model is 

calibrated to several different storms. These events represent storms of different 

volumes, intensities, and distributions. It is desirable to calibrate to recorded flow and 

stage information at different locations within the subwatershed. 

The model is considered verified when, for a set of comparable independent events, 

and without any model adjustments, stage, flow, and volume information are in 

reasonable agreement with measured data. 

5.4.4.1 Available Streamflow and Precipitation Gaging Station Records 

Rainfall depth, rainfall distribution, flow rate, flow volume, and water surface elevation 

are examples of calibration data. When selecting a calibration storm, data must be of 

sufficient temporal resolution to detail variations in intensity. Data should be recently 

acquired so that current land use and hydraulic conditions in the study area are 

accurate. To account for the non-uniform spatial distribution inherent in precipitation 

patterns in Florida, it is desirable to model rainfall depth and distribution at various 

locations throughout the subwatershed. One stage gage and numerous rainfall depth 

gages were utilized for the verification in the Turkey Creek Subwatershed. 

The U.S. Geological Survey maintained a streamflow gaging station on the Little 

Alafia River near Hopewell, from 1966 to 1979. The Survey located the gage on the 

State Road 60 bridge. These data are not utilized in the calibration of the Turkey 

Creek Subwatershed model because the land use and drainage system during the 

period of record may differ substantially from the abstracted hydrologic system. 





The Southwest Florida Water Management District, U.S. Geological Survey, and 

National Oceanographic and Atmospheric Administration report rainfall depths at a 

number of locations within and near the Turkey Creek Subwatershed. The locations 

of gages of interest are shown on Figure 5.4-4, the Alafia River Watershed 

precipitation gage location map. Specifically, the Dover, Pleasant Grove, Medard 

Lake, Hopewell, Plant City, Valrico, Alafia, and Lakeland rainfall gages are used for 

depth, distribution, or both depth and distribution in the Turkey Creek Subwatershed 

model calibration/verification. 

5.4.4.2 Calibration and Verification Storm Events 

The Turkey Creek Subwatershed is calibrated to the September 4-7, 2004 Hurricane 

Frances event, at Medard Reservoir. This is a stage calibration: flow data do not exist 

in the Turkey Creek Subwatershed for this event. Hourly stage data was acquired for 

this gage. Rainfall data for the calibration of the Turkey Creek subwatershed was 

established using 3 gages, the Dover DV-1, Dover DV-2 and Medard Lake gages. 

The rainfall totals for these three gages are 11.98 inches, 8.68 inches, 10.22 inches 

respectively. Each gage used its own rainfall distribution from the acquired rainfall 

data. The spatial distribution of the influence of each gage on subbasin areas was 

assigned using the Thiessen polygon method. This method assigns the “area of 

influence” of each gage rainfall data by using perpendicular bisectors to create 

polygons which are then intersected with the subbasin polygons to allocate the rainfall 

data within the model framework. 

Verification of the Turkey Creek Subwatershed model was performed using rainfall 

and lake stage data for the September 5-8, 1988 storm event and the December 9- 

14, 1997 El Nino storm event. The four-day storm from September 5-8, 1988 was 

actually a series of 3 individual storm events that occurred at roughly 24-hour 

intervals. An average measured rainfall for the following five selected rainfall gaging 

stations were computed for use in verification: Dover, Plant City, Valrico, Pleasant 

Grove, and Alafia. The total four-day precipitation depths recorded at these sites 

range from 9.37 inches to 13.81 inches; the average depth at the five stations is 11.87 

inches. To facilitate hourly distribution of the rainfall depth over this event, it was 

necessary to use hourly data from the National Oceanographic and Atmospheric 

Administration precipitation station at Lakeland. The distribution recorded at the 

Lakeland gage was selected for use in the verification of the Turkey Creek 

Subwatershed model because no local distribution exists for the 1988 event, and the 

Lakeland distribution correlates to the stage time-to-peak on the Medard Reservoir. 







MCINTOSH RD 

4 

Legend 

USGS Streamflow Gage 

Rainfall Gage 

County Line 



Major Roads 




Suite 120 


41 

301 

75 

75 

BUCKHORN 

301 

BIG BEND RD 

Notes: 

92 

VALRICO 


532 

RIVER WEST 

02301638 

BELL 


FISHHAWK BLVD 


MAP ID USGS SITE NAME 

02301368 PLEASANT GROVE RESERVOIR AT PLEASANT GROVE, FL 

02301000 NORTH PRONG ALAFIA RIVER AT KEYSVILLE, FL 

02301500 ALAFIA RIVER AT LITHIA, FL 

02301638 ALAFIA RIVER AT BELL SHOALS NEAR RIVERVIEW, FL 

02301300 SOUTH PRONG ALAFIA RIVER NEAR LITHIA, FL 

391 

S FORBES RD 

02301500 

FISHHAWK 

BOYETTE RD 


RIVER EAST 

31 

672 

1:180,000 

39 

0 5,000 10,000 20,000 

Feet 

0 1.25 2.5 5 

531 

Miles 

S PARK RD 

ENGLISH 

39 

320 TURKEY 

257 

60 

02301368 9 

252 

358 

204 

574 

401 

428 


02301300 

94 

Filename: 

Fig5_4 

_4.mxd 


Map Date: 



N/A 

POLK CO 

02301000 

107 

5 

596 

NORTH 

PRONG 

SOUTH 

PRONG 

Prepared By: 

Yoav 

Rappaport 

258 

426 

231 

176 

37 

60 

262 

171 

201 

213 

103 

458 

481 

438 


Precipitation and Streamflow Gages Loc. 








The preceding average five-day total rainfall for the gages of interest for the 

September 1988 verification storm event is 1.4 inches. This corresponds to the 

bottom boundary of the Antecedent Moisture Condition II range for this verification 

storm. 

The five-day storm from December 9-14, 1997 began as a few days of light rain that 

was followed by two heavy days during which most of the total rainfall volume fell. An 

average measured rainfall for the following six selected rainfall gaging stations were 

computed for use in this verification storm event: Dover DV-1, Plant City, Valrico, 

Medard Lake, Hopewell, and Dover Park. The total five-day precipitation depths 

recorded at these sites range from 4.98 inches to 6.79 inches, and the average depth 

at the six stations is approximately 5.80 inches. To facilitate hourly distribution of the 

rainfall depth over this event, the hourly data from the SWFWMD Pleasant Grove 

recording gage were used. The preceding average five-day total rainfall for the six 

gages of interest for the December 1997 verification event is 1.8 inches. This 

corresponds to the Antecedent Moisture Condition II range for this verification storm. 

5.4.4.3 Results 

Figure 5.4-5 shows the comparison of the recorded and simulated Medard Lake stage 

for the 2004 Hurricane Frances event. The figure shows an extremely good 

correlation of peak water surface elevation in timing, shape and magnitude. Although 

stage data were not recorded during the reservoir’s peak, it can be seen from the 

shape of the graph that the simulated peak is most likely close to the recorded peak. 

The recession portion of the simulation is a bit high. This is almost certainly due to 

the manually operable weir gate (4’ x 4’ sluice gat at elevation 54.09 NAVD88) at the 

lake outfall structure. It is highly likely that, in lieu of an eminent storm event (or 

during), the gates would be opened in some fashion, increasing the outflow. Without 

gate operation data available this could not be modeled accordingly. 

Figures 5.4-6, and 5.4-7 show comparisons of the recorded and simulated Medard 

Lake stage during the 1988 and 1997 verification events, respectively. The figures 

also show good correlation for both shape and timing at Medard Lake, although both 

verification events are both peak high for the simulation period. This again is likely 

due to the fact that the operational gate, for the simulated, are always in their closed 

or up position and the gates were most likely opened to some degree at some 

particular time during the actual storm event. Without the exact time and elevations of 

which the gates are moved a good verification could not be achieved. For purposes 

of verifying the model and considering the unknowns with the operational gate, the 

plots are within a reasonable range. 





FIGURE 5.4-5: Turkey Creek at Medard Reservoir 


Hourly Stage Data 

64 

64 

Recorded 

Simulated 

Elevation (ft NAVD88) 

63 

63 

62 

62 

61 

61 

60 

60 

59 

9/4/2004 

9/5/2004 

9/6/2004 

Time (days) 

9/7/2004 

9/8/2004 

9/9/2004 


September 5 - 15, 1988 Verification Storm Event 

68 

67 

Recorded 

Simulated 

66 


65 

64 

63 

62 

61 

60 

59 

58 

9/5/1988 

9/6/1988 

9/7/1988 

9/8/1988 

9/9/1988 

9/10/1988 

9/11/1988 

9/12/1988 

9/13/1988 

9/14/1988 

Time (days) 






December 9 - December 19, 1997 Verification Storm Event 

62.0 

61.5 

Recorded 

Simulated 


61.0 

60.5 

60.0 

59.5 

59.0 

58.5 

58.0 

12/9/1997 

12/10/1997 

12/11/1997 

12/12/1997 

12/13/1997 

12/14/1997 

12/15/1997 

12/16/1997 

12/17/1997 

12/18/1997 

12/19/1997 

Time (days) 

Additionally, detailed lake stage data are not available for the September 1988 

verification storm event, as the Southwest Florida Water Management District reports 

only an average daily elevation at Medard Lake during this period of record. These 

elevations are assumed to occur at noon for construction of the elevation-time plot on 

Figure 5.4-5. The U.S. Geological Survey reports a peak elevation of 62.83 ft NAVD 

on September 7 and 8. This elevation is assumed to occur on September 7 at 11 PM 

and at 12 Midnight, for construction of the elevation-time plot on Figure 5.4-5. It is 

therefore not known exactly when the water-surface elevation on Medard Lake peaks. 

The corresponding model peak water-surface elevation prediction is 65.28 feet, on 

September 8, 1988 between 2 and 5 AM. 

Figure 5.4-7 shows the peak lake water surface elevation recorded on December 14, 

1997 at 7 AM is 60.62 feet. The corresponding model peak lake water surface 

elevation is 61.42 feet, also on December 14, 1997 at 4 PM. Timing of the peak lags 

by 9 hours and water-surface elevation deviates by 0.80 feet for this verification storm 

event. 





Data limitations exist in developing the hydrodynamic verification model of the Turkey 

Creek Subwatershed. These limitations include uncertainty with respect to rainfall 

depth and distribution, especially for the 1988 event. Given these limitations and the 

great degree of change that has occurred within the subwatershed since 1988, the 

calibration and verification effort is a success. Success is measured by the degree of 

agreement obtained in simulating peak water-surface elevation and time-to-peak, for 

both the September 1997 calibration event and the both the September 1988 and 

December 1997 verification events. 


5.5 ENGLISH CREEK SUBWATERSHED 





The English Creek Subwatershed, located in the eastern portion of Hillsborough 

County, is 37.8 square miles in area. Figure 5.5-1 shows the drainage basin as it is 

defined for this study. The basin is roughly bounded by Interstate 4 to the north, 

James Redman Parkway (CR 39) to the west, and the Lakeland Regional Airport to 

the northeast. The north-south county line between Hillsborough and Polk Counties 

divides the subwatershed with about two thirds of the basin in Hillsborough County 

and one third in Polk County. Flow generally originates in the eastern and northern 

headwaters of the watershed and flows in a southwesterly direction. The English 

Creek Subwatershed outfalls at its confluence with the North Prong Alafia River 6.0 

miles upstream of the North Prong Alafia River crossing at County Road 39. 

Originally, the upper watershed consisted of a series of lakes, isolated wetlands and 

depressions where surface drainage was poorly developed. The Florida Geological 

Survey of 1966 describes numerous “perennial and ephemeral swamps and basins of 

interior drainage” across the flatlands of the region. Historically, Howell Branch and 

English Creek drained the lower watershed via small tributaries as it still does today in 

areas not hydrologically altered by mining or agricultural activities. Development of 

the northeastern portion of the English Creek Subwatershed has impacted the surface 

hydrology. These effects are readily observed on aerial photographs of the 

subwatershed. 



English Creek Subwatershed has been segregated into four major drainage 

segments. 

English Creek 

The English Creek main channel originates south of Interstate 4 and west of Coronet 

Road. The stream channel profile begins at approximately 135 ft-NAVD and drops 40 

feet to County Line Road, 3 miles downstream. Throughout this reach the stream 

travels through flat land regions marked with pockets of agriculture and bordered to 

the west with mining activities. 

The main channel of English Creek meanders southeast into Polk County for about 1 

mile and then winds west into Hillsborough County. From the point at which it 

crosses into Polk County, the stream channel remains in a relatively natural condition 

to its outfall at the North Prong of the Alafia River. It travels a distance of 

approximately 4 miles, falling another 45 feet to the outfall elevation at 52.0 feet 

NAVD. 





Horton Branch 

The headwaters of Horton Branch were originally a series of isolated wetlands in the 

southwest corner of the subwatershed, occasionally filling and over flowing to the 

Horton Branch in a west to east direction. However the physiography of this area has 

been significantly altered primarily due to phosphate mining and to agriculture. This 

reach drops 60 feet from 112.8 ft NAVD to 52.0 ft NAVD at the English Creek main 

channel 3,700 feet above the confluence with the North Prong Alafia River. 

Howell Branch 

Howell Branch, for the most part, is a series of interconnected wetlands and wet 

depressions that were altered in the mid 40's and 50's as a result of agricultural 

practices. The drainage system originates at the northwestern boundary of the basin, 

just south of the Seaboard Coastline Railroad and continues southeast to the main 

English Creek Channel. This reach begins at an elevation of 125.7 ft NAVD and falls 

60 feet over a 3.7-mile reach. 

Howell Creek 

Howell Creek is a series of isolated wetlands, high ground water areas and 

depressions that have been channelized to accommodate agricultural practices. Very 

little of the natural landscape remains. 


Existing land use conditions in the English Creek Subwatershed were determined 

using the methodology described in Chapter 4. The resultant existing land use map 

of the English Creek Subwatershed used for model development purposes is shown 

in Figure 5.5-2. This land use coverage was intersected with the subbasin 

delineations using GIS overlay techniques to develop an accurate measurement of 

the distribution of the various land use classifications within each of the defined 

subbasins in the watershed. 


N PARK RD 

4 

92 

S COLLINS ST 

ENGLISH CREEK 


DRANE FIELD RD 

HOWELL BRANCH 

HOWELL CREEK 


Polk Co 

Legend 

County Line 




Roads 




Suite 120 



39 

Notes: 

60 

HOWELL BRANCH 

HORTON BRANCH 

ENGLISH CREEK 

1:72,000 

NORTH PRONG MAIN STEM 

0 3,000 6,000 12,000 

Feet 

0 0.5 1 2 

Miles 

60 

Filename: 

Fig5_5_ 

1.mxd 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 


English Creek Subwatershed 



J:\DATA\260247_Alafia_WMP_Update\GIS\Maps\MXD\Report\Subwatersheds\ENGLISH\Fig5_5_1.mxd






percentages in the English Creek Subwatershed: 

TABLE 5.5-1 ENGLISH CREEK SUBWATERSHED 



TOTAL 

AREA 

(acres) 

PERCENTAGE OF 

SUBWATERSHED 

(%) 








Forest 2,321 9.6% 


Transportation/Communications/Utilities 1,296 5.4% 




Water 667 2.8% 

Wetland 2,769 11.5% 

Total: 24,176 100.0% 

Agricultural land uses, which include cropland, pastureland, and row and tree crops, 

are the largest single land use in the English Creek Subwatershed, comprising over 

30 percent of the subwatershed. Low density residential development (mostly rural) 

comprises over 14 percent of the subwatershed. Nearly 20 percent of the 

subwatershed remains as natural landforms (Openland Rangeland and Forest). 


wetlands. 





5.5.1.3 Soils 

Figure 5.5.3 presents the hydrologic soils classification map of the English Creek 

Subwatershed. The following table lists a composite breakdown of the distribution of 

the hydrologic soil types within the English Creek Subwatershed. It can be seen that 

over 50% of the watershed is comprised of soils that are classified as hydrologic soil 

group B/D. The hydrologic soil group C comprises over 24% of the basin, with most 

of these occurring in the central regions of the basin. There are very few hydrologic 

soil group D soils, which generally includes wetlands. Soils in the subwatershed, as 

categorized by the Natural Resources Conservation Service (NRCS), consist 

predominantly of fine sands of the Myakka (B/D), Seffner (C), Zolfo (C), and Orlando 

(A) series. 

TABLE 5.5-2 ENGLISH CREEK SUBWATERSHED 


HYDROLOGIC SOIL 

GROUP 

TOTAL AREA 

(acres) 

PERCENTAG 

OF SUBWATERSHED 

(%) 

A 3,079 12.7% 

B 0 0.0% 

B/D 12,184 50.4% 

C 6,010 24.9% 

D 2,465 10.2% 

Water 437 1.8% 

Total: 24,176 100.0% 


N PARK RD 

4 

92 


Suite 120 


Notes: 


39 

S COLLINS ST 

HOWELL BRANCH 

60 

HOWELL CREEK 

1:72,000 

HOWELL BRANCH 

HORTON BRANCH 

ENGLISH CREEK 












1900/2600 - OPEN LAND 





5000 - WATER 




Legend 

County Line 



Roads 



ENGLISH CREEK 

0 3,000 6,000 12,000 

Feet 

0 0.5 1 2 

Miles 


Polk Co 


60 


Filename: 

Fig5_5_ 

2.mxd 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 







N PARK RD 

4 

92 

S COLLINS ST 

ENGLISH CREEK 



HOWELL BRANCH 

HOWELL CREEK 


Polk Co 


A 

B 

B/D 

C 

D 

Water 

Legend 

County Line 



Roads 




Suite 120 



39 

Notes: 

60 

HOWELL BRANCH 

HORTON BRANCH 

ENGLISH CREEK 

1:72,000 


0 3,000 6,000 12,000 

Feet 

0 0.5 1 2 

Miles 

60 

Filename: 

Fig5_5_ 

3.mxd 

Map Date: 



N/A 

Prepared By: 

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Rappaport 











English Creek lies in the upper portion of the Alafia watershed and as such is 

contained primarily in the Polk Upland physiographic province. Elevations in the 

extensive Polk Upland range between 100 and 130 feet NAVD. The western edge of 

the Polk Upland is defined by the presence of the first of several paleo-shoreline 

scarps associated with the Pleistocene Ice-Age sea level fluctuations beginning at 

elevations of about 30 to 35 feet NAVD. Located above this scarp, English Creek is 

characterized by upland areas consisting of rolling hills and features associated with 

older marine terraces including sinkholes, depressions, ponds and swamps. 

At its confluence with the North Prong Alafia River, English Creek is a hardwood 

floodplain wetland at elevation 52 ft NAVD. The creek rises 4 feet in the first mile at 

the SR 60 crossing. From there the creek continues to rise over the next 2.5 miles to 

an elevation of 77 ft NAVD at the County Line Road. Traveling northeast into Polk 

County the creek invert is 89 ft NAVD at the confluence of Hamilton Branch and 

Airport Branch. The northernmost ridgeline is at an elevation of 144 ft NAVD. Total 

topographic relief throughout the basin is 90 feet. 

English Creek runs generally in a north-south direction and is roughly 9.5 miles long. 

Several named tributaries feed into the Creek. Some of the more prominent land 

features include the Lakeland Linder Airport in the northeast portion of the basin. 

There are also substantial areas that have or are in the process of being mined for 

phosphates. I-4 is just north of the basin. Major roadways include SR 92, SR 60, 

Coronet Road and County Line Road that separates Hillsborough and Polk Counties. 


Information describing the drainage facilities of the study area was compiled from a 

variety of sources and methods. Hydraulic data for culverts, bridges, control 

structures, and channel cross sections were obtained from as-built construction plans, 

previous studies, development plans, roadway plans, and field measurements. Data 

collected included elevations, lengths, dimensions, construction materials, channel 

vegetation, structure entrance and exit conditions, and any other pertinent features. 

This task required a considerable amount of effort, but it was deemed necessary to 

develop the appropriate level of detail to accurately define the hydrologic and 

hydraulic conditions of the study area. The following is a discussion of the sources 

and methods used to collect this information. Sources of data for individual elements 

of the hydraulic network are referenced in the model input file as comments and 

documented in the project files. 


Tomasino and Associates surveyed 70 structures and 162 cross sections in the 

English Creek Subwatershed for the original 2001 Alafia River WMP study. Structure 

survey data included information about the type of structure, dimensions, invert and 

weir overtop elevations. Cross section data were provided 50 feet upstream and 





downstream of surveyed structures. Cross section survey information included 

elevations across channel cross section, from top of bank to top of bank, and water 

surface elevations. Most locations were photographed. No new survey was 

performed as part of this model update. 


The methodology employed in the hydrologic model development for the 

subwatersheds in the Alafia River Watershed is discussed in Chapter 4. This 

methodology is consistent for the English Creek Subwatershed as well. 


The English Creek Subwatershed is divided into 255 individual subbasins. The 

subbasins range in size from 2.9 to 852 acres. The average subbasin size is 95 

acres. The nomenclature convention described earlier was employed also for the 

English Creek Subwatershed model. In this case, the two digit prefix "79XXXX" refers 

to the English Creek Subwatershed model junction nodes and subbasin designations. 



this study for each subbasin in the English Creek Subwatershed by an area-weighted 



were generated based on Table 4.5-1 values (See Chapter 4) for the English Creek 

Subwatershed. The resulting final subbasin runoff curve numbers for the English 

Creek Subwatershed are located in the updated Alafia River ArcGIS geodatabase. 






The English Creek Subwatershed hydraulic model is extensive, with 357 junctions 

and 207 closed conduits, 180 regular open channels, and 212 weirs. The model uses 

a link-node description of the surface drainage system to facilitate the discrete 

representation of the physical prototype. 


There are 207 closed conduits in the model as either circular, rectangular, elliptical, 

and/or arch pipes. The English Creek model also includes numerous bridge spans 

that were represented as equivalent conduits in the manner previously described in 

Chapter 4. 






Within the English Creek Subwatershed hydraulic model, there are 212 weir 

connections that are specified to represent various components of the basinwide 

drainage system. Weirs represent road overtops, pond overflow or overland flow. 

Closed basins such as those representing mined areas include berm overtop weirs for 

extreme cases of flood events. 


There are 180 irregular channel cross sections input to the English Creek 

Subwatershed model that are used to define the open channel systems and natural 

floodplains of the basin. In most cases, surveyed cross-section information was 

extended based on the SWFWMD topographic maps to provide for full floodplain 

definition. For the open channel segments within the English Creek Subwatershed 

model representation, the Manning’s n values were either confirmed or adjusted 

during the model calibration process. For the most part, the channel roughness 

coefficients ranged from a low of 0.035 for the “cleanest” channel reaches to 0.080 for 

the most highly vegetated. The floodplain roughness coefficients ranged from 0.080 

to 0.13. 


The English Creek Subwatershed has two boundary conditions with adjacent 

watersheds. Both of these boundary conditions are “popoff” locations where 

floodwaters discharge to the Hillsborough River Watershed. At E. Ohio St. (located 

off Park Rd. near Plant City), stormwater that would sheetflow west down the street is 

represented by an overland weir connection to a constant time-stage boundary node. 

The other is a driveway culvert located along Son Keen Rd. on the boundary with the 

Hillsborough River Watershed that also discharges to constant time-stage boundary 

node. 


Model Calibration for the English Creek Subwatershed was performed in conjunction 

with the North Prong Alafia River Subwatershed by examining the entire model for the 

watershed. The gaging station for calibration is located at the Keysville Road Bridge 

crossing of the North Prong Alafia River, downstream of the combined flow of both 

drainage basins. The process is fully described in the North Prong Alafia River 

section of the report. 


5.6 NORTH PRONG ALAFIA RIVER SUBWATERSHED 





The North Prong Alafia River Basin consists of approximately 98.3 square miles and 

is located east of English Creek; south of Interstate 4; west of State Road 37 and 

north of Porter Road. The subwatershed lies in eastern Hillsborough and western 

Polk Counties, with the majority of the subwatershed, approximately 82 square miles, 

in Polk County. Figure 5.6-1 depicts the boundaries of the subwatershed. Flow 

originates in the eastern headwaters of the watershed and flows in a generally 

western direction. The watershed outfalls at the confluence with the South Prong 

Alafia River, and from this point westward these two systems form the main stem of 

the Alafia River. The confluence is located approximately 0.5 miles east of County 

Road 39. 

The majority of the land use within the watershed has been modified for agricultural, 

phosphate mining and residential development. Historically the upper watershed 

consisted of a series of lakes, isolated wetlands and depressions that over flowed 

from one to the other eventually discharging to the main channel segment. Few of 

these natural wetlands and drainage ways remain, especially in Polk County. The 

eastern and southern portions of the subwatershed have been highly altered due to 

phosphate mining. The large pits and settling ponds created by the mining activity 

have left numerous closed basins within the subwatershed. 

The largest major water body that still resembles a natural system is Scott Lake, 

located in the northeast corner of the subwatershed. Other major features are SR 37, 

which bisects the subwatershed north to south, and SR 60, which runs through the 

center of the subwatershed east to west. The town of Mulberry is the largest 

metropolis in the subwatershed, and it is centered at the intersection of SR 37 and SR 

60. 



North Prong Alafia River Basin has been segregated into five major drainage 

segments. 

North Prong Alafia River Main Channel 

The North Prong Alafia River main channel originates just east of SR 37 in Polk 

County. The stream channel profile begins at approximately 117 ft NAVD and has 

been previously channelized for the most part. Residential, mining and agricultural 

practices have all but eliminated all but the main conveyance system. 

Sloman Branch 

The Sloman Branch originates south of Nichols Road and north of Edison Road, just 

west of the county line. The flow is from south to north into the main conveyance 





system. The land use has been greatly affected by phosphatic mining and 

agriculture. 

Poley Creek 

The Poley Creek drainage is located south of Medulla Road and west of SR 37, within 

the northeast corner of the North Prong Alafia River Basin. This creek is entirely 

within Polk County and is not within this plan’s scope of services. However, based on 

detailed study data, the system was added in this model. Flow is north to south to the 

main conveyance system. 

Lake Drain 

Lake Drain is entirely within Polk County and is a tributary of Poley Creek. 

Historically, the drainage was a series of isolated wetlands, ponds, and depressions 

that under large storm events would sheet flow in a southwesterly direction to Poley 

Creek. As a result of agricultural and residential development, the drainage has been 

channelized. In fact, Scott Lake is now drained to Poley Creek through this outfall. 

Thirty-Mile Creek 

Thirty Mile Creek is just east of Sloman Branch. The flow is from east to northwest to 

the main conveyance. The surrounding land use has been greatly affected due to 

mining. All but the main system has been altered. 


Existing land use conditions in the North Prong Alafia River Subwatershed were 

defined by use of digital coverages obtained from the Southwest Florida Water 

Management District (SWFWMD) Geographic Information System (GIS) database. 

These 1990 GIS coverages are based on the Florida Land Use and Cover 

Classification System (FLUCCS). As discussed previously, the original set of 

SWFWMD land use classifications was consolidated into a set of fourteen. 

The resultant existing land use map of the North Prong Alafia River Subwatershed 

that was used for model development purposes is shown in Figure 5.6-2. This land 

use coverage was intersected with the subbasin delineations using GIS overlay 

techniques to develop an accurate measurement of the distribution of the various land 

use classifications within each of the defined subbasins in the watershed. 






percentages in the North Prong Alafia River Subwatershed: 

TABLE 5.6-1 NORTH PRONG SUBWATERSHED 



TOTAL 

AREA 

(acres) 

PERCENTAGE OF 

SUBWATERSHED 

(%) 




Commercial 1,148 1.8% 



Cropland and Pasture land 5,038 8.0% 

Forest 3,137 5.0% 


Transportation/Communications/Utilities 756 1.2% 




Water 1,809 2.9% 

Wetland 6,421 10.2% 

Total: 62,918 100.0% 

It is apparent from this table, and by visual inspection of the original Southwest 

Florida Water Management District 1995 land use coverage and U.S. Geological 

Survey quadrangle that land use in the North Prong Alafia River Subwatershed is 

dominated by either active mine lands, reclaimed mine lands, or lands owned by mine 

interests that are yet to be mined; nearly 44 percent of the subwatershed is classified 

by SWFWMD as mined lands. Agricultural land uses, which include cropland, 

pastureland, and row and tree crops, comprise 8 percent of the subwatershed. 

Residential development, mostly low and medium density, comprises nearly 20 

percent of the subwatershed. Approximately 11 percent of the subwatershed remains 

as natural landforms. Approximately 13 percent of the subwatershed is comprised of 

waterbodies and wetlands. 


4 


Polk Co 

POLEY CREEK 

LAKE DRAIN 

540 

Scott 

Lake 

60 

CARTER RD 

39 

POLEY CREEK 

37 

Legend 

County Line 




Roads 




Suite 120 


ALAFIA RIVER 


SOUTH PRONG MAIN STEM 

Notes: 

SLOMAN BRANCH 


THIRTY MILE CREEK 


1:100,000 

640 

0 3,000 6,000 12,000 

Feet 

0 0.5 1 2 

Miles 

Filename: 

Fig5_6_ 

1.mxd 

60 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 


North Prong Alafia River Subwatershed 



J:\DATA\260247_Alafia_WMP_Update\GIS\Maps\MXD\Report\Subwatersheds\N_PRONG\Fig5_6_1.mxd


4 











1900/2600 - OPEN LAND 





5000 - WATER 




Legend 

County Line 



Roads 




Suite 120 


ALAFIA RIVER 

39 


Notes: 


60 

SLOMAN BRANCH 



Polk Co 

1:100,000 

0 3,000 6,000 12,000 

Feet 

0 0.5 1 2 

Miles 

POLEY CREEK 


POLEY CREEK 


Filename: 

Fig5_6_ 

2.mxd 

640 

LAKE DRAIN 

Map Date: 



N/A 

37 

Prepared By: 

Yoav 

Rappaport 

CARTER RD 

60 

540 

Scott 

Lake 










5.6.1.3 Soils 

Soils within the North Prong Alafia River Subwatershed were categorized according to 

this hydrologic soil group classification system, as defined by the Natural Resource 

Conservation Service. Similar to the calculation of land use acreages, the distribution 

of hydrologic soil types within each subbasin was determined by intersection of the 

soils coverage in the GIS database with the subbasin delineations. Figure 5.6-3 

presents the North Prong Alafia River Subwatershed hydrologic soils classification 

map that was developed for this study. The following table lists a composite 

breakdown of the distribution of the hydrologic soil types within the North Prong Alafia 

River Creek Basin: 

TABLE 5.6-2 NORTH PRONG SUBWATERSHED 



GROUP 

TOTAL AREA 

(acres) 

PERCENTAGE OF 

SUBWATERSHED 

(%) 

A 20,552 32.7% 

B 5 0.0% 

B/D 13,921 22.1% 

C 15,490 24.6% 

D 10,527 16.7% 

Water 2,423 3.9% 

Total 62,918 100.0% 

It can be seen that over 32% of the watershed is comprised of soils that are classified 

as hydrologic soil group A. Nearly 25% of the basin is classified as hydrologic soil 

group C soils and another 22% as soil group B/D. There are very few hydrologic soil 

group B soils that occur in the subwatershed. A large portion of soils is classified as 

Arents or man-made soils due to remnants of past mining activity. Soils in the 

subwatershed, as categorized by the Natural Resources Conservation Service 

(NRCS), consist predominantly of fine sands of the Chandler (A), Lake (A), 

Tavares(A), Myakka (B/D), Winder (B/D), Zolfo (C), and Sparr (C) series. 


The North Prong Alafia River Subwatershed lies between the English Creek 

Subwatershed and the South Prong Alafia River Subwatershed. It is roughly 12 miles 

long in a north-south direction and 9 miles wide in an east-west direction with the river 

generally flowing in a west to east direction. The majority of the subwatershed is 

located in Polk County. 





The North Prong Alafia River Watershed is classified as a part of the central 

Highlands physiographic province. The Central Highlands are gently undulating to 

rolling areas. Lakeland Ridge, the westernmost of three north-south ridges in Polk 

County, forms the eastern boundary of the North Prong Alafia River. The Polk 

Uplands generally range in elevation from 100 to 130 feet above NAVD. Topographic 

relief over the subwatershed is 115 feet. 

The 1966 Florida Geological Survey, Report of Investigations No. 44 states that the 

Lakeland Ridge is, as are all three ridges, being slowly lowered and dissected by 

sinkholes. The Lakeland Ridge has numerous large non-lake sinks, although the 

eastern boundary of the subwatershed has been completely altered by mining activity. 



Plans for the “Carlton Arms of Lakeland”, the Nichols Mine, and the Mobile Mine were 

used as sources of information. Information containing dragline crossings of the North 

Prong Alafia River by AGRIFOS were also used. These plans were obtained from 

either the Southwest Florida Water Management District’s permit records or from Polk 

County. 

Roadway Plans 

All of the latest available roadway plans were utilized for the update of the Alafia River 

WMP. 


For the original 2001 Alafia River WMP study, Tomasino & Associates and Wilson 

Miller & Associates surveyed approximately 13 structures and 27 cross sections in the 

Hillsborough County portion of the North Prong Alafia River Subwatershed. 

Information collected at the structure surveys included type of structure, dimensions, 

material type, inverts and weir overtop elevations. Upstream and downstream 

channel cross-sections were taken at each structure location. Cross section surveys 

included data on location, orientation, ground and water surface elevations. No new 

survey was performed as part of this model update. 

Parsons also conducted field observations within the North Prong Alafia River 

Subwatershed at flood problem areas and at structure locations that were not 

contracted for professional survey. Neither professional survey nor field observations 

were conducted within Polk County. 




methodology is consistent for the North Prong Subwatershed as well. 


4 


Polk Co 

POLEY CREEK 

LAKE DRAIN 

540 

Scott 

Lake 

60 

CARTER RD 

39 

POLEY CREEK 

37 


A 

B 

B/D 

C 

D 

Water 

Legend 

County Line 



Roads 




Suite 120 


ALAFIA RIVER 



SLOMAN BRANCH 


Notes: 



1:100,000 

640 

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Feet 

0 0.5 1 2 

Miles 

Filename: 

Fig5_6_ 

3.mxd 

60 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 











The North Prong Alafia River Subwatershed was divided into a total of 241 discrete 

subbasins that range in size from 13.8 to 2399 acres. The average subbasin size is 

approximately 261 acres. The delineation of individual subbasins was dictated to a 

large extent by the primary drainage network itself and the need to properly define the 

contributing drainage area to individual elements of the conveyance system and 

storage facilities. 

The North Prong Alafia River Subwatershed is subdivided into its 241 individual 

subbasins. The nomenclature convention for the SWMM model representation 

assigns the subbasin name corresponding to the model junction (node) that serves as 

the outfall for the subbasin. The first two digits of the six-digit code refer to the major 

subwatershed, as a part of the Alafia River Watershed. In this case, “78XXXX” refers 

to the North Prong Alafia River Subwatershed. In some cases, a model junction may 

have more than one individual subbasin which discharges to it. In such instances, the 

additional subbasin names will be sequential and not the same as the receiving 

junction name. Subbasin designations were also selected to segregate drainage 

areas of homogeneous land use and/or define the complete contributing drainage 

area of a secondary drainage system at its outfall to the modeled primary network. 



this study for each subbasin in the North Prong Alafia River Subwatershed by an 



runoff curve numbers were generated based on Table 4.5-1 values (See Chapter 4). 

The resulting final subbasin runoff curve numbers for the North Prong Alafia River 

Subwatershed are presented in the updated Alafia River ArcGIS geodatabase 





Only a small portion of the North Prong Alafia River Subwatershed lies within 

Hillsborough County. While it was necessary to account for attenuation and proper 

surface water runoff from the Polk County portion of the watershed in order to 

accurately model the Hillsborough County portion of the subwatershed, it was not 

within the scope of this study to provide more than that. Available topographic 

mapping was limited along the eastern side of the subwatershed, as was other 

hydrologic information. The main channel system through Polk County was modeled 

based on available FEMA data and cross sections. The North Prong Alafia River 

Subwatershed hydraulic model is quite comprehensive. It comprises a total of 280 

junctions and 386 links in its structure, including 240 conduits, and 146 weirs. 






The hydrodynamic model of the North Prong Alafia River Subwatershed consists of a 

network of open channel segments, culverts, bridges, phosphate mine storage areas, 

weirs, lakes, ponds, and wetlands. These hydrologic elements comprise the primary 

drainage system. The model uses a conduit-junction abstraction of the drainage 

system. A junction is a discrete location in the system where mass is conserved. 

Conduits connect junctions; conduits convey water through the system. The network 

of junctions and conduits serves as the computational framework for the Extended 

Transport Block. As previously noted, Hillsborough County uses a six-character code 

to describe the subwatershed. The first two digits refer to subwatershed: “78xxxx” 

refers to the North Prong Alafia River Subwatershed. The next four characters follow 

an ascending progression from downstream points of the system upstream. By 

convention, the identification of a conduit between two junctions is the same as the 

name of the upstream junction, with a one-character prefix that designates the type of 

conduit. The following prefixes are used in this model: 

• 1-5: closed conduit 

• 6: overland flow connection 

• 7: roadway overtop weir 

• 8: sharp-crested or broad-crested weir 

• 9: designates an open channel 



within the North Prong Alafia River Subwatershed, it was important that all significant 

storage facilities and their hydraulic functions be defined. As described in Chapter 4, 

the initial (starting) water surface elevations for these variable storage facilities were 










The North Prong Alafia River Subwatershed model includes 90 closed conduits that 

take the various forms of circular, rectangular, elliptical, and/or arch pipes that are 

allowed by the EXTRAN model formulation. Data are from surveys, and other backup 

data. Bridge spans were represented as either an open channel or some combination 

of equivalent closed conduits, typically rectangular box culverts with different 

dimensions and inverts. This scheme allows for the surcharge condition to be 

modeled. 






Within the North Prong Alafia River Subwatershed hydraulic model, there are a total 

of 146 weir connections that are specified to represent these various components of 

the basin wide drainage system. These various components can be overtopping of 

roadways at channel crossings, pond banks, control structures and overland flow. All 

closed basins associated with phosphate mines include a top-of-bank weir to allow 

overtopping of the storage area during extreme flood events. Similarly, all road 

crossings also include a top-of-road weir. 


Within the North Prong Alafia River Subwatershed model representation, there are a 

total of 150 channel cross sections that are used to define the open channel systems 

and natural floodplains of the basin. The natural overbank floodplain was explicitly 

modeled so as to include both floodplain storage and its conveyance function. For 

this reason most of the surveyed channel cross section data was extended based on 

topographic maps to define the full extent of this floodplain. Manning’s coefficients 

were assigned to the channel reach, and also to the left and right floodplain reaches. 

Selection of the Manning’s coefficient was based on vegetation, meander, bottom 

material, and depth of flow. Values were supported by published guides and past 

modeling experience. 









stage information at different locations within the subwatershed. The model is 

considered verified when, for a set of comparable independent events, and without 

any model adjustments, stage, flow, and volume information are in reasonable 

agreement with measured data. 


Within the North Prong Alafia River Subwatershed, historical streamflow and 

precipitation data are readily available to meet the set of conditions listed above for 

the purpose of model calibration and verification. Parsons obtained hourly streamflow 

and stage data from the U.S. Geological Survey streamflow gaging station 

(02301000), which is located on the upstream side of the Keysville Road bridge, 

approximately 0.6 miles upstream from CR 39. The USGS has operated this 

streamflow gaging station within the basin continuously from May 1950 to the present. 

Over this 58-year period of record, the selected maximum instantaneous peak flow 

that was recorded was 9,570 cfs on September 11, 1960. At that time, the maximum 





observed flood elevation was 53.52 ft NAVD, approximately 15.6 feet deep above the 

channel bottom. The USGS rates the relative accuracy of the streamflow gaging data 

at this station as "good", indicating that about 95 percent of the daily discharges are 

within 10 percent of their true values. 

It should be noted that the location of the USGS streamflow gaging station on the 

North Prong Alafia River is approximately 3.0 miles downstream of its confluence with 

English Creek. Therefore, the measured streamflow data includes the flow from the 

English Creek Subwatershed, and model calibration to this data provides the basis for 

calibration of the English Creek Subwatershed model. 

Recorded precipitation data for gages in the vicinity of the North Prong Alafia River 

and English Creek Subwatersheds were obtained from the Southwest Florida Water 

Management District (SWFWMD) and the National Oceanographic and Atmospheric 

Administration (NOAA). The locations of the nearby gages that were operating during 

the period of record for which corresponding streamflow gaging data are available are 

shown on the Alafia River precipitation gage location map shown in Figure 5.1-5. 

From this map, it can be seen that there are more than twenty historical precipitation 

gaging stations located within the geographic proximity of the North Prong Alafia 

River and English Creek Subwatersheds. It should be considered that, for most of 

those stations shown, the historical data consist only of daily accumulations of 

recorded precipitation and that the time of day of gage observation will differ between 

sites. For most of the period of record (until the last ~8 years), the only recording 

precipitation gaging stations (i.e. hourly data) that were in operation were those 

NOAA stations at the Tampa International Airport, Parrish, and Lakeland, and one 

SWFWMD station located at Pierce (in Polk County). Most recently, the SWFWMD 

has installed and operated recording precipitation stations at an additional seven 

locations in the geographic vicinity, those SCADA stations being the Medard Lake 

(Pleasant Grove), Mulberry, Dover DV-1, Four Corners, Thatcher, Alafia, and Starling 

stations. 


Calibration of the North Prong Alafia River and English Creek Subwatershed 

contributing runoff was performed using rainfall and streamflow gaging station data for 

the September 4-7, 2004 (Hurricane Frances) historical storm event as the basis for 

adjusting the initial model input data, including the hydraulic input parameters. The 

verification of the model was conducted using the September 5-8, 1988 and the 

December 9-14, 1997 historical storm events. 

The North Prong/English Creek Subwatersheds are calibrated to the September 4-7, 

2004 Hurricane Frances event, at USGS gaging station 02301000. Stage and flow 

data were readily available for this gage during the calibration period. Rainfall data 

for the calibration of this drainage area was established using 4 gages, the Lakeland 

Public works, Pierce, Country Oaks and Medard Lake gages. The rainfall totals for 

these four gages are 10.47 inches, 7.61 inches, 12.03 and10.22 inches respectively 





with the Pierce gage having the greatest area of influence. Each gage used its own 

rainfall distribution from the acquired rainfall data as all had 1-hour rainfall totals. The 

spatial distribution of the influence of each gage on subbasin areas was assigned 

using the Thiessen polygon method. This method assigns the “area of influence” of 

each gage rainfall data by using perpendicular bisectors to create polygons which are 

then intersected with the subbasin polygons to allocate the rainfall data within the 

model framework. 

Verification of the model at this gage was performed using the September 5-8, 1988 

historical storm event and the December 9-14, 1997 historical storm events. The 

four-day storm that occurred from September 5-8, 1988 was actually a series of 3 

individual storm events that occurred at roughly 24-hour intervals. Because of the 

relative scarcity of data of available hourly recorded data for this event, the combined 

North Prong Alafia River and English Creek Subwatershed areas were divided into 

zones that reflected similar rainfall patterns during this event, since it was apparent 

that precipitation was not spatially uniform over the total drainage basin. Because of 

the large variance between gaging station totals, it was considered more prudent to 

utilize the average precipitation over these “zones” rather than use the individual 

records with a Thiessen weighting procedure, thus reducing any bias induced by 

potentially erroneous individual records. This potentially wide range of recorded 

precipitation over the expanse of the subwatershed leads to uncertainties in the 

model calibration process that are lessened through such an averaging procedure. 

A total measured rainfall of 7.00 inches was used from gaging station at Lakeland 

Linder Airport to represent the storm event as it occurred over the English Creek 

Subwatershed. A similar amount of rain was recorded over the northern portion of the 

North Prong Alafia River Subwatershed, and an average of 7.19 inches was 

computed for use in the model simulations. Stations selected for this computation 

were the Lakeland Tower, Lakeland NOAA and Mulberry precipitation gages. 

Average rainfall of 8.52 inches was calculated for the southern portion of the North 

Prong Alafia River Subwatershed (including Thirty-Mile Creek and the South Prong 

Alafia River) using the Mulberry, Pierce, Hookers Prairie, SPCW, Haynesworth, Big 

Four Mine, and Ft. Green precipitation gaging stations. 

To facilitate hourly distribution of the total rainfall volume over the course of the 

September 1988 storm event, it was decided to use the hourly data from the NOAA 

precipitation station at Lakeland (Polk County). The distribution recorded at the 

Lakeland gage was selected for use in the physical calibration of the combined North 

Prong Alafia River and English Creek Subwatershed model because, of the few such 

records available, it appeared to best correlate to the streamflow gaging station 

records in terms of timing. 

Antecedent Moisture Condition (AMC) was used to determine the degree to which the 

soil column is moistened at the beginning of a storm event. For the Alafia River 

Watershed update, the AMC II condition was used for modeling. The preceding 5-day 





total rainfall for the September 1988 calibration storm event for the precipitation gages 

that were used for the combined North Prong Alafia River and English Creek model 

calibration generally fell within the 1.4 to 2.1 inch range that defines an AMC II 

condition. 

The five-day storm from December 9-14, 1997 provided the basis for a second model 

verification storm event. It began as a few days of light rain that were followed by two 

heavy days during which most of the total rainfall volume fell. An average measured 

rainfall for the following seven selected rainfall gaging stations were computed for use 

in this verification storm event to represent the rainfall in the upper North Prong Alafia 

River Subwatershed: Lakeland South, Lakeland Tower, Pierce, Pierce Agrico, 

Mulberry ROMP and Mulberry. The total five-day precipitation depths recorded at 

these sites range from 4.98 inches to 5.75 inches, and the average depth at the five 

stations is 5.34 inches. The data were very consistent throughout this geographic 

region. The English Creek Subwatershed precipitation data were also somewhat 

uniform, with totals somewhat greater in this zone. An average total rainfall of 5.77 

inches was calculated from the Medard, Mulberry ROMP, Plant City, Lakeland, 

Mulberry and Hopewell precipitation gaging stations. Again, the preceding 5-day total 

rainfall for this event generally fell within the AMC II range for the gaging stations 

located within the watersheds. To facilitate hourly distribution of the rainfall depth 

over this event, the hourly data from the SWFWMD Pleasant Grove recording gage 

were used. 


Calibration Parameters 

As documented in previous model calibration discussions, most of the SWMM model 

input data are used simply to describe the geometry and size of the hydrologic and 

hydraulic units of the study area and are subject to very little interpretation. Those 

model parameters that can be considered to be calibration parameters include: 

• Runoff curve numbers (CNs) for different soil groups and land use 

classifications, 

• Channel, floodplain, and culvert roughness coefficients (Manning's n) and 

loss coefficients, 

• Times of concentration for individual subbasins, and 

• Unit hydrograph shape factors. 

In the SWMM model calibration for the North Prong Alafia River Subwatershed, these 

parameters were initially derived using accepted methods and values derived from 

literature research and from past model applications in the region. Their final values 

were ultimately derived through the model calibration process. 





Channel and floodplain roughness coefficients (Manning's n) were calibrated by using 

the rating curve developed by the USGS for its streamflow gaging station as the 

means of comparison. A rating curve is the relationship between stage (elevation) 

and discharge at a particular location along the length of a stream channel. The 

USGS establishes this relationship through a series of flow measurements, 

determined by measuring velocities across a flow transect, at times of different flow 

conditions at that same location. The scatter in the measured flow data points is an 

indication of the accuracy of the gaging station, as was previously discussed. Once 

established, the rating curve is then used to convert stage measurements at the 

gaging station to streamflow. Therefore, for the SWMM model to accurately 

reproduce both the historical streamflow and stage hydrographs at the USGS 

streamflow gaging station, it must also match the rating curves at the station. If a 

reasonable fit to the rating curve is not attained, you cannot have a good calibration of 

both stage and flow at that location. 

The method for calibrating to the gaging station rating curve was to adjust the channel 

and floodplain Manning's n values in the most immediate downstream channel 

reaches from the gaging station location at the Keysville Road bridge. Since a rating 

curve is available only at the gaging station, there is insufficient information to 

calibrate the channel roughness coefficients for the entirety of the North Prong Alafia 

River and English Creek Subwatersheds. What this exercise provided was the basis 

for the estimation of the channel and floodplain roughness coefficients in the other 

channel reaches of the basin. References found in engineering literature were also 

used in this process. 

Calibration and Verification Results 

The Alafia River model was calibrated to the September 4, 2004 through the 

September 9, 2004 Hurricane Frances storm event. Figures 5.6-4 and 5.6-5 show 

comparisons of the recorded and simulated flows and stages at the USGS 02301000 

streamflow gaging station at Keysville Rd. For this calibration simulation, it was 

necessary to initiate flows that matched existing flows at the gage prior to the onset of 

the storm event, approximately 525 cfs on September 4, 12:00 AM, by creating 

baseflow using the HCSWMM “D” card input. Simulation results for both stage and 

flow hydrographs compare extremely well in shape, timing and magnitude including a 

well simulated recession limb. A peak stage of 52.83 NAVD was recorded on 

September 6 at 12:00 PM and the corresponding simulated peak stage is 53.34 an 

hour earlier at 11:00 PM. Recorded peak flow at the gage was 9550 cfs, which 

compares well with the simulated peak flow of 9400 cfs, while the simulated peak 

does occur 2 hours earlier than the recorded. 

The verification event for the combined Alafia River model was run for a 10-day time 

period from September 5 through September 14, 1988 because of the importance to 

consider both the peak conditions in the watershed and the recession limb of the flood 

hydrograph during calibration. Figures 5.6-6 and 5.6-7 show comparisons of the 

recorded and simulated flows and stages, respectively, at the USGS streamflow 





gaging station at the Keysville Road bridge. The model formulation was adjusted at 

the initiation of the event by the addition of groundwater baseflows in the 

subwatersheds that amounted to a total of 160 cfs at this location. As can be seen in 

the two figures, there is very good correlation during peak flow conditions in both the 

magnitude and timing of flows and flood elevations. 

The peak flow that was recorded at the gaging station on September 7, 1988 was 

4660 cfs. The corresponding model prediction is 5625 cfs, an over-simulation of 

approximately 20%. The model also deviates by only 0.44 feet from the maximum 

flood elevation that was recorded (50.79 ft NAVD observed versus 51.23 ft NAVD 

simulated). The overall hydrograph shapes for stage and flow also compare quite 

well. 

Verification of the combined Alafia River model was also conducted by the simulation 

of the 11-day time period from December 9 through December 19, 1997. Figures 5.6- 

8 and 5.6-9 show comparisons of the recorded and simulated flows and stages, 

respectively, at the USGS streamflow gaging station at the Keysville Road bridge. 

The model formulation was, again, adjusted at the initiation of the event by the 

addition of groundwater baseflows in the subwatersheds that amounted to 

approximately 160 cfs at this location. 





FIGURE 5.6-4: North Prong Alafia River at Keysville 

(USGS 02301000) September 4-10, 2004 Calibration Storm Event 

12000 

11000 

10000 

Recorded 

Simulated 

9000 


8000 

7000 

6000 

5000 

4000 

3000 

2000 

1000 

0 

9/4/2004 

9/5/2004 

9/6/2004 

9/7/2004 

Time (days) 

9/8/2004 

9/9/2004 



56 

54 

Recorded 

Simulated 


52 

50 

48 

46 

44 

42 

9/4/2004 

9/5/2004 

9/6/2004 

9/7/2004 

9/8/2004 

9/9/2004 

Time (days) 








7000 

6500 

6000 

5500 

5000 

4500 

4000 

3500 

3000 

2500 

2000 

1500 

1000 

500 

0 

Recorded 

Simulated 

9/5/88 

9/6/88 

9/7/88 

9/8/88 

9/9/88 

9/10/88 

9/11/88 

9/12/88 

9/13/88 

9/14/88 

9/15/88 

Time (days) 




54 

53 

52 

51 

50 

49 

48 

47 

46 

45 

44 

43 

42 

41 

40 

Recorded 

Simulated 

9/5/88 

9/6/88 

9/7/88 

9/8/88 

9/9/88 

9/10/88 

9/11/88 

9/12/88 

9/13/88 

9/14/88 

9/15/88 

Time (days) 







6000 

5500 

5000 

Recorded 

Simulated 

4500 


4000 

3500 

3000 

2500 

2000 

1500 

1000 

500 

0 

12/9/1997 

12/10/1997 

12/11/1997 

12/12/1997 

12/13/1997 

12/14/1997 

Time (days) 

12/15/1997 

12/16/1997 

12/17/1997 

12/18/1997 

12/19/1997 



52 

51 

50 

Recorded 

Simulated 


49 

48 

47 

46 

45 

44 

43 

42 

41 

40 

12/9/1997 

12/10/1997 

12/11/1997 

12/12/1997 

12/13/1997 

12/14/1997 

Time (days) 

12/15/1997 

12/16/1997 

12/17/1997 

12/18/1997 

12/19/1997 





As can be seen in the two figures, although the general timing and shape of the 

hydrographs compare quite well, the model does over-predict the peak flow 

conditions at the gage. The peak flow that was recorded at the gaging station on 

December 13, 1997 was 3288 cfs. The corresponding model prediction is 5030 cfs. 

In spite of this, the model deviates by only 0.9 feet from the maximum flood elevation 

that was recorded (49.85 ft NAVD observed versus 50.74 ft NAVD simulated). 

Considering the land use changes within this portion of the watershed and quality of 

the calibration for the model configuration, this is a reasonable verification of the 

model. It is likely that the lack of available storage in the upper part of this basin for 

our model setup is the reason for the excess flows in this verification simulation. 

Figure 5.6-10 shows a comparison of the model results to the USGS streamflow 

gaging station rating curve. As can be seen from this plot, the model hydraulic 

representation is a close match to the station record at this location. Therefore, the 

channel and floodplain roughness coefficients that are used in the model for this 

channel segment are judged to be well-suited. 

55 


(USGS Gage Number 02301000) Rating Curve Comparison 

50 

Stage (ft NAVD) 

45 

40 

USGS Rating Curve 

Simulated 

35 

0 2000 4000 6000 8000 10000 12000 14000 



5.7 SOUTH PRONG ALAFIA RIVER SUBWATERSHED 





The South Prong Alafia River Subwatershed is located in the southeast portion of the 

Alafia River Watershed, in both Hillsborough and Polk Counties. The subwatershed, 

shown in Figure 5.7-1, drains 134 square miles. Flow in the South Prong Alafia River 

originates in the southeast, flows east, then north. The South Prong Alafia River 

discharges to the Alafia River at a location one-half mile upstream of the South 

County Road 39 Bridge over the Alafia River. 

The subwatershed is roughly bounded by the following landmarks: County Road 39 to 

the east; State Road 674 to the south; State Road 37 to the west; and Lithia-Pinecrest 

Road to the north. The Hillsborough-Polk County Line bisects the subwatershed into 

approximately equal east and west halves; a line that begins at the intersection of 

Gray Road and South County Road 39 and extends in an easterly direction bisects 

the subwatershed into approximately equal north and south halves. The 

subwatershed is approximately nine miles long, along the central north-south axis; 

and seventeen miles long, along the central east-west axis. 

The natural hydrologic system in the South Prong Alafia River Subwatershed 

probably consisted of isolated wetlands; swamps and depression areas in the east; 

and small lake, depression areas, and wetland systems in the west and north. The 

eastern area probably only discharged to the South Prong Alafia River during large 

storm events. Historically, connections between the South Prong Alafia River and the 

western and northern areas were probably more direct than connections in the 

eastern area. Anthropogenic land use changes from the natural condition to 

phosphate mining and agriculture significantly altered the hydrologic system in the 

subwatershed. 

Ground elevations range from 30 ft NAVD in the northwest, near the outfall of South 

Prong Alafia River into the Alafia River, to 180 ft NAVD in the east. This 150-foot 

elevation change occurs over 22 miles following the South Prong Alafia River in a 

general U-shape, or 15 miles following a straight line. Subwatershed slope is 

approximately seven feet per mile, or 0.1 percent. 


The South Prong Alafia River -- the major drainage feature in the subwatershed -- and 

five minor drainage features comprise the primary drainage system. This subsection 

contains descriptions of these six drainage features. 





South Prong Alafia River (main channel) 

South Prong Alafia River originates in Hookers Prairie, a wetland area southeast of 

Bradley Junction. The channel profile ranges from 29 feet NAVD at the Alafia River to 

120 feet NAVD at the upstream end. The South Prong Alafia River discharges to the 

Alafia River in Section 19, Township 30, Range 22. The South Prong Alafia River is 

22 miles long. Channel slope is 4.1 feet per mile or 0.07 percent. 

The South Prong Alafia River flows through seven hydraulic structures within 

Hillsborough County. The following six roads cross the South Prong Alafia River: 

Lithia-Pinecrest Road, Jameson Road, Thatcher Road, Kingsford-Four Corners Mine 

Road, Fort Lonesome Plant Road, and Bethlehem Road. A drag-line crossing was 

constructed in the late 1990s just downstream of the Fort Lonesome Plant Road. IMC 

Agrico Company, a phosphate mining company, uses the dragline crossing to move 

heavy mine equipment from one side of the river to the other. The South Prong Alafia 

River drains 85,751 acres, or 134 square miles, at its outfall to the Alafia River. 

West Branch South Prong Alafia River 

West Branch South Prong Alafia River originates near a reclaimed mining area 

southeast of the Blue Cemetery in Section 25, Township 30, Range 22. The channel 

profile ranges from 34 feet NAVD at the South Prong Alafia River to 128 feet NAVD at 

the upstream end. The outfall of the West Branch South Prong Alafia River to the 

South Prong Alafia River is in Section 21, Township 30, Range 22. The West Branch 

South Prong Alafia River is 3.6 miles long. Channel slope is 26.1 feet per mile or 0.49 

percent. 

The West Branch South Prong Alafia River flows through 10 hydraulic structures. 

The following five roads cross the West Branch South Prong Alafia River: Dry Bridge 

Road, East Keysville Road, George Smith Road, Gina Trail and Lithia-Pinecrest 

Road. West Branch South Prong Alafia River drains approximately 2,895 acres, or 

4.5 square miles, at its outfall to the South Prong Alafia River. 

Mizelle Creek 

Mizelle Creek originates near a series of mining areas southeast of George Smith 

Road. The channel profile ranges from 36 ft NAVD at the South Prong Alafia River to 

141 feet NAVD at the upstream end. The outfall of Mizelle Creek to the South Prong 

Alafia River is in Section 28, Township 30, Range 22. Mizelle Creek is 4.7 miles long. 

Channel slope is 22.4 feet per mile or 0.43 percent. 

Mizelle Creek flows through 4 hydraulic structures. East Keysville Road and Walter 

Hunter Road cross Mizelle Creek. Mizelle Creek drains 6,783 acres, or 10.6 square 

miles, at its outfall to the South Prong Alafia River. 



ALAFIA RIVER 

N PRONG MAIN STEM 



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Chito Branch 

Chito Branch originates near a mining area west of County Road 39 in Section 7, 

Township 31, and Range 22. The channel profile ranges from 41 feet NAVD at the 

South Prong Alafia River to 87 feet NAVD at the upstream end. The outfall of Chito 

Branch to the South Prong Alafia River is in Section 33, Township 30, Range 22. 

Chito Branch is 4.6 miles long. Channel slope is 10.1 feet per mile or 0.20 percent. 

Chito Branch flows through 4 hydraulic structures. Wendel Avenue and South County 

Road 39 cross Chito Branch. Chito Branch drains 5,105 acres, or 8.0 square miles, 

at its outfall to the South Prong Alafia River. 

Hurrah Creek 

Hurrah Creek originates in a series of cascading wetlands west of County Road 39 in 

Section 1, Township 32, Range 21. The channel profile ranges from 55 NAVD feet at 

the South Prong Alafia River to 80 feet NAVD at the upstream end. The outfall of 

Hurrah Creek to the South Prong Alafia River is in Section 20, Township 31, Range 

22. Hurrah Creek is 4.1 miles long. Channel slope is 5.7 feet per mile or 0.11 

percent. 

Hurrah Creek flows through 2 hydraulic structures. County Road 39 and County 

Road 672 cross Hurrah Creek. Hurrah Creek drains 6,834 acres, or 10.7 square 

miles, at its outfall to the South Prong Alafia River. 

Lewis Branch flows through 2 hydraulic structures. There are no road crossings on 

Lewis Branch. Lewis Branch drains 1,682 acres, or 2.6 square miles, at its outfall to 

Chito Branch. 

Lake Branch 

Lake Branch originates near large mining areas in Section 12, Township 31, Range 

22. The channel profile ranges from 71 feet NAVD at the South Prong Alafia River to 

140 feet NAVD at the upstream end. The Lake Branch outfall to the South Prong 

Alafia River is in Section 2, Township 32, Range 22. Boggy Branch is 5.3 miles long. 

Channel slope is 13.0 feet per mile or 0.25 percent. 

Lake Branch flows through 4 hydraulic structures. Fort Lonesome Plant Road 

crosses Lake Branch. IMC Agrico Company also constructed a dragline crossing 

similar to the one on the South Prong Alafia River. Lake Branch drains 14,094 acres, 

or 22.0 square miles, at the South Prong Alafia River. 


Existing land use in the South Prong Alafia River Subwatershed is defined with 

update to the Southwest Florida Water Management District's 2006 Geographic 

Information System land use coverage. This District coverage is based on the Florida 

Department of Transportation's Florida Land Use and Cover Classification System, or 





FLUCCS. The methods used to update the District's coverage are outlined in Chapter 

2. 

It is important to note that this update is done for hydrologic modeling purposes only. 

Hillsborough County's Stormwater Management Model is based on the Soil 

Conservation Service Curve Number method. Chapter 4 contains a description of the 

method. Calibration of the South Prong Alafia River Subwatershed model with the 

Curve Number method is sensitive to the infiltration capacity and percent impervious 

cover of various surface types. Changes to the District's land use coverage are done 

to increase the accuracy of the hydrodynamic model. 

It is appropriate for governments to promulgate multiple land use designations; 

political, zoning, and hydrologic land uses might be defensible and different for the 

same parcel of land. It is not appropriate for governments to require that the same 

political, zoning, and hydrologic land use exist for a parcel of land. The District's 

coverage is therefore updated for hydrologic modeling reasons, and might be referred 

to as a hydrologic land use. 

Hydrologic land use for the South Prong Alafia River Subwatershed is shown on 

Figure 5.7-2. These data are combined with Southwest Florida Water Management 

District soils data to develop subbasin curve numbers. 













1900/2600 - OPEN LAND 





5000 - WATER 




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Land use in the South Prong Alafia River Subwatershed is detailed in the following 

table. 

TABLE 5.7-1 SOUTH PRONG SUBWATERSHED 



TOTAL 

AREA 

(acres) 

PERCENTAGE OF 

SUBWATERSHED 

(%) 








Forest 4,604 5.2% 


Transportation, Communications & Utilities 22 0.0% 




Water 531 0.6% 

Wetland 8,228 9.6% 

Total: 85,917 100.0% 

Mine activities are the largest single land use in the South Prong Alafia River 

Subwatershed, comprising nearly 63 percent of the total subwatershed area. 

Agricultural land uses constitute nearly 15 percent of the subwatershed. Residential 

development comprises approximately 3 percent. Less than 10 percent of the 

subwatershed remains as natural landforms. Waterbodies and wetlands constitute 

approximately 10 percent of the subwatershed. These landforms store or attenuate 

runoff during extreme flooding events. 

The active mine lands classification does not include reclaimed mine lands. Visual 

inspection of the original Southwest Florida Water Management District 2006 land use 

coverage and U.S. Geological Survey quadrangle show that approximately two-thirds 

of the South Prong Alafia River Subwatershed is associated with phosphate mining. 

These lands can be grouped into one of the following four classes: active mine lands, 

reclaimed mine lands, lands owned by mine interests that are yet to be mined, and 

lands owned by mine interests that can not be mined. Reclaimed mine lands, lands 

owned by mine interests that are yet to be mined, and lands owned by mine interests 

that can not be mined are represented in the tabulation by the current landform, such 

as forest, open land and rangeland, water, or wetlands. 





5.7.1.3 Soils 



dual hydrologic soil group classification, B/D, is assigned to soils that are saturated 

throughout much of the soil column due to a high surficial water table during the wet 

season. Infiltration is impeded and the soil acts as a D soil. When the water table is 

lower the soil acts as a B soil: a well drained soil. 

Figure 5.7-3 shows hydrologic soil classifications for the South Prong Alafia River 

Subwatershed. The U.S. Natural Resource Conservation Service identifies 66 unique 

soil species in the South Prong Alafia River Subwatershed. Arents, Winder Fine 

Sand, Hydraquents, Myakka Fine Sand, Neilhurst Sand are the dominant soil species 

in the subwatershed. The following table lists a composite breakdown of the 

distribution of the hydrologic soil types within the South Prong Alafia River 

Subwatershed. 

TABLE 5.7-2 SOUTH PRONG SUBWATERSHED 



GROUP 

TOTAL AREA 

(acres) 

PERCENTAGE OF 

SUBWATERSHED 

(%) 

A 22,029 25.7% 

B 0 0.0% 

B/D 28,009 32.7% 

C 19,200 22.2% 

D 14,277 16.6% 

Water 2,401 2.8% 

Total 85,917 100.0% 

Approximately 60% of the subwatershed is comprised of either Type B/D or Type A 

soils. Type B/D soils are assumed to act as a composite of Type B and Type D soils 

for hydrodynamic model calibration purposes. For the South Prong Alafia River 

Subwatershed calibration, it was necessary to assume that Type B/D soils act closer 

to Type B than Type D soils under normal conditions. 


The South Prong Alafia River is roughly an L-Shape. The downstream north-south 

leg is approximately nine miles long; the upstream east-west leg is approximately 13 

miles long. The majority of the named tributaries join the river along the north-south 

leg. Hurrah Creek and Chito Branch drain the area west of the north-south leg. 

Mizelle Creek, Boggy Branch, and Lake Branch drain the majority of the area north of 



ALAFIA RIVER 





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A 

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the east-west leg. Major, named tributaries that drain to the South Prong Alafia River 

do not exist south of the east-west leg. 

Historically, a hill at elevation 160 feet NAVD existed to the northeast of the South 

Prong Alafia River, near Sections 1, 2, 11, and 12, Township 31, Range 22. The hill 

formed the uplands for most of the named tributaries east and north of the South 

Prong Alafia River. The hill may have been significantly altered by phosphate mine 

activities. A railroad line is oriented in a northwest-southeast direction, to the 

northeast of the hill. In most areas, the railroad separates the South Prong Alafia 

River and North Prong Alafia River subwatersheds. 

A defined ridge at elevation 170 feet NAVD exists along the eastern watershed divide. 

The ridge separates the Alafia and Peace River Watersheds. Hooker's Prairie is 

located west of the ridge. The area between the ridge and the Hillsborough-Polk 

County line has been extensively altered by phosphate mine activities. 

A saddle point exists along the southwest watershed divide. The saddle point is 

located on the western edge of Section 1, Township 32, Range 21, at elevation 90. 

This saddle point divides the upstream end of Chito Branch from the Little Manatee 

River Watershed, to the south. A number of less well defined saddle points and 

subwatershed pop-offs exist along the western subwatershed divide, between the 

South Prong Alafia River and Fishhawk Creek subwatersheds. The Tampa Bay 

Regional Reservoir is proposed to be located along this divide. 

Enormous closed basins, some in excess of 1,000 acres, exist throughout the 

phosphate mine lands. The mine typically retains stormwater that falls within these 

basins for use in the phosphate mine process. Where areas are reclaimed to a premine 

condition, stormwater will enter the surface water drainage system. Flood 

hazards will likely increase. 


Information describing the drainage facilities of the study area was compiled from a 

variety of sources and methods. Hydraulic data for culverts, bridges, control 

structures, and channel cross sections were obtained from as-built construction plans, 

previous studies, development plans, roadway plans, and field measurements. Data 

collected included elevations, lengths, dimensions, construction materials, channel 

vegetation, structure entrance and exit conditions, and any other pertinent features. 

This task required a considerable amount of effort, but it was deemed necessary to 

develop the appropriate level of detail to accurately define the hydrologic and 

hydraulic conditions of the study area. Sources of data for individual elements of the 

hydraulic network are referenced in the model input file as comments and 

documented in the project files. 






Edgemon Land Surveying of Plant City and Strayer Surveying and Mapping of Venice 

surveyed approximately 65 structures and approximately 150 cross sections in the 

South Prong Alafia River Subwatershed for the original 2001 Alafia River WMP study. 

Data from almost all of these surveys are incorporated into the model. For hydrologic 

structures, such as culverts or bridges, Edgemon and Strayer collected location, 

orientation, invert and weir overtop elevations, dimensions, material type, water 

surface elevations, and cross sections at the upstream and downstream ends of the 

structure. Edgemon and Strayer collected location, orientation, ground and water 

surface elevations for cross sections. Edgemon and Strayer photographed most 

locations. No additional surveys or field measurements were needed for the update 

of this subwatershed. 




methodology is consistent for the South Prong Subwatershed. 


The South Prong Alafia River Subwatershed is divided into 282 discrete subbasins, to 

provide the level of detail necessary to define the primary and portions of the 

secondary drainage system. Subbasins within Hillsborough County range in area 

from 10 to 3651 acres. The following needs drive subbasin delineation: 

• definition of contributing drainage area to elements of the primary drainage 

system 

• definition of contributing drainage area to a storage element 

• segregation of drainage areas as a function of homogeneous land use 

Subbasin delineations are much coarser within Polk County. Detailed modeling of 

this portion of the watershed was not included in the contract of the original Alafia 

River study, nor was it included in this model update. It was, however, imperative to 

the quality of the overall model to account for the inflows from the Polk County 

portions of the watershed to attain reasonable results for the Hillsborough County 

portion of the model. A minimum level of detail was given to the areas in Polk County 

such that the magnitude and timing of flows from this portion of the model could be 

simulated. Only large storage areas were delineated as subbasins in Polk County. 

Hillsborough County’s naming convention derives subbasin name from the junction to 

which the subbasin drains. The convention dictates a six-character numerical code 

for each subbasin. The first two digits refer to subwatershed. “77xxxx” refers to the 

South Prong Alafia River Subwatershed. 





Hillsborough County supplied DEM data were the principle data source for subbasin 

delineation. Land use changes from natural landforms to mine lands interrupts 

natural overland flow patterns within the subwatershed. 



this study for each subbasin in the South Prong Alafia River Subwatershed by an 




for the South Prong Alafia River Subwatershed. The resulting final subbasin runoff 

curve numbers for the South Prong Alafia River Subwatershed are presented in the 

updated Alafia River ArcGIS geodatabase 


The time of concentration represents the time required for a particle of water to travel 

from the most distant point in the subbasin to the subbasin outlet. Hillsborough 

County adopted a standard method for time-of-concentration calculation. The 

Stormwater Management Technical Manual documents the method. 

Time of concentration is the sum of travel times for consecutive flow components 

within the subbasin. The manual details methods to compute flow times for overland 

flow, sheetflow, shallow concentrated flow, and open channel flow. Formulae are a 

function of slope and flow path. 

Lengths of overland flow and slope data are from topographic data. Surface 

roughness, represented by the Manning’s roughness coefficient, is from literature 

values, expressed as a function of land cover shown on aerial photography. The 

shallow concentrated flow and channel flow components of the time of concentration 

calculation are a function of length and velocity. Times of concentration values from 

the original 2001 study were used if the subbasin delineation did not substantially 

change. New Tc values were calculated for all other subbasins. All subbasin Tc 

values and new Tc flowpath data are located in the updated Alafia River ArcGIS 

geodatabase. Note that the minimum subbasin Tc is assumed as 10 minutes. 


During this model update substantial research was accomplished regarding the 

determination of the reclamation status of the phosphate mining areas. This task was 

imperative to generate model network that could realistically approximate flow 

contributions from the vast mining areas in this portion of the watershed. Research 

included, data obtained from the FDEP website and an interview with staff members 

at Mosaic, Inc. to help Parsons ascertain which mining areas are active mining and 

which are reclaimed or under reclamation. Using these two sources of information, 

balanced with the use of any obtained mining plans and the most recent aerial 

photography, it was determined on a case by case basis whether the mining basin 





was active or reclaimed. If it was determined that the mining area was active, the 

basin was assumed to be “closed”, that is, the basin, although part of the model 

network, would have no runoff contribution. This assumption was made based on 

regulations for phosphate mining activity which state that active mining areas should 

be designed to not discharge runoff up to the 100-year storm event. All of these 

“closed” basins (active mining areas) were modeled with a starting elevation of 400 ft 

NAVD with a 1000 foot long weir at elevation 500 ft NAVD. These model parameters 

are fictional and were designated such that, the basins would still be included in the 

model network but have no flow contribution into the model drainage system for any 

of the design storm events. These data (fictional weir and junction data) could also 

be easily identified in model datasets by searching or sorting the data. 

For mining areas that were determined to be reclaimed, either from FDEP obtained 

data, ERP data and/or aerial photography, DEM topography was used to create 

overland weir or channel reaches in the model. In some cases structure data from 

ERP or DEP permits were available, if so, they were included. In some rare cases, 

where it was very obvious that some kind of structure (culvert) existed under a road or 

berm based on aerial and DEM data, culverts were “assumed” using best engineering 

judgment. These model reaches are commented as such in the model input file as 

“assumed”. These assumed reaches were necessary to allow discharge from basins 

where it was obvious that the only means of discharge could not be over road or berm 

tops. 


The South Prong Alafia River Subwatershed hydrodynamic model resolution includes 

a total of 356 junctions and 572 linkages in its structure, including 329 conduits and 

243 weirs. 



within the South Prong Alafia River Subwatershed, it was important that all significant 

storage facilities and their hydraulic functions be defined. As described in Chapter 4, 

the initial (starting) water surface elevations for these variable storage facilities were 














The model includes 175 closed conduits for the South Prong Alafia River 

Subwatershed. These closed conduits take the form of circular, rectangular, elliptical, 

or arch pipes. Data are from surveys, and other backup data. 



conduits. In the South Prong Alafia River Subwatershed model, a small number of 

bridge spans are modeled as the respective surveyed cross-section, with additional 

roughness coded to represent friction loss associated with piers. Where bridges 

experience full-flow conditions, the depth of the channel cross section is limited to the 

elevation of the low chord. This strategy allows the surcharge condition to be 

modeled. In most cases, bridge structures are modeled using the guidelines 

described in Section 4 for abstraction of an equivalent combination of box culverts, 

with different dimensions and inverts. 


The model includes 243 weir connections for the South Prong Alafia River 

Subwatershed. These weirs model the overtopping of control structures, pond banks, 

roadways at channel crossings, and overland flow. Data for crest elevations and 

widths are form structure surveys, construction plans, and field measurements. All 

closed basins associated with phosphate mines include a top-of-bank weir to allow 

overtopping of the storage area during extreme flood events. All road crossings 

include a top-of-road weir to allow overtopping of the road during extreme flood 

events. Roadway overtopping is simulated with broad-crested weirs. Weir crest 

elevations are from structure surveys or topographic maps. Overland flow provides a 

conduit for floodwater to circumvent the normal flowpath in the drainage system. 

Weirs simulate these drainage paths, with weir crest elevations and lengths from 

topographic maps. 


The model includes 154 open channel conduits for the South Prong Alafia River 

Subwatershed. These irregular cross section data define the low flow channel and 

overbank floodplain of natural cross sections. It is necessary to code the natural 

overbank floodplain explicitly so that both floodplain storage and conveyance 

functions are modeled. The most current, detailed, and representative data for any 

particular reach of the open channel system are coded. In many cases, channel 

cross-section data from surveys are extended with data from topographic maps to 

define the full extent of the natural floodplain. 










supported by published guides and past modeling experience. These values were 

confirmed or adjusted during model calibration. 


Interbasin transfer of flow between the South Prong Alafia River Subwatershed and 

the Little Manatee Watershed at a low topographic point on the common watershed 

boundary was determined to exist during the range of storm events analyzed. The 

quantity and nature of this interconnection was not defined for this model update. The 

boundary inflow hydrograph established during the original 2001 Alafia River WMP 

study was on old data. Currently, the Little Manatee Watershed has not been 

updated to accuracy and detail of the Alafia River Watershed. Based on the flat 

nature of the area in question and without a thorough re-coordination of the boundary 

condition, it was assumed that the net effect of the boundary is zero and no flow 

interaction is modeled. This assumption was made because is not known which 

direction boundary flows would go. Assuming a free flow (outflow) would most likely 

be less reasonable than no outflow at all and also be less conservative. It is 

recommended that this boundary condition be analyzed when the Little Manatee 

Watershed update is in progress. 














Rainfall depth, rainfall distribution, flow rate, flow volume, and water surface elevation 

are examples of calibration data. When selecting a calibration storm, data must be of 

sufficient temporal resolution to detail variations in intensity. Data should be recently 

acquired so that current land use and hydraulic conditions in the study area are 

accurate. To account for the non-uniform spatial distribution inherent in precipitation 

patterns in Florida, it is desirable to model rainfall depth and distribution at various 

locations throughout the subwatershed. 

Over the historical record, three streamflow gaging stations have been operated in the 

South Prong Alafia River Subwatershed and were considered for use in model 





calibration and verification. The U.S. Geological Survey collected discharge data at 

Station Number 02301314, Mizelle Creek near Keysville, in 1975 and 1976. The 

USGS also collected discharge data at Station Number 274517082034100, Terry's 

Tributary near Fort Lonesome Transect B, in 1982. These data were not utilized in 

the calibration of the South Prong Alafia River Subwatershed model because of the 

short period of operation and because the land use and drainage system during the 

period of record may differ substantially from the abstracted hydrologic system. 

The U.S. Geological Survey has collected discharge data since 1962 at Station 

Number 02301300, South Prong Alafia River near Lithia. The gage is located at the 

right bank, 12 feet upstream of the Jameson Road Bridge, approximately 1.5 miles 

upstream of Halls Branch, five miles southeast of Lithia, and 7.6 miles upstream of 

the mouth of the South Prong Alafia River. These data were utilized in the calibration 

of the South Prong Alafia River Subwatershed model. 

The Southwest Florida Water Management District, U.S. Geological Survey, and 

National Oceanographic and Atmospheric Administration report precipitation depth at 

a number of locations within and near the South Prong Alafia River Subwatershed. 

The locations of gages of interest have been previously shown on Figure 5.1-5, the 

Alafia River Watershed precipitation gage location map. Specifically, the Big Four 

Mine, Haynesworth, Herring, Hooker's Prairie, Hurrah Tower, Kingsford, Lonesome, 

Pierce, Pierce (Agrico), South Central, SPCW, Welcome Tower, Medard Lake ,Balm 

Park (romp 49) and Thatcher (ROMP 48) rainfall gages are the most pertinent sites 

used for depth, distribution, or both depth and distribution in the South Prong Alafia 

River Subwatershed model calibration. It should be considered that, for most of those 

stations shown, the historical data consist only of daily accumulations of recorded 

precipitation and that the time of day of gage observation will differ between sites. 

For most of the period of record (until the last 10 years), the only recording 

precipitation gaging stations (i.e. hourly data) that were in operation were those 

NOAA stations at the Tampa International Airport, Parrish, and Lakeland, and one 

SWFWMD station located at Pierce (in Polk County). Most recently, the SWFWMD 

has installed and operated recording precipitation stations at an additional seven 

locations in the geographic vicinity, those SCADA stations being the Medard Lake 

(Pleasant Grove), Mulberry, Dover DV-1, Four Corners, Thatcher, Alafia, Welcome 

Tower and Starling stations. 


Calibration of a South Prong Alafia River Subwatershed hydrodynamic model was 

performed using rainfall and streamflow gaging station data for the September 4-7, 

2004 historical storm event as the basis for adjusting the initial model input data, 

including both hydrologic and hydraulic input parameters. The verification of the 

model was conducted using rainfall and streamflow gaging station data for the 

September 5-8, 1988 historical storm event and the December 9-14, 1997 historical 

storm event. This is a stage and discharge calibration. 





The four-day storm that occurred from September 4-7, 2004 was a slow moving 

hurricane (Frances) that passed over the Alafia Watershed moving from east to west, 

it was one of several hurricanes to hit the state in 2004. For the calibration event, 

several rainfall recording gages had quality hourly data that was sufficient for creating 

Thiessen polygon rainfall “zones”. As described in previous calibration discussions, 

Thiessen polygon “area of influence” weighting system was applied on a subbasin 

level to establish calibration rainfall data. 

The five gages used for this calibration were; Lake Medard (ROMP 61), Alafia, Pierce, 

Balm Park (ROMP 49) and Welcome Tower with rainfall totals of; 10.22, 9.4, 7.61, 

9.07 and 6.18 inches respectively. Considering the spatial distribution of the rainfall 

gage locations, using the Thiessen polygon weighting system was deemed 

appropriate. 

The four-day storm event that occurred from September 5-8, 1988 was actually a 

series of 3 individual storm events that occurred at roughly 24-hour intervals. The 

South Prong Alafia River Subwatershed was divided into zones that reflected similar 

rainfall patterns during this event, since it was apparent that precipitation was not 

spatially uniform over the total drainage basin. Because of the large variance 

between recorded gaging station totals it was considered more prudent, for this 

verification event, to utilize the average precipitation over these “zones” rather than 

use the individual records with a Thiessen weighting procedure, thus reducing any 

bias induced by potentially erroneous individual records. This potentially wide range 

of recorded precipitation over the expanse of the subwatershed leads to uncertainties 

in the model calibration process that are lessened through such an averaging 

procedure. 

An average total measured rainfall of 11.40 inches was calculated for 3 selected 

gaging stations (Herring, Hurrah Tower, and Lonesome) to represent the storm event 

as it occurred over the southwestern portion of the South Prong Alafia River 

Subwatershed during this event. A substantially lower amount of rain was recorded 

over the southeastern of the subwatershed, and an average of 8.82 inches was 

computed for use in the model simulations. Stations selected for this computation 

were the Hookers Prairie, SPCW, Haynesworth, Big Four Mine, Ft. Green, and Pierce 

Agrico precipitation gages. Average rainfall of 12.76 inches was assigned to the 

northern portion of the subwatershed using the South Central precipitation gaging 

station as the basis. 


September 1988 storm event, it was decided to use the hourly data from the Pierce 

precipitation station. The distribution recorded at this gage, obtained from the 

SWFWMD, was selected for use in the physical calibration of the South Prong Alafia 

River Subwatershed model because, of the few such records available, it appeared to 

best correlate to the streamflow gaging station records in terms of timing. 





Model verification was also conducted using the December 9-14, 1997 storm event. 

This five-day storm began as a few days of light rain that was followed by two heavy 

days during which most of the total rainfall volume fell. An average measured rainfall 

for the following six selected rainfall gaging stations were computed for use in this 

verification storm event to represent the rainfall in the upper (southern) South Prong 

Alafia River Subwatershed: Kingsford, Big Four Mine, Herring, Pierce Agrico, 

Thatcher, and Haynesworth. The total five-day precipitation depths recorded at these 

sites range from 5.01 inches to 5.86 inches, and the average depth at the five stations 

is 5.43 inches. The data were very consistent throughout this geographic region. The 

northern South Prong Alafia River Subwatershed precipitation data were also 

somewhat uniform, with totals somewhat greater in this zone. An average total 

rainfall of 6.38 inches was calculated from the Alafia, Balm, Valrico and Hopewell 

precipitation gaging stations. To facilitate hourly distribution of the rainfall depth over 

this event, the hourly data from the SWFWMD Pleasant Grove and Thatcher 

recording gages were used, respectively. 

Antecedent soil moisture condition is an important consideration in the calibration 

process. The degree to which the soil column is moistened at the beginning of a 

storm event can be a significant factor in the amount of storm runoff that is generated. 

The more saturated the soil, the greater the amount of runoff. A commonly used index 

for this condition is the Antecedent Moisture Condition (AMC), which uses the total 

amount of rainfall in the previous 5 days as a measure. Descriptions of the three 

AMC levels are the following: 

AMC CONDITION 

TOTAL 5-DAY 

ANTECEDENT 

RAINFALL 

(inches) 

I Less than 1.4 

II 1.4 to 2.1 

III Over 2.1 

DESCRIPTION 

Soils dry, but not to wilting 

point; lowest runoff potential 

Average soil conditions and 

runoff potential 

Soils moist, but not saturated; 

highest runoff potential 

For the Alafia River Watershed update, the AMC II condition was used for modeling. 

The preceding 5-day rainfall totals for the precipitation gages that were used for the 

South Prong Alafia River model calibration generally fell within the 1.4 to 2.1 inch 

range that defines an AMC II condition. 











* Runoff curve numbers (CNs) for different soil groups and land use 


* Channel, floodplain, and culvert roughness coefficients (Manning's n) and 


* Times of concentration for individual subbasins, and 

* Unit hydrograph shape factors. 

In the SWMM model calibration for the South Prong Alafia River Subwatershed, these 

parameters were initially derived using accepted methods and values derived from 

literature research and from past model applications in the region. Their final values 

were ultimately derived through the model calibration process. 

















reaches from the gaging station location at the Jameson Road bridge. Since a rating 


calibrate the channel roughness coefficients for the entirety of the South Prong Alafia 

River. What this exercise provided was the basis for the estimation of the channel 

and floodplain roughness coefficients in the other channel reaches of the basin. 

References found in engineering literature were also used in this process. 





Calibration Results 

Figures 5.7-4 and 5.7-5 show comparisons of the recorded and simulated stage and 

flow at the USGS streamflow gaging station at Jameson Road for the September 

2004 calibration storm event. The model formulation was adjusted at the initiation of 

the event by the addition of groundwater baseflows in the subwatershed that 

amounted to approximately 325 cfs at this location. The figures show good 

correlation in timing, shape, peak stage and total volume of runoff. The peak watersurface 

elevation and discharge at Station Number 02301300, recorded at 7 PM on 

September 6, 2004 were 56.81 feet NAVD and 2,630 cfs, respectively. The 

corresponding calibrated model peak water-surface elevation and discharge, 

predicted by the model at 4 PM on September 6, 2004 are 57.31 feet and 3,050 cubic 

feet per second, respectively. The peak water surface elevation deviates by 0.50 

feet; peak discharge deviates by 520 cfs, and timing is nearly coincident. The amount 

of surface storage in the subwatershed is vast. The initial elevations in all of these 

mines are unknown at the time of the storm event (initial stages can only be 

estimated based on DEM and aerial photography data) and the amount of available 

storage based on the initial elevations governs much of the flow at this location. This 

is certainly the reason for the over-estimation of the flows. Considering these 

unknowns in model setup, the calibration should be deemed a success. 

The verification of the South Prong Alafia River model was conducted by the 

simulation of the 9-day time period from September 5 - 14, 2004 and the 10-day time 

period from December 9 - 18, 1997. Figures 5.7-6 through 5.7-9 show comparisons 

of the recorded and simulated flows and stages, respectively, at the USGS 

streamflow gaging station at the Jameson Road bridge for both verification events. 

The model formulation was adjusted at the initiation of the event by the addition of 

groundwater baseflows in the subwatershed upstream of the gage location that 

amounted to a total of 140 cfs for the 1988 event and 102 cfs for the 1997 event. As 

can be seen in both event simulations, the model again over-predicts the peak flow 

conditions at the gage in both the magnitude of flows and flood elevations. The timing 

and shape for both events is very good. Once again, the initial stages in the large 

number of mine storage areas are assumed both verification events (using DEM and 

aerial photography). Considering this unknown amount of available storage at the 

time of the storm and amount of changes in the mining areas (new mines and 

reclaimed mines) these verification model simulations are judged to be more than 

sufficient. 





FIGURE 5.7-4: South Prong Alafia River at Jameson Road 


4000 

3500 

Recorded 

Simulated 

3000 


2500 

2000 

1500 

1000 

500 

0 

9/4/2004 

9/5/2004 

9/6/2004 

9/7/2004 

9/8/2004 

9/9/2004 

Time (days) 



58 

Recorded 

Simulated 

57 


56 

55 

54 

53 

9/4/2004 

9/5/2004 

9/6/2004 

9/7/2004 

9/8/2004 

9/9/2004 

Time (days) 







4000 

3500 

Recorded 

Simulated 

3000 


2500 

2000 

1500 

1000 

500 

0 

9/5/88 

9/6/88 

9/7/88 

9/8/88 

9/9/88 

9/10/88 

9/11/88 

9/12/88 

9/13/88 

9/14/88 

9/15/88 

Time (days) 



60 

59 

Recorded 

Simulated 

58 


57 

56 

55 

54 

53 

52 

51 

50 

9/5/88 

9/6/88 

9/7/88 

9/8/88 

9/9/88 

9/10/88 

9/11/88 

9/12/88 

9/13/88 

9/14/88 

9/15/88 

Time (days) 







2000 

1800 

Recorded 

Simulated 

1600 


1400 

1200 

1000 

800 

600 

400 

200 

0 

12/9/97 

12/10/97 

12/11/97 

12/12/97 

12/13/97 

12/14/97 

12/15/97 

12/16/97 

12/17/97 

12/18/97 

12/19/97 

Time (days) 



57 

56 

Recorded 

Simulated 


55 

54 

53 

52 

51 

12/9/97 

12/10/97 

12/11/97 

12/12/97 

12/13/97 

12/14/97 

12/15/97 

12/16/97 

12/17/97 

12/18/97 

12/19/97 

Time (days) 





Figure 5.7-10 shows a comparison of the U.S. Geological Survey rating curve for 

Station Number 02301300 and rating data from the model simulation. The rating 

curve matches reasonably over the range of the higher flows. The rating falls short by 

approximately one half foot for flows in the 500-1000 cfs range. HCSWMM is 

somewhat limited in variance of manning’s n value allocation within model channel 

cross-section, this reduces the ability to precisely match the USGS rating curve. 

Overall, these data compare within reasonable limits. 

60 

FIGURE 5.7-10: South Prong Alafia River 


55 


50 

USGS Rating curve 

Simulated 

45 

0 500 1000 1500 2000 2500 3000 3500 



5.8 ALAFIA RIVER MAIN STEM SUBWATERSHED 




5.8.1 Basin Description 

The Alafia River Main Stem Subwatershed encompasses the remaining 44.6-squaremile 

portion of the Alafia River Watershed that was not defined by the previously 

designated seven subwatersheds. It includes the Alafia River main channel from its 

outfall at the south end of Hillsborough Bay to Keysville Road, along with numerous 

small tributary systems that drain directly to the river. Runoff from the majority of the 

subwatershed drains into the river directly through roughly 40 small, previously 

unnamed creeks, together with Rice Creek, which is the only major waterway in the 

system. The drainage basin, shown in Figure 5.8-1, has its geographic boundary 

defined as follows: Hillsborough Bay to the east, Keysville Road to the west, 

Gibsonton City to the northeast, and cities of Riverview and Bloomingdale to the 

south. The general flow direction of the Alafia River is from east to west. The most 

upstream point of the subwatershed is at the Keysville Road bridge crossing of the 

North Prong Alafia River where the USGS streamflow gaging station is located. The 

Alafia River discharges to the Hillsborough Bay about 1 mile west of Bayshore Road 

Bridge. 

The natural hydrologic system in the Alafia River Main Stem Subwatershed consists 

of an aggregation of small lakes, natural depressions, and wetland systems 

overflowing through numerous natural sloughs and small springs to the river. Rice 

Creek, approximately 2.3 miles in length and joining the river near the McMullen Road 

from south, is the only major natural conveyance system in the subwatershed. 

However, progressive urban and suburban development in the recent decades has 

resulted in significant changes in the hydrologic characters of the subwatershed. An 

increase in residential and commercial land use has resulted in more impervious land 

surfaces that subsequently generate more polluted stormwater runoff. Negative 

effects of urbanization and development on the natural watershed environment, such 

as increased contributions from stormwater pollutant loading and increased reports of 

flooding incidents, have been documented since the early 1980’s. 

The Alafia River flows from east to west and the main channel exhibits a very flat bed 

slope of 1.76 feet per mile or 0.03 percent in average. Major highways bridge the 

Alafia River at US Highway 41, Interstate I-75, US Highway 301, Bell Shoals Road, 

State Road 640 (also Lithia-Pinecrest Road), and State Road 39. The Alafia River 

Main Stem Subwatershed is characterized by generally flat topography throughout 

most of the watershed, which is typical of southern Florida conditions. Most terrain 

ranges from nearly level areas with numerous intermittent marshes, swamps, sinks, 

lakes, and springs, to gently undulating areas that extend from the northwestern 

corner southeastward across the subwatershed. The north central portion of the 

subwatershed contains a number of depressions (sinkholes) with no defined drainage 

outlets that act as closed basins except for extreme storm events. 






The Alafia River Main Stem Subwatershed has about 40 minor tributaries as shown in 

Figure 5.8-1. The Rice Creek tributary and the Alafia River main channel are the only 

waterways described in detail in this report. 

Alafia River Main Channel 

The Alafia River headwaters are located in Polk County, from where the river flows in 

a generally westerly direction into Hillsborough Bay at East Tampa. The Alafia River 

main channel, located in the Main Stem Subwatershed has its most upstream location 

about 0.12 miles east of State Road 39. The River Main Channel outfalls to 

Hillsborough Bay about 1 mile west of US Highway 41. The river channel profile 

starts at elevation 28 ft NAVD at the North Prong and South Prong confluence point 

and ends at –12 ft NAVD at Hillsborough Bay. The Alafia River main channel in the 

subwatershed is 22.7 miles long with an average bed slope of 0.03 percent. All 

elevations are referenced to the North American Vertical Datum (NAVD) of 1988. The 

1992 Federal Emergency Management Agency (FEMA) Flood Insurance Study was 

used to define channel cross-sections of interest in the study together with the main 

channel bed profiles. Gage records on the Alafia River at USGA Gage Station at 

Lithia Pinecrest Road Bridge were used for hydraulic/hydrologic model calibration. 

There are a total of six bridges crossing the Alafia River along the main channel 

segment, including the US Highway 41 bridge, the Interstate 75 bridge, the US 

Highway 301 bridge, the Bell Shoals Road bridge, the Lithia Pinecrest Road bridge, 

and the State Road 39 bridge. A service railroad also crosses Alafia River near US 

Highway 41. 

Along the river from downstream to upstream, major tributary systems joining Alafia 

River include Rice Creek, Buckhorn Creek, Bell Creek, Fishhawk Creek, and Turkey 

Creek. Except Rice Creek, all these tributaries are covered in other sections of this 

chapter. 

Rice Creek Tributary 

Rice Creek is a major tributary that originates north of Rhodine Road in Section 33, 

Township 30, Range 20. The stream channel profile starts at elevation 36 NAVD at 

FEMA Rice Creek Junction K and remains in a relatively natural condition 

downstream to its outfall to the Alafia River immediately north of the McMullen Loop 

Road Bridge. Along Rice Creek main channel, there are four road crossings, 

including McMullen Loop Road, Balm Riverview Road, Boyette Road, and Rhodine 

Road. 

The Rice Creek drainage basin has undergone extensive change over the past 25 

years. Of the total 3,200 acres in the drainage basin, residential areas account for 

970 acres or nearly one third of the basin, with most of the high or medium density 

residential areas centralized along Boyette Road and Balm Riverview Road. 







E LUMSDEN RD 

Legend 

County Line 




Roads 




Suite 120 



ALAFIA RIVER 


BELL CREEK 

BOYETTE RD 

Notes: 


ALAFIA RIVER 



1:60,000 

0 1,500 3,000 6,000 

0 0.25 0.5 1 

Miles 

Feet 

BOYETTE RD 

TURKEY CREEK 

Filename: 

Fig5_8_ 

1E.mxd 



Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 

39 


Figure: 5.8-1(E) - Drainage System Map 

Alafia River Main Stem Subwatershed 




J:\DATA\260247_Alafia_WMP_Update\GIS\Maps\MXD\Report\Subwatersheds\RIVER_E\Fig5_8_1E.mxd




75 

ALAFIA RIVER 

41 

Legend 

County Line 




Roads 




Suite 120 


ALAFIA RIVER 

GIBSONTON DR 

Notes: 

301 

RICE CREEK 

1:60,000 

0 1,500 3,000 6,000 

0 0.25 0.5 1 

Miles 

Feet 

BOYETTE RD 

Filename: 

Fig5_8_ 

1W.mxd 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 

Figure: 5.8-1(W) - Drainage System Map 




J:\DATA\260247_Alafia_WMP_Update\GIS\Maps\MXD\Report\Subwatersheds\RIVER_E\Fig5_8_1W.mxd





Significant development within the Rice Creek contributing drainage area includes 

Camp Christina YMCA Park, Christina Subdivision Phase II and III, Riverview High 

School, Boyette Animal Hospital, and Rice Creek RV Park. 

Significant wetland areas are located in the east central potion of the basin that is 

east of McMullen Road. These wetlands are generally bounded in closed basins with 

no apparent drainage outlets. Under extreme flood conditions, excessive runoff from 

these closed basins spills into a small, natural, open-channel ditch that flows 

westward to Rice Creek. Four road-crossing culverts at Shadow Run Boulevard, 

McMullen Road (2), and Balm Riverview Road hydraulically define this secondary 

branch. The branch discharges into Rice Creek at 35 ft NAVD just west of Balm 

Riverview Road. 

Much of the southernmost parts of the Rice Creek contributing drainage basin 

contribute little or no flow to the ditch except during perhaps the most extreme storm 

events. Highly permeable sands and deep water table characterize this region of the 

Rice Creek basin, located roughly south of Tucker Road. Forest, cropland, and 

pastureland constitute the majority of the land use with a few undisturbed wetlands 

and lakes near northwest of Rhodine Road. 


Existing land use conditions in the Alafia River Main Stem Subwatershed were 

determined based upon the digital coverage from the Southwest Florida Water 

Management District (SWFWMD) Geographic Information System (GIS) database. 

Readers are referred to Chapter 4 for detailed discussion on land use classification. 

The original SWFWMD land use database was further verified and updated in this 

study for two reasons. First, a number of new developments on the Alafia River Main 

Stem Subwatershed in the past ten years have significantly altered the land use 

characteristics in some area. This information must be updated in the original 

SWFWMD land use database so as to reflect a consistent and up-to-date set of 

hydrologically valid land use coverage. Second, large areas of open, undeveloped 

land that were observed to be contained within the confines of the commercial, 

industrial, institutional, and transportation/communications/utilities parcels were 

segregated from these parcels digitally and reclassified as open land. 

The resultant land use map of the Alafia River Main Stem Subwatershed for existing 

conditions is shown in Figure 5.8-2. 





The following table summarizes the land use acreage and percentage in the Alafia 

River Main Stem Subwatershed: 

TABLE 5.8-1 ALAFIA MAIN STEM SUBWATERSHED 



TOTAL 

AREA 

(acres) 

PERCENTAGE OF 

SUBWATERSHED 

(%) 








Forest 3,407 11.9% 


Transportation, Communications and Utilities 171 0.6% 




Water 1,267 4.4% 

Wetland 4,482 16.0% 

Total: 28,536 100.0% 

Low and medium density residential development constitute approximately one third 

of the subwatershed. High density residential development comprises another 10 

percent. Cropland and pastureland constitute nearly 12 percent of the subwatershed. 

Forestland, most notably centralized in the southern portion of the subwatershed from 

Fishhawk Creek to South Prong Alafia River, accounts another 12 percent. It is also 

indicated that less than 6 percent of the subwatershed remains as open land. 


wetlands that serve to store stormwater runoff during extreme flooding events. 

5.8.1.3 Soils 



dual hydrologic soil group classification, B/D, is assigned to soils that are saturated 

throughout much of the soil column due to a high surficial water table during the wet 

season. Infiltration is impeded and the soil acts as a D soil. When the water table is 

lower the soil acts as a B soil: a well drained soil. Figure 5.8-3 shows the hydrologic 

soil classification map for the Alafia River Main Stem Subwatershed. 


E LUMSDEN RD 











1900/2600 - OPEN LAND 





5000 - WATER 




Legend 

County Line 


Suite 120 





Roads 



ALAFIA RIVER 


BELL CREEK 

BOYETTE RD 

Notes: 


ALAFIA RIVER 



1:60,000 

0 1,500 3,000 6,000 

Feet 

0 0.25 0.5 1 

Miles 

BOYETTE RD 

TURKEY CREEK 

Filename: 

Fig5_8_ 

2E.mxd 



Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 

39 


Figure: 5.8-2(E) - Existing Land Use Map 








LITHIA PINECREST 











1900/2600 - OPEN LAND 





5000 - WATER 




Legend 

County Line 



Roads 




Suite 120 


Notes: 

41 

ALAFIA RIVER 

GIBSONTON DR 

1:60,000 

0 1,500 3,000 6,000 

75 

Feet 

0 0.25 0.5 1 

Miles 

301 

Filename: 

Fig5_8_ 

2W.mxd 

Map Date: 

BOYETTE RD 

RICE CREEK 



N/A 

Prepared By: 

Yoav 

Rappaport 

Figure: 5.8-2(W) - Existing Land Use Map 






E LUMSDEN RD 


A 

B 

B/D 

C 

D 

Water 

Legend 

County Line 


Suite 120 





Roads 



ALAFIA RIVER 


BELL CREEK 

BOYETTE RD 

Notes: 


ALAFIA RIVER 



1:60,000 

0 1,500 3,000 6,000 

Feet 

0 0.25 0.5 1 

Miles 

BOYETTE RD 

TURKEY CREEK 

Filename: 

Fig5_8_ 

3E.mxd 



Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 

39 


Figure: 5.8-3(E) - Soils Map 









75 

ALAFIA RIVER 

41 


A 

B 

B/D 

C 

D 

Water 

Legend 

County Line 



Roads 




Suite 120 


ALAFIA RIVER 

GIBSONTON DR 

Notes: 

301 

RICE CREEK 

1:60,000 

0 1,500 3,000 6,000 

Feet 

0 0.25 0.5 1 

Miles 

BOYETTE RD 

Filename: 

Fig5_8_ 

3W.mxd 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 

Figure: 5.8-3(W) -Soils Map 









The following table summarizes the soil group distribution in acres and percentage for 

the subwatershed. 

TABLE 5.8-2 ALAFIA MAIN STEM SUBWATERSHED 



GROUP 

TOTAL AREA 

(acres) 

PERCENTAGE OF 

SUBWATERSHED 

(%) 

A 8,665 30.3% 

B 0 0.0% 

B/D 11,871 41.8% 

C 5,501 19.2% 

D 1,531 5.3% 

Water 969 3.4% 

Total: 28,536 100.0% 

Nearly 42 percent of the subwatershed is comprised of hydrologic soil group B/D 

soils. The next largest soil group in the subwatershed is 30 percent of group A soil, 

which, by definition, has very high infiltration capacity. Most of the group A soils occur 

in the northern portion of the subwatershed adjacent to the southwestern Turkey 

Creek Subwatershed and southeastern Buckhorn Creek Subwatershed. Hydrologic 

group C soils, with slow infiltration, account for another 19 percent of the 

subwatershed. Hydrologic group D soils comprise only 5 percent, representing 

wetland areas sporadically located in the subwatershed. 


The Alafia River Watershed is located in the Gulf and Atlantic Coastal Plain 

physiographic province of the United Sates. The Alafia River Main Stem 

Subwatershed is characterized as from sandy and poorly drained coastal lowlands to 

uplands. Soils in the flat areas are typically acidic because of the dominant types of 

vegetation and the lack of underground drainage. The terrain of the subwatershed 

ranges from nearly level areas with numerous intermittent marches, swamps, sinks, 

lakes, and springs, to gently undulating uplands and running hills. East of U.S. 

Highway 301, the subwatershed is characterized by upland areas with older marine 

terraces including sinkholes, depressions, ponds and swamps. 

The Alafia River headwaters are located in Polk County, from where the river flows in 

a generally westerly direction into Hillsborough Bay. Land surface elevations in the 

Alafia River Subwatershed range from sea level along the south end of the 

Hillsborough Bay to more than 110 ft NAVD at the northeast corner of the 

subwatershed. The lower Rice Creek reach has an elevation of 5 ft NAVD or lower 

near its confluence with Alafia River. The creek traverses a flat floodplain and 





reaches its upland elevation of 80 ft NAVD or higher at the southern corner of the 

subwatershed. 

Northeast of Lithia-Pinecrest Road in the central portion of the subwatershed, there 

are many closed basins with no positive outfalls. Some of these closed basins also 

encompass sinkholes, some in excesses of 20 feet in depth. These sinkholes serve 

as natural storage to hold stormwater runoff during extreme storm events. 

5.8.1.5 Previous Studies and Sources of Information 

Extensive efforts were made on literature review for this study to collect model input 

data for the Alafia River Main Stem Subwatershed. This section summarizes the 

primary sources of information. Detailed original data is documented in the project 

Notebooks. 

Previous Studies 

The only previous flood study on Alafia River prior to the original 2001 WMP study is 

contained in the 1992 “Flood Insurance Study, Hillsborough County, Florida” by the 

Federal Emergency Management Agency (FEMA). The purpose of this study was to 

investigate the existence and severity of flood hazards in the Unincorporated Areas of 

Hillsborough County, Florida. This study included the entire Alafia River main stem, 

North Prong and South Prong Alafia River, and Rice Creek. The HEC-2 backwater 

model was used to compute flood profiles of the main channels of Alafia River and 

Rice Creek. Information on the river main channel cross-sections and bed profiles 

from the FEMA HEC-2 model was directly used to construct the SWMM model in our 

study. For purposes of this update the original 2001study and model were the basis 

for the “starting point” of input data. 


Residential and commercial plans of grading, drainage, and stormwater management 

construction were obtained from the Hillsborough County archives and South Florida 

Water Management District permit files. Any commercial or subdivision development 

plans constructed since the original 2001 study was modeled until the year 2006 were 

obtained and explicitly modeled in this update. Much of the new development is 

located in the west potion of the subwatershed. 

Roadway Plans 

Any new roadway plans constructed since the original 2001 study were obtained and 

reviewed for new drainage information whether the data was newly constructed or 

existing data that was peripheral information within the plans. Roadway plan data 

was collected from the FDOT or from the ERP data obtained the SWFWMD. 


Parsons contracted professional surveyors from Tomasino Associates, Wilson Miller, 

Inc., and Edgemon Land Surveying, Inc. to provide surveys of approximately 96 

structures and approximately 218 cross sections in the Alafia River Main Stem 





Subwatershed for the original 2001 WMP Study. For hydraulic structures, including 

culverts, bridges, manholes, and pond control structures, the surveyors collected data 

on location, orientation, inverts, road top elevations, water surface elevations, ground 

elevations, pipe dimensions and material type. For cross sections, the surveyors 

collected location, orientation, and station-elevation pairs. In addition, Parsons staff 

conducted between 110 and 140 field observations within the Alafia River Main Stem 

Subwatershed. These observations were made at flood problem areas where no 

information was available either from existing plans or professional surveyors. 

For this Update of the Alafia River WMP, 27 new locations were surveyed. These 

locations were previously modeled using field observation performed in the 2001 

study. Locations were chosen based on their importance relative to flood impacts 

within the watershed. 




methodology is consistent for the Main Stem Prong Subwatershed. 


The subwatershed is divided into 663 subbasins whose areas range from 0.5 to 784 

acres. The average subbasin area is 43 acres. Using Hillsborough County’s naming 

convention, each subbasin is represented by a unique six-digit number that is the 

same as the junction node number to which the subbasin drains. In the Alafia River 

Main Stem Subwatershed, most of the junction (and subbasins) numbers have a 

prefix of “70” except for those in the Rice Creek Tributary, where the prefix is “71”. 

The principal data source for basin delineation is Hillsborough County supplied DEM. 

Other documents, such as grading, drainage, and construction plans from the 

SWFWMD Environmental Resource Permits (ERPs), Hillsborough County 

construction plans, and FDOT Roadway plans, provide additional details that is often 

necessary in newly developed areas. 



this study for each subbasin in the Alafia River Main Stem Subwatershed by an areaweighted 

averaging procedure that assigned a universal CN value to each 



for the Alafia River Main Stem Subwatershed. The resulting final subbasin runoff 

curve numbers for the Alafia River Main Stem Subwatershed are presented in the 

updated Alafia River ArcGIS geodatabase 









As discussed in Chapter 4, the hydraulic model used for this study was a version of 

the EXTRAN block of the U.S. Environmental Protection Agency Stormwater 

Management Model, Version 4.31b (SWMM) Extended Transport Block (EXTRAN) 

that was modified by Hillsborough County for use in its watershed management 

planning program 


The Alafia River Main Stem Subwatershed hydrodynamic model resolution includes a 

total of 1079 junctions and 1839 linkages in its structure, including, 350 irregular open 

channels, 4 pump stations, and 1011 weirs. 


Stormwater management facilities such as detention ponds and retention ponds, 

together with lakes, wetlands, and natural depressions comprise these variable 

storage junctions The EXTRAN model requires the stage-area data input for every 

variable-storage junction for the entire water-quantity attenuation depth (note some 

need additional extension of this depth for the sake of model stability). This 

information was obtained from the DEM dataset or available record plans where DEM 

data did not match existing conditions of the model domain (i.e. topographic void 

area). 


Closed conduits take the form of circular, rectangular, elliptical, and arch. 

Dimensional parameters of the closed conduits were from past plans, field surveys, 

and some direct measurements by Parsons staff. There are 474 closed conduits in 

the Alafia River Main Stem Subwatershed hydraulic model. 



conduits. In the Alafia River Main Stem Subwatershed model, most of the larger 

bridge spans are modeled as the respective surveyed cross-section, with additional 

roughness coded to represent friction loss associated with piers. Where bridges 

experience full-flow conditions, the depth of the channel cross section is limited to the 

elevation of the low chord. This strategy allows the surcharge condition to be 

modeled. In most cases, bridge structures are modeled using the guidelines 

described in Section 4 for abstraction of an equivalent combination of box culverts, 

with different dimensions and inverts. The model includes numerous equivalent 

sections for bridges. 






The model includes 1011 weir connections for the Alafia River Main Stem 

Subwatershed hydraulic model. These weirs model the overtopping of control 

structures, pond banks, roadways at channel crossings, and overland flow. Data for 

crest elevations and widths are form structure surveys, construction plans, and field 

measurements. All closed basins associated with phosphate mines include a top-ofbank 

weir to allow overtopping of the storage area during extreme flood events. All 

road crossings include a top-of-road weir to allow overtopping of the road during 

extreme flood events. Roadway overtopping is simulated with broad-crested weirs. 

Weir crest elevations are from structure surveys or topographic maps. Overland flow 

provides a conduit for floodwater to circumvent the normal flowpath in the drainage 

system. Weirs simulate these drainage paths, with weir crest elevations and lengths 

from topographic maps. 


The Alafia River Main Stem Subwatershed hydraulic model has 350 open channels. 

These irregular cross section data define the low flow channel and overbank 

floodplain of natural cross sections. It is necessary to code the natural overbank 

floodplain explicitly so that both floodplain storage and conveyance functions are 

modeled. The most current, detailed, and representative data for any particular reach 

of the open channel system are coded. In many cases, channel cross-section data 

from surveys are extended with data from topographic maps to define the full extent 

of the natural floodplain. Channel cross-section data for the Alafia River main 

channel were obtained exclusively from the 1992 FEMA HEC-2 Model and 

incorporated in the exact same format as the original source. 






supported by published guides and past modeling experience. These values were 

confirmed or adjusted during model calibration. In the Alafia River Main Stem 

Subwatershed model, Manning’s roughness coefficients (n) range from 0.035 for the 

“cleanest” channels reaches to 0.08 for highly vegetated reaches. Floodplain 

roughness coefficients range from 0.08 to 0.18. 

5.8.3.6 Basin Boundary Conditions 

The HCSWMM model requires specification of hydraulic boundary conditions at all 

outfall points of the model schematic. In the Alafia River Watershed application, the 

primary watershed outlet is located at the downstream end of the river itself where it 

discharges to Hillsborough Bay. A constant tailwater boundary condition representing 

the water elevation of the bay, a tidal waterbody, was specified at elevation 1.09 ft 

North American Vertical Datum (NAVD) for all model simulations. This elevation 

represents a high tide condition. 





Additionally, 3 other boundary conditions were identified during this model update. All 

three are overland weirs which represent “popoff” elevations to the Little Bullfrog 

Watershed to constant time-stage boundary nodes. These locations are; just south of 

Nundy Ave, just to the south of the I-75/Gibsonton Rd intersection and west of Hwy 

301 near Berner Lane. These hydraulic connections are only breached during 

extreme storm events. 














Within the Alafia River Subwatershed, historical streamflow and precipitation data are 

readily available to meet the set of conditions listed above for the purpose of model 

calibration and verification. Parsons obtained hourly streamflow and stage data from 

the U.S. Geological Survey streamflow gaging station (02301500), which is located on 

the downstream side of the Lithia-Pinecrest Road bridge. The USGS has operated 

this streamflow gaging station within the basin continuously from October 1932 to the 

present. Over the past 60-year period of record, the selected maximum 

instantaneous peak flow that was recorded was 20,300 cfs on September 12, 1960. 

At that time, the maximum observed flood elevation was 30.07 ft NAVD, 

approximately 21 feet deep above the channel bottom. The USGS rates the relative 

accuracy of the streamflow gaging data at this station as "good", indicating that about 

95 percent of the daily discharges are within 10 percent of their true values. 

Recorded precipitation data for gages in the vicinity of the Alafia River Watershed 

were obtained from the Southwest Florida Water Management District (SWFWMD) 

and the National Oceanographic and Atmospheric Administration (NOAA). The 

locations of these gages that were operating during the period of record for which 

corresponding streamflow gaging data are available are shown on the Alafia River 

precipitation gage location map shown in Figure 5.4-4. From this map, it can be seen 

that there are more than thirty historical precipitation gage stations located within the 

geographic proximity of the watershed. It should be considered that, for most of those 

stations shown, the historical data consist only of daily accumulations of recorded 





precipitation and that the time of day of gage observation will differ between sites. 

For most of the period of record (until the last 5 years), the only recording precipitation 

gaging stations (i.e. hourly data) that were in operation were those NOAA stations at 

the Tampa International Airport, Parrish, and Lakeland, and one SWFWMD station 

located at Pierce (in Polk County). Most recently, the SWFWMD has installed and 

operated recording precipitation stations at an additional seven locations in the 

geographic vicinity, those SCADA stations being the Medard Lake (Pleasant Grove), 

Mulberry, Dover DV-1, Four Corners, Thatcher, Alafia, and Starling stations. 

It is noted that the Alafia River streamflow gage station is located downstream of the 

confluence of the North Prong Alafia River, the South Prong Alafia River, English 

Creek, and Turkey Creek. These subwatersheds comprise the great majority of the 

contributing drainage area to this gage location. Therefore, the efficacy of the 

previously documented subwatershed model calibrations performed for these major 

subwatersheds dictate to a large extent the composite watershed model response to 

historical storm events at this gage station and its accuracy. For the purpose of 

calibrating and verifying the Alafia River Main Stem Subwatershed model to these 

streamflow gaging data, it was required at this point that all the subwatershed 

components be combined with it into a single Alafia River Watershed model. 


As in all other streamflow recording gage locations described in previous sections, the 

calibration of a comprehensive Alafia River Watershed hydrodynamic model was 

performed using rainfall and streamflow gaging station data for the September 4-7, 

2004 historical storm event as the basis for adjusting the initial model input data, 

including both hydrologic and hydraulic input parameters. The verification of the 

model was conducted using the September 5-8, 1988 and the December 9-14, 1997 

historical storm events. 

The four-day storm that occurred from September 5-8, 1988 was actually a series of 3 

individual storm events that occurred at roughly 24-hour intervals. The combined 

Alafia River Watershed model was divided into nine separate zones that reflected 

similar rainfall patterns during this event, since it was apparent that precipitation was 

not spatially uniform over the entire drainage basin. Because of the large variance 

between gaging station totals, it was considered more prudent to utilize the average 

precipitation over these “zones” rather than use the individual records with a Thiessen 

weighting procedure, thus reducing any bias induced by potentially erroneous 

individual records. This potentially wide range of recorded precipitation over the 

expanse of the subwatershed leads to uncertainties in the model calibration process 

that are lessened through such an averaging procedure. 

The nine geographic zones that were defined to represent this event and the average 

total rainfall calculated for each are as follows: (1) lower Alafia River, Buckhorn Creek, 

northern Bell Creek, and northern Fishhawk Creek, 10.87 inches; (2) Turkey Creek 

and upper Alafia River, 11.87 inches; (3) southern Bell Creek and southern Fishhawk 





Creek, 11.86 inches; (4) English Creek, 7.00 inches; (5) northern North Prong, 7.19 

inches; (6) Thirty-Mile Creek, 8.52 inches; (7) northern South Prong, 12.76 inches; (8) 

southwestern South Prong, 11.40 inches; and (9) southeastern South Prong, 8.82 

inches. 


September 1988 storm event, hourly data from three recording precipitation stations 

were used; the Lakeland, Parrish, and Pierce stations. These rainfall distributions 

were selected for use in the physical calibration of the combined Alafia River 

Watershed model because, of the few such records available, they appeared to best 

correlate to the streamflow gaging station records in terms of timing. 

As discussed in previous sections of this chapter, the preceding 5-day total rainfall for 

all the precipitation gages that were used in model calibration and verification events 

generally fell within the 1.4 to 2.1 inch range that defines an AMC II condition. 

The five-day storm from December 9-14, 1997 provided the basis for an additional 

model verification storm event. It began as a few days of light rain that was followed 

by two heavy days during which most of the total rainfall volume fell. Precipitation 

was more spatially uniform over the Alafia River Watershed during this event, and the 

model subbasins were segregated into just four zones of similar rainfall pattern. The 

four geographic zones that were defined to represent this event and the average total 

rainfall calculated for each are as follows: (1) lower and upper Alafia River, Buckhorn 

Creek, Bell Creek, northern South Prong, and Fishhawk Creek, 6.38 inches; (2) 

Turkey Creek, English Creek and lower North Prong, 5.77 inches; (3) upper North 

Prong, 5.34 inches; and, (4) upper South Prong, 5.43 inches. To facilitate hourly 

distribution of the rainfall depth over this event, the hourly data from the SWFWMD 

Pleasant Grove, Dover DV-1, Mulberry, and Thatcher recording gages were used. 

The distributions recorded at these gages were assigned for use in this storm event 

simulation based on geographic proximity. 







It was previously noted that the Alafia River streamflow gage station is located 

downstream of the confluence of the North Prong Alafia River, the South Prong Alafia 

River, English Creek, and Turkey Creek. These subwatersheds comprise the great 

majority of the contributing drainage area to this gage location. Therefore, the 

efficacy of the previously documented subwatershed model calibrations performed for 

these major subwatersheds dictate to a large extent the composite watershed model 

response to historical storm events at this gage station and its accuracy. 





* Runoff curve numbers (CNs) for different soil groups and land use 


* Channel, floodplain, and culvert roughness coefficients (Manning's n) and 


* Times of concentration for individual subbasins, and 

* Unit hydrograph shape factors. 

In the SWMM model calibration for the Alafia River Watershed, these parameters 

were initially derived using accepted methods and values derived from literature 

research and from past model applications in the region. Their final values were 

ultimately derived through the model calibration process. 





















reaches from the gaging station location at the Keysville Road bridge. Since a rating 


calibrate the channel roughness coefficients for the entirety of the Alafia River. What 

this exercise provided was the basis for the estimation of the channel and floodplain 

roughness coefficients in the other channel reaches of the basin. References found in 

engineering literature were also used in this process. 

Calibration and Verification Results 

The combined Alafia River Watershed model was run for a 10-day time period from 

September 4 through September 14, 2004 because of the importance to consider 

both the peak conditions in the watershed and the recession limb of the flood 

hydrograph during calibration. It is also important to note that, for this storm event, 

the USGS indicated that for site 02301500, Alafia River at Lithia, unit value data 

(hourly) was deleted for August 16, 2004-November 11, 2004 due to erratic readings 

when the orifice was covered. Average daily data for stage and flow was estimated 

and approved for publication. This data was used and compared to average daily 

totals calculated from model simulations. Figures 5.8-4 and 5.8-5 show comparisons 

of the recorded and simulated (average daily) flows and stages, respectively, at the 

USGS streamflow gaging station at the Lithia-Pinecrest Road bridge. The model 

formulation was adjusted at the initiation of the event by the addition of groundwater 

baseflows in the subwatersheds that amounted to a total of 1200 cfs at this location to 

match existing flows at the onset of the storm event. As can be seen in the two 

figures, there is fairly good correlation during peak flow conditions in both the 

magnitude and timing of flows and flood elevations. The peak stage and flow for the 

model simulation were 27.8 ft NAVD and 10,704 cfs respectively. The recession limb 

of the simulation is slightly high, but considering the absence of hourly data at this 

gage with using the average daily data the calibration is considered to be a success. 

A second gage approximately 4 miles downstream of the 02301500 gage at Lithia- 

Pinecrest Road was also used for the calibration of the Alafia River. A gage (USGS 

02301638) was installed in 1998 at Bell shoals Rd. as part of the flow withdrawal 

analysis for the C.W. Bill Young Regional Reservoir. This is a stage gage only and no 

flow data is available for this location. 15-minute stage data was obtained from 

Tampa Bay Water, who owns the reservoir, and used for adjusting model parameters 

in the calibration process. Although this data is only stage it was of better quality than 

the 02301500 gage because of its frequency of temporal data points. Figure 5.8-6 

shows the stage comparison at the Bell Shoals Rd. gage location. As can be seen in 

the graph, a reasonable correlation for the model simulation of shape, timing and 

magnitude was achieved. The recorded peak stage at 02301638 was 18.63 ft NAVD 

compared to the simulated peak stage 18.2 ft NAVD, a difference of only 0.43 feet. 

The model simulation hydrograph does not peak as sharp as the recorded data, and 

coincident stage at initiation of the model run was not achieved. 





FIGURE 5.8-4: Alafia River at Lithia (USGS 02301500) 


Estimated Daily Average Flow 

12000 

Recorded 

10000 

Simulated 


8000 

6000 

4000 

2000 

0 

9/4/2004 

9/5/2004 

9/6/2004 

9/7/2004 

9/8/2004 

9/9/2004 

Time (days) 

9/10/2004 

9/11/2004 

9/12/2004 

9/13/2004 

9/14/2004 

FIGURE 5.8-5: Alafia River at Lithia 

September 4 -14, 2004 Calibration Storm Event 

Estimated Daily Average Stage 

32 

30 

Recorded 

Simulated 

28 


26 

24 

22 

20 

18 

16 

14 

9/4/2004 

9/5/2004 

9/6/2004 

9/7/2004 

9/8/2004 

9/9/2004 

9/10/2004 

9/11/2004 

9/12/2004 

9/13/2004 

9/14/2004 

Time (days) 






22 

20 

18 

16 

14 

12 

10 

8 

6 

4 

2 

0 

FIGURE 5.8-6: Alafia River at Bell Shoals (USGS 02301638) 


Recorded 

Simulated 

9/4/2004 

9/5/2004 

9/6/2004 

9/7/2004 

9/8/2004 

9/9/2004 

9/10/2004 

Time (days) 





No survey was available for the channels in the vicinity of this area except the FEMA 

cross section from the 1970’s. It is likely that the channel shape or invert may be 

slightly off which would shift the initial stage of the model run down to the recorded. 

Without new survey data model randomly changing channel configuration in the 

model data is not warranted. Even considering this potential discrepancy, the 

calibration is with reasonable limits. 

The combined Alafia River Watershed model was run for a 10-day time period from 

September 5 through September 14, 1988 because of the importance to consider 

both the peak conditions in the watershed and the recession limb of the flood 

hydrograph during calibration. Figures 5.8-7 and 5.8-8 show comparisons of the 

recorded and simulated flows and stages, respectively, at the USGS streamflow 

gaging station at the Lithia-Pinecrest Road bridge. The model formulation was 

adjusted at the initiation of the event by the addition of groundwater baseflows in the 

subwatersheds that amounted to a total of 400 cfs at this location. As can be seen in 

the two figures, there is fairly good correlation during peak flow conditions in both the 

magnitude and timing of flows and flood elevations. 

The peak flow that was recorded at the gaging station was 9453 cfs and occurred at 9 

AM on September 7, 1988. The corresponding model prediction is 11,328 cfs with 

near coincident timing, an over-simulation of approximately 20%. The model only 

deviates by 0.65 feet from the maximum flood elevation that was recorded (27.8 ft 

NAVD observed versus 28.45 ft NAVD simulated). This deviation is likely attributed to 

a collective of factors including, 20 years of land use changes, phosphate mining flux, 

simulation of initial storage capacity and rainfall data. Overall, the verification for the 

1988 event is acceptable. 

A second verification of the Alafia River Watershed model was conducted by the 

simulation of the 10-day time period from December 9 - 18, 1997. Figures 5.8-9 and 

5.8-10 show comparisons of the recorded and simulated flows and stages, 

respectively, at the USGS streamflow gaging station at the Lithia-Pinecrest Road 

bridge. The model formulation was adjusted at the initiation of the event by the 

addition of groundwater baseflows in the subwatersheds that amounted to a total of 

approximately 400 cfs at this location. As can be seen in the two figures, the model 

does over-predict the peak flow conditions at the gage in both the magnitude of flows 

and flood elevations. The peak flow that was recorded at the gaging station on 

December 14, 1997 was 4564 cfs. The corresponding model prediction is 5761 cfs 

with near coincident timing. In addition, the model deviates by 1.6 feet from the 

maximum flood elevation that was recorded (23.1 ft NAVD observed versus 24.7 ft 

NAVD simulated). Again the overall timing and shape of the hydrographs are quite 

good. 







14000 

12000 

Recorded 

Simulated 

10000 


8000 

6000 

4000 

2000 

0 

9/5/88 

9/6/88 

9/7/88 

9/8/88 

9/9/88 

9/10/88 

Time (days) 

9/11/88 

9/12/88 

9/13/88 

9/14/88 

9/15/88 



30 

28 

Recorded 

Simulated 

26 

24 


22 

20 

18 

16 

14 

12 

10 

9/5/88 

9/6/88 

9/7/88 

9/8/88 

9/9/88 

9/10/88 

Time (days) 

9/11/88 

9/12/88 

9/13/88 

9/14/88 

9/15/88 







7000 

6000 

Recorded 

Simulated 

5000 


4000 

3000 

2000 

1000 

0 

12/9/97 

12/10/97 

12/11/97 

12/12/97 

12/13/97 

12/14/97 

Time (days) 

12/15/97 

12/16/97 

12/17/97 

12/18/97 

12/19/97 



26 

24 

Recorded 

Simulated 

22 

Elevation (ft NAVD) 

20 

18 

16 

14 

12 

10 

12/9/97 

12/10/97 

12/11/97 

12/12/97 

12/13/97 

12/14/97 

Time (days) 

12/15/97 

12/16/97 

12/17/97 

12/18/97 

12/19/97 





Figure 5.8-11 shows a comparison of the model results to the USGS streamflow 

gaging station rating curve. As can be seen from this plot, the model hydraulic 

representation is a close match to the station record at this location. Therefore, the 

channel and floodplain roughness coefficients that are used in the model for this 

channel segment (0.060 and 0.160, respectively) are judged to be well-suited. 

Given the limitations of the available precipitation data by which the combined Alafia 

River Watershed model was calibrated, and the great degree of spatial variation in the 

precipitation that was observed over the watershed during the 1988 and 1997 storm 

events, the model calibration and verification effort were considered a moderate 

success as measured by the degree of agreement that was obtained in simulating the 

measured flow and stage data for these three events. It is also important to note the 

importance of the model limitations related to the gross assumptions with respect to 

the hydrologic response of lands owned by phosphate interests, specifically in Polk 

County, and the constant land use and land cover change which exists on these 

lands. Further definition of these factors is necessary to enhance the accuracy and 

utility of model results in these uppermost portions of the Alafia River Watershed. 

35 

FIGURE 5.8-11: Alafia River at Lithia Pinecrest Rd 


30 

25 


20 

15 

10 

USGS Rating curve 

Simuated 

5 

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 






5.9 VALRICO SUBWATERSHED 


The Valrico Subwatershed is located in the northwest portion of the Alafia River 

Watershed, in Hillsborough County. The subwatershed, shown in Figure 5.9-1, has a 

drainage area of 5.8 square miles. The area borders the Delaney Creek and 

Pemberton-Baker Creek watersheds. This subwatershed is actually its own 

watershed and does not drain to the Alafia River Watershed. This subwatershed is 

closed during all rainfall events; stormwater runoff ponds in large natural depressions 

and constructed stormwater management facilities. Nearly all ponded water exits the 

system by evaporation or infiltration during the dry portion of the hydrologic cycle. 

Stormwater that escapes entrapment in upland stormwater management facilities and 

natural depressed areas migrates to a chain of stormwater management facilities 

near the corner of State Road 60 and Valrico Road. This chain of ponds is the low 

point in the subwatershed. Stormwater is pumped from these ponds to the northwest 

into Lake Valrico in the Pemberton-Baker Creek Watershed. 

Hydrologic connections do not exist between this closed subwatershed and the Alafia 

River Watershed. This area was adopted into the Alafia River Watershed during the 

original 2001 study as part of the Turkey Creek subwatershed and is now its own 

subwatershed for the purposes of this update. 


There are no primary drainage systems within this subwatershed all runoff discharges 

directly to internally draining ponds or wetlands. 


Existing land use conditions in the Valrico Subwatershed were determined based 

upon the digital coverage from the Southwest Florida Water Management District 

(SWFWMD) Geographic Information System (GIS) database. Readers are referred to 

Chapter 4 for detailed discussion on land use classification. 

The original SWFWMD land use database was further verified and updated in this 

study for two reasons. First, a number of new developments on the Valrico 

Subwatershed in the past ten years have altered the land use characteristics in some 

areas. This information must be updated in the original SWFWMD land use database 

so as to reflect a consistent and up-to-date set of hydrologically valid land use 

coverage. Second, large areas of open, undeveloped land that were observed to be 

contained within the confines of the commercial, industrial, institutional, and 

transportation/communications/utilities parcels were segregated from these parcels 

digitally and reclassified as open land. 







WASHINGTON RD 

E BRANDON BLVD 

S VALRICO RD 

60 

S MILLER RD 

S SAINT CLOUD AVE 

S MULRENNAN RD 

S DOVER RD 

Legend 

County Line 




Roads 




Suite 120 



Notes: 

DURANT RD 

E LUMSDEN RD 

1:24,000 

0 600 1,200 2,400 

Feet 

0 0.125 0.25 0.5 

Miles 

Filename: 

Fig5_9_ 

1.mxd 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 


Valrico Subwatershed 



J:\DATA\260247_Alafia_WMP_Update\GIS\Maps\MXD\Report\Subwatersheds\VALRICO\Fig5_9_1.mxd





The resultant land use map of the Alafia River Main Stem Subwatershed for existing 

conditions is shown in Figure 5.9-2. 

TABLE 5.9-1 VALRICO SUBWATERSHED LAND USE 


TOTAL 

AREA 

(acres) 

PERCENTAGE OF 

SUBWATERSHED 

(%) 






Open Land and Rangeland 191 5.1% 

Cropland and Pastureland 98 2.6% 

Forest 130 3.5% 


Transportation, Communications & Utilities 42 1.1% 




Water 14 0.4% 

Wetland 39 1.0% 

Total 3723 100.0% 

Residential land use dominates the Valrico subwatershed with over 80 percent of the 

subwatershed’s land use. The highly urbanized and populated area only consists of 3 

percent agricultural and 5 percent open lands. The internally draining soils allow for 

smaller stormwater facilities and maximization of a developed area. 

5.9.1.3 Soils 

Figure 5.9-3 shows hydrologic soil classifications for the Valrico Subwatershed. The 

following table lists a composite breakdown of the distribution of the hydrologic soil 

types within the Valrico Subwatershed. 98 percent of the subwatershed is comprised 

of Type A soils. Less than one percent each of Type B/D, Type D, and Type C soils 

exist in the area. 





TABLE 5.9-2 VALRICO SUBWATERSHED SOILS 


GROUP 

TOTAL AREA 

(acres) 

PERCENTAGE OF 

SUBWATERSHED 

(%) 

A 3,663 98.4% 

B 0 0.0% 

B/D 25 0.7% 

C 29 0.8% 

D 6 0.2% 

Water 0 0.0% 

Total: 3,723 100.0% 


WASHINGTON RD 











1900/2600 - OPEN LAND 





5000 - WATER 




Legend 

County Line 



Roads 




Suite 120 




Notes: 

S VALRICO RD 

60 

DURANT RD 

S MILLER RD 


E LUMSDEN RD 

1:24,000 

0 600 1,200 2,400 

Feet 

0 0.125 0.25 0.5 

Miles 


Filename: 

Fig5_9_ 

2.mxd 

Map Date: 



N/A 

S DOVER RD 

Prepared By: 

Yoav 

Rappaport 







WASHINGTON RD 


A 

B 

B/D 

C 

D 

Water 

Legend 

County Line 



Roads 




Suite 120 




Notes: 

S VALRICO RD 

60 

DURANT RD 

S MILLER RD 


E LUMSDEN RD 

1:24,000 

0 600 1,200 2,400 

Feet 

0 0.125 0.25 0.5 

Miles 


Filename: 

Fig5_9_ 

3.mxd 

Map Date: 



N/A 

S DOVER RD 

Prepared By: 

Yoav 

Rappaport 











Rolling sand hills dominate the terrain in the Valrico Subwatershed. The karst area 

made up of entirely closed basins has elevations that range from 133 ft NAVD down 

to 33 ft NAVD less than 2 miles away. The most prominent ridge in the subwatershed 

extends from the Valrico Lookout Tower near the intersection of Dover Road and 

State Road 60 to the Diamond Hills Golf Course, just east of the Valrico Wastewater 

Treatment Plant. The ridge is along the western edge of the Turkey Creek 

Subwatershed, with elevations above 130 feet NAVD. 




development. In the Valrico Subwatershed approximately 80% of the entire basin is 

comprised of developed land use, with most of this development constructed within 

the last 20 years. Because of wealth of new development plans available, no survey 

was necessary to facilitate the model development for this area. 













The Valrico subwatershed area is an unique area to Hillsborough County with unique 

hydrologic characteristics. As discussed previously in this section, almost the entire 

subwatershed consists of Type A soils. These sandy soils can have a very high 

percolation rate. As also discussed previously in this section, this subwatershed is 

made up completely of internally draining closed basins. For this reason it was 

prudent to carefully examine the hydrologic method for this model update. 

The model hydrology and hydraulics were first run using the CN method within the 

HCSWMM software. As in the original 2001 Alafia River WMP study, model peak 

stages in several areas were extremely high. Model results and floodplain for the 

100yr/24 hr event using the CN method were presented to County staff. County staff 

confirmed that model stage results in most of the subwatershed were “unreasonably” 

high, even for a 100-year event. This opinion was based on empirical data and the 

lack of evidence that flood stages were ever close to these model results (i.e. no 





flooding complaints were reported for these areas and no high water flood marks 

could be verified anywhere close to the flood results). 

The SWFWMD, in their effort to submit updated FEMA floodplain maps for Hernando 

County, had encountered similar model result issues for karst areas where closed 

basins internally drained into sandy Type A soils using the CN hydrologic modeling 

approach. To resolve this problem, the SWFWMD (in cooperation with Streamline 

Technologies) developed a methodology for generating hydrologic parameters for use 

in the Green and Ampt (GA) hydrologic method. This hydrologic method for 

calculating runoff is based on soil infiltration rates, hydraulic conductivity and pressure 

head. The District (and their consultants) had good success with using this method to 

develop models (and floodplain maps) that generated more reasonable and realistic 

flood stages in areas that shared similar geological characteristics to that of Valrico 

Subwatershed area. 

Armed with this knowledge, Parsons took it upon itself to customize an impervious 

area land use table to the Valrico Subwatershed and use the NRCS SSURGO (Soil 

Survey Geographic) Database as input parameters to develop runoff hydrographs 

using the GA method. ArcGIS subroutines and the Interconnected Channel and Pond 

Routing (ICPR) v3 software were utilized to quickly generate the data. 

Because the HCSWMM software is equipped to only handle the CN method for 

hydrology, CNs were back-calculated using the NRCS CN and potential maximum 

soil retention equations based on the runoff values generated from the GA hydrology 

for the Valrico Subwatershed. Documentation regarding the details of methods and 

procedures for generating GA parameters and how ICPR formulates the data are 

found in Appendix A. 

Modeled peak stages calculated from using the (GA back-calculated) curve numbers 

in HCSWMM were much more reasonable in all areas of the subwatershed. County 

staff and Parsons reviewed the results of this modeling experiment and agreed that 

this method was more acceptable for purposes of mapping floodplains in this specific 

area of the study area. 


The Valrico Subwatershed is divided into 113 discrete subbasins, to provide the level 

of detail necessary to define and the primary and portions of the secondary drainage 

system. Subbasins range in area from 1.1 to 201 acres, and the average subbasin 

area is 33 acres. 

The following needs drive subbasin delineation: 

* definition of contributing drainage area to elements of the primary drainage 

system 





* definition of contributing drainage area to some elements of the secondary 

drainage system 

* definition of contributing drainage area to the outfall of a secondary drainage 

system into the primary drainage system 

* definition of contributing drainage area to a stormwater management facility 

* definition of contributing drainage area to a storage element 

* segregation of drainage areas as a function of homogeneous land use 

Figure 5.9-1 shows subbasin delineations within the Valrico Subwatershed. The 

Valrico Subwatershed observes a "759xxx" series and junction and subbasin 

numbers that fall between 706850 and 706880. The Hillsborough County supplied 

DEM dataset in addition to obtained development grading plans were used to build 

the subbasin dataset. 

5.9.2.2 Curve Numbers 

As previously discussed, the CN method was not used to calculate the CNs. The CN 

data was generated using back-calculated CNs based on the GA methodology. The 

resulting final subbasin runoff curve numbers for the Valrico Subwatershed are 

presented in the updated Alafia River ArcGIS geodatabase 





As discussed in Chapter 4, the hydraulic model used for this study was a version of 

the EXTRAN block of the U.S. Environmental Protection Agency Stormwater 

Management Model, Version 4.31b (SWMM) Extended Transport Block (EXTRAN) 

that was modified by Hillsborough County for use in its watershed management 

planning program 


The Valrico Subwatershed hydraulic model comprises a total of 121 junctions and 145 

linkages in its structure, 3 irregular open channels, 2 pump stations, and 129 weirs. 


Stormwater management facilities, lakes, natural depressions, and wetlands control 

drainage at some locations. The Extended Transport Block allows the user to specify 

a variable stage-area relationship at junctions. Hillsborough County DEM data and 

other backup data are used to develop these relationships. 

The initial water-surface elevations at these junctions are from three methods. On 

wet stormwater-management facilities, where a control structure exists to discharge 

stormwater into the surface-water drainage system, the starting water-surface 

elevation is the crest elevation of the control weir, or the invert elevation of the bleed- 





down orifice. On dry stormwater-management facilities, where stormwater seeps into 

the ground or evaporates, the starting water-surface elevation is the pond bottom. 

For natural ponds, lakes, and wetlands, the starting water-surface elevation is the 

normal high water elevation. If normal high water elevations do not exist in backup 

data, the starting water-surface elevation is some gross approximation of the normal 

high water elevation. 


The model details approximately 13 closed conduits, for the Valrico Subwatershed. 

Closed conduits take the form of circular, rectangular, elliptical, or arch pipes. Data 

are from construction plans or field measurements. 

5.9.3.4 Weirs 

The model includes 129 weir connections for the Valrico Subwatershed. Weirs model 

the overtopping of control structures, pond banks, roadways at channel crossings, 

and overland flow. Data for crest elevations and widths are from construction plans 

and field measurements. All stormwater management ponds include a top-of-bank 

weir to allow overtopping of the pond bank during extreme flood events. All road 

crossings include a top-of-road weir to allow overtopping of the road during extreme 

flood events. Roadway overtopping is simulated with broad-crested weirs. Weir crest 

elevations are from structure surveys, construction plans, or topographic maps. 

Overland flow provides a conduit for floodwater to circumvent the normal flowpath in 

the drainage system. Weirs simulate these drainage paths, with weir crest elevations 

and lengths from topographic maps. 


The model details only 3 irregular cross sections, for the Valrico Subwatershed. 

Irregular cross section data define the low flow channel and overbank floodplain of 

natural cross sections. It is necessary to code the natural overbank floodplain 

explicitly so that both floodplain storage and conveyance functions are modeled. The 

most current, detailed, and representative data for any particular reach of the open 

channel system are coded. There are no significant streamflow channels in the 

Valrico subwatershed. 

5.9.3.6 Basin Boundary Conditions 

One boundary condition exists for the Valrico Subwatershed. The boundary condition 

is for discharge north, to Lake Valrico. A pump station is located on N. Valrico Rd. 

just north of SR 60. This pump station is coded into the model and pumps to Lake 

Valrico to facilitate flood relief from North. Valrico Road. The Lake is a boundary 

condition represented by a constant time-stage junction in the model. 


. 

Chapter 6 

parsons


Chapter 6 – Existing Conditions Flood Level of Service 

CHAPTER 6 

EXISTING CONDITIONS FLOOD LEVEL OF SERVICE 

Upon completion of the development and calibration of the hydrologic and hydraulic 

model(s) of the Alafia River Watershed primary drainage systems, the next step of 

the flooding conditions analysis was to apply the model(s) to assess the 

performance of the basin-wide drainage facilities for a given set of design storm 

events. Results of these simulations were then analyzed with respect to 

Hillsborough County’s adopted flooding level of service (LOS) criteria to identify 

locations within the watershed where the LOS criteria are not being met. These 

were compared to known flooding problem areas which were identified during the 

1997, 1998, and 2004 (Hurricane Frances) flood events to prepare an assessment 

of the existing flooding conditions within the watershed, and to target the principle 

areas to be addressed in the development of the watershed management plan. 

6.1 DESIGN STORM EVENTS 

Level of service is a functional performance designation given to public works 

facilities that provides a way of grading facility efficiency and prioritizing facility 

upgrades. The Stormwater Management Element of the Comprehensive Plan for 

Unincorporated Hillsborough County defines flood level of service by the attainment 

of incremental performance milestones during severe storms. This requires the 

definition of a set of hypothetical design storm events with defined attributes of total 

rainfall depth, temporal distribution, and recurrence interval (or frequency of 

occurrence). It is an assumption of these analyses that the rainfall intensity is 

spatially and temporally uniform and equivalent at all points within the 

watershed-in-question. Accordingly, this type of hypothetical design storm will 

sometimes generate conservative designs of stormwater management facilities. 

Hillsborough County has adopted as the basis for the evaluation of flooding 

conditions in the Alafia River Watershed the 2.33-year, 5-year, 10-year, 25-year, 50- 

year and 100-year return period, 24-hour duration design storm events. The total 

24-hour rainfall depths are listed below for each of the return periods. 

The total 24-hour rainfall depths associated with the design storms were determined 

based on the SWFWMD Environmental Resource Permitting (ERP) Information 

Manual (February 1996). These depths are expressed for the Alafia River 

Watershed as a function of annual exceedance probability and average recurrence 

interval, and are the result of region-wide probabilistic analyses of historic maximum 

annual rainfall depths over a long period of record. Annual exceedance probability 

is an expression of risk. It is the probability that, in any given year, the maximum 

annual 24-hour rainfall depth will exceed the cited rainfall depth. 




The table below represents the rainfall depths used for the design storm events for 

the Alafia River Watershed Management Plan Update. As can be seen in the table 

design storm rainfall depths varied across the watershed for some of the design 

events. This was done at the recommendation of the County. The rational is that 

the Alafia River Watershed spans over 30 miles from east to west and, in some 

cases, across more than one isohyetal rainfall contour established for design storm 

data. 

Design Storm Event 

Rainfall Depth (in.) 

Western Portion 

Rainfall Depth (in.) 

Eastern Portion 

Mean Annual 4.5 4.5 

5-year/24-hour 5.5 5.5 

10-year/24-hour 7 6.5 

25-year/24-hour 8 8 

50-year/24-hour 10 9 

100-year/24-hour 11 10 

It should be noted that the design storm event depth citations are the product of 

historical analyses of a very long period of record. Every subsequent year that 

passes can potentially change these estimates, as additional data are added to the 

period of record. However, it is unlikely that any given year alone will skew the 

long-term analyses. 

Average recurrence interval is another way of expressing annual exceedance 

probability. The average recurrence interval is simply the inverse of annual 

exceedance probability. Recurrence intervals represent long-term average periods 

between events. Rare events may occur at shorter intervals, or even within the 

same year. For instance, it can be stated that, over a long period of time, 10 years 

is the average period between the occurrences of two maximum annual 24-hour 

rainfall depths greater than 6.5 inches. 

The average recurrence interval concept can be very misleading to non-technical 

individuals. A temptation exists to conclude that if a 100-year storm occurs, 100 

years must pass before another 100-year storm will occur. Assume that it were 

possible to continuously replay a 100-year time period, and record the maximum 

annual rainfall depth in each year of each realization of the 100-year period. More 

often than not, the 100-year depth will only be exceeded once in any set of 100-year 

time periods. However, some sets of 100-year periods will include multiple 

exceedances of the 100-year depth, and some will include no exceedances of the 

100-year depth. The standard Flood Insurance Study text published by the Federal 

Emergency Management Agency's National Flood Insurance Program for numerous 

communities across the United States contains the following insightful statement: 




“The risk of having a flood that equals or exceeds the 100-year flood 

(1-percent chance of annual exceedance) in any 50-year period is 

approximately 40 percent (4 in 10); for any 90-year period, the risk 

increases to approximately 60 percent (6 in 10).” 

It is important to note that there is an inherent assumption in the design storm 

approach that the hypothetical design rainfall event with a given recurrence interval 

will produce a flood with the same recurrence interval, and at all locations within the 

watershed. This is not necessarily the case; a 24-hour duration storm with a 100- 

year rainfall depth may not produce a 100-year peak flood flow, or a 100-year 

floodplain. Variations in antecedent soil moisture conditions, water table, rainfall 

distribution, and initial lake elevations will effect the convolution of the occurrence 

probability of a rainfall depth to the occurrence probability of a flood elevation or 

floodplain. 

In accordance with SWFWMD design criteria, the SCS Type II Florida-Modified 

rainfall distribution curve was used to distribute the total storm depth over the 24- 

hour storm duration. This reference is consistent with that cited in the Hillsborough 

County Stormwater Management Technical Manual (SMTM). The following figure 

and table present this cumulative temporal rainfall distribution, which is based on a 

balanced storm method that centers the highest rainfall intensities at the middle of 

the 24-hour storm duration. As shown, the design storm is represented in 30- 

minute increments of rainfall calculated by multiplying the total storm depth by the 

incremental changes in the cumulative distribution curve. The product of this 

procedure is called a design storm hyetograph. 

SCS Type II Florida-Modified Rainfall Distribution for 24-Hour Duration Storm 

100% 

Cumulative Depth [%] 

80% 

60% 

40% 

20% 

0% 

0 6 12 18 24 

Duration [hrs] 




Time 

(hours) 

Cumulative % 

of Total 

Storm Depth 

Time 

(hours) 

Cumulative 

% of Total 

Storm Depth 

Time 

(hours) 

Cumulative 

% of Total 

Storm Depth 

0.0 0.000 8.5 0.148 16.5 0.882 

0.5 0.006 9.0 0.164 17.0 0.893 

1.0 0.012 9.5 0.181 17.5 0.904 

1.5 0.019 10.0 0.201 18.0 0.913 

2.0 0.025 10.5 0.226 18.5 0.923 

2.5 0.032 11.0 0.258 19.0 0.931 

3.0 0.039 11.5 0.308 19.5 0.940 

3.5 0.047 12.0 0.607 20.0 0.948 

4.0 0.054 12.5 0.719 20.5 0.955 

4.5 0.062 13.0 0.757 21.0 0.962 

5.0 0.071 13.5 0.785 21.5 0.969 

5.5 0.080 14.0 0.807 22.0 0.976 

6.0 0.089 14.5 0.826 22.5 0.983 

6.5 0.099 15.0 0.842 23.0 0.989 

7.0 0.110 15.5 0.857 23.5 0.995 

7.5 0.122 16.0 0.870 24.0 1.000 

8.0 0.134 

6.2 LEVEL OF SERVICE DESIGNATIONS 

Within the Stormwater Management Element of the Hillsborough County 

Comprehensive Plan, flood levels of service (LOS) are described as specific 

designations given to the service provided by a stormwater facility in terms of the 

frequency/duration (e.g., 10-year/24-hour) of the rainfall event that a particular 

facility can accommodate without causing floodwaters to rise above an acceptable 

level at that facility. The four flood level designations, A, B, C, and D that were in 

place when the original study was performed are as follows: 

• Level A – No significant street flooding 

• Level B – No major residential yard flooding 

• Level C – No significant structure flooding 

• Level D – No limitation on flooding 

It can be inferred from these designations that Level A is meant to be the highest 

service level and Level D the lowest. However, it can be seen that the criteria are 

somewhat subjective in the interpretation of what is defined as “significant” flooding. 

Also, this definition of level-of-service designations assumes that structures are 

elevated above yards, and yards are elevated above streets. This assumption is 

not valid everywhere in Hillsborough County, as streets are elevated above 

structures in many locations. Therefore, locations exist where Level A is satisfied 




(i.e. streets do not flood), but Level C is not satisfied because structures flood. This 

ambiguity in the LOS definitions can make the application and interpretation of the 

flooding level of service concept a challenge. 

The term “significant flooding” which is used in the County’s Comprehensive Plan is 

interpreted to refer to flooding which prohibits the use of a roadway by vehicles (i.e. 

nuisance and minor flooding are not to be included in the definitions of flooding). 

The LOS definition that has been adopted by the County for use within this analysis 

establishes the assigned LOS designation based primarily on the road crown 

elevation, and relates the existence of significant street, yard and/or structure 

flooding to the depth of flooding of the street. 

Numerical criteria were adopted as a means of providing measurable depth 

definitions of “significant flooding” for determining existing LOS in the original study 

and are being used in this update. Two new LOS designations, D* and O were 

added to provide greater problem definition in assessing existing LOS. 

It should be noted that the LOS designations were redefined in updates to the 

Hillsborough County Comprehensive Plan since the original study was performed 

and are as follows: 

• Level A - No significant street flooding. All lanes are drivable*. 

• Level B - Minor street flooding. At least one lane drivable* 

• Level C - Street flooding. Flooding depth above road crown is less than one 

foot. 

• Level D - No limitation on flooding 

*The term drivable defined as less than or equal to three (3) inches of water 

above the crown of the road. 




It is assumed that while the definition of Levels B and C in the current LOS have 

been revised, that the level of protection is still the same. Note that the current 

level-of-service for Levels B and C have been included in parentheses in the 

following table. 

Flooding 

Level of 

Service 




Management Plan Definition 

A No significant street flooding Street flooding is less than 3” above 

the crown of road 

B 

C 

No major residential yard flooding (Minor 

street flooding. At least one lane 

drivable) 

No significant structure flooding (Level C 

- Street flooding. Flooding depth above 

road crown is less than one foot.) 

Street flooding is more than 3” 

above the crown of road, but less 

than 6” 


above the crown of road, but less 

than 12” 

D No limitation on flooding Street flooding is more than 12” 

above the crown of road 

D* No limitation on flooding* Flood elevation is greater than 

finished floor elevation, and street 

flooding is less than 12” above the 

crown of road 

O N/A No structure and no street to 

compare with flood elevation 

Hillsborough County has assigned three levels of service to all its major stormwater 

conveyance systems: (a) Adopted, (b) Target, and (c) Ultimate, as defined below: 

(a) The Adopted Level of Service describes the existing condition: the response of 

the existing stormwater conveyance system to the suite of hypothetical design 

storm events. 

(b) Hillsborough County's goal is to achieve the Target Level of Service throughout 

the county. Target level of service is uniform throughout the county and 

promulgated by the Board of County Commissioners in the Comprehensive 

Plan. 

(c) Ultimate Level of Service is a practical goal, where physical or environmental 

constraints prohibit the achievement of the target level of service. It is stated in 

the Comprehensive Plan that at some locations, "physical and/or environmental 

constraints will not allow an existing system to be modified to the Target (level of 

service)." At these defined locations, the ultimate level of service is deemed the 

highest achievable. 




The goal of the County’s Watershed Management Planning program is to develop a 

capital improvement program to improve the flooding level of service for all 

watersheds from the adopted to either the target or ultimate LOS. The Board of 

County Commissioners, in the Comprehensive Plan, promulgated the 25-year/24- 

hour/B flooding level of service as the target level of service for all watersheds 

within the county. The ultimate LOS standards have not been determined for the 

major stormwater conveyance systems located outside of the areas for which 

completed watershed management plans currently exist. These standards are to be 

established via the Comprehensive Stormwater Management Master Planning 

Program, of which this study is a part. 

The Board promulgated the 10-year/24-hour/B flooding level of service as the 

Ultimate level of service in the Buckhorn Creek Subwatershed of the Alafia River 

Watershed. The Comprehensive Plan contains the following passage: 

“The 10-year/24-hour/B level has been identified as the ultimate level 

of service standard for the major stormwater conveyance system 

located within the Buckhorn Creek subbasin. This lower ultimate 

level of service was chosen due to environmental constraints 

associated with the most downstream reaches of the subbasin which 

prohibit channel modifications of any significance.” 

The Buckhorn Creek Subwatershed is the only basin within the Alafia River 

Watershed with a promulgated ultimate level of service. The County must therefore 

develop a capital improvement program within the Buckhorn Creek Subwatershed 

to improve the flood level of service provide by the major conveyance system, such 

that land and structures do not flood during a 10-year/24-hour duration design storm 

event. 

The capital improvement recommendations developed for this Alafia River 

Watershed Management plan recognize an ultimate 10-year/24-hour/B flood level of 

service goal in the Buckhorn Creek Subwatershed. The capital improvement 

recommendations developed for this plan consider, in all other basins of the Alafia 

River Watershed, recognition of the promulgated 25-year/24-hour/B target flood 

level of service as the goal. This means that a limited amount of street flooding is to 

be tolerated, but no major residential yard flooding or structure flooding is 

acceptable in the Alafia River Watershed for these respective design storm events. 

Additionally, where "physical and/or environmental constraints will not allow an 

existing system to be modified to the target level (of service)" within the watershed 

but outside the Buckhorn Creek Subwatershed, the capital improvement 

recommendations developed for this watershed plan acknowledge an appropriate 

reduced ultimate flood level of service. 




6.3 LEVEL OF SERVICE ANALYSIS METHODOLOGY 

The methodology used to assess the flooding levels of service provided by the 

Alafia River Watershed major drainage system was to use the County DEM dataset 

and compare the SWMM model results of the design storm events to road and 

residential finished floor slab elevations at selected points throughout the 

watershed. Survey data and/or as-built construction plans compiled from various 

sources for the purpose of this study were also utilized extensively in this effort 

when they were available. These sources included: 

• Environmental Resource Permits at the Southwest Florida Water 


• Stormwater management master plans, comprehensive plans, and 

Development of Regional Impact plans at Hillsborough County 

• Conventional field survey by Edgemon Land Surveying, Wilson Miller, 

Tomasino and Associates, and Strayer Surveying and Mapping 

For this Update to the WMP study, the first step was to examine the existing LOS 

points established during the original 2001 Alafia River WMP study. At each point 

location the structure and road elevation associated with the point was verified or 

changed to be more accurate based on the new topographic DEM dataset obtained 

from the County. While validating point road and structure elevations to evaluated, 

the node associated with that points (to be compared to) was also confirmed. It is 

important to compare the correct LOS point elevation to the intended model junction 

elevation. 

Once this was accomplished, new LOS points were added to the dataset at every 

location where the model updated, this included; new subdivisions, road crossings, 

commercial development and newly constructed Capital Improvement Projects. 

Points were placed as geographically correct as possible, but also located such that 

spatial referencing could be used if possible. 

The County flood complaint database was also considered during this project task. 

A LOS point was created in the vicinity of every flooding complaint location as to 

ascertain the LOS at these locations. This was a critical step. 

Parsons utilized this general methodology to establish the flooding LOS elevations 

at close to a thousand locations throughout the Alafia River Watershed. These 

locations are listed in the following subwatershed narratives. Due to the high 

degree of uncertainty in the derivation of these elevations, it is emphasized that the 

assessment of the flooding LOS provided within the watershed and the identification 

of problem areas should be confirmed. This assessment should be supplemented 

with further investigations in the form of field surveys of streets and residential 




finished floor slab elevations to confirm the existence and/or magnitude of the LOS 

deficiencies and flooding problems that are identified in the subsequent sections. 

Once the set of street and structure flooding elevations were determined and 

compared to the model results for the 2.33-, 5-, 10-, 25-, 50-, and 100-year design 

storm events, it was a relatively simple procedure to assign the appropriate flooding 

LOS provided at each individual location for existing conditions in the watershed. 

Because the County has recently adopted a LOS by subbasin approach, the County 

asked if Parsons would convert the LOS by point location to a LOS by subbasin. 

This was accomplished by associating the junction related to the points with the 

subbasin. When doing this conversion it was noticed that, at road crossings, if a 

road was a subbasin divide, the subbasin downstream may not have a level of 

service point to associate with. The junction associated with the LOS point would 

have the upstream junction related to it. This is the junction that would typically 

represent the flood depth over the road. For this reason quantifying subbasins 

areas or numbers (how many) may not always give an accurate gage of the LOS for 

a specific watershed or subwatershed. 





6.4.1 Historical Flooding Problems 

Hillsborough County Central Service Unit Reported Problems 

In 2001, Parsons interviewed the Hillsborough County Central Service Unit, the 

branch of the County that performs maintenance of the drainage system in the 

Buckhorn Creek Subwatershed. The Unit reported 11 locations that experience 

recurring flood problems. Locations are detailed Table 6.4-1 and shown on Figure 

6.4-1. 

1997/1998 El Nino Floods 

From late September 1997 through January 1998, a series of extreme storm events 

and continuous wet weather patterns in central Florida generated some of the worst 

flooding conditions recorded in the last 20 years. The flooding began on September 

26, 1997 when a total of 12.41 inches of rainfall was recorded at the Alafia 

precipitation gage over a 36-hour time period. Flooding conditions would have been 

much worse than observed had the region not experienced a relatively dry summer 

season beforehand. The second round of this period of wet weather was a 4-day 

period from December 10 through 13, when a cold front moved into west-central 

Florida and stalled, resulting in heavy showers and thunderstorms over the area. A 

total of 5.85 inches of precipitation were recorded at the Alafia gage over this 4-day 

period. Another frontal system delivered an additional 4.16 inches from December 

25th through 27th, and the monthly total rainfall was 12.56 inches. Finally, another 

storm front delivered a total of 8.24 inches of rain on February 17, 1998 to culminate 

this series of events. 

2004 Hurricane Frances Floods 

Hurricane Frances made landfall on the west coast of Florida on September 4, 2004 

and emerged onto the Gulf of Mexico north of Tampa on September 8, 2004 

resulting in a total of 9.4 inches of precipitation at the USGS Alafia gage. Flooding 

in the Alafia watershed began on September 6, 2004. Incidents reported from this 

event were added to the Hillsborough County flood database. 

Four Complaints located within the Buckhorn Creek Subwatershed are listed in 

Table 6.4-1, and the locations of the individual complaints are plotted in Figure 6.4- 

1. There were a total of 25 individual flooding complaints within the Buckhorn Creek 

Subwatershed. It can be seen from close examination of Table 6.4-1 that a number 

of these complaints were repetitive (i.e. same location). It is also noted that the 

County database does not include a description of the nature of the problem for 

those complaints that were reported during the February 1998 flooding event, thus 

limiting its interpretive usefulness. 




Table 6.4-1 

Buckhorn Creek Subwatershed Reported Flooding Problems 

INFORMATION 

SOURCE 

MAP REFERENCE 

NUMBER 

LOCATION 

DESCRIPTION 


Central Service Unit 

45 Guiles Road at Buckhorn Springs Manor and St. Marks UCC Road and yard flooding reported 

46 Hurley Ditch north of Bloomingdale Ave Heavy channel vegetation and sedimentation. Central Service Unit to conduct regular maintenance. 

47 Bell Shoals Rd south of Bloomingdale Ave. Bell Shoals Rd and Bloomingdale Ave road flooding reported 

48 Bell Shoals Rd and Bell Shoals Ln Residential yard flooding from depressional area off Bell Shoals Lane due to no outfall connection 

49 Ronelle Ditch at confluence with Buckhorn Creek Channel bank erosion at confluence of channels. Central Service Unit to place riprap protection. 

50 Barkfield Street Road flooding from high tailwater condition in Tanglewood Canal west of Kings Ave 

51 Tanglewood Canal Heavy channel vegetation and sedimentation. Central Service Unit to conduct regular 6 month maintenance schedule. 

53 Bloomingfield Dr Pond Outfall Maintenance and repair or reconstruction of pond outfall needed. 

54 Shady Nook Dr Pond Outfall Maintenance and repair or reconstruction of pond outfall needed. No access. 

55 Holland Drive Yard and road flooding from channel backup 

56 Misty Oaks Place Pond Pond flooding. Maintenance and repair or reconstruction of pond outfall needed. 

September 1997 

Flood Complaints 

14 Barkfield Ave Roadway flooded from 6" - 18" deep and one house was flooded at 623 Barkfield 

15 Bell Shoals Road Flooding was observed on this road adjacent to the new Kash N Karry near Bloomingdale Ave 

16 Bloomingdale Road east of Bell Shoals Rd Flooding of Bloomingdale Ave in front of the new Kash N Karry 

December 1997 Flood 

Complaints 

355 White Cedar Way Dirt washed out of ditches and threatening to damage sidewalks. Central Service Unit to repair ditches and erosion around sidewalks. 

259 Gulf Heights Circle Pond flooding. Citizen requesting pump. Pond is designed to be a percolation system with a 6" perforated drain. 

January 1998 Flood 

Complaints 

667 2227 Hickory Ridge Drive No information available 

671 3609 John Moore Road No information available 

679 1510 Nittany Ct. No information available 

803 2714 Golf Heights Cir No information available 

805 1202 Bloomingdale Avenue No information available 

806 2232 Village Court No information available 

940 624 Barkfield Street No information available 

954 229 Craft Road No information available 

967 3609 John Moore Road No information available 

986 3111 Rolling Acres Place No information available 

993 3802 Sweetleaf Court No information available 

996 2225 Village Court No information available 

998 120 W. Bloomingdale Avenue No information available 

1007 3068 Wister Circle No information available 

1082 2243 Eagle Bluff Drive No information available 


Hurricane Frances 


2013 John Moore Rd. North pond flooded at this location 

2018 Big Pine Drive Stormwater pond overflowing. Pond is high now but not overflowing. Inlet at end of street has water in about 4" below the ... 

2059 Orangepointe Rd. from Greenrock Pl. to Casaba Loop No information available 

2063 John Moore Rd. from El Greco Dr. to E. Bloomingdale Ave. Road flooding observed. 

2064 John Moore Rd. from Craft Rd. to El Greco Dr. No information available 






806 

996 


Flooding Complaints 

Legend 

Public Meeting 

Service Unit 

Frances Sept 2004 

January 1998 

December 1997 


County Line 


Suite 120 





Roads 



355 

Serv_51 


Notes: 

ALAFIA RIVER 

Serv_50 

S KINGS AVE 

Serv_49 


760 

14 

940 

998 

1:24,000 

JOHN MOORE RD 

2064 

2063 

671 

967 

2013 

0 600 1,200 2,400 

Feet 

0 0.125 0.25 0.5 

Miles 


954 


Serv_55 


993 

Filename: 

Fig6_4_ 

1.mxd 

Serv_56 


Serv_47 

Serv_54 

Serv_53 

Map Date: 


15 


N/A 

Serv_48 


2059 

Prepared By: 

Yoav 

Rappaport 

2018 

805 

GUILES RD 

HURLEY DITCH 

986 

Serv_45 

Serv_46 

679 

803 

667 

1082 

1007 

Figure: 6.4-1 - Historical Flood Complaint 





AL




6.4.2 Existing Conditions Model Simulation Results 

Using the design storm events as the basis for simulations, the hydrologic/hydraulic 

computer model was run to generate predictions of basinwide flooding conditions 

for the existing land use conditions and the existing drainage facilities throughout 

the Buckhorn Creek Subwatershed. For the purpose of this study, existing 

conditions refers to Year 2006 land use conditions and drainage facilities. Table 6.4- 

2 is a maximum flood elevation summary that lists the peak flood stages at each of 

the model nodes along the main conveyance systems for the various design storms. 

Table 6.4-3 presents a summary of the model-simulated peak flows at selected 

locations within the basin. 

Table 6.4-3 

Buckhorn Creek Subwatershed Peak Flows at Selected Locations 

Location 

Buckhorn Creek at 

Mouth (9720020) 

Buckhorn Creek at 

Kings Avenue 

(9720220) 

Buckhorn Creek at John 

Moore Rd (9720320) 

Buckhorn Creek at Bell 

Shoals Rd (9720680) 

Tanglewood Ditch at 

Mouth (9722000) 

Craft Road Ditch at 

Craft Road (9725080) 

Hurley Ditch at 

Bloomingdale Ave 

(9728160) 

Bloomingdale System at 

Mouth (9723000) 

2.33-year 

(cfs) 

5-year 

(cfs) 

10-year 

(cfs) 

25-year 

(cfs) 

50-year 

(cfs) 

100-year 

(cfs) 

611 804 1125 1282 1653 1931 

433 550 720 864 1348 1594 

400 510 665 813 1279 1524 

266 320 398 436 523 571 

149 203 284 338 427 468 

69 92 165 233 423 553 

70 143 247 351 519 605 

82 102 131 148 174 187 






TABLE 6.4-2 

ALAFIA RIVER WATERSHED MANAGEMENT PLAN UPDATE 

BUCKHORN CREEK SUBWATERSHED EXISTING CONDITIONS FLOOD ELEVATIONS SUMMARY 

24-HOUR DURATION DESIGN STORM 

MODEL MAXIMUM FLOOD ELEVATION, ft NAVD 88 

JUNCTION LOCATION DESCRIPTION 2.33-YEAR 5-YEAR 10-YEAR 25-YEAR 50-YEAR 100-YEAR 

Buckhorn Creek from Alafia River to Bloomingdale Avenue Bridge 

702400 Alafia River 4.77 5.99 7.37 9.11 10.40 11.44 

720020 Buckhorn Creek 5.84 6.73 7.40 9.11 10.40 11.44 



720080 Bloomingdale Ave Bridge Span (d/s) 17.02 17.62 18.26 18.61 19.71 20.23 

720100 Bloomingdale Ave Bridge Span (u/s) 17.06 17.66 18.31 18.66 19.79 20.31 

Buckhorn Creek from Bloomingdale Avenue Bridge to John Moore Road Bridge 


720140 Creek Bridge Road (d/s) 19.50 20.34 21.36 21.85 23.43 24.11 

720160 Creek Bridge Road (u/s) 19.65 20.52 21.59 22.10 23.81 24.72 

720180 Kings Ave (d/s) 22.64 23.13 23.76 24.23 25.69 26.46 

720200 Kings Ave (u/s) 22.71 23.22 23.86 24.34 25.83 26.60 

720220 Buckhorn Creek @ Trib C Outfall 24.42 25.02 25.74 26.24 27.57 28.17 

720240 Buckhorn Creek @ Trib D Outfall 25.44 26.18 27.05 27.70 29.12 29.62 




720320 John Moore Road (d/s) 29.45 30.14 30.76 31.32 32.58 33.06 

720340 John Moore Road (u/s) 29.52 30.28 31.00 31.60 32.89 33.41 

Buckhorn Creek from John Moore Road Bridge to Bell Shoals Road 

720360 Bloomingdale Ave (u/s) 29.60 30.39 31.17 31.83 32.95 33.45 

720380 Bloomingdale Plaza Entrance Rd. (d/s) 29.72 30.50 31.28 31.92 32.98 33.46 

720400 Bloomingdale Plaza Entrance Rd. (u/s) 29.97 30.88 31.89 32.67 33.40 33.75 

720420 Bloomingdale Plaza Mitigation Area 30.18 31.07 32.06 32.84 33.66 34.06 


720460 Dirt Drive (d/s) 31.11 31.45 32.27 33.07 33.92 34.28 

720480 Dirt Drive (u/s) 31.58 31.86 32.36 33.11 33.94 34.30 


720520 Buckhorn Creek @ Trib GG Outfall 33.07 33.23 33.46 33.87 34.30 34.62 

720540 Holland Drive (d/s) 34.26 34.50 34.77 35.06 35.35 35.46 

720560 Holland Drive (u/s) 35.24 35.63 35.91 36.10 36.38 36.49 

720580 Forest Bridge Road (d/s) 37.80 38.57 39.44 39.86 40.43 40.65 

720600 Forest Bridge Road (u/s) 39.43 40.49 41.63 41.79 41.99 42.12 

720620 Buckhorn Creek @ Bloomingdale West Outfall 40.62 41.33 42.32 42.56 43.06 43.42 

720640 Brookside Manor Road (d/s) 42.34 42.86 43.62 43.94 44.64 45.13 

720660 Brookside Manor Road (u/s) 43.19 44.12 45.59 46.32 47.49 47.72 

720680 Buckhorn Creek @ Trib F Outfall 45.47 46.04 46.96 47.46 48.33 48.55 

720700 Buckhorn Creek @ NE Trib Outfall 45.54 46.09 47.00 47.49 48.35 48.57 

Buckhorn Creek from Bell Shoals Road to Bloomingdale Avenue 

728000 Bell Shoals Rd (u/s) 45.96 46.30 49.00 49.47 49.80 49.91 


728010 Lake BL-3 46.77 47.17 49.02 49.51 49.85 49.97 

728020 Savanah Landings Junction Manhole 47.71 48.27 49.99 50.46 50.90 51.12 

728030 Junction Manhole 49.42 50.23 52.11 52.66 53.65 54.35 

728040 Savanah Landings Wetland Outfall 51.50 51.68 52.32 52.66 53.12 53.29 

728060 Savanah Landings Wetland 51.56 51.73 52.34 52.66 53.10 53.26 

728065 Springvale Drive Junction Box 53.76 54.80 55.70 56.02 56.37 56.51 

728066 Lake J-2 Outfall 53.89 55.07 55.79 56.11 56.53 56.68 

728067 Lake J-2 53.91 55.09 55.80 56.12 56.54 56.69 

728069 Manhole 53.92 55.13 55.91 56.25 56.73 56.93 

728071 Lake J-1 53.97 55.21 56.08 56.45 57.43 57.76 

728073 Lake M-2 Outfall 63.75 63.97 64.22 64.39 64.78 65.02 

728075 Lake M-2 64.04 64.21 64.45 64.60 64.96 65.19 

728077 Lake C 65.43 65.76 66.24 66.56 67.11 67.30 

728080 Lake BL-1 55.80 56.08 56.35 56.48 56.69 56.80 

728089 Lake K 56.21 56.48 56.91 57.20 57.74 58.00 

728090 Natures Way Blvd Wetland 56.14 56.44 56.81 57.01 57.33 57.48 

728092 Lake V 56.85 57.05 57.24 57.34 57.52 57.61 

728094 Lake E-2 65.05 65.36 65.92 66.27 66.91 67.22 

728096 Lake E-1 65.09 65.44 66.04 66.44 67.11 67.42 

728099 Lake D 66.62 66.86 67.22 67.43 67.91 68.18 

Hurley Ditch System 


728120 Bloomingdale Ave Control Weir 56.70 57.80 58.32 58.64 59.21 59.50 

728140 Dirt Road (u/s) 58.81 59.01 59.22 59.40 59.68 59.84 

728160 Pond 58.95 59.27 59.60 59.83 60.12 60.27 

728180 Dirt Road (u/s) 59.44 59.75 60.16 60.39 60.78 60.97

TABLE 6.4-2 






728200 Hurley Ditch @ Bloomingdale HS Pond Outfall 59.65 60.15 60.68 60.93 61.32 61.51 

728220 Bloomingdale HS Pond Outfall 60.00 60.80 61.37 61.60 61.86 61.99 

728240 Bloomingdale HS Pond 60.99 61.49 61.72 61.84 62.05 62.14 

728260 Bloomingdale HS Pond 61.06 61.62 61.95 62.13 62.50 62.69 

728270 Bloomingdale HS Wetland Outfall 61.81 62.03 62.28 62.43 62.71 62.88 

728280 Bloomingdale HS Wetland 61.88 62.10 62.36 62.51 62.81 62.97 

728290 Guiles Road Sidewalk (d/s) 66.30 66.59 66.88 67.02 67.29 67.43 

728295 Guiles Road (d/s) 67.17 67.48 67.64 67.73 67.87 67.94 

728300 Guiles Road (u/s) 68.08 68.53 68.62 68.66 68.74 68.79 

728320 Lithia Pinecrest (d/s) 69.62 70.03 70.37 70.56 70.98 71.20 

728340 Lithia Pinecrest (u/s) 70.42 71.80 72.48 72.74 73.32 73.51 

728245 Bloomingdale HS Wetland Mitigation Area 60.72 60.82 60.92 60.97 61.05 61.09 

728255 Bloomingdale HS South Pond 60.72 60.83 60.98 61.11 61.57 61.73 

728282 Buckhorn Springs Manor Pond 62.14 62.23 62.37 62.53 62.82 62.99 

728305 Lithia Pinecrest/Guiles Rd 68.12 68.40 68.86 69.01 69.12 69.21 

728307 Lithia Pinecrest (u/s) 68.96 69.53 71.16 71.76 72.17 72.31 

728312 Timber Knolls Pond 70.03 70.43 71.07 71.50 72.36 72.68 

728345 Golf Heights Cir Pond 78.25 78.79 80.11 80.18 80.32 80.38 

Northeast Tributary System 

729000 Bloomingdale Square Entrance Dr (d/s) 45.55 46.10 47.00 47.49 48.35 48.56 

729020 Bloomingdale Square Entrance Dr (u/s) 45.74 46.29 47.04 47.31 47.63 47.73 

729040 Bloomingdale Square Entrance Dr (d/s) 45.76 46.31 47.04 47.30 47.62 47.72 

729060 Bloomingdale Square Entrance Dr (u/s) 45.96 46.53 47.13 47.23 47.52 47.59 

729070 Bell Shoals Rd (d/s) 45.96 46.54 47.13 47.23 47.50 47.56 


729100 Bloomingdale Ave (d/s) 47.95 48.19 48.98 49.41 50.86 51.36 


Bloomingdale West System 

720624 Bloomingdale West Pond 44.23 44.41 44.62 44.74 44.92 45.01 

720626 Buttonwood Ct Pond 44.29 44.54 45.02 45.33 45.85 46.08 

720628 Wetland 53.76 53.98 54.37 54.62 55.11 55.21 

720629 Wetland 57.16 57.36 57.69 57.92 58.39 58.62 

720632 Canoga Park Pond 52.03 52.28 52.41 52.48 52.59 52.64 

Tributary GG System 

726000 Holland Dr (u/s) 33.43 34.20 35.22 35.73 36.39 36.59 

726010 Ditch 37.23 37.42 37.79 38.52 39.90 40.15 

726020 Maze Ln (d/s) 37.75 37.85 38.14 38.97 40.41 40.70 

726040 Maze Ln (u/s) 39.10 39.72 40.23 40.58 41.30 41.50 

726060 Wetland 39.30 39.81 40.32 40.88 42.71 43.24 

726080 Publix Pond A 43.35 43.80 44.11 44.17 44.79 44.94 

726100 Publix Parking Lot Pond 43.87 44.63 45.39 45.73 46.83 46.96 


726120 Wetland/Dunkin Donuts Pond 47.96 48.35 48.92 49.28 49.93 50.13 

726140 AC Self Storage Entrance Rd (u/s) 48.02 48.42 49.03 49.39 49.94 50.14 



Tributary C System 

723000 Rembrandt Dr (d/s) 24.89 25.18 25.77 26.25 27.58 28.18 

723020 Rembrandt Dr (u/s) 27.10 27.37 27.51 27.59 27.76 28.21 

723040 Bloomingdale Ave (d/s) 28.04 28.16 28.24 28.26 28.29 28.31 


723055 Bloomingdale Ave Pond 50 30.13 30.67 31.04 31.17 31.38 31.47 

723065 Lake 27.79 27.91 28.26 28.63 29.41 29.83 

Tributary D System 

724000 Ronele Dr (d/s) 26.11 26.47 27.06 27.70 29.12 29.62 

724020 Ronele Dr (u/s) 26.25 26.75 27.26 27.71 29.26 29.86 

724040 Dirt Drive (d/s) 26.69 27.13 27.55 27.74 29.28 29.89 

724060 Dirt Drive (u/s) 27.39 28.41 29.33 29.51 29.74 29.93 

724080 Huntington Lake Outfall 27.55 28.48 29.36 29.52 29.77 29.97 

724100 Huntington Lake 26.96 27.43 28.25 29.16 29.79 29.99 

Tributary F System 

727000 Rosemead Lane (d/s) 45.92 46.41 47.11 47.56 48.37 48.58 

727020 Redondo Drive (u/s) 47.55 48.42 49.10 49.31 49.61 49.76 

727040 Redondo Dr Pond 48.26 48.92 49.52 49.69 49.93 50.03 

727050 Green Hollow Lane @ Briar Lake Dr 48.76 49.68 50.47 50.83 51.26 51.45 

727060 Wetland 51.19 51.52 52.49 53.21 54.21 54.56

TABLE 6.4-2 






727070 Natures Way Blvd 53.17 54.28 56.49 58.21 59.29 59.71 

727080 Lake M-1 57.86 58.11 58.54 58.84 59.57 59.96 

727110 Lake H-2 Outfall 61.48 61.55 61.66 61.73 61.86 61.93 

727120 Lake H-2 64.89 65.33 65.91 66.29 66.92 67.16 

727130 Bloomingdale GC Manhole 64.95 65.39 65.97 66.34 66.96 67.22 

727145 Lake H-1 64.95 65.39 65.97 66.35 66.96 67.22 

727180 Lake F-3 65.33 65.67 66.23 66.54 67.15 67.43 

727200 Lake F-2 65.54 65.87 66.32 66.55 67.16 67.43 

727220 Lake F-1 65.52 65.87 66.30 66.55 67.16 67.43 

727125 Lake G 65.56 65.68 65.95 66.30 66.92 67.18 

727127 Lake W-1 67.00 67.14 67.35 67.48 67.74 67.85 

Craft Road Ditch System 

725000 Wetland 29.82 30.48 31.13 31.62 32.87 33.38 

725020 Ditch @ Bloomingdale Villas Outfall 31.27 31.35 31.70 31.96 32.99 33.49 

725040 Craft Road (d/s) 31.60 31.85 32.56 32.98 33.72 34.06 

725060 Craft Road (u/s) 32.36 33.33 34.53 34.70 35.04 35.23 

725080 Ditch 32.81 33.64 34.67 34.94 35.47 35.73 

725100 Ditch @ Bloomingdale Village Outfall 33.11 33.85 34.81 35.12 35.74 36.04 

725120 Ditch 47.20 49.75 49.80 49.82 49.89 49.99 

725200 Bryan Road (d/s) 34.23 34.95 36.00 36.65 37.67 38.12 

725220 Bryan Road (u/s) 37.89 39.05 39.28 39.41 39.64 39.75 

725240 Sidewalk (u/s) 39.52 39.76 39.99 40.13 40.38 40.51 

725260 Ditch Control Weir & Orifice (u/s) 39.55 39.81 40.08 40.25 40.57 40.73 

725280 Ditch @ Bryan Manor Outfall 39.64 39.99 40.55 40.91 41.58 41.88 

725300 Ditch @ Footbridge 39.72 40.21 40.86 41.24 41.88 42.18 

725320 Ditch @ Belle Timber Outfall 39.74 40.23 40.89 41.27 41.92 42.22 



725025 Bloomingdale Villas Pond 32.58 32.81 32.96 33.03 33.16 33.39 

725104 Bloomingdale Village Pond 32.94 33.49 34.30 34.98 35.96 36.20 

725105 Bloomingdale Village Offsite Diversion (u/s) 33.12 33.85 34.82 35.14 35.78 36.20 

725121 Farm Pond 34.32 34.63 36.00 36.65 37.67 38.12 

725123 Brentridge Dr Retention Pond/Sinkhole 53.85 54.71 55.57 55.61 55.81 55.95 

725125 Brooker Rd Sinkhole 56.45 56.78 57.20 57.46 57.95 58.18 

725126 Bryan Manor Retention Pond 62.21 62.31 62.40 62.45 62.53 62.57 

725127 Burns MS West Pond 59.97 60.30 60.81 61.10 61.16 61.20 

725129 Burns MS East Pond 54.09 54.99 56.45 57.43 59.36 60.31 

725130 Brooker Rd Depression 56.09 56.73 57.61 58.16 59.19 59.82 

725135 Bell Shoals Baptist Retention Pond #2 64.26 64.70 65.41 65.91 66.88 67.32 

725224 Bryan Estates Retention Pond 47.53 48.19 49.30 49.67 50.38 50.58 

725285 Bryan Manor South Pond (north) 39.64 39.99 40.56 40.91 41.58 41.89 

725290 Bryan Manor South Pond (south) 39.64 39.99 40.56 40.91 41.58 41.88 

725324 Bell Timbre Pond 43.15 43.42 43.60 43.66 43.79 43.91 

725328 Bell Shoals CC Pond 44.98 45.33 45.90 46.28 47.36 47.85 

725330 Strawberry Lane Pond 46.02 46.43 48.19 49.77 50.45 50.55 

725362 Guiles Road Sinkhole (south) 51.42 52.03 52.82 53.30 54.14 54.55 

725364 Guiles Road Sinkhole (north) 57.20 57.34 57.57 57.71 57.95 58.05 

Tanglewood Ditch System 

722000 Ditch @ Kingswood ES Outfall 21.75 22.38 23.12 23.56 24.32 25.00 

722020 Ditch @ J.C. Handley Park Outfall 23.92 24.52 25.24 25.65 26.26 26.49 

722040 Ditch @ J.C. Handley Park Outfall 25.80 26.25 26.81 27.14 27.63 27.83 

722060 Ditch @ La Brisas & Offsite Drainage Diversion Outfalls 28.48 29.11 29.90 30.25 30.77 30.97 

722080 Ditch @ Random Oaks Outfall 28.54 29.17 29.97 30.32 30.85 31.05 

722100 Ditch @ Providence Lakes No. 6 Outfall 28.58 29.21 30.01 30.35 30.88 31.09 

722120 Dirt Road (d/s) 28.69 29.36 30.16 30.47 30.99 31.19 

722140 Dirt Road (u/s) 28.77 29.56 30.52 30.91 31.64 31.88 



722065 Offsite Drainage Diversion Inlet 31.06 31.40 31.78 31.98 32.39 32.62 

722084 Random Oaks Pond 3 29.30 30.20 31.24 31.56 31.90 32.07 



722104 Providence Lakes No. 6 29.08 29.44 30.08 30.54 31.38 31.77 




722122 Ditch 28.73 29.40 30.19 30.50 31.01 31.20 

722126 Ditch @ Kings Ave 28.75 29.42 30.20 30.51 31.02 31.21 


722166 Providence Lakes No. 8 30.01 30.48 31.19 31.61 32.42 32.82







6.4.3 Flooding Level of Service Analysis 

Table 6.4-4 shows the level of service currently being estimated for each of 113 

locations identified within the Buckhorn Creek Subwatershed that were selected 

specifically for this purpose. As previously discussed, the County has adopted for 

the Buckhorn Creek Subwatershed a minimum basinwide goal of Level ‘B’ for the 

10-year, 24-hour design storm event. Based on this criterion, there are only 13 

locations identified in Table 6.4-4 where the County’s minimum acceptable level of 

service is not met, as indicated by shaded cells in the table. Additionally, the level of 

service matrix is also a useful way of identifying additional problem areas and 

showing the severity of a flooding problem. For instance, even though the adopted 

County LOS criterion is for yard flooding during the 10-year storm event, chronic 

flooding of a street for the 2-year or 5-year storm event might be judged to be as 

important an issue. Figure 6.4-2 shows the LOS by subbasin as required by County 

standards. 

Similarly, structural flooding during the 25-year storm event might also be 

designated as an equal problem. The analysis does not show cases of structural 

flooding likely to occur during the more frequent storms. One of the reasons for this 

conclusion is probably the lack of surveying data to assess structural flooding in 

more detail. Another reason is that this study encompassed strictly the capacity 

analysis of the main basin drainage system. Flooding problems could also be 

caused by constrictions in the secondary system, which was not part of this study. 

However, the solution of those problems is much less complicated if the primary 

system has the capacity to accept the additional runoff flows. 

The results of the LOS analysis were compared to the flooding complaint records 

for the 1997/1998 El Nino and 2004 Hurricane Frances flooding events and there is 

good correlation between listed problem areas that might be impacted by conditions 

in the primary drainage system and the problem areas which were identified in 

Table 6.4-4. 

Complaint record sites not shown as problem areas in Table 6.4-4 (and similar 

tables for each of the subwatersheds discussed in subsequent sections of this 

report) are generally an indication of secondary system problems or possible 

maintenance problems. A more detailed discussion of the problem areas that were 

identified as primary drainage system deficiencies is presented in Chapter 13 of this 

report. 






LEGEND 

Minimum Acceptable Level of Service Not Met 

TABLE 6.4-4 


BUCKHORN CREEK SUBWATERSHED EXISTING CONDITIONS LEVELS OF SERVICE ANALYSIS 

STREET STRUCTURE 24-HOUR DURATION DESIGN STORM 

PUBLIC/ MODEL FLOODING FLOODING MAXIMUM FLOOD ELEVATION, ft NAVD 88 FLOODING LEVEL OF SERVICE PROVIDED 

S-T-R LOCATION DESCRIPTION PRIVATE JUNCTION ELEV., ft NAVD 88 ELEV., ft NAVD 88 2.33-YR 5-YR 10-YR 25-YR 50-YR 100-YR 2.33-YR 5-YR 10-YR 25-YR 50-YR 100-YR 

9-30-20 HOUSE NEAR WATSON RD PUBLIC 720024 0.00 35.50 33.00 33.17 33.43 33.62 34.04 34.26 A A A A A A 

3-30-20 BLOOMINGDALE AVE @ BUCKHORN CRK PUBLIC 720100 28.30 25.10 17.06 17.66 18.31 18.66 19.79 20.31 A A A A A A 

3-30-20 CREEKRIDGE RD PUBLIC 720120 29.10 27.10 19.00 19.79 20.70 21.15 22.51 23.10 A A A A A A 

3-30-20 BLUFFVIEW LN PUBLIC 720120 29.10 27.10 19.00 19.79 20.70 21.15 22.51 23.10 A A A A A A 

3-30-20 CREEKBRIDGE RD @ BUCKHORN CRK PUBLIC 720160 27.00 28.50 19.65 20.52 21.59 22.10 23.81 24.72 A A A A A A 

3-30-20 DENHAM RD PUBLIC 720160 31.10 32.60 19.65 20.52 21.59 22.10 23.81 24.72 A A A A A A 

3-30-20 HOUSE NEAR DOE CT PRIVATE 720180 0.00 30.10 22.64 23.13 23.76 24.23 25.69 26.46 A A A A A A 

3-30-20 SANDERS PARK PRIVATE 720185 0.00 29.10 26.64 26.93 27.33 27.56 27.99 28.18 A A A A A A 

3-30-20 KINGS AVE @ BUCKHORN CRK PUBLIC 720200 29.60 30.10 22.71 23.22 23.86 24.34 25.83 26.60 A A A A A A 

3-30-20 EL GRECO DR PUBLIC 720245 30.60 31.50 29.07 29.36 29.78 30.03 30.46 30.64 A A A A A A 

3-30-20 VAN GOGH @ BUCKHORN CRK PRIVATE 720300 0.00 30.60 28.17 28.95 29.86 30.58 32.15 32.69 A A A A D* D* 

3-30-20 EL GRECO DR PUBLIC 720302 30.10 32.60 30.33 30.42 30.54 30.62 32.15 32.70 A B B C D D 

3-30-20 EL GRECO DR & JOHN MOORE RD PRIVATE 720320 0.00 30.60 29.45 30.14 30.76 31.32 32.58 33.06 A A D* D* D* D* 

2-30-20 JOHN MOORE RD PUBLIC 720340 33.50 32.40 29.52 30.28 31.00 31.60 32.89 33.41 A A A A D* D* 

11-30-20 HIDDEN LAKE DR & JOHN MOORE RD PRIVATE 720362 0.00 36.60 35.77 35.94 36.16 36.31 36.84 37.04 A A A A D* D* 

2-30-20 E BLOOMINGDALE AVE PUBLIC 720400 33.40 32.60 29.97 30.88 31.89 32.67 33.40 33.75 A A A D* D* D* 

2-30-20 BLOOMINGDALE AVE @ BUCKHORN CRK PUBLIC 720400 0.00 32.60 29.97 30.88 31.89 32.67 33.40 33.75 A A A D* D* D* 

11-30-20 CAGLE RD & JOHN MOORE RD PUBLIC 720420 32.10 32.60 30.18 31.07 32.06 32.84 33.66 34.06 A A A D* D D 

2-30-20 E BLOOMINGDALE AVE PUBLIC 720464 33.40 34.80 32.24 32.81 33.27 33.47 33.93 34.29 A A A A C C 

11-30-20 HOLLAND DR & BLOOMINGDALE AVE PRIVATE 720500 0.00 33.50 31.60 31.90 32.38 33.13 33.96 34.33 A A A A D* D* 

11-30-20 HOLLAND DR @ BUCKHORN CRK PUBLIC 720560 35.40 36.10 35.24 35.63 35.91 36.10 36.38 36.49 A A C C D* D 

11-30-20 FOREST HILLS RD @ BUCKHORN CRK PUBLIC 720600 41.50 42.10 39.43 40.49 41.63 41.79 41.99 42.12 A A A B B D* 

11-30-20 WINDTREE CT PUBLIC 720624 46.00 47.30 44.23 44.41 44.62 44.74 44.92 45.01 A A A A A A 

11-30-20 SHADY NOOK DR PUBLIC 720624 45.00 47.30 44.23 44.41 44.62 44.74 44.92 45.01 A A A A A A 

11-30-20 BAYFIELD DR PRIVATE 720628 0.00 54.50 53.76 53.98 54.37 54.62 55.11 55.21 A A A D* D* D* 

11-30-20 EMBERWOOD DR PUBLIC 720629 57.80 58.60 57.16 57.36 57.69 57.92 58.39 58.62 A A A A C D* 

11-30-20 ROSEMEAD LN PUBLIC 720680 48.30 49.90 45.47 46.04 46.96 47.46 48.33 48.55 A A A A A B 

3-30-20 PROVIDENCE TRACE CIR PUBLIC 722020 31.10 32.00 23.92 24.52 25.24 25.65 26.26 26.49 A A A A A A 

3-30-20 VIOLA LN @ COUNTRYSIDE ST PUBLIC 722040 27.10 30.60 25.80 26.25 26.81 27.14 27.63 27.83 A A A A C C 

4-30-20 LAS BRISAS DR & ACAPULCO DR PUBLIC 722060 30.10 32.00 28.48 29.11 29.90 30.25 30.77 30.97 A A A A C C 

4-30-20 ERHARDT DR PRIVATE 722065 0.00 34.20 31.06 31.40 31.78 31.98 32.39 32.62 A A A A A A 

4-30-20 WELLMAN DR PUBLIC 722086 32.40 33.40 29.33 30.23 31.38 31.94 32.62 32.86 A A A A A B 

4-30-20 YEAGER CT PUBLIC 722088 32.70 33.70 29.68 30.92 32.65 33.24 33.94 34.18 A A A C D D 

4-30-20 WHITE CEDAR WY (PROVIDENCE LAKE 4) PUBLIC 722106 32.20 33.40 28.90 29.39 30.11 30.59 31.45 31.84 A A A A A A 

3-30-20 BARKFIELD ST PUBLIC 722127 29.00 29.50 28.75 29.43 30.21 30.36 30.51 30.61 A B D D D D 

3-30-20 S KINGS AVE PUBLIC 722127 32.30 30.50 28.75 29.43 30.21 30.36 30.51 30.61 A A A A D* D* 

34-29-20 HATCHER LOOP DR PUBLIC 722192 32.80 33.80 31.37 31.44 31.58 31.69 31.93 32.04 A A A A A A 

34-29-20 ENGLISH BLUFFS CT PUBLIC 722192 33.30 35.20 31.37 31.44 31.58 31.69 31.93 32.04 A A A A A A 

3-30-20 REMBRANDT DR @ TRIB C PUBLIC 723020 27.20 29.10 27.10 27.37 27.51 27.59 27.76 28.21 A A B B C D 

3-30-20 BLOOMINGDALE AVE @ TRIB C PUBLIC 723055 31.40 0.00 30.13 30.67 31.04 31.17 31.38 31.47 A A A A A A 

3-30-20 RONELLE DR @ TRIB D PUBLIC 724020 29.90 30.80 26.25 26.75 27.26 27.71 29.26 29.86 A A A A A A 

3-30-20 DIRT RD @ TRIB D PRIVATE 724060 0.00 30.10 27.39 28.41 29.33 29.51 29.74 29.93 A A A A A A 

3-30-20 PRINCETON ST PUBLIC 724080 28.50 29.50 27.55 28.48 29.36 29.52 29.77 29.97 A A C D D D 

3-30-20 SOUTHWOOD COVE & KINGS COVE PRIVATE 724100 0.00 29.60 26.96 27.43 28.25 29.16 29.79 29.99 A A A A D* D* 

2-30-20 JOHN MOORE RD @ BUCKHORN CRK PUBLIC 725000 31.10 32.40 29.82 30.48 31.13 31.62 32.87 33.38 A A A C D D 

2-30-20 CRAFT RD (D/S) PRIVATE 725020 0.00 33.10 31.27 31.35 31.70 31.96 32.99 33.49 A A A A A D* 

2-30-20 BLOOMINGDALE VILLAS CT PUBLIC 725025 32.90 34.70 32.58 32.81 32.96 33.03 33.16 33.39 A A A A B B 

2-30-20 CRAFT RD PUBLIC 725060 34.30 34.60 32.36 33.33 34.53 34.70 35.04 35.23 A A A D* D* D* 

2-30-20 MINUTEMAN LN PUBLIC 725102 35.30 37.50 33.11 33.85 34.81 35.08 35.97 36.27 A A A A C C 

2-30-20 BRYAN RD (D/S) PRIVATE 725121 0.00 36.50 34.32 34.63 36.00 36.65 37.67 38.12 A A A D* D* D* 

2-30-20 E BRENTRIDGE DR PUBLIC 725123 54.00 55.00 53.85 54.71 55.57 55.61 55.81 55.95 A C D D D D 

2-30-20 BRYAN RD PUBLIC 725126 62.10 65.30 62.21 62.31 62.40 62.45 62.53 62.57 A A B B B B 

2-30-20 BRYAN TERRACE DR PUBLIC 725126 63.10 65.10 62.21 62.31 62.40 62.45 62.53 62.57 A A A A A A 

2-30-20 BRYAN RD PUBLIC 725127 61.10 64.50 59.97 60.30 60.81 61.10 61.16 61.20 A A A A A A 

2-30-20 BURNS MIDDLE SCHOOL PRIVATE 725129 0.00 64.50 54.09 54.99 56.45 57.43 59.36 60.31 A A A A A A 

35-29-20 BROOKER RD PUBLIC 725130 58.00 55.80 56.09 56.73 57.61 58.16 59.19 59.82 D* D* D* D* D D 

35-29-20 BELL SHOALS BAPTIST & OVERHILL DR PUBLIC 725135 69.20 69.50 64.26 64.70 65.41 65.91 66.88 67.32 A A A A A A

LEGEND 


TABLE 6.4-4 


BUCKHORN CREEK SUBWATERSHED EXISTING CONDITIONS LEVELS OF SERVICE ANALYSIS 




2-30-20 BRYAN RD (U/S) PRIVATE 725220 38.90 41.60 37.89 39.05 39.28 39.41 39.64 39.75 A A B C C C 

2-30-20 RAPID FALLS DR PUBLIC 725224 50.30 51.70 47.53 48.19 49.30 49.67 50.38 50.58 A A A A A B 

2-30-20 OAK CREEK DR PUBLIC 725285 39.90 41.00 39.64 39.99 40.56 40.91 41.58 41.89 A A C D D D 

2-30-20 BELLE TIMBRE AVE PUBLIC 725324 44.20 44.50 43.15 43.42 43.60 43.66 43.79 43.91 A A A A A A 

2-30-20 BELL SHOALS CHURCH OF CHRIST PRIVATE 725328 0.00 53.10 44.98 45.33 45.90 46.28 47.36 47.85 A A A A A A 

1-30-20 BELL SHOALS AVE & BELL SHOALS LN PUBLIC 725360 48.40 48.70 47.04 48.54 48.71 48.83 49.04 49.13 A A D* D* D* D* 

1-30-20 HOUSE NEAR GUILES RD PRIVATE 725364 0.00 56.20 57.20 57.34 57.57 57.71 57.95 58.05 D* D* D* D* D* D* 

11-30-20 HOLLAND DR @ TRIB GG PUBLIC 726000 35.60 35.60 33.43 34.20 35.22 35.73 36.39 36.59 A A A D* D* D* 

11-30-20 MAZE LN @ TRIB GG PUBLIC 726040 40.10 40.50 39.10 39.72 40.23 40.58 41.30 41.50 A A A D* D D 

11-30-20 BELL SHOALS RD PUBLIC 726065 46.40 47.10 41.70 42.09 44.21 46.11 46.85 46.99 A A A A B C 

2-30-20 E BLOOMINGDALE AVE PUBLIC 726100 48.10 50.40 43.87 44.63 45.39 45.73 46.83 46.96 A A A A A A 

2-30-20 E BLOOMINGDALE AVE PUBLIC 726100 45.30 0.00 43.87 44.63 45.39 45.73 46.83 46.96 A A A B D D 

2-30-20 DUNKIN DONUTS & SCHLOTZSKYS PRIVATE 726120 0.00 50.40 47.96 48.35 48.92 49.28 49.93 50.13 A A A A A A 

2-30-20 E BLOOMINGDALE AVE PUBLIC 726140 49.60 51.60 48.02 48.42 49.03 49.39 49.94 50.14 A A A A B C 

1-30-20 BELL SHOALS RD PUBLIC 726180 52.00 0.00 48.07 48.49 49.14 49.53 50.15 50.40 A A A A A A 

11-30-20 MAGENTA WAY PUBLIC 727004 47.60 49.60 46.70 46.92 47.19 47.59 48.37 48.58 A A A A C C 

11-30-20 REDONDO DR PUBLIC 727040 48.90 49.70 48.26 48.92 49.52 49.69 49.93 50.03 A A C C D D 

12-30-20 NATURES WAY BLVD & BRIAR LAKE DR PUBLIC 727080 60.00 62.30 57.86 58.11 58.54 58.84 59.57 59.96 A A A A A A 

13-30-20 SPRING WAY CIR PUBLIC 727085 65.70 66.70 64.20 64.76 65.22 65.45 65.82 65.98 A A A A A B 

12-30-20 RAINBROOK CIR PUBLIC 727120 65.50 66.90 64.89 65.33 65.91 66.29 66.92 67.16 A A B C D D 

12-30-20 BELL SHOALS RD @ BUCKHORN CREEK PUBLIC 728005 49.00 50.10 46.54 46.92 48.81 49.28 49.57 49.65 A A A B C C 

12-30-20 GREENSTONE PL PUBLIC 728010 49.10 49.90 46.77 47.17 49.02 49.51 49.85 49.97 A A A B C D* 

12-30-20 SAVANNAH LANDINGS AVE PUBLIC 728025 51.30 52.60 51.16 51.23 51.49 51.63 51.81 51.87 A A A B C C 

12-30-20 FAWN LAKE PL PUBLIC 728035 0.00 56.30 52.68 54.02 54.28 54.35 54.47 54.55 A A A A A A 

12-30-20 ORANGEPOINTE RD PUBLIC 728060 53.00 54.50 51.56 51.73 52.34 52.66 53.10 53.26 A A A A A B 

12-30-20 SPRINGVALE DR & BIG PINE DR PUBLIC 728063 55.80 56.00 55.79 56.06 56.33 56.46 56.66 56.76 A D* D* D* D* D* 

12-30-20 PINE KNOT DR PUBLIC 728063 56.00 56.00 55.79 56.06 56.33 56.46 56.66 56.76 A D* D* D* D* D* 

12-30-20 SPRINGVALE DR PUBLIC 728067 55.00 57.20 53.91 55.09 55.80 56.12 56.54 56.69 A A C D D D 

12-30-20 MURRAY DALE DR PUBLIC 728067 56.00 57.20 53.91 55.09 55.80 56.12 56.54 56.69 A A A A C C 

12-30-20 MURRAY DALE DR PUBLIC 728071 57.00 59.50 53.97 55.21 56.08 56.45 57.43 57.76 A A A A B C 

12-30-20 BELLEGRANDE DR & CALLISTA AVE PUBLIC 728075 64.90 66.50 64.04 64.21 64.45 64.60 64.96 65.19 A A A A A B 

12-30-20 CLARION DR PUBLIC 728075 64.40 66.50 64.04 64.21 64.45 64.60 64.96 65.19 A A A A C C 

12-30-20 HOLLEMAN DR & SCOVILL LN PUBLIC 728077 67.80 68.80 65.43 65.76 66.24 66.56 67.11 67.30 A A A A A A 

12-30-20 HOLLEMAN DR & NATURES WAY BLVD PUBLIC 728089 58.00 59.00 56.21 56.48 56.91 57.20 57.74 58.00 A A A A A A 

12-30-20 KINGSFORD PL & NATURES WAY BLVD PUBLIC 728089 57.60 58.60 56.21 56.48 56.91 57.20 57.74 58.00 A A A A A B 

7-30-21 NATURES WAY BLVD PUBLIC 728092 56.80 59.00 56.85 57.05 57.24 57.34 57.52 57.61 A B B C C C 

7-30-21 NORTHRIDGE DR PUBLIC 728092 56.90 58.40 56.85 57.05 57.24 57.34 57.52 57.61 A A B B C C 

12-30-20 BLOOMINGDALE AVE & HURLEY RD PUBLIC 728101 57.80 57.80 55.87 56.16 56.64 56.79 57.09 57.23 A A A A A A 

1-30-20 HURLEY RD @ BLOOMINGDALE AVE PUBLIC 728108 57.80 0.00 56.70 57.78 58.19 58.39 58.81 59.00 A A B C D D 

1-30-20 COLONIAL RIDGE DR PUBLIC 728112 64.00 62.00 60.23 60.43 60.65 60.77 60.95 61.03 A A A A A A 

1-30-20 DIRT RD PRIVATE 728140 0.00 62.10 58.81 59.01 59.22 59.40 59.68 59.84 A A A A A A 

1-30-20 HURLEY POND LN PUBLIC 728164 61.00 62.10 58.60 58.99 59.51 59.83 60.13 60.27 A A A A A A 

1-30-20 BLOOMINGDALE HIGH PUBLIC 728240 61.60 63.50 60.99 61.49 61.72 61.84 62.05 62.14 A A A A B C 

1-30-20 BLOOMINGDALE HIGH PUBLIC 728255 62.90 63.50 60.72 60.83 60.98 61.11 61.57 61.73 A A A A A A 

1-30-20 GUILES RD PUBLIC 728274 70.50 75.60 70.38 70.55 70.69 70.80 70.97 71.07 A A A B B C 

6-30-21 WISTER CIR PUBLIC 728282 63.10 64.60 62.14 62.23 62.37 62.53 62.82 62.99 A A A A A A 

6-30-21 GUILES RD PUBLIC 728300 68.40 72.90 68.08 68.53 68.62 68.66 68.74 68.79 A A A B B B 

6-30-21 LITHIA PINECREST RD @ CHELSEA WOODS PUBLIC 728308 72.60 71.70 70.38 70.45 71.18 71.78 72.21 72.34 A A A D* D* D* 

1-30-20 TIMBER KNOLL DR PUBLIC 728312 73.00 74.30 70.03 70.43 71.07 71.50 72.36 72.68 A A A A A A 

6-30-21 GOLF HEIGHTS CIR PUBLIC 728345 80.10 81.10 78.25 78.79 80.11 80.18 80.32 80.38 A A A A A B 

11-30-20 BELL SHOALS RD PUBLIC 729060 47.10 0.00 45.96 46.53 47.13 47.23 47.52 47.59 A A A A B B 

12-30-20 BELL SHOALS RD @ BLOOMINGDALE SQ PUBLIC 729080 47.00 49.10 46.24 46.90 47.22 47.29 47.64 47.72 A A A B C C 

12-30-20 BLOOMINGDALE & BELL SHOALS SHOPPING PUBLIC 729088 50.50 52.50 47.94 48.37 49.64 50.42 50.77 50.89 A A A A B B 

1-30-20 BLOOMINGDALE AVE PUBLIC 729090 52.90 0.00 50.05 50.20 52.01 52.95 53.27 53.39 A A A A B B 

12-30-20 LAKE BREEZE PL PUBLIC 729105 55.10 56.20 52.65 53.16 53.88 54.23 54.39 54.45 A A A A A A 

1-30-20 COLONIAL RIDGE DR PUBLIC 729135 63.10 64.40 59.79 60.47 61.44 62.05 62.43 62.53 A A A A A A

Level of Service 

A 

B 

C 

D/D* 

Polk Co. 

O 

Legend 

County Line 


Suite 120 






Notes: 


ALAFIA RIVER 

S KINGS AVE 


1:24,000 

JOHN MOORE RD 

0 600 1,200 2,400 

Feet 

0 0.125 0.25 0.5 

Miles 




Filename: 

Fig6_4_ 

2.mxd 

Map Date: 




N/A 


Prepared By: 

Yoav 

Rappaport 

GUILES RD 

HURLEY DITCH 


Figure: 6.4-2 - Existing Level of Service 





AL






Hillsborough County Central Service Unit Reported Problems 

In 2001, Parsons interviewed the Hillsborough County South Service Unit, the 

branch of the County that performs maintenance of the drainage system in the Bell 

Creek Subwatershed. The Unit reported 5 locations that experience recurring flood 

problems. Locations are detailed Table 6.5-1 and shown on Figure 6.5-1. 


As was discussed earlier in this Chapter, the commencement of the El Nino storms 

generated some very serious flooding conditions in Hillsborough County as well as 

other parts of central Florida. It was due to these extreme storm events that 

Hillsborough County began compiling a list of flooding complaints to be incorporated 

into this report. 




resulting in a total of 9.4 inches of precipitation at the USGS Alafia River gage. 

Flooding in the Alafia watershed began on September 6, 2004. Incidents reported 

from this event were added to the Hillsborough County flood database. 

Like most municipalities in central Florida, Hillsborough County was besieged by 

flooding complaints from local residents over the course of the 1997/1998 El Nino 

and 2004 Hurricane Frances floods. In an effort to address reported flooding 

concerns, a record was complied which was provided to Parsons to utilize for the 

purpose of this study. The locations of the individual complaints are plotted in 

Figure 6.5-1, and the complaints that were located within the Bell Creek 

Subwatershed are listed in Table 6.5-1. There were a total of 9 individual flooding 

complaint records within the Bell Creek Subwatershed due to the El Nino and 

Hurricane Frances storm events. 




Table 6.5-1 

Bell Creek Subwatershed Reported Flooding Problems 

INFORMATION 

SOURCE 

MAP REFERENCE 

NUMBER 

LOCATION 

DESCRIPTION 


South Service Unit 


Complaints 


Complaints 

Alafia River WMP 

October Public 

Meeting Complaints 

62 Hobsom-Simmons Rd. approximately 1 mile south of Boyette Poorly drained area. 

Rd 

65 Boyette Springs Subdivision detention pond "C" Outfall - 24" Pond design issue - BMP is pumped to wetlands during large storm events. 

RCP 

66 Sedgebrook Drive @ Crispwood Court Roadway flooding due to springs under roadway. Hillsborough County installed underdrains. 

67 Sedgebrook Drive South of Crispwood Court Roadway flooding due to springs under roadway. Hillsborough County installed underdrains. 

68 Heron Hills Lane Roadway flooding due to springs under roadway. Hillsborough County installed underdrains. 

225 Boyette Road @ Tampa Bay Academy Flooding was investigated. John Martis determined that regrading of the swale near the new driveway culvert would alleviate the flooding. No action 

was taken. 

534 23701 Lakehills Drive No information available 

660 12308 Elnora Drive No information available 

686 10126 Sedgebrook Drive No information available 

1074 16163 Boyette Road No information available 

1137 11009 Balm-Riverview Road No information available 

18 Boyette Springs Park Playing fields flood as well as lower Sedgebrook Drive. This flooding is eroding the asphalt. Resident stated "there has been a lot of construction 

above this area and a lot of sand and debris has entered the street drainage system." 




2001 13902 Balm Riverview Rd. @ Big Bend Rd. Road flooding. 

2003 Oxbridge Crest Place @ Big Bend Rd. Road flooding. Need to update drainage system. 



75 

301 

BOYETTE RD 

Serv_67 

Serv_66 

686 

Meet_18 

BELL CREEK 

FISHHAWK BLVD 


327 

Meet2_2 

Lake Grady 


Legend 


Service Unit 


January 1998 

December 1997 


County Line 



Roads 




Suite 120 


BIG BEND RD 


1137 

2003 2001 

Notes: 

Serv_68 

660 

534 

BOGGY CREEK 

BELL CREEK 

BOGGY CREEK 

BELL CREEK 


1:52,000 

0 1,250 2,500 5,000 

Feet 

0 0.25 0.5 1 

Miles 

1074 

Filename: 

Fig6_5_ 

1.mxd 

Serv_62 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 

672 










Using the design storm events as the basis for simulations, the hydrologic/hydraulic 

computer model was run to generate predictions of basinwide flooding conditions 

for the existing land use conditions and the existing drainage facilities throughout 

the Bell Creek Subwatershed. For the purpose of this study, existing conditions 

refer to Year 2006 land use conditions and drainage facilities. Table 6.5-2 is a 

maximum flood elevation summary that lists the peak flood stages at each of the 

model nodes along the main conveyance systems for the various design storms. 

Table 6.5-3 presents a summary of the model-simulated peak flows at selected 

locations within the basin. 

Table 6.5-3 

Bell Creek Subwatershed Peak Flows at Selected Locations 

Location 

Bell Creek at Mouth 

(9730000) 

Bell Creek u/s of Rhodine 

Road (9730850) 

Boggy Branch at Mouth 

(9731050) 

Pelleham Branch at Mouth 

(9730580) 

Pelleham Branch u/s of 

Edgeknoll Drive (9730640) 

Tributary 731402 at Mouth 

(9731405) 

Tributary 703700 at Mouth 

(9703705) 

Tributary 703700 d/s of 

Boyette Road (9703740) 

2.33-year 

(cfs) 

5-year 

(cfs) 

10-year 

(cfs) 

25-year 

(cfs) 

50-year 

(cfs) 

100-year 

(cfs) 

1522 2188 3555 4472 6345 7281 

1098 1694 3002 3758 5376 6208 

465 645 901 1134 1520 1692 

577 757 1076 1257 1640 1789 

399 537 787 951 1233 1335 

665 809 1108 1373 2004 2327 

185 260 377 461 617 693 

21 33 43 57 95 118 


Table 6.5-4 shows the level of service currently being estimated for each of 56 

locations identified within the Bell Creek Subwatershed. As previously discussed, 

the County has adopted the Target Level of Service for the Bell Creek 

Subwatershed, which is a minimum basin-wide goal of Level ‘B’ for the 25-year, 24- 

hour design storm event. Based on this criterion, there are four locations identified 

in Table 6.5-4 where the County’s minimum acceptable level of service is not met, 

as indicated by shaded cells in the table. Additionally, the level of service matrix is 

also a useful way of identifying additional problem areas and showing the severity of 

a flooding problem. Figure 6.5-2 shows the LOS by subbasin as required by County 

standards. 






TABLE 6.5-2 


BELL CREEK SUBWATERSHED EXISTING CONDITIONS FLOOD ELEVATIONS SUMMARY 




Bell Creek Main Channel to Lake Grady 

703700 * Alafia River @ Bell Creek Confluence 9.44 11.30 13.06 15.09 16.54 17.70 

730000 * Bell Creek [23-30-20] 9.44 11.30 13.06 15.09 16.54 17.70 

730050 * Bell Creek [23-30-20] 13.20 14.37 16.09 16.98 18.53 19.21 

730100 * Foot Bridge (W of Waterford Sub) (d/s) 15.39 16.54 18.38 19.33 20.97 21.65 

730150 * Foot Bridge (W of Waterford Sub) (d/s) 15.48 16.65 18.54 19.53 21.23 21.94 

730200 * Boyette Rd Bridge Span (d/s) 17.25 18.37 20.16 21.13 22.79 23.50 

730250 * Boyette Rd Bridge Span (u/s) 17.38 18.48 20.26 21.22 22.89 23.60 

730300 * Bell Creek [23-30-20] 19.31 20.49 22.31 23.29 25.00 25.73 

730348 * Bell Creek [23-30-20] 19.85 20.99 22.75 23.71 25.40 26.12 

730350 * Foot Bridge (W of Boyette Spr Sect A Sub) (d/s) 20.62 21.62 23.26 24.18 25.79 26.50 

730400 * Foot Bridge (W of Boyette Spr Sect A Sub) (u/s) 20.67 21.68 23.34 24.25 25.88 26.59 

730450 * Bell Creek [26-30-20] 25.53 26.65 28.23 29.02 30.33 30.85 

730500 * Lake Grady Dam Outfall 25.93 27.02 28.62 29.44 30.82 31.36 

730525 * Lake Grady Dam Outfall 28.17 29.30 31.30 33.03 36.62 38.03 

Lake Grady 

730550 * Lake Grady (Northern Portion) 37.76 38.39 39.48 40.12 41.30 41.85 

730750 * Lake Grady (Southern Portion) 37.82 38.48 39.65 40.33 41.57 42.14 

Bell Creek Main Channel from Lake Grady to Headwaters 

730800 * Rhodine Rd (u/s) 44.97 47.04 47.73 48.02 48.57 48.82 

730850 * Bell Creek [1-31-20] 45.18 47.19 48.04 48.44 49.22 49.58 

730950 * Bell Creek [1-31-20] 45.29 47.28 48.22 48.68 49.57 49.99 

731250 * Bell Creek [6-31-21] 47.35 47.87 48.83 49.37 50.38 50.85 

731300 * Bell Creek [6-31-21] 50.78 51.85 53.16 53.88 55.18 55.75 

731350 * Dirt Rd (d/s) 53.93 54.62 55.45 55.89 56.69 57.12 

731400 * Dirt Rd (u/s) 54.23 54.76 55.61 56.06 56.90 57.35 

731402 * Dirt Rd (d/s) [7-31-21] 59.22 60.05 60.95 61.47 62.37 62.77 

731600 * Dirt Rd (u/s) [7-31-21] 59.29 60.13 61.07 61.60 62.55 62.97 

731650 * Bell Creek [7-31-21] 60.13 60.84 61.72 62.22 63.12 63.54 

731700 * Dirt Rd (d/s) [7-31-21] 69.68 70.12 70.69 70.99 71.56 71.83 

731750 * Dirt Rd (u/s) [7-31-21] 69.85 70.30 70.92 71.25 71.89 72.20 

731800 * Bell Creek [18-31-21] 73.32 73.69 74.15 74.38 74.90 75.15 

731850 * Bell Creek [18-31-21] 84.52 84.89 85.31 85.51 85.98 86.20 

731900 * Balm-Boyette Rd (d/s) 102.61 102.87 103.18 103.33 103.76 103.94 

732000 * Balm-Boyette Rd (u/s) 104.16 105.47 107.25 108.52 109.37 109.56 

732100 * Bell Creek [19-31-21] 107.55 107.91 108.37 108.67 109.56 109.78 

732150 * Dirt Rd (d/s) [19-31-21] (200" N of Mill Breeze Ave) 110.70 111.10 111.54 111.79 112.17 112.33 

732200 * Dirt Rd (u/s) [19-31-21] (200" N of Mill Breeze Ave) 111.52 111.73 112.03 112.22 112.55 112.72 

732250 * Dirt Rd (d/s) [19-31-21] (W of Jay Mar Farm #2) 115.83 115.88 115.94 115.97 116.02 116.04 

732300 * Dirt Rd (u/s) [19-31-21] (W of Jay Mar Farm #2) 117.20 117.40 117.68 117.85 118.16 118.31 

731855 * Balm-Boyette Rd (d/s) [18-31-21] 103.37 103.62 103.99 104.18 104.55 104.71 

731865 * Balm-Boyette Rd (u/s) [18-31-21] 103.43 103.73 104.18 104.44 104.97 105.25 

Boggy Branch 

731050 * (d/s) Dam Spillway [1-31-20] 52.17 52.59 53.08 53.46 54.02 54.24 

731070 * Pond 55.21 56.73 58.64 59.31 59.82 60.00 

731075 * Boggy Branch [1-31-20] 57.42 57.90 59.09 59.77 60.39 60.63 

731080 * Boggy Branch [1-31-20] 62.43 62.87 63.45 63.76 64.25 64.45 

731085 * Big Bend Rd (d/s) 64.97 65.12 65.31 65.43 65.61 65.69 

731090 * Big Bend Rd (u/s) 65.62 65.82 66.11 66.27 66.53 66.65 

731095 * Boggy Branch [12-31-20] 77.25 77.82 78.52 78.88 79.41 79.67 

731097 * (d/s) Dam Spillway [12-31-20] 79.27 79.94 80.59 80.90 81.36 81.54 

731100 * Dam Outfall 83.60 84.18 84.91 85.27 85.88 86.18 

731110 * Dam Outfall Control Weir 83.83 84.44 85.10 85.36 85.93 86.23 

731120 * Lake 85.05 85.15 85.32 85.47 86.00 86.29 

731125 * Boggy Branch [11-31-20] 85.43 85.71 86.06 86.24 86.57 86.70 

731135 * Boggy Branch [11/14-31-20] 90.55 90.93 91.36 91.63 92.11 92.32 

731140 * Boggy Branch [14-31-20] 92.87 93.06 93.29 93.42 93.63 93.72 

731150 * Boggy Branch [14-31-20] 105.35 105.58 105.87 106.03 106.31 106.43 

731170 * Boggy Branch [23-31-20] 120.16 120.20 120.27 120.32 120.41 120.46 

731180 * Boggy Branch [13-31-20] 94.02 94.28 94.63 94.81 95.14 95.29 

731195 * Boggy Branch [13-31-20] 104.40 104.64 104.98 105.18 105.48 105.61 

731205 * Grass Rd (d/s) [13-31-20] 116.27 116.52 116.64 116.70 116.78 116.83 

731210 * Grass Rd (u/s) [24-31-20] 116.89 117.11 117.31 117.45 117.64 117.73 

730745 * Wetland Ditch [Goodson Farm #2 24-31-20] 123.05 123.12 123.22 123.27 123.38 123.43

TABLE 6.5-2 






Pelleham Branch 

730580 * Donnymoore Dr (d/s) Pelleham Branch [35-30-20] 39.19 39.83 40.72 41.14 42.14 42.62 

730585 * Donnymoore Dr (u/s) Pelleham Branch [35-30-20] 39.61 40.51 42.47 43.80 45.44 45.70 

730587 * Pond [35-30-20] 53.06 53.52 54.24 54.72 55.68 56.15 

730590 * N-S Ditch W of Tralee Dr [35-30-20] 65.32 65.53 65.82 65.98 66.31 66.45 

730595 * Wetland 73.89 74.19 74.60 74.85 75.29 75.49 

730600 * Pelleham Branch [34-30-20] 48.97 49.64 50.10 50.21 50.62 50.84 



730620 * Rhodine Rd (d/s) 64.95 65.79 67.09 67.73 68.61 68.83 

730622 * Wetland 72.12 72.25 72.43 72.55 72.79 72.92 

730625 * Rhodine Rd (u/s) 65.38 66.60 68.72 69.63 70.08 70.19 

730630 * Edgeknoll Dr (d/s) 67.31 68.38 70.03 70.80 71.58 71.81 

730635 * Edgeknoll Dr (u/s) 67.97 69.56 70.71 71.21 71.90 72.13 


730645 * Balm-Riverview Rd (d/s) 75.40 75.49 75.60 75.61 75.62 75.64 

730650 * Balm-Riverview Rd (u/s) 75.96 76.42 77.03 77.19 77.38 77.53 

718240 * Lower Alafia Basin (Rice Creek) 76.24 76.41 76.61 76.72 77.33 77.49 

730660 * Pelleham Branch Wetland System [3-31-20] 75.96 76.42 77.03 77.19 77.57 78.05 


730670 * Spottswood Dr (d/s) 71.41 71.66 71.92 72.00 72.62 72.83 

730675 * Spottswood Dr (u/s) 71.59 72.06 72.61 72.87 73.11 73.14 

730680 * Glennwood Dr (d/s) 79.39 79.53 79.53 79.59 80.14 80.31 

730685 * Glennwood Dr (u/s) 80.29 80.76 81.28 81.57 81.78 81.81 


730705 * Lenwood Ln (d/s) 72.90 73.79 74.76 75.41 75.75 75.90 

730710 * Lenwood Ln (u/s) 73.33 75.30 76.06 76.25 76.37 76.43 

730712 * Closed Basin [3-31-20] 71.84 72.13 72.56 72.84 73.39 73.66 

730715 * Entrance Way (d/s) 79.94 80.10 80.33 80.46 80.74 80.87 

730720 * Entrance Way (u/s) 81.39 81.42 81.48 81.51 81.58 81.61 

730725 * Anderson Dr (d/s) 80.54 80.77 81.05 81.11 81.27 81.31 

730730 * Anderson Dr (u/s) 81.69 81.80 81.90 81.96 82.05 82.10 

730735 * Big Bend Rd (d/s) 84.81 84.91 85.04 85.12 85.27 85.33 

730740 * Big Bend Rd (u/s) 85.30 85.37 85.48 85.55 85.68 85.75 

730741 * Driveway (d/s) [14-31-20] 109.11 109.63 110.19 110.49 110.95 111.16 

730742 * Driveway (u/s) [14-31-20] 109.98 110.23 110.55 110.74 111.16 111.37 


730700 * Shelby Dr (d/s) 75.48 76.19 76.33 76.40 76.51 76.55 

731040 * Shelby Dr (u/s) 78.23 78.55 78.98 79.24 79.73 79.95 

731020 * Lovers Ln (d/s) 76.13 76.97 77.52 77.65 77.83 77.91 

731025 * Lovers Ln (u/s) 76.36 77.43 78.59 78.88 79.30 79.47 


Tributary 731402 

731405 * Trib 731402 [7-31-21] 59.25 60.09 61.00 61.52 62.44 62.84 

731410 * Balm-Boyette Rd (d/s) 59.33 60.18 61.12 61.65 62.59 63.01 

731415 * Balm-Boyette Rd (u/s) 59.35 60.26 61.31 61.92 63.01 63.47 

731420 * Dirt / Grass Rd (d/s) [6-31-21] 59.37 60.28 61.32 61.93 63.01 63.47 

731423 * Dirt / Grass Rd (u/s) [6-31-21] 60.06 61.67 62.76 63.10 63.67 63.98 

731425 * Dirt Rd (d/s) [6-31-21] 63.42 63.77 64.20 64.46 64.91 65.11 

731435 * Dirt Rd (u/s) [6-31-21] 66.79 67.87 68.28 68.51 68.96 69.15 

731455 * Abandoned Seaboard Coast RR [8-31-21] 66.89 67.17 67.97 68.26 68.68 68.89 

731460 * Trib 731402 [8-31-21] 69.55 70.02 70.53 70.81 71.28 71.46 

731470 * Trib 731402 [8-31-21] 70.71 71.16 71.70 71.96 72.42 72.61 

731475 * Dirt Rd (d/s) [8-31-21] 77.26 77.26 77.52 77.60 77.75 77.83 

731480 * Dirt Rd (u/s) [8-31-21] 77.85 77.94 78.19 78.28 78.44 78.51 

731485 * Abandoned Seaboard Coast RR (d/s) [5-31-21] 79.09 79.68 80.72 80.94 81.27 81.41 

731490 * Abandoned Seaboard Coast RR (u/s) [5-31-21] 80.06 80.44 80.78 81.00 81.35 81.50 

731495 * Trib 731402 [8-31-21] 71.26 71.66 72.14 72.44 72.91 73.11 

731500 * Trib 731402 [8-31-21] 71.41 71.81 72.34 72.62 73.03 73.21 

731525 * Dirt Rd (d/s) [5-31-21] 80.45 80.79 81.00 81.08 81.27 81.36 

731535 * Dirt Rd (u/s) [5-31-21] - (d/s) Agric. BMP 81.56 81.75 81.88 81.94 82.06 82.11 

731505 * Dirt Rd (d/s) [5-31-21] 80.59 80.61 80.64 80.65 80.68 80.69 

731510 * Dirt Rd (u/s) [5-31-21] - W of Hobson Simmons Rd. 81.69 81.77 81.88 81.95 82.08 82.15

TABLE 6.5-2 







703705 * Carr Rd (d/s) [23-30-20] 13.91 14.85 15.05 15.19 16.54 17.70 

703710 * Carr Rd (u/s) [23-30-20] 17.00 17.82 18.21 18.44 18.82 18.98 

703715 * Trib 703700 [22-30-20] 23.57 24.39 25.35 25.76 26.46 26.72 

703719 * 44.93 45.10 45.35 45.37 45.41 45.42 

703720 * Riverglen Sub Lake "K" Outfall 56.47 56.79 61.08 61.79 62.87 63.08 

703725 * Riverglen Sub Lake "K" 60.38 60.70 61.32 61.90 62.95 63.16 

703727 * Riverglen Sub Lake "D" Outfall 60.86 61.76 64.26 65.53 66.90 67.08 

703730 * Riverglen Sub Lake "D" 65.51 66.24 66.86 67.00 67.20 67.27 

703735 * Tampa Bay Academy 73.04 73.13 73.21 73.27 73.36 73.39 

703737 * Trib 703700 [22-30-20] 49.73 50.07 50.35 50.64 51.34 51.70 

703740 * Boyette Rd (d/s) [22-30-20] 54.33 54.58 54.78 54.99 55.52 55.78 

703745 * Boyette Rd (u/s) [22-30-20] 54.55 54.87 55.12 55.41 56.24 56.63 

703750 * Boyette Springs Existing Pond Outfall 58.65 58.89 58.96 59.19 59.59 59.73 

703752 * Boyette Springs Existing Pond Outfall 60.06 60.19 61.01 63.21 66.51 67.29 

703755 * Boyette Springs Existing Pond 63.27 63.40 63.91 64.28 66.57 67.34 

703757 * Boyette Springs Detent Pond "D" Outfall 63.44 63.58 65.21 67.79 71.22 71.41 

703760 * Boyette Springs Detent Pond "D" 69.29 70.09 70.78 71.00 71.34 71.50 

703775 * Boyette Springs Detent Pond "B" 69.32 70.13 70.98 71.44 72.44 72.93 

730499 * Boyette Springs Detent Pond "C" 69.33 70.18 71.46 72.21 73.22 73.29 

703780 * Boyette Springs Detent Pond "H" Outfall 66.09 66.46 66.56 66.92 67.47 67.63 

703782 * Boyette Springs Detent Pond "H" Outfall 66.57 68.21 68.90 69.17 69.29 69.33 

703785 * Boyette Springs Detent Pond "H" 68.18 68.39 68.93 69.19 69.31 69.35





LEGEND 


TABLE 6.5-4 


BELL CREEK SUBWATERSHED EXISTING CONDITIONS LEVELS OF SERVICE ANALYSIS 




23-30-20 BOYETTE RD (BRIDGE) PUBLIC 730250 29.6 44.6 17.38 18.48 20.26 21.22 22.89 23.60 A A A A A A 

23-30-20 CREEK MANOR CT PUBLIC 730250 25.9 26.9 17.38 18.48 20.26 21.22 22.89 23.60 A A A A A A 

23-30-20 BELL CREEK DR PUBLIC 730310 27.5 27.5 20.74 20.90 22.32 23.30 25.00 25.73 A A A A A A 

23-30-20 SEDGEBROOK DR PUBLIC 730320 28.3 30.2 23.84 24.18 24.64 24.87 25.18 25.73 A A A A A A 

23-30-20 PINTAIL CT PUBLIC 730320 29.6 31.9 23.84 24.18 24.64 24.87 25.18 25.73 A A A A A A 

26-30-20 ELEMENTARY SCHOOL "J" PUBLIC 730330 47.1 56.4 44.10 44.64 45.17 45.35 45.63 45.74 A A A A A A 

26-30-20 CRESTFIELD DR PUBLIC 730400 51.5 52.8 20.67 21.68 23.34 24.25 25.88 26.59 A A A A A A 

26-30-20 DEEPBROOK DR PUBLIC 730400 43.3 44.9 20.67 21.68 23.34 24.25 25.88 26.59 A A A A A A 

26-30-20 DEEPBROOK DR & SUNBURST PL PUBLIC 730410 52.3 54.4 31.13 31.57 32.30 32.81 33.83 34.12 A A A A A A 

26-30-20 CRESTFIELD DR & OMEGA WAY PUBLIC 730415 56.8 61.9 55.64 55.88 56.26 56.49 56.78 56.88 A A A A A A 

27-30-20 WEXFORD HILLS RD PUBLIC 730470 60.5 72.6 60.60 60.66 60.73 60.78 60.86 60.90 A A A B B B 

26-30-20 SHADOW RUN BLVD PUBLIC 730550 44.6 0.0 37.76 38.39 39.48 40.12 41.30 41.85 A A A A A A 

26-30-20 LAKE HILLS DR PUBLIC 730550 48.9 42.6 37.76 38.39 39.48 40.12 41.30 41.85 A A A A A A 

35-30-20 CLOSED BASIN 730587 PRIVATE 730550 0.0 58.5 37.76 38.39 39.48 40.12 41.30 41.85 A A A A A A 



26-30-20 SHADOW RUN BLVD\LK GRADY PRIVATE 730550 0.0 42.1 37.76 38.39 39.48 40.12 41.30 41.85 A A A A A A 

35-30-20 GLENHILL DR PUBLIC 730585 73.5 74.6 39.61 40.51 42.47 43.80 45.44 45.70 A A A A A A 

35-30-20 DONNEYMOOR DR PUBLIC 730585 44.8 47.4 39.61 40.51 42.47 43.80 45.44 45.70 A A A A C C 

27-30-20 HOOT OWL CT PUBLIC 730595 75.5 77.9 73.89 74.19 74.60 74.85 75.29 75.49 A A A A A A 

3-31-20 RHODINE RD PUBLIC 730620 75.1 0.0 64.95 65.79 67.09 67.73 68.61 68.83 A A A A A A 

2-31-20 RHODINE RD PUBLIC 730625 69.4 67.8 65.38 66.60 68.72 69.63 70.08 70.19 A A D* D* D* D* 

3-31-20 EDGEKNOLL DR PUBLIC 730635 69.7 70.0 67.97 69.56 70.71 71.21 71.90 72.13 A A D D D D 

3-31-20 HOUSE NEAR FLD_PLAIN PRIVATE 730640 0.0 71.4 69.73 70.54 71.44 71.90 72.53 72.74 A A D* D* D* D* 

3-31-20 BALM RIVERVIEW RD PUBLIC 730650 78.1 77.3 75.96 76.42 77.03 77.19 77.38 77.53 A A A A D* D* 

2-31-20 SPOTTSWOOD DR PUBLIC 730675 73.3 74.9 71.59 72.06 72.61 72.87 73.11 73.14 A A A A A A 

2-31-20 GREENLAND DR PUBLIC 730685 81.7 82.2 80.29 80.76 81.28 81.57 81.78 81.81 A A A A A A 

2-31-20 SHELBY DR PUBLIC 730700 76.1 78.9 75.48 76.19 76.33 76.40 76.51 76.55 A A A B B B 

3-31-20 LENWOOD LN PUBLIC 730710 75.8 77.3 73.33 75.30 76.06 76.25 76.37 76.43 A A B B C C 

3-31-20 CLOSED BASIN 730712 PRIVATE 730712 0.0 77.6 71.84 72.13 72.56 72.84 73.39 73.66 A A A A A A 

3-31-20 ENTRANCE WAY @ BALM RIVERVIEW RD PUBLIC 730720 81.3 82.5 81.39 81.42 81.48 81.51 81.58 81.61 A A A A B B 

10-31-20 ANDERSON DR PUBLIC 730730 81.6 82.6 81.69 81.80 81.90 81.96 82.05 82.10 A A B B B C 

10-31-20 BIG BEND RD @ BALM RIVERVIEW RD PUBLIC 730740 85.0 86.9 85.30 85.37 85.48 85.55 85.68 85.75 B B B C C C 

14-31-20 DIRT DRIVEWAY PUBLIC 730742 112.5 122.2 109.98 110.23 110.55 110.74 111.16 111.37 A A A A A A 

36-30-20 HIDDEN VALLEY LN\LK GRADY PRIVATE 730750 0.0 51.1 37.82 38.48 39.65 40.33 41.57 42.14 A A A A A A 




2-31-20 DIRT ROAD PRIVATE 730785 0.0 77.1 71.30 71.38 71.47 71.53 71.64 71.69 A A A A A A 


3-31-20 TRTMENT PLANT PRIVATE 730814 79.5 81.5 78.63 78.84 79.14 79.32 79.69 79.87 A A A A A B 

10-31-20 BRENFORD CREST DR PUBLIC 730828 81.9 83.7 80.95 81.10 81.32 81.46 81.74 81.89 A A A A A A 

36-30-20 LYNNETREE LN PRIVATE 730975 73.9 0.0 70.66 70.91 71.32 71.58 72.03 72.23 A A A A A A 

36-30-20 DIRT RD TO AG\FARM HOUSE PRIVATE 730975 0.0 74.2 70.66 70.91 71.32 71.58 72.03 72.23 A A A A A A 

2-31-20 LOVERS LN PUBLIC 731025 80.8 82.4 76.36 77.43 78.59 78.88 79.30 79.47 A A A A A A 

11-31-20 HOUSE NEAR POND PRIVATE 731040 0.0 81.9 78.23 78.55 78.98 79.24 79.73 79.95 A A A A A A 

12-31-20 DIRT RD @ LAKE OUTFALL PRIVATE 731120 0.0 86.8 85.05 85.15 85.32 85.47 86.00 86.29 A A A A A A 

6-31-21 TRAILS END LN (DIRT RD) PRIVATE 731260 0.0 78.9 67.00 67.22 67.53 67.78 69.41 70.28 A A A A A A 


7-31-21 BALM BOYETTE RD (BRIDGE) PUBLIC 731415 61.5 62.1 59.35 60.26 61.31 61.92 63.01 63.47 A A A B D D 

7-31-21 DIRT RD PRIVATE 731435 0.0 85.1 66.79 67.87 68.28 68.51 68.96 69.15 A A A A A A 

9-31-21 HOBSON SIMMONS RD PUBLIC 731518 84.7 0.0 81.89 82.05 82.27 82.42 83.37 84.16 A A A A A A 

5-31-21 HOBSON SIMMONS RD PUBLIC 731530 85.0 0.0 83.96 84.62 84.89 85.02 85.09 85.12 A A A A A A 

18-31-21 BALM BOYETTE RD PUBLIC 731865 109.5 0.0 103.43 103.73 104.18 104.44 104.97 105.25 A A A A A A 

18-31-21 BALM BOYETTE RD PUBLIC 732000 108.8 0.0 104.16 105.47 107.25 108.52 109.37 109.56 A A A A C C 

19-31-21 HOUSE NEAR FLD_PLAIN PRIVATE 732100 0.0 117.6 107.55 107.91 108.37 108.67 109.56 109.78 A A A A A A






BOYETTE RD 

FISHHAWK BLVD 

301 

BELL CREEK 


Lake Grady 


BELL CREEK 

BOGGY CREEK 


A 

B 

C 

D/D* 

Polk Co. 

O 

Legend 

County Line 





Suite 120 


Notes: 

BOGGY CREEK 

1:52,000 

BELL CREEK 

0 1,250 2,500 5,000 

Feet 

0 0.25 0.5 1 

Miles 

Filename: 

Fig6_5_ 

2.mxd 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 

672 









Two of the four locations identified in Table 6.5-4 where the County’s minimum 

acceptable level of service criteria are structure flooding one is in the vicinity of a 

private road the other is in the vicinity of a Hillsborough County Road. The other 

two locations are identified as LOS Level C and D and are on Hillsborough County 

Roads. None of these LOS violations are substantiated by flooding complaints. 






Hillsborough County Service Unit Reported Problems 



Fishhawk Creek Subwatershed. The Unit reported one location that experiences 

recurring flood problems. The location is detailed Table 6.6-1 and shown on Figure 

6.6-1. 






into this report. However, while other subwatersheds had numerous complaints 

filed during this time period, the Fishhawk Creek Subwatershed, being largely 

undeveloped, was not unduly remonstrative of the excessive rainy conditions. 







Like most municipalities in central Florida, Hillsborough County was besieged by 

flooding complaints from local residents over the course of the 1997/1998 El Nino 

and 2004 Hurricane Frances floods. In an effort to address reported flooding 

concerns, a record was complied which was provided to Parsons to utilize for the 

purpose of this study. Complaints located within the Fishhawk Creek Subwatershed 

are listed in Table 6.6-1, and the locations of the individual complaints are plotted in 

Figure 6.6-1. There were a total of 4 individual flooding complaint records within the 

Fishhawk Creek Subwatershed. It can be seen from close examination of Table 

6.6-1 that a number of these complaints were repetitive (i.e. same location). It is 

also noted that the County database does not include a description of the nature of 

the problem for those complaints that were reported during the February 1998 

flooding event, thus limiting its interpretive usefulness. 




Table 6.6-1 

Fishhawk Creek Subwatershed Reported Flooding Problems 

INFORMATION 

SOURCE 

MAP REFERENCE 

NUMBER 

LOCATION 

DESCRIPTION 




Complaints 

72 Boyette and Dorman Road Road/Road Flooding / Poorly Drained/ 

658 17724 & 17726 Dorman Road No information available 

715 6440 Lithia Pinecrest Road No information available 

1075 16206 Boyette Rd No information available 




2026 

Browning Road from Red Bird Lane to Dairy Road 

No information available 






ALAFIA RIVER 

ALAFIA RIVER 

ALAFIA RIVER 

BOYETTE RD 

FISHHAWK BLVD 



658 

715 

RICE CREEK 

Serv_72 

2026 


1075 

BOYETTE RD 


Legend 


Service Unit 


January 1998 

County Line 



Roads 




Suite 120 



Notes: 


1:60,000 


0 1,500 3,000 6,000 

Feet 

0 0.25 0.5 1 

Miles 

DOE BRANCH 

CW Bill 

Young 

Regional 

Reservoir 

Filename: 

Fig6_6_ 

1.mxd 

672 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 

39 










In order to predict basinwide flooding conditions for the existing land use conditions 

and the existing drainage facilities throughout the Fishhawk Creek Subwatershed, 

the hydrologic/hydraulic computer model was run for the design storm events. For 

the purpose of this study, existing conditions refer to Year 2006 land use conditions 

and drainage facilities. A maximum flood elevation summary is given in Table 6.6-2 

that lists the peak flood stages at each of the model nodes along the main 

conveyance systems for the various design storms. A summary of the modelsimulated 

peak flows at selected locations in the basin is presented in Table 6.6-3 

Table 6.6-3 

Fishhawk Creek Subwatershed Peak Flows at Selected Locations 

Location 

Fishhawk Creek at Mouth 

(9740000) 

Fishhawk Creek at 

Fishhawk Creek Blvd 

(9740125) 

Doe Branch at Mouth 

(9743000) 

Long Flat Creek at Mouth 

(9744150) 

Little Fishhawk Creek at 

Mouth (9746000) 

Confluence of Tributary 1 to 

LFC and LFC at 746350 

(9746350) 

Little Fishhawk Creek at 

Boyette Road (9746550) 

2.33-year 

(cfs) 

5-year 

(cfs) 

10-year 

(cfs) 

25-year 

(cfs) 

50-year 

(cfs) 

100-year 

(cfs) 

1340 1907 2785 3422 4713 5357 

1341 1907 2785 3426 4716 5363 

668 994 1329 1527 1803 1972 

293 406 601 744 1070 1291 

733 1060 1582 1939 2696 3054 

560 804 1167 1406 1884 2101 

203 292 411 480 608 664 


The County has adopted the Target Level of Service for the Fishhawk Creek 

Subwatershed. As discussed previously, this is a minimum basin-wide goal of Level 

‘B’ for the 25-year, 24-hour design storm event. Table 6.6-4 shows the level of 

service currently being estimated for each of 42 locations identified within the 

watershed. Based on the adopted criterion, there are two locations identified in 

Table 6.6-4 where the County’s minimum acceptable level of service is not met, as 

indicated by shaded cells in the table. Complaint record sites not shown as a 

problem area in Table 6.6-4 are generally an indication of secondary system 

problems or possible maintenance problems. A detailed discussion of the problem 

areas that were identified as primary drainage system deficiencies is presented in 

Chapter 13 of this report. Figure 6.6-2 shows the LOS by subbasin as required by 

County standards. 






TABLE 6.6-2 


FISHHAWK CREEK SUBWATERSHED EXISTING CONDITIONS FLOOD ELEVATIONS SUMMARY 




* Main Channel 

704900 * Alafia River @ Fishhawk Creek Confluence 18.66 20.65 22.55 24.80 26.45 27.79 

740100 * Fishhawk Blvd (u/s) 20.69 22.12 23.81 24.82 26.52 27.79 

740125 * Fishhawk Creek Streamflow Gaging Station 20.78 22.23 23.92 24.94 26.63 27.79 

740150 * Fishhawk Creek 22.53 23.87 25.41 26.34 27.90 28.59 











741000 * SCRR Railroad 45.23 46.12 47.31 48.04 49.32 49.87 

* Abandoned SCRR to CSXT RR ext. 

741100 * 47.30 48.04 49.00 49.62 50.75 51.23 

741150 * 48.78 49.55 50.50 51.10 52.18 52.65 

741250 * Boyette Road Bridge (d/s) 52.69 53.37 54.24 54.77 55.71 56.11 

741300 * Boyette Road Bridge (u/s) 52.75 53.46 54.47 55.09 56.24 56.73 

741350 * Tributary 5 Confluence 53.58 54.25 55.20 55.79 56.90 57.37 

741400 * Doe Branch Confluence 55.27 56.02 57.04 57.67 58.79 59.26 

741450 * 56.27 56.78 57.68 58.30 59.40 59.82 

741500 * Dirt Road (u/s) 56.85 57.66 59.24 60.37 62.94 64.09 

741550 * 60.98 61.43 62.06 62.42 63.42 64.40 

741600 * 63.73 64.13 64.64 64.94 65.64 65.97 

741625 * 66.86 67.31 67.80 68.11 68.92 69.26 

741650 * 67.47 67.89 68.40 68.72 69.53 69.89 

741660 * 69.35 69.69 70.12 70.41 71.09 71.41 

741680 * 71.91 72.24 72.66 72.94 73.66 73.94 

741700 * 72.91 73.15 73.45 73.66 74.27 74.56 

741750 * 78.50 78.93 79.43 79.72 80.50 80.84 

741800 * 78.52 78.95 79.45 79.74 80.53 80.87 

741825 * 78.83 79.13 79.62 79.93 80.79 81.16 

741827 * 79.99 80.38 80.66 80.98 81.38 81.58 

741845 * 84.52 85.14 85.85 86.28 87.40 87.86 

* CSXT RR ext. to terminus 

741850 * Abandoned RR 85.11 85.52 86.19 86.61 87.71 88.18 

741900 * 88.05 88.33 88.58 88.80 89.38 89.63 

741950 * 95.15 95.42 95.76 95.96 96.30 96.45 

742000 * 107.23 107.67 108.22 108.54 109.09 109.33 

742010 * 107.27 107.72 108.28 108.61 109.18 109.43 

742050 * 122.47 122.70 122.98 123.13 123.39 123.51 

742075 * 123.08 123.22 123.42 123.55 123.78 123.88 

* End of Main Channel 

* Tributary 6 Doe Branch 

743000 * Doe Branch 65.09 65.48 65.78 65.88 65.97 66.02 

743025 * Doe Branch 67.86 68.38 69.12 69.58 70.30 70.64 

743050 * Doe Branch 75.07 75.73 76.41 76.81 77.54 77.85 

743100 * Doe Branch 78.52 78.96 79.43 79.70 80.12 80.33 

743125 * Doe Branch 81.64 81.87 82.16 82.33 82.65 82.80 

743130 * Doe Branch 83.26 83.62 84.07 84.34 84.80 85.01 

743150 * Doe Branch 85.75 85.92 86.10 86.21 86.41 86.49 

743200 * Doe Branch 88.11 88.35 88.58 88.72 88.94 89.01 

743250 * Doe Branch 89.22 89.49 89.85 90.04 90.31 90.41 

743260 * Doe Branch 89.48 89.83 90.30 90.59 91.11 91.30 

743270 * Doe Branch 90.66 90.84 91.00 91.10 91.27 91.33 

743300 * Doe Branch 90.69 90.88 91.05 91.14 91.31 91.37 

743325 * Doe Branch 90.71 90.91 91.14 91.27 91.53 91.62 

* Tributary 2 to Doe Branch (Annie's Creek) 

743053 * 79.08 79.82 80.69 81.28 82.08 82.43 

743056 * 85.98 86.17 86.36 86.48 86.69 86.77 

743059 * 90.06 90.25 90.46 90.57 90.77 90.85 

743062 * Road crossing 90.81 91.10 91.49 91.74 92.16 92.19

TABLE 6.6-2 


FISHHAWK CREEK SUBWATERSHED EXISTING CONDITIONS FLOOD ELEVATIONS SUMMARY 




743063 * 92.36 92.71 93.26 93.56 93.87 94.00 

743070 * 99.38 99.54 99.75 99.95 100.16 100.30 

743077 * Road crossing 102.51 102.54 102.56 102.57 102.58 102.73 

743080 * 104.41 104.76 104.99 105.10 105.28 105.35 

* Tributary 8B of Fishhawk Creek Long Flat Creek 

744000 * 66.82 66.99 67.25 67.44 67.81 68.02 

744002 * 69.56 69.71 69.98 70.17 70.52 70.73 

744050 * 73.51 73.96 74.58 74.96 75.65 76.03 

744100 * 77.75 78.22 78.64 78.82 79.14 79.37 

744150 * 81.36 81.76 82.25 82.55 83.12 83.42 

744175 * 84.40 84.69 85.15 85.41 85.87 86.13 

744200 * 87.11 87.33 87.60 87.77 88.10 88.30 

744250 * 91.58 91.76 91.99 92.13 92.41 92.58 

744260 * 94.19 94.27 94.40 94.48 94.66 94.78 

744290 * 94.29 94.41 94.63 94.78 95.18 95.50 

744300 * 94.31 94.44 94.66 94.82 95.23 95.56 

744350 * 96.61 96.83 97.09 97.24 97.57 97.69 

744400 * 96.66 96.87 97.14 97.30 97.64 97.77 

744425 * 101.81 102.21 102.61 102.84 103.34 103.51 

744430 * 101.88 102.28 102.70 102.95 103.47 103.66 

744450 * 105.53 105.68 106.01 106.25 106.77 107.01 

744500 * 119.00 119.07 119.21 119.32 119.66 119.84 

744510 * 121.63 121.66 121.73 121.79 121.94 122.02 

744550 * 123.66 123.72 123.88 124.04 124.24 124.31 

744600 * 125.63 126.14 126.31 126.39 126.53 126.60 

* Little Fishhawk Creek 

705300 * Outfall Node for Little Fishhawk to Alafia 19.92 21.84 23.71 25.94 27.56 28.85 

746000 * Survey Location X105 19.92 21.84 23.71 25.94 27.56 28.85 

746025 * Survey Location 22.71 23.62 24.81 25.94 27.56 28.85 

746050 * Wood Plank Bridge (d/s) 28.20 28.98 29.74 30.13 30.88 31.17 

746100 * Wood Plank Bridge (u/s) 29.12 29.75 30.44 30.81 31.53 31.85 

746150 * Fishhawk Blvd Bridge (d/s) 30.60 31.37 32.27 32.73 33.54 33.86 

746200 * Fishhawk Blvd Bridge (u/s) 31.12 32.03 32.92 33.32 34.03 34.32 

746250 * 31.68 32.72 33.82 34.36 35.33 35.72 

746300 * Survey Location S108 42.56 43.20 44.00 44.46 45.20 45.47 

746350 * 52.12 53.04 54.06 54.58 55.46 55.81 

746400 * 68.73 69.27 69.94 70.24 70.74 70.96 

746410 * 68.80 69.36 70.03 70.33 70.84 71.05 

746420 * 68.93 69.63 70.48 70.67 70.98 71.16 

746550 * 71.49 72.01 72.55 72.82 73.25 73.42 

746560 * 71.64 72.29 73.12 73.63 74.56 74.98 

746625 * 71.69 72.35 73.17 73.68 74.59 75.01 

746810 * 71.71 72.35 73.17 73.68 74.60 75.01 

746820 * 73.53 74.26 75.16 75.50 75.95 76.19 

* Tributary 1 

747000 * Confluence 59.10 59.31 59.78 60.08 60.55 60.76 

747050 * Abandoned RR 65.99 66.45 67.04 67.42 68.10 68.37 

747100 * Dorman Road - (d/s) 69.76 70.19 70.71 71.04 71.54 71.74 

747150 * Dorman Road - (u/s) 70.05 70.67 71.61 72.22 72.47 72.56 

747200 * Boyette Road (d/s) 73.05 73.46 73.88 74.09 74.42 74.57 

747225 * Boyette Road (u/s) 74.00 74.80 75.02 75.13 75.32 75.40 

747250 * 77.42 77.98 78.49 78.79 79.11 79.31 

747350 * 90.43 90.70 90.98 91.12 91.46 91.64 

747500 * 94.60 94.90 95.29 95.50 95.80 95.92 

747550 * Cross Section Survey X109 (Modified) 97.99 98.29 98.68 98.90 99.27 99.43

LEGEND 


TABLE 6.6-4 


FISHHAWK CREEK SUBWATERSHED EXISTING CONDITIONS FLOODING LEVELS OF SERVICE ANALYSIS 




19-30-21 FISHHAWK BLVD PUBLIC 740100 38.1 0.00 20.69 22.12 23.81 24.82 26.52 27.79 A A A A A A 

30-30-21 HERONGLEN DR PUBLIC 740458 46.7 0.00 40.64 40.96 41.32 41.61 42.46 42.93 A A A A A A 

29-30-21 OSPREY RIDGE DR PUBLIC 740466 75.1 0.00 73.66 73.99 74.47 74.78 75.26 75.40 A A A A A B 

19-30-21 EAGLEMOUNT CIR PUBLIC 740474 74.2 75.00 72.82 72.96 73.14 73.24 73.41 73.49 A A A A A A 

19-30-21 HERONPARK PL PUBLIC 740474 75.6 75.00 72.82 72.96 73.14 73.24 73.41 73.49 A A A A A A 

29-30-21 HERONGLEN DR PUBLIC 740476 75.4 75.40 73.27 73.54 73.95 74.22 74.57 74.73 A A A A A A 

5-31-21 BOYETTE RD PUBLIC 740715 85.6 0.00 83.21 83.48 83.94 84.22 84.79 85.09 A A A A A A 



34-30-21 BOYETTE RD PRIVATE 741165 0.0 80.10 76.93 77.22 77.67 77.96 78.50 78.74 A A A A A A 


33-30-21 BOYETTE RD PUBLIC 741300 55.6 0.00 52.75 53.46 54.47 55.09 56.24 56.73 A A A A C D 


9-31-21 HOBSON SIMMONS RD PRIVATE 741825 78.2 89.60 78.83 79.13 79.62 79.93 80.79 81.16 C C D D D D 

2-31-21 NEAL RD PUBLIC 743040 80.1 85.00 79.71 79.81 79.98 80.07 80.23 80.30 A A A A A A 

36-30-21 Structure near Red Bird La PRIVATE 743062 0.0 94.10 90.81 91.10 91.49 91.74 92.16 92.19 A A A A A A 

25-30-21 HOUSE NEAR RED BIRD LN PRIVATE 743080 0.0 107.10 104.41 104.76 104.99 105.10 105.28 105.35 A A A A A A 

12-31-21 Unnamed Dirt Road PRIVATE 743200 0.0 89.60 88.11 88.35 88.58 88.72 88.94 89.01 A A A A A A 

12-31-21 WENDEL AVE PUBLIC 743325 92.1 93.10 90.71 90.91 91.14 91.27 91.53 91.62 A A A A A A 

22-31-21 Entrance to SECty Landfill PUBLIC 744600 126.2 0.00 125.63 126.14 126.31 126.39 126.53 126.60 A A A A B B 


20-30-21 Osprey Park Place PRIVATE 746125 0.0 63.50 56.28 56.38 56.51 56.58 56.72 56.79 A A A A A A 

29-30-21 OSPREY RIDGE DR PUBLIC 746137 73.7 75.10 67.27 67.48 67.78 67.97 68.34 68.60 A A A A A A 

29-30-21 OSPREY RIDGE DR PUBLIC 746140 73.9 77.40 72.56 72.75 73.02 73.19 73.50 73.64 A A A A A A 

20-30-21 DORMAN RD PUBLIC 746200 68.2 0.00 31.12 32.03 32.92 33.32 34.03 34.32 A A A A A A 


21-30-21 FISHHAWK CROSSING BLVD PUBLIC 746375 57.5 0.0 52.21 53.22 54.43 55.12 56.42 57.01 A A A A A A 

22-30-21 FALCONRIDGE RD PUBLIC 746470 74.1 75.6 71.47 71.74 72.11 72.34 72.78 72.98 A A A A A A 

22-30-21 HAWKRIDGE RD PUBLIC 746520 82.6 83.80 72.21 72.50 72.90 73.15 73.57 73.64 A A A A A A 


22-30-21 HARRIERRIDGE PL PUBLIC 746590 75.3 76.40 73.48 73.65 73.88 74.00 74.56 74.98 A A A A A A 

22-30-21 Falconridge Road - West (Triple) PUBLIC 746620 74.1 76.20 72.65 72.79 73.13 73.63 74.59 75.01 A A A A B C 

22-30-21 Falconridge Road - East PUBLIC 746650 76.4 77.60 74.60 74.86 75.20 75.38 75.67 75.77 A A A A A A 


26-30-21 6440 Lithia Pinecrest Road (Church) PRIVATE 746715 0.0 108.60 105.33 105.39 105.45 105.49 105.54 105.57 A A A A A A 

22-30-21 FALCONCREEK PL PUBLIC 746850 80.6 81.80 78.49 78.71 79.00 79.16 79.46 79.59 A A A A A A 


28-30-21 DORMAN RD PUBLIC 747032 79.4 0.00 78.85 79.25 79.44 79.46 79.48 79.49 A A A A A A 

27-30-21 Dorman Road d/s PRIVATE 747100 0.0 72.00 69.76 70.19 70.71 71.04 71.54 71.74 A A A A A A 

27-30-21 DORMAN RD PUBLIC 747150 72.1 80.10 70.05 70.67 71.61 72.22 72.47 72.56 A A A A B B 

27-30-21 BOYETTE RD PUBLIC 747225 74.6 76.10 74.00 74.80 75.02 75.13 75.32 75.40 A A B C C C 

26-30-21 LITHIA RANCH RD PUBLIC 747490 94.5 0.00 93.14 93.29 93.52 93.67 94.04 94.23 A A A A A A





ALAFIA RIVER 

ALAFIA RIVER 

ALAFIA RIVER 

BOYETTE RD 

FISHHAWK BLVD 



RICE CREEK 


BOYETTE RD 


A 

B 

C 

D/D* 

Polk Co. 

O 

Legend 

County Line 





Suite 120 



Notes: 


1:60,000 


0 1,500 3,000 6,000 

Feet 

0 0.25 0.5 1 

Miles 

DOE BRANCH 

CW Bill 

Young 

Regional 

Reservoir 

Filename: 

Fig6_6_ 

2.mxd 

672 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 

39 











Hillsborough County East Service Unit Reported Problems 

In 2001, Parsons interviewed the Hillsborough County Central and East Service 

Unit, the branches of the County that perform maintenance of the drainage system 

in the Turkey Creek Subwatershed. These Units reported 14 locations that 

experience recurring flood problems. Locations are detailed Table 6.7-1 and shown 

on Figure 6.7-1. 













Local residents besieged Hillsborough County with complaints during the El Nino 

and 2004 Hurricane Frances floods. Hillsborough County compiled a cursory digital 

database of complaints. Complaint locations in the Turkey Creek Subwatershed 

are listed in Table 6.7-1; locations are shown on Figure 6.7-1. Hillsborough County 

recorded 24 flood complaints in the Turkey Creek Subwatershed. The County El 

Nino and Hurricane Frances database only contains locations within the Turkey 

Creek Subwatershed. Details of the complaint or follow-up action by County 

personnel were not recorded in the Turkey Creek Subwatershed. 




Table 6.7-1 

Turkey Creek Subwatershed Reported Flooding Problems 

INFORMATION 

SOURCE 

MAP REFERENCE 

NUMBER 

LOCATION 

DESCRIPTION 


Central Service Unit 44 

Southeast of Murray Farm Rd and Juanita Dr 

Inadequite Conveyance System 


East Service Unit 


Complaints 

6 N Dover Rd south of Seaboard Coastline Railroad Poorly Drained 

7 Fietzway Rd east of Sydney Washer Rd Road Flooding - Poorly Drained 

8 Jerry Smith Rd south of Blankenship Rd Road Flooding - Poorly Drained 

9 Southwest of Seaboard Coastline Railroad and S Forbes Rd Houses at Low Elevations 

10 Southeast of Lone Oak Rd and Webber Rd Houses at Low Elevations 

11 Southeast of Jerri Lynn Ct and Mud Lake Rd Impermeable Agriculture Liner 

12 North of Hollaway Rd, west of Pippin Rd Channel Flooding - Maintenance Issue 

13 Southeast of Sparkman Rd and James L Redmond Pkwy Sedimentation Problem 

16 Colson Rd and Seaboard Coastline Railroad Missing Drainage Structure 

17 South of Cowart Rd, east of Cameron Rd Poorly Drained 

26 SR 60, east of Hans Ln Poorly Drained 

33 East of S Dover Rd, north of Seaboard Coastline Railroad Mine Leeching 

36 East of CR 39, south of Seaboard Coastline Railroad Dam Failure 

273 E. Kilgore Culverts under repair, but now driveway is under water. Referred to East Service Unit to handle - maintenance issue. 


Complaints 

699 5308 S. Calhoun Road No information available 

703 5710 W. Farkas Road\1378 E. Trapnell Road No information available 

705 3026 Gerald Hall Rd. No information available 

717 4301 Lott Avenue No information available 

733 3710 S. Turkey Creek Road No information available 

744 727 Swilley Lp. No information available 

1010 3101 Blount Road No information available 

1020 6101 Durant Road No information available 

1059 3904 Turkey Creek Rd No information available 

1063 4808 W. Summerall / 8110 Claxton Lane No information available 

1064 805 W. Swilley Road No information available 

1065 4603 W. Trapnell Road\4603 W. Trapnell Rd No information available 

1108 3710 S. Turkey Creek Rd No information available 




2052 N. Dover Rd. from Thomas Cooper Ln. to Salem Church Rd. Road flooding. Possibly raise road @ low point or provide/evaluate existing size of structures. 

2045 Mud Lake Rd. from Holloway Rd. to Bugg Rd. Road flooding. Bay head on each side of roadway could cause flooding 

2046 Holloway Rd. from Drawdy Rd. to Wallace Rd. No information available 

2049 Holloway Rd. from James L. Redman Pkwy. To Armor Rd. Ditch needs cleaning. Pipe full of silt 

2033 Cameron Rd. from Cowart Rd. to dead end Road flooding. Property lower than roadway. 

2075 Evelyn Lakes Dr. from Sparkman Rd. to dead end Yard flooding. Conveyance system is functioning. Culvert under Evelyn Lakes is open. Ditches are dry on either side of cross drain. 

2048 Caruthers Rd. from dead end to Sydney Rd. No information available 

2009 Sapp Road & Johnson Road North of intersection is underwater. It appears that the ditches along the north side of Johnson Rd. have been filled in. 

2047 S. Forbes Rd. from Jerry Smith Rd. to Sydney Rd. Road flooding. 

2051 Downing Street from Nelson Ave. to Sydney Dover Rd. No information available 


4 

92 

S COLLINS ST 



Legend 


Service Unit 


January 1998 

December 1997 

County Line 



Roads 




Suite 120 


E LUMSDEN RD 



Notes: 

Serv_6 

2052 

2051 

2048 

Serv_7 

Serv_26 

S FORBES RD 

TURKEY CREEK 

Serv_9 

1:72,000 

0 1,500 3,000 6,000 

0 0.25 0.5 1 


Feet 

Miles 


Serv_8 

60 699 

60 

Serv_33 

1010 

2047 

703 

1020 

1052 

1065 

1108 

1059 

717 

1063 

733 

Serv_10 

2046 


Medard 

Reservoir 

Filename: 

Fig6_7_ 

1.mxd 

Serv_44 

2045 

Serv_11 

Serv_12 

1064 

Map Date: 



N/A 

744 

732 

2009 

2049 

Serv_13 



Prepared By: 

Yoav 

Rappaport 

705 

273 

Serv_16 

Serv_36 

2075 

2033 

700 

Serv_17 


Polk Co 










To assess flood hazard, the suite of six design storms is run through the 

hydrodynamic model of the Turkey Creek Subwatershed. These simulations reflect 

existing conditions, defined as circa 2006 land use and drainage system conditions. 

Table 6.7-2 (on the next page) lists peak-flood elevations at junctions of interest as 

a function of recurrence interval. Table 6.7-3 summarizes simulated peak flows at 

selected locations within the subwatershed as a function of recurrence interval. 

Table 6.7-3 

Turkey Creek Subwatershed Simulated Peak Flows at Selected Locations 

Location 

Turkey Creek Outfall to the 

Alafia River (9750050) 

Turkey Creek at State Road 

60 (9752600) 

Turkey Creek at Sydney 

Road (9754197) 

Little Alafia River Outfall to 

Turkey Creek (9755002) 

Medard Reservoir Outfall 

(9755350) 

Little Alafia River at State 

Road 60 (9756018) 

2.33-year 

(cfs) 

5-year 

(cfs) 

10-year 

(cfs) 

25-year 

(cfs) 

50-year 

(cfs) 

100-year 

(cfs) 

1105 1611 2120 2809 3241 3721 

897 1315 1738 2320 2656 3137 

650 862 1070 1374 1574 1744 

541 723 906 1171 1351 1542 

217 315 355 419 452 485 

1099 1494 1925 2546 2966 3259 






TABLE 6.7-2 


TURKEY CREEK SUBWATERSHED EXISTING CONDITIONS FLOOD ELEVATIONS SUMMARY 




Turkey Creek 

750000 Turkey Creek, S10 T30 R21 27.09 28.13 29.13 30.54 31.66 32.62 

751200 Turkey Creek S03 T30 R21 31.44 32.90 34.18 35.46 36.05 36.65 

751400 U/S Side Durant Road, Turkey Creek S03 T30 R21 33.32 34.59 35.64 36.82 37.40 38.03 

751500 U/S Side Seaboard Coastline Railroad, Turkey Creek S34 T29 R21 36.38 37.37 38.21 39.06 39.52 39.97 

752500 U/S Side East State Road 60, Turkey Creek S22 R29 R21 51.25 52.75 54.34 56.37 57.69 58.61 

753400 U/S Side Garland Branch Road, Turkey Creek S15 R29 R21 60.76 61.27 61.73 62.18 62.47 62.75 

754200 U/S Side Sydney Road, Turkey Creek S10 R29 R21 73.11 73.84 74.62 75.55 76.08 76.61 

754400 U/S Side Caruthers Road, Turkey Creek S10 R29 R21 75.63 76.24 76.53 76.84 77.04 77.27 

754900 U/S Side Downing Street, Turkey Creek S3 R29 R21 94.23 94.43 94.55 94.71 94.79 94.85 

754950 U/S Side Rev. Dr. Martin Luther King Jr. Boulevard, Turkey Creek S3 108.60 109.39 110.34 110.93 111.49 112.05 

Turkey Creek Tributary A 

753000 Turkey Creek S22 R29 R21 57.36 58.24 58.94 59.57 59.97 60.35 

753118 U/S Side Jerry Smith Road 67.90 68.42 68.69 69.02 69.22 69.41 

753170 U/S Side Turkey Creek Road 81.13 81.80 82.10 82.58 82.80 83.00 

753180 U/S Side Lone Oak Road 89.05 89.68 90.29 90.72 90.85 90.96 

753260 U/S Side West Trapnell Road 99.66 99.77 99.84 99.94 99.99 100.04 

Turkey Creek Tributary B 

754002 Turkey Creek S15 R29 R21 69.93 70.79 71.40 71.97 72.30 72.62 

754020 U/S Side South Forbes Road 78.49 78.94 79.27 79.58 79.77 79.91 

754040 U/S Side Jerry Smith Road 88.10 88.34 88.44 88.57 88.65 88.72 

754080 U/S Side Charleston Avenue 103.16 103.26 103.34 103.45 103.52 103.59 

754120 U/S Side Sydney Road 111.61 111.89 112.14 112.30 112.40 112.50 

754160 U/S Side Turkey Creek Road 117.57 117.98 118.36 118.92 119.19 119.36 

Little Alafia River 

751000 U/S Side Utility Easement Bridge, Turkey Creek, S03 T30 R21 27.94 29.45 30.70 32.01 32.70 33.34 

755250 U/S Side Seaboard Coastline Railroad, Little Alafia River, S02 T30 R2 34.86 36.04 36.46 37.12 37.45 37.76 

755300 U/S Side Durant Road, Little Alafia River, S02 T30 R21 35.04 36.13 36.54 37.18 37.50 37.81 

755500 U/S Side Turkey Creek Road, Little Alafia River, S36 T29 R21 37.05 37.50 37.68 37.98 38.17 38.37 

755600 Medard Reservoir, S36 T29 R21 60.61 61.27 61.92 63.15 63.85 64.54 

756020 U/S Side State Road 60, Little Alafia River S24 T29 R21 64.37 64.99 65.74 67.27 68.24 69.00 

756320 U/S Side Mud Lake Road, Little Alafia River S19 T29 R22 74.04 74.62 75.31 76.34 76.80 77.20 

756500 Little Alafia River S17 T29 R22 96.38 96.77 97.12 97.54 97.85 98.16 

756420 U/S Side Holloway Road, Little Alafia River S19 T29 R22 86.06 86.70 87.26 87.60 87.77 87.91 

Little Alafia River Tributary A 

755002 Little Alafia River, S02 T30 R21 29.24 30.27 31.11 32.26 32.90 33.49 

755010 Little Alafia River Tributary A, S02 T30 R21 42.02 42.69 43.18 43.77 44.14 44.53 

755030 U/S Side Turkey Creek Road, Little Alafia River Tributary A, S11 T30 48.45 49.00 49.50 50.23 50.59 50.83 

Grassy Creek 

756100 Little Alafia River S19 T29 R22 71.87 72.29 72.77 73.55 73.88 74.12 

756120 U/S Side Holloway Road, Grassy Creek S18 T29 R22 82.47 82.70 82.83 83.01 83.11 83.19 

756170 U/S Side Trapnell Road, Grassy Creek S07 T29 R22 101.71 102.18 102.65 103.70 104.55 105.21 

756180 U/S Side Murray Farms Road, Grassy Creek S07 T29 R22 108.06 108.77 109.37 109.93 110.12 110.29 

756190 U/S Side Mud Lake Road, Grassy Creek S07 T29 R22 118.65 118.80 118.91 119.03 119.11 119.18 

Medard Tributary A 

757200 U/S Side County Road 39, Medard Tributary A, S29 T29 R22 79.23 79.92 80.50 81.22 81.64 82.20 

757300 U/S Side Old Hopewell Road, Medard Tributary A, S29 T29 R22 93.47 94.17 94.88 95.94 96.52 96.75 

757400 U/S Side State Road 60, Medard Tributary A, S29 T29 R22 103.81 104.38 104.86 105.59 106.01 106.38








Table 6.7-4 shows level-of-service estimates for 154 locations-of-interest in the 

Turkey Creek Subwatershed. Hillsborough County adopted Level of Service B for 

the 25-year, 24-hour design-storm event. Thirty-one locations do not meet this 

target in these subwatersheds. Figure 6.7-2 shows the LOS by subbasin as 

required by County standards. 

The level-of-service matrix is useful for identifying additional problem areas and 

communicating the severity of flood problems. For example, although the adopted 

criteria addresses yard flooding -- Level of Service B -- during the 25-year event, 

flooding of a street for the 2-year or 5-year event might also be important. 

Only one of the flood complaints correlates with level-of-service problem areas 

identified in this analysis. The following issues can contribute to the lack of 

correlation between this level-of-service analysis and the flood complaint database: 

• The Hillsborough County flood complaint database only contains 

addresses of individuals that filed complaints. The database does not 

contain detailed backup information required to make meaningful, 

defensible correlation with this level-of-service analysis. For example, a 

caller may complain that the arterial road, on which they must travel to 

evacuate, is flooded. If the location of the flood problem is not proximate 

to the caller's address, correlation is not possible. 

• This analysis details the primary drainage system, and portions of the 

secondary drainage system. Half the database complaints, based on the 

best available information, are in the tertiary drainage system. 

• Hillsborough County's February 6, 2001 level-of-service formulation 

assigns Level of Service A to locations where the 25-year, 24-hour watersurface 

elevation is less than three inches above the crown of the road. 

The formulation assigns Level of Service B to locations where the 25- 

year, 24-hour water-surface elevation is between three inches and six 

inches above the crown of the road. It is therefore possible -- under the 

County's formulation -- for a road that is flooded by as much as six inches 

of water to be deemed acceptable. Under the County's Level of Service 

formulation, roads that were submerged by five inches of water in the El 

Nino floods are acceptable even though the road is dangerous and 

impassable. Other, rational Level of Service formulations, which are not 

counterintuitive, are possible and perhaps preferable. 

• Hillsborough County's level-of-service analysis is based on design 

storms. These storms are hypothetical. Flood complaints are from real 

storms. The hypothetical design storm may not correlate with the reality 

of the real storm. 




• Hillsborough County expresses flood hazard risk as a function of rainfall 

depth. Risk should be expressed as a function of flood severity. Flood 

severity and rainfall depth do not always correlate. Other types of 

analyses, such as Monte Carlo simulations of continuous simulation 

analyses, introduce less error into the expression of risk. 

• Hillsborough County's level-of-service formulation does not provide for 

analysis of flood problems that do not relate to water-surface elevation, 

such as damaged flood control structures, erosion issues, and agricultural 

drainage practices. 

By comparison to Table 6.7-1, it can be assumed that most of the historical flooding 

complaint record sites not shown as a problem area in Table 6.7-4 are generally an 

indication of secondary system problems or possible maintenance problems. A 

detailed discussion of the problem areas that were identified as primary drainage 

system deficiencies is presented in Chapter 13 of this report. 


LEGEND 


TABLE 6.7-4 


TURKEY CREEK SUBWATERSHED EXISTING CONDITIONS LEVELS OF SERVICE ANALYSIS 




19-29-21 E STATE ROAD 60 PUBLIC 759300 67.4 0.0 61.54 61.61 61.89 62.02 62.22 62.31 A A A A A A 

17-29-21 Seaboard Coastline RR PUBLIC 758820 80.6 0.0 75.48 75.58 75.73 75.82 75.94 75.98 A A A A A A 

17-29-21 Salem Church Rd PUBLIC 758810 76.5 0.0 75.49 75.68 76.04 76.34 76.59 76.62 A A A A A A 

17-29-21 N DOVER RD PUBLIC 758720 74.1 74.8 67.21 67.56 67.94 68.52 68.93 69.35 A A A A A A 


20-29-21 N DOVER RD PUBLIC 758498 63.3 0.0 63.15 63.52 63.95 64.52 64.81 65.12 A A C D D D 

20-29-21 N DOVER RD PUBLIC 758390 69.1 77.5 65.47 65.82 66.36 66.76 67.86 68.76 A A A A A A 

21-29-21 Williams Swamp PRIVATE 758350 0.0 80.1 63.15 63.52 63.95 64.52 64.81 65.11 A A A A A A 

29-29-21 S DOVER RD PUBLIC 758130 78.4 0.0 74.90 75.61 77.03 78.13 78.56 78.74 A A A A A B 

22-29-22 CAMERON RD PUBLIC 757560 119.2 122.5 118.98 119.25 119.52 119.88 119.91 119.95 A A B C C C 

21-29-22 COLSON RD PUBLIC 757520 115.4 115.5 113.10 113.39 113.61 113.89 114.06 114.22 A A A A A A 

21-29-22 MCDONALD RD PUBLIC 757480 112.0 112.0 110.07 110.40 110.73 111.16 111.43 111.67 A A A A A A 


21-29-22 CLARENCE GORDON JR RD PUBLIC 757465 117.8 116.5 111.80 112.07 112.33 112.67 112.88 113.07 A A A A A A 

21-29-22 MCDONALD RD PUBLIC 757425 110.0 113.4 109.94 110.06 110.09 110.13 110.14 110.25 A A A A A B 


21-29-22 JAMES L REDMAN PKY PUBLIC 757400 109.4 0.0 103.81 104.38 104.86 105.59 106.01 106.38 A A A A A A 

29-29-22 OLD HOPEWELL RD PUBLIC 757300 96.3 0.0 93.47 94.17 94.88 95.94 96.52 96.75 A A A A A B 

29-29-22 S COUNTY ROAD 39 PUBLIC 757200 87.0 0.0 79.23 79.92 80.50 81.22 81.64 82.20 A A A A A A 

32-29-22 S COUNTY ROAD 39 PUBLIC 757190 96.4 0.0 96.36 96.45 96.52 96.61 96.66 96.70 A A A A B B 

32-29-22 S COUNTY ROAD 39 PUBLIC 757189 96.4 0.0 96.35 96.44 96.51 96.60 96.65 96.69 A A A A B B 

29-29-22 CASSELS RD PUBLIC 757134 90.7 95.6 86.84 86.94 87.04 87.19 87.28 87.37 A A A A A A 

5-29-22 CHARLIE GRIFFIN RD PUBLIC 756900 139.7 140.8 136.47 136.87 137.22 137.79 138.21 138.60 A A A A A A 

8-29-22 Residential Road PRIVATE 756860 0.0 137.1 133.68 134.47 134.86 135.03 135.12 135.20 A A A A A A 

8-29-22 W JOHNSON RD PUBLIC 756840 134.7 135.2 133.64 134.45 134.82 134.93 134.99 135.04 A A A A B B 

8-29-22 Unnamed Creek East of Trapnell School PRIVATE 756820 0.0 135.3 131.45 131.55 131.73 131.99 132.12 132.22 A A A A A A 

8-29-22 W TRAPNELL RD PUBLIC 756756 113.3 113.6 113.12 113.35 113.44 113.54 113.60 113.65 A A A B B D* 

17-29-22 PIPPIN RD PUBLIC 756754 111.8 112.2 111.33 111.72 111.90 112.06 112.14 112.21 A A A B B D* 

8-29-22 W JOHNSON RD PUBLIC 756745 135.0 135.3 131.79 132.00 132.20 132.61 132.99 133.32 A A A A A A 

8-29-22 W TRAPNELL RD PUBLIC 756700 111.8 112.4 109.20 110.39 111.10 111.96 112.06 112.16 A A A A B B 

17-29-22 HOUSE NEAR ALAFIA CREEK ST PRIVATE 756640 0.0 110.5 109.01 109.34 109.74 110.29 110.41 110.67 A A A A A D* 

17-29-22 Unnamed Creek East of Trapnell School S17 T29 R PRIVATE 756618 0.0 109.1 102.96 103.26 103.44 104.11 104.72 105.18 A A A A A A 

9-29-22 SPARKMAN RD PUBLIC 756560 127.5 130.6 126.68 127.53 127.62 127.73 127.85 128.02 A A A A B C 


8-29-22 W TRAPNELL RD PUBLIC 756550 115.7 0.0 112.19 112.52 112.92 113.82 114.39 114.73 A A A A A A 

8-29-22 E TRAPNELL RD PUBLIC 756548 117.0 118.8 113.89 114.22 114.52 114.90 115.02 115.10 A A A A A A 




17-29-22 Unnamed Creek North of Berea Church PRIVATE 756520 0.0 105.6 100.86 101.27 101.63 102.04 102.25 102.41 A A A A A A 

17-29-22 PIPPIN RD PUBLIC 756510 100.7 99.3 100.00 100.70 101.14 101.57 101.79 101.93 D* D* D* D* D* D* 

17-29-22 Little Alafia River S17 T29 R22 PRIVATE 756500 0.0 98.6 96.38 96.77 97.12 97.54 97.85 98.16 A A A A A A 


17-29-22 PIPPIN RD PUBLIC 756422 106.7 107.5 105.61 106.23 106.58 106.68 106.73 106.77 A A A A A A 

18-29-22 HOLLOWAY RD PUBLIC 756420 87.0 92.0 86.06 86.70 87.26 87.60 87.77 87.91 A A B C C C 

17-29-22 HOUSE NEAR HOLLOWAY RD PRIVATE 756417 0.0 116.0 113.63 113.89 114.12 114.39 114.54 114.67 A A A A A A 

20-29-22 BUGG RD PUBLIC 756410 98.5 99.6 96.20 97.64 98.67 99.26 99.54 99.76 A A A C D D 

19-29-22 BUGG RD PUBLIC 756405 85.9 88.6 84.81 86.03 86.16 86.49 86.61 86.76 A A B C C C 

19-29-22 MUD LAKE RD PUBLIC 756320 75.5 0.0 74.04 74.62 75.31 76.34 76.80 77.20 A A A C D D 

7-29-22 SAM ASTIN RD PUBLIC 756195 123.5 126.5 122.29 123.18 123.58 123.67 123.71 123.75 A A A A A B 

7-29-22 MUD LAKE RD PUBLIC 756190 120.7 120.8 118.65 118.80 118.91 119.03 119.11 119.18 A A A A A A 

8-29-22 W JOHNSON RD PUBLIC 756190 135.5 136.5 118.65 118.80 118.91 119.03 119.11 119.18 A A A A A A 

7-29-22 MURRAY FARMS RD PUBLIC 756180 109.7 110.9 108.06 108.77 109.37 109.93 110.12 110.29 A A A A B C 


7-29-22 MUD LAKE RD PUBLIC 756164 110.3 111.7 109.76 110.31 110.51 110.73 110.86 110.98 A A A B C C 


18-29-22 JERRI LYNN CT PUBLIC 756162 104.2 105.6 103.75 104.29 104.40 104.54 104.61 104.68 A A A B B B 

18-29-22 MUD LAKE RD PUBLIC 756160 100.3 0.0 98.86 99.51 99.97 100.20 100.33 100.42 A A A A A A 

13-29-21 DRAWDY RD PUBLIC 756154 92.2 0.0 92.29 92.46 92.59 92.99 93.26 93.48 A B B C D D 

13-29-21 DRAWDY RD PUBLIC 756153 92.3 96.1 91.82 92.39 92.51 92.96 93.24 93.45 A A A C C D 

18-29-22 D/S Side Drawdy Rd PRIVATE 756152 0.0 91.7 91.60 92.06 92.43 92.94 93.22 93.43 A D* D* D* D* D*

LEGEND 


TABLE 6.7-4 






18-29-22 MUD LAKE RD PUBLIC 756123 86.3 88.6 84.05 85.08 85.73 86.48 86.61 86.72 A A A A B B 

18-29-22 HOLLOWAY RD PUBLIC 756120 82.6 83.1 82.47 82.70 82.83 83.01 83.11 83.19 A A A B D* D* 

13-29-21 HOLLOWAY RD PUBLIC 756118 86.9 88.6 86.36 86.94 87.05 87.18 87.52 87.91 A A A B C D 

24-29-21 Holloway-Drawdy Agriculture Pond PRIVATE 756116 0.0 90.0 84.82 85.41 86.11 87.02 87.49 87.88 A A A A A A 

24-29-21 DRAWDY RD PUBLIC 756115 87.7 0.0 85.68 86.04 86.10 87.01 87.48 87.87 A A A A A A 

18-29-22 HOLLOWAY RD PUBLIC 756109 81.9 84.8 80.41 81.98 82.13 82.29 82.38 82.44 A A A B B C 

19-29-22 MUD LAKE RD PUBLIC 756094 77.8 81.1 76.71 77.87 78.04 78.22 78.32 78.41 A A A B C C 

24-29-21 WALLACE RD PUBLIC 756056 84.4 86.0 84.49 84.57 84.64 84.82 84.97 85.09 A A A B C C 

25-29-21 W STATE ROAD 60 PUBLIC 756020 70.4 64.0 64.37 64.99 65.74 67.27 68.24 69.00 D* D* D* D* D* D* 

24-29-21 CALHOUN RD PUBLIC 756016 85.7 86.1 84.08 84.59 84.76 84.88 84.94 85.00 A A A A A A 

24-29-21 WALLACE RD PUBLIC 756010 68.0 68.8 63.85 64.19 64.89 65.62 66.06 67.19 A A A A A A 

24-29-21 W STATE ROAD 60 PUBLIC 756010 69.0 69.0 63.85 64.19 64.89 65.62 66.06 67.19 A A A A A A 

30-29-22 HAYNSWORTH DR PUBLIC 756008 82.6 0 82.21 82.53 82.55 82.58 82.60 82.61 A A A A A A 

25-29-21 Medard Park North Area PRIVATE 755770 0.0 72.6 70.74 71.18 71.57 72.10 72.42 72.60 A A A A A A 

25-29-21 PANTHER LOOP PUBLIC 755760 74.2 0.0 63.13 63.54 63.93 64.48 64.80 65.11 A A A A A A 

25-29-21 EDWARD MEDARD PKY PUBLIC 755700 69.6 0.0 59.89 60.18 60.44 60.78 60.99 61.19 A A A A A A 

36-29-21 TURKEY CREEK RD PUBLIC 755500 46.2 0.0 37.05 37.50 37.68 37.98 38.17 38.37 A A A A A A 

2-30-21 DURANT RD PUBLIC 755300 44.0 39.6 35.04 36.13 36.54 37.18 37.50 37.81 A A A A A A 


2-30-21 Little Alafia River, S02 T30 R21 PRIVATE 755150 0.0 35.6 30.09 31.18 31.63 32.43 33.05 33.63 A A A A A A 

2-30-21 Residential Drive PRIVATE 755105 0.0 32.4 29.97 31.10 31.55 32.38 33.01 33.60 A A A A D* D* 


1-30-21 Rural Road PRIVATE 755040 0.0 56.6 52.20 52.53 52.78 53.09 53.27 53.45 A A A A A A 

12-30-21 TURKEY CREEK RD PUBLIC 755030 50.4 49.6 48.45 49.00 49.50 50.23 50.59 50.83 A A A D* D* D* 

12-30-21 TURKEY CREEK RD PUBLIC 755026 63.6 0.0 62.78 63.56 63.73 63.84 63.91 63.98 A A A A B B 

11-30-21 SUMMERALL RD PUBLIC 755024 63.5 0.0 62.46 63.15 63.61 63.76 63.84 63.91 A A A B B B 

34-28-21 MARTIN LUTHER KING BLVD PUBLIC 754960 111.9 112.6 109.38 109.58 110.40 110.91 111.48 112.04 A A A A A A 

34-28-21 MARTIN LUTHER KING BLVD PUBLIC 754950 110.5 111.4 108.60 109.39 110.34 110.93 111.49 112.05 A A A B D* D 


2-29-21 Forbes Rd N of Downing St PUBLIC 754910 110.6 109.7 108.60 108.92 109.12 109.26 109.33 109.45 A A A A A A 

3-29-21 DOWNING ST PUBLIC 754900 94.2 94.8 94.23 94.43 94.55 94.71 94.79 94.85 A A B C C D* 

2-29-21 S FORBES RD PUBLIC 754550 103.1 105.6 103.21 103.28 103.33 103.40 103.45 103.52 A A A B B B 

2-29-21 MAYO LN PUBLIC 754540 97.4 99.0 97.49 97.56 97.64 97.72 97.77 97.82 A A A B B B 

2-29-21 S FORBES RD PUBLIC 754530 95.0 97.3 90.53 91.29 91.60 92.09 92.59 93.12 A A A A A A 

2-29-21 S Forbes Rd S of Downing St PUBLIC 754520 93.3 94.3 90.14 90.72 91.27 92.00 92.51 93.04 A A A A A A 

10-29-21 CARUTHERS RD PUBLIC 754400 76.2 0.0 75.63 76.24 76.53 76.84 77.04 77.27 A A B C C D 

10-29-21 Caruthers Rd (d/s) PRIVATE 754398 0.0 75.4 75.21 75.53 75.85 76.41 76.70 77.04 A D* D* D* D* D* 

10-29-21 CARUTHERS RD PUBLIC 754280 75.7 78.2 74.68 75.42 75.86 76.35 76.66 77.01 A A A C C D 

10-29-21 Turkey Creek Tributary C PRIVATE 754260 0.0 76.5 74.25 74.95 75.45 76.14 76.51 76.93 A A A A D* D* 

10-29-21 SYDNEY RD PUBLIC 754220 72.9 75.7 73.70 74.41 75.03 75.88 76.33 76.80 C D D D D D 

10-29-21 SYDNEY RD PUBLIC 754200 72.9 72.5 73.11 73.84 74.62 75.55 76.08 76.61 D* D* D D D D 


11-29-21 JERRY SMITH RD PUBLIC 754195 94.7 97.6 92.31 92.52 93.38 94.93 95.06 95.16 A A A A B B 





2-29-21 SYDNEY RD PUBLIC 754120 111.2 112.8 111.61 111.89 112.14 112.30 112.40 112.50 B C C D D D 

2-29-21 Seaboard Coastline RR Bypass PUBLIC 754116 111.9 0.0 111.07 111.81 112.06 112.22 112.31 112.40 A A A B B C 

11-29-21 Turkey Creek Acres Pond PRIVATE 754110 0.0 106.5 105.45 105.63 105.73 105.89 105.99 106.09 A A A A A A 

11-29-21 MICHAEL DAVID DR PUBLIC 754100 0.0 105.1 104.61 104.73 104.82 104.94 105.00 105.06 A A A A A A 

11-29-21 CHARLESTON AVE PUBLIC 754080 102.9 103.9 103.16 103.26 103.34 103.45 103.52 103.59 B B B C C C 

11-29-21 JERRY SMITH RD PUBLIC 754040 88.0 89.5 88.10 88.34 88.44 88.57 88.65 88.72 A B B C C C 

11-29-21 S FORBES RD PUBLIC 754020 79.0 78.7 78.49 78.94 79.27 79.58 79.77 79.91 A D* D* D* D* D* 

14-29-21 HOUSE NEAR TOUCHSTONE RD PRIVATE 754019 0.0 79.7 78.22 78.95 79.27 79.58 79.77 79.92 A A A A D* D* 

15-29-21 SYDNEY WASHER RD PUBLIC 753580 79.9 80.3 78.53 79.30 79.92 80.12 80.20 80.26 A A A A B B 

21-29-21 SYDNEY WASHER RD PUBLIC 753360 64.3 0.0 59.20 60.04 60.81 62.01 62.69 63.14 A A A A A A 

21-29-21 SYDNEY WASHER RD PUBLIC 753360 63.0 0.0 59.20 60.04 60.81 62.01 62.69 63.14 A A A A A A 

22-29-21 FIETZWAY RD PUBLIC 753355 62.5 62.9 58.79 58.98 59.15 59.54 59.85 60.19 A A A A A A 

12-29-21 Walden Lake Pond N PRIVATE 753280 0.0 115.9 114.11 114.18 114.23 114.30 114.34 114.38 A A A A A A 

11-29-21 TURKEY CREEK RD PUBLIC 753270 99.3 100.0 98.64 99.44 99.58 99.72 99.80 99.88 A A B B C C 

12-29-21 W TRAPNELL RD PUBLIC 753260 99.6 100.8 99.66 99.77 99.84 99.94 99.99 100.04 A A A B B B 

13-29-21 HOLLOWAY RD PUBLIC 753186 91.6 92.6 90.47 90.51 90.55 90.60 90.64 90.67 A A A A A A

LEGEND 


TABLE 6.7-4 






13-29-21 LONE OAK RD PUBLIC 753184 90.6 90.6 89.02 89.18 89.31 89.53 89.85 90.12 A A A A A A 

13-29-21 LONE OAK RD PUBLIC 753180 90.4 90.0 89.05 89.68 90.29 90.72 90.85 90.96 A A D* D* D* D* 

14-29-21 TURKEY CREEK RD PUBLIC 753170 82.0 84.2 81.13 81.80 82.10 82.58 82.80 83.00 A A A C C D 

14-29-21 Residential Drive PRIVATE 753149 0.0 83.6 76.56 77.35 77.59 78.49 78.84 79.09 A A A A A A 

24-29-21 HOLLOWAY RD PUBLIC 753145 82.6 0.0 80.46 81.07 81.84 82.70 82.91 83.05 A A A A B B 

14-29-21 TURKEY CREEK RD PUBLIC 753143 82.0 82.6 80.09 80.76 81.34 82.13 82.25 82.35 A A A A B B 

23-29-21 CONNELL RD PUBLIC 753132 80.0 81.5 80.05 80.11 80.16 80.21 80.25 80.28 A A A A B B 

14-29-21 W O GRIFFIN RD PUBLIC 753122 77.4 77.0 73.67 73.71 73.75 73.79 73.81 73.84 A A A A A A 

23-29-21 JERRY SMITH RD PUBLIC 753118 68.0 65.5 67.90 68.42 68.69 69.02 69.22 69.41 D* D* D* D D D 

12-29-21 Walden Lake Pond L PRIVATE 753098 0.0 125.3 122.98 123.20 123.42 123.73 123.92 124.10 A A A A A A 

12-29-21 Walden Lake Pond M PRIVATE 753096 0.0 115.0 110.31 110.63 110.98 111.56 111.97 112.19 A A A A A A 

12-29-21 BARRET AVE PUBLIC 753096 113.5 115.0 110.31 110.63 110.98 111.56 111.97 112.19 A A A A A A 


11-29-21 EDWARDS RD PUBLIC 753090 95.0 94.8 94.71 94.88 95.04 95.20 95.28 95.37 A D* D* D* D* D* 

11-29-21 W TRAPNELL RD PUBLIC 753085 93.5 92.3 92.15 92.42 92.71 93.19 93.50 93.64 A D* D* D* D* D* 

14-29-21 Unnamed Creek South of Turkey Creek Church PRIVATE 753081 0.0 84.2 81.51 81.93 82.23 82.64 82.86 83.11 A A A A A A 

14-29-21 JERRY SMITH RD PUBLIC 753080 74.6 76.8 73.90 74.86 75.20 75.58 75.80 76.08 A B C C D D 

23-29-21 JERRY SMITH RD PUBLIC 752950 73.4 74.3 73.42 73.46 73.48 73.51 73.53 73.54 A A A A A A 

23-29-21 JERRY SMITH RD PUBLIC 752630 72.3 73.7 72.45 72.51 72.57 72.64 72.68 72.72 A A B B B B 

22-29-21 Starlight Family Mobile Home Park PRIVATE 752610 0.0 53.0 54.95 55.31 55.57 56.48 57.76 58.67 D* D* D* D* D* D* 

22-29-21 Western Atkins Ranch Natural Depression PRIVATE 752525 0.0 60.6 59.39 59.69 59.96 60.31 60.43 60.48 A A A A A A 

27-29-21 E STATE ROAD 60 PUBLIC 752500 57.6 0.0 51.25 52.75 54.34 56.37 57.69 58.61 A A A A A D 

26-29-21 Citrus Hills R.V. Park PRIVATE 752499 0.0 68.1 57.26 57.71 58.11 58.58 58.79 58.97 A A A A A A 




3-30-21 Turkey Creek S03 T30 R21 PRIVATE 751300 0.0 34.6 32.14 33.48 34.64 35.85 36.43 37.03 A A D* D* D* D* 

3-30-21 Yukon Rd PRIVATE 751200 0.0 37.5 31.44 32.90 34.18 35.46 36.05 36.65 A A A A A A 

3-30-21 Turkey Creek S03 T30 R21 PRIVATE 751100 0.0 32.1 29.42 30.87 32.09 33.44 34.11 34.77 A A A D* D* D* 

10-30-21 CHERRY OAK DR PUBLIC 750100 36.7 38.0 30.28 31.27 32.70 33.60 34.40 34.54 A A A A A A





S FORBES RD 


Polk Co 


TURKEY CREEK 


A 

B 

C 

D/D* 

Polk Co. 

O 

Legend 

County Line 





Suite 120 



Notes: 

ALAFIA RIVER 


1:72,000 

0 1,500 3,000 6,000 


60 60 

Feet 

0 0.25 0.5 1 

Miles 


Medard 

Reservoir 

Filename: 

Fig6_7_ 

2.mxd 

Map Date: 



N/A 


Prepared By: 

Yoav 

Rappaport 









6.8 English Creek Subwatershed 


Hillsborough County Service Unit Reported Problems 



English Creek Subwatershed. The Unit reported 10 locations that experience 


6.8-1. 













Hillsborough County was besieged by flooding complaints from local residents over 

the course of the 1997/1998 El Nino and 2004 Hurricane Frances floods. In an 

effort to address reported flooding concerns, a record was complied which was 

provided to Parsons to utilize for the purpose of this study. Complaints located 

within the English Creek Subwatershed are listed in Table 6.8-1, and the locations 

of the individual complaints are plotted in Figure 6.8-1. There were a total of 26 

individual flooding complaint records within the English Creek Subwatershed. It can 

be seen from close examination of Table 6.8-1 that a number of these complaints 

were repetitive (i.e. same location). It is also noted that the County database does 

not include a description of the nature of the problem for those complaints that were 

reported during the February 1998 flooding event, thus limiting its interpretive 

usefulness. 




Table 6.8-1 

English Creek Subwatershed Reported Flooding Problems 

INFORMATION 

SOURCE 

MAP REFERENCE 

NUMBER 

LOCATION 

DESCRIPTION 





2 East Service Unit Road Flooding 


4 East Service Unit Channel Flooding - Maintenance Issue 


14 East Service Unit Houses at Low Elevations 

15 East Service Unit Poorly Drained 

18 East Service Unit Missing Drainage Structure 




None 


Complaints 216 Baron Drive Happy Homes Mobile Park. County investigated and the park is in a low area. No apparent solution. 


Complaints 




698 3609 C.A. Bugg Road No information available 

700 1712 Cowart Road No information available 

728 3607 Nesmith Road\4806 Nesmith Road No information available 

730 4202 Peacock Road\2022 1/2 Pleasant Acre Dr\2011 P No information available 

731 2238 Retreat Lane No information available 

739 3615 Smith Ryals Rd.\4509 Smith Ryals Road No information available 

742 1602 Sparkman Rd. No information available 

1017 3203 Clemons Road No information available 

1018 2201 Clemons Rd No information available 

1019 4806 Coronet Road No information available 

1028 4707 Horton Rd No information available 

1051 2505 S. Wiggins Road No information available 

2010 Howell Road 

Flood water crossed the road from south to north. This flooding has to be investigated as one drainage basin. An additional retention pond 

with an outfall has to be built to attenuate the stormwater before discharge. 

2011 E. Trapnell Rd. & Raye Ann Rd. 

Flood water was ponding where Trapnell Rd. intersects with Raye Ann Rd. This flooding has to be investigated further as one drainage basin. 

There is no outlet. 

2015 Medulla Rd. from S. Wiggins Rd. to S. County Line Rd. Road flooding. Blocked storm drain flooding multiple properties. 

2016 Jim Johnson Rd, & Tom Brewer Ln. 

Yard flooding. Problem needs to be directed to planning and growth management. Private property owner is developing land that is causing 

drainage problem at an existing site with mobile homes. 

2022 Frank Moore Rd. from Medulla Rd. to Coronet Rd. 

Road flooding. There is a lack of a drainage system. Thus, an open ditch or swale or an underground conveyance piping with DBI and swale 

is needed. Master plan study of this area must be done. Culvert pipe collapsed. 

2027 Old Hopewell Rd. from Henry George Rd. to Smith Ryals Rd. Road Flooding. Water standing in intersection. 

2028 Smith Ryals Rd. from Holloman Rd. to Old Hopewell Rd. Road Flooding. Water standing in intersection. 

2030 Colson Rd. from Ruby Jo Dr. to Horton Rd. No information available 

2031 Horton Rd. from Berry Rd. to Nesmith Rd. No water on street at this time. Ditch blocked with debris 

2032 Nesmith Rd. from Berry Rd. to Joe King Rd. (S. of English Rd.) Yard flooding. No flooding at time. Some property lower than roadway. 




Table 6.8-1 

English Creek Subwatershed Reported Flooding Problems 

INFORMATION 

SOURCE 

MAP REFERENCE 

NUMBER 

LOCATION 

DESCRIPTION 




2034 Sparkman Rd. from Evelyn Lake Dr. to Lazy Pond Dr. Ditch cleaning needed 

2035 E. Trapnell Rd. from Tommy Brock Pl. to Jap Tucker Rd. No information available 



2038 Sparkman Rd. & Nesmith Rd. (from Clemons Rd. to Coronet Rd.) 

The flood water was ponding in the Nesmith Road intersection. There is no outlet for this water anywhere. A retention pond would need to be 

built to percolate the stormwater. 

2039 Clemons Rd. from Jim Johnson Rd. to Howell Rd. Road flooding. 

2040 Coronet Rd. from Howell Rd. to Coronet Rd. No flooding at time of inspection. 

Flooding on road row due to lack of drainage system. Open ditch and piping system to convey water. Drainage system needs to be 

2041 Coronet Rd. from Medulla to Frank Moore Rd. (Howell Rd. to Coronet Rd.) connected to Howell Rd. or Sparkman Rd. through Nesmith Rd. 

2042 Nesmith Rd. from E. Trapnell Rd. to E. Merrin Rd. Road flooding. Water on roadway North of Merrin Rd 

2043 S. Wiggins Rd. from Medulla Rd. to Clay Turner Rd. Drainage system needs cleaning. Growth in ditch is bad. 

2044 Lindsey Rd. from Kirkland Rd. to S. Wiggins Rd. Ditches & pipes need cleaning out. 

2050 Son Keen Rd. from E. U.S. 92 to city limits Ditches slowing draining down. 

2074 Clemons Rd. from Jim Johnson Rd. to Howell Rd. No information available 






4 

N PARK RD 

730 

2050 

Serv_2 

Serv_5 

92 

S COLLINS ST 

ENGLISH CREEK 


Serv_3 

2044 

Serv_4 



Legend 


Service Unit 


January 1998 

County Line 



Roads 




Suite 120 


Serv_14 


Serv_15 

39 

698 

Serv_19 

HOWELL BRANCH 

2034 

2035 

731 

Serv_18 

2027 

Notes: 

742 

2036 

2037 

1018 

2016 

2074 

2015 

2040 

1019 2022 

2039 

2043 

Serv_20 

2041 2010 

2038 

1017 

2011 

60 

HOWELL CREEK 

739 

1028 

2030 

2028 

HOWELL BRANCH 

2031 

Serv_22 

HORTON BRANCH 

1051 

728 

2032 

2042 

ENGLISH CREEK 


Polk Co 

1:72,000 

60 


0 3,000 6,000 12,000 

Feet 

0 0.5 1 2 

Miles 

Filename: 

Fig6_8_ 

1.mxd 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 










The hydrologic/hydraulic computer model was run to generate predictions of 

flooding conditions for the existing land use conditions and the existing drainage 

facilities throughout the English Creek subwatershed using the design storm events 

as the basis for simulations. In this study, Year 2006 land use conditions and 

drainage facilities are considered to be the existing conditions. Table 6.8-2 is a 

maximum flood elevation summary that lists the peak flood stages at each of the 

model nodes along the main conveyance systems for the various design storms. 

The following Table 6.8-3 presents a summary of the model-simulated peak flows at 

selected locations within the subwatershed. 

Table 6.8-3 

English Creek Subwatershed Peak Flows at Selected Locations 

Location 2.33- 

year 

(cfs) 

English Creek at Mouth 

(9790200) 

English Creek at SR 60 

(9791400) 

Howell Branch at Mouth 

(9791600) 

English Creek at County 

Line Rd (9793802) 

Airport Trib at Mouth 

(9794000) 

English Creek at County 

Line Rd (9796400) 

Howell Branch at Trapnell 

Road (9791828) 

Howell Creek at Trapnell 

Road (9792098) 

Howell Creek at Jim 

Johnson Road (9792138) 

5-year 

(cfs) 

10-year 

(cfs) 

25-year 

(cfs) 

50-year 

(cfs) 

100-year 

(cfs) 

2924 3865 4933 6632 7679 8833 

2868 3768 4816 6507 7647 8795 

2865 3725 4782 6218 7186 8202 

1401 1904 2459 3228 3801 4324 

1860 2408 3013 3920 4538 5178 

512 691 866 1160 1348 1537 

488 654 833 1115 1280 1416 

612 845 1074 1427 1663 1893 

413 536 641 784 868 1002 






TABLE 6.8-2 


ENGLISH CREEK SUBWATERSHED EXISTING CONDITIONS FLOOD ELEVATIONS SUMMARY 




English Creek from North Prong to Howell Branch 

783000 *NORTH PRONG ALAFIA RIVER CONFLUENCE 60.43 61.78 63.07 64.81 65.85 66.85 

790200 *ENG- 117, S36-T29-R22 61.04 62.30 63.53 65.23 66.25 67.24 

790400 *ENG- 117, S36-T29-R22 65.08 65.57 66.04 66.71 67.35 68.15 

790600 *ENG- 118, S36-T29-R22 67.41 68.13 68.82 69.75 70.28 70.82 

790800 *ENG- 119, S36-T29-R22 68.48 69.29 70.05 71.08 71.69 72.28 

791000 *ENG- 452, S25-T29-R22 70.37 71.17 71.94 73.01 73.65 74.26 

791198 *ENG- 450 B, S25-T29-R22 72.00 73.20 74.21 75.48 76.22 76.92 

791200 *SR-60 HWY ENG- 450, S25-T29-R22 72.11 73.35 74.44 75.94 76.80 77.54 

791400 *ENG- 113, S25-T29-R22 72.29 73.53 74.63 76.13 77.00 77.75 

791600 *ENG- 115, S25-T29-R22 72.98 74.04 75.06 76.51 77.35 78.09 


790810 *SWFWMD AERIAL MEASURED XS S36/T29/R22 69.81 69.96 70.10 71.10 71.70 72.29 

790820 *SWFWMD AERIAL MEASURED XS S25/T29/R22 76.25 76.55 76.80 77.20 77.44 77.66 

790828 *ENG-451B 91.47 91.81 92.03 92.41 92.63 92.80 

790830 *ENG-451A 92.63 93.93 95.18 95.92 96.02 96.10 

Horton Branch 

790210 *HOPEWELL MINE UNIT 8, X-D3 (Adjusted) 65.10 65.37 65.63 65.92 66.26 67.24 

790220 1 *HOPEWELL MINE UNIT 8, X-D2 (Adjusted) 72.61 72.77 72.95 73.20 73.36 73.52 

790230 *HOPEWELL MINE UNIT 8, X-D1 (Adjusted) 77.67 78.01 78.41 78.83 79.09 79.31 

790240 *HOPEWELL MINE UNIT 8, X-A2 S27/T29/R22 86.02 86.28 86.56 86.92 87.16 87.38 

790250 *HOPEWELL MINE UNIT 8, X-A1 S27/T29/R22 88.67 89.47 89.80 90.18 90.38 90.57 

790260 *HOPEWELL MINE UNIT 8, X-A S27/T29/R22 96.38 96.59 96.79 97.06 97.23 97.38 

790270 *SWFWMD Topo 113.17 113.26 113.34 113.46 113.54 113.61 

Tributary1200 

791210 *ENG-C114 PBSJ-S25-T29-R22 72.30 73.54 74.63 76.14 77.01 77.76 

791218 *ENG-P453B, S25-T29-R22 87.30 87.63 87.94 88.07 88.36 88.70 

791220 *ENG-453 COUNTY LINE RD, S25-T29-R22 89.77 91.28 92.90 94.93 95.67 96.00 

791228 *ENG-P453A, S30-T29-R23 93.02 93.08 93.44 95.10 95.84 96.20 

791230 *MEASURED SHEPHARD RD XING, S30-T29-R23 94.61 94.78 94.92 95.20 95.91 96.28 

791236 *MEASURED, S19-T29-R23 103.66 104.02 104.31 104.68 104.89 105.09 

791238 *MEASURED CORONET RD XING, S19-T29-R23 107.98 108.11 108.21 108.35 108.44 108.52 


791250 *MEASURED, S30-T29-R23 97.92 98.28 98.59 99.00 99.24 99.47 

791252 *MEASURED CORONET RD XING, S30-T29-R23 102.30 102.45 102.59 102.78 102.90 103.00 

Sam Hicks Branch 

791298 ENG-454B, S25-T29-R22 72.11 73.36 74.44 75.94 76.80 77.54 

791300 ENG-454 DIRT RD XING, S25-T29-R22 72.13 73.37 74.46 75.96 76.82 77.56 

791302 *ENG-454A, S25-T29-R22 76.60 77.08 77.52 78.03 78.30 78.53 

791310 *ENG-456, S26-T29-R22 81.17 81.59 81.93 82.35 82.61 82.84 

791338 *ENG-455A, S26-T29-R22 86.84 87.06 87.25 87.51 87.68 87.82 

791340 *ENG-455 HORTON RD, S26-T29-R22 89.55 89.68 89.79 89.93 90.02 90.11 

791342 *ENG-455B, S26-T29-R22 93.92 94.12 94.28 94.44 94.54 94.67 

791350 *ENG-116A, S26-T29-R22 99.98 100.21 100.39 100.64 100.85 101.05 

791356 *ENG-455A, S26-T29-R22 104.47 104.65 104.72 104.86 105.01 105.12 

791358 *ENG-435 SMITH RYALS, S23-T29-R22 105.38 106.16 106.96 107.85 108.06 108.21 


791318 *ENG-493A 92.35 92.58 92.79 93.08 93.21 93.33 

791320 *ENG-493 SAM HICKS RD 92.73 93.17 93.66 94.58 95.10 95.58 

791322 *ENG-493B 94.94 95.22 95.47 95.79 95.95 96.00 

791328 ENG-492 HWY 60 96.77 97.18 97.62 98.44 99.05 99.46 

Tributaries 

791380 *MEASURED, S26-T29-R22 97.51 97.76 97.98 99.61 100.00 100.36 

791370 *MEASURED, S26-T29-R22 93.98 94.23 94.47 95.23 95.98 96.52 

791355 *ENG-436, S26-T29-R22 100.00 100.26 100.46 100.72 100.92 101.12 

791389 *ENG-439A 101.11 101.18 101.24 101.33 101.39 101.44 

791390 *ENG-439 HORTON RD, S23-T29-R22 103.05 103.39 103.67 103.94 104.08 104.20 

Howell Branch 

791618 *S- 430 75.44 76.05 76.58 77.31 77.80 78.49 

791620 *S- 430 75.60 76.26 76.86 77.68 78.16 78.76 

791622 *ENG- 430A, S24-T29-R22 78.68 79.40 80.02 80.82 81.26 81.67

TABLE 6.8-2 






791678 *ENG- 429B 79.40 80.11 80.69 81.46 81.90 82.30 

791680 *ENG- 429, NESMITH RD S24-T29-R23 79.87 80.90 81.40 82.08 82.48 82.82 

791682 *ENG- 429A, S23-T29-R22 82.85 83.47 84.01 84.76 85.19 85.58 

791700 *ENG- 111, S23-T29-R22 83.01 83.67 84.22 85.00 85.45 85.86 

791740 *S-426, S14-T29-R22 84.06 84.66 85.26 86.09 86.58 87.02 

791760 *ENG- XS107, S14-T29-R22 89.32 90.36 91.25 92.34 92.91 93.41 

791778 *ENG- 425B, S14-T29-R22 89.73 90.58 91.36 92.40 92.94 93.43 

791780 *ENG- 425 PAVED ROAD XING, S14-T29-R22 93.07 93.52 93.93 94.50 94.85 95.22 

791782 *ENG- 425A, S14-T29-R22 93.33 93.89 94.37 95.03 95.41 95.79 

791820 *ENG- C109, S24-T29-R22 94.87 95.29 95.67 96.22 96.54 96.86 

791828 *ENG- 428B, S14-T29-R22 94.97 95.38 95.79 96.37 96.70 97.03 

791830 *ENG- 428, Smith Ryals Rd. S14-T29-R22 95.22 95.91 96.58 96.94 97.14 97.36 

791832 *ENG- 428A, S15-T29-R22 95.99 96.51 97.04 97.46 97.69 97.90 

791840 *ENG- C112, S15-T29-R22 97.67 98.02 98.31 98.66 98.86 99.04 

791898 *ENG- 449A, S15-T29-R22 99.03 99.43 99.74 100.20 100.47 100.71 

792000 *ENG- 449 TRAPNELL RD, S15-T29-R22 99.23 99.75 100.19 100.76 100.99 101.17 

792002 *ENG- 449B, S10-T29-R22 102.76 103.12 103.37 103.70 103.91 104.12 

792008 *ENG- 482A, S10-T29-R22 103.35 103.55 103.72 103.97 104.16 104.34 

792012 *ENG- 482B, S10-T29-R22 103.44 103.67 103.88 104.18 104.40 104.60 

792020 *ENG- C123, S10-T29-R22 106.53 107.07 107.50 108.06 108.28 108.48 

792028 *ENG- 481B, S10-T29-R22 115.97 116.37 116.79 117.33 117.58 117.77 

792030 *ENG- 481 JAP TUCKER RD, S10-T29-R22 117.34 118.32 119.01 119.21 119.30 119.38 

792038 *ENG- 483E, S10-T29-R22 122.01 122.14 122.21 122.29 122.32 122.36 

792040 *ENG- 483A RR XING, S10-T29-R22 125.54 126.04 126.42 126.89 127.15 127.38 

792042 *S-483B 126.33 126.70 126.96 127.31 127.51 127.74 

792048 *S-491A 127.75 128.02 128.24 128.52 128.68 128.83 

792050 *S-491 SPARKMAN RD 129.44 129.52 129.57 129.65 129.70 129.74 

Tributary1622 

791628 *ENG- 441B, S23-T29-R22 92.37 92.76 93.03 93.29 93.32 93.39 

791630 *ENG- 441, S23-T29-R22 92.43 92.82 93.08 93.35 93.38 93.46 

791638 *ENG- 440B, S23-T29-R22 92.84 93.46 93.74 94.04 94.11 94.16 

791640 *ENG- 440, S23-T29-R22 97.46 98.03 98.09 98.15 98.17 98.18 

791645 *ENG- 440A, S24-T29-R22 97.83 98.19 98.25 98.30 98.33 98.34 

791650 *FIELD MEASURE* 102.79 104.71 105.27 105.82 106.11 106.38 


791710 *ENG- 442B, S23-T29-R22 87.53 87.76 87.97 88.21 88.37 88.50 

791718 *ENG- 442, HORTON RD, S23-T29-R22 88.24 88.34 88.42 88.52 88.58 88.66 


791790 *ENG- C108, S14-T29-R22 93.33 93.90 94.37 95.03 95.41 95.79 

791796 *ENG- 424B, S14-T29-R22 104.85 105.08 105.29 105.60 105.80 105.95 

791798 *S-424, Brairwood Rd. 105.90 106.34 106.83 108.06 108.13 108.17 

791800 *ENG- 424A-Modified 107.25 107.50 107.70 108.33 108.49 108.61 

791802 *S-423B 108.41 108.68 108.89 109.29 109.50 109.66 

791803 *S-423, Briarwood Rd. 108.81 109.58 110.05 110.21 110.28 110.34 

791804 *S-423A 110.00 110.26 110.46 110.84 111.02 111.19 

791806 *S-422B 110.76 111.18 111.52 111.76 111.81 111.85 


791848 *ENG- 448B, S15-T29-R22 102.76 103.10 103.35 103.65 103.80 103.95 

791850 *ENG- 448 DIRT RD XING, S15-T29-R22 104.44 105.24 105.39 105.56 105.65 105.73 

791852 *ENG- 448A, S15-T29-R22 104.61 105.36 105.54 105.76 105.87 105.98 

791858 *S-447 CMP d/s 104.93 105.58 105.82 106.07 106.22 106.35 

791860 *S-447 CMP u/s 105.44 106.17 106.34 106.53 106.63 106.73 

791862 *S-446 106.04 106.55 106.77 107.04 107.17 107.37 

791864 *S-446 108.59 108.74 108.85 108.98 109.07 109.19 

791868 *S- 108.64 108.81 108.94 109.11 109.21 109.37 

791870 * 109.68 109.83 109.93 110.06 110.13 110.24 

791878 *ENG- 444B, S15-T29-R22 111.98 112.43 112.73 113.20 113.61 114.28 

791880 *ENG- 444 JAP TUCKER RD, S15-T29-R22 113.37 114.00 114.56 115.56 116.58 117.05 

791882 *ENG- 444A, S15-T29-R22 114.64 114.89 115.02 115.82 116.67 117.16 

791888 *ENG- 443B, S15-T29-R22 114.91 114.99 115.07 115.86 116.69 117.18 

791890 *S-443 RR CROSSING 118.73 119.94 120.78 121.43 121.59 121.70 

791875 0 109.68 109.83 109.94 110.07 110.13 110.24 

Howell Creek 

792098 *ENG- 427B, S11-T29-R22 95.06 95.53 95.95 96.53 96.88 97.22 

792100 *ENG- 427 TRAPNELL RD, S10-T29-R22 95.39 96.11 96.69 97.23 97.53 97.80

TABLE 6.8-2 






792102 *S-427A - m 98.28 98.85 99.31 99.89 100.23 100.52 

792110 *ENG- C122, S11-T29-R22 98.60 99.21 99.71 100.35 100.71 101.03 

792118 *ENG- 469B, S11-T29-R22 103.97 104.51 104.98 105.53 105.91 106.26 

792120 *ENG- 469 SPARKMAN RD, S11-T29-R22 104.22 105.04 105.64 106.19 106.53 106.85 

792122 *ENG- 469A, S10-T29-R22 105.03 105.53 106.11 106.64 106.97 107.26 

792130 *ENG- C124, S10-T29-R22 106.96 107.55 107.97 108.49 108.80 109.06 

Upper Howell Creek 

792138 *Jim Johnson Road (d/s) [ENG-474] 109.56 110.24 110.71 111.25 111.51 111.86 

792140 *Jim Johnson Road (u/s) [ENG-474] 109.65 110.38 110.96 111.61 111.94 112.42 

792198 *SCL RR (d/s) [ENG-475] 116.47 116.88 117.22 117.72 118.15 118.58 

792200 *SCL RR (u/s) [ENG-475] 118.79 120.52 122.41 125.51 126.79 126.94 

792216 *Dirt Road (d/s) [ENG-476] 119.39 120.73 122.52 125.55 126.82 126.97 

792218 *Dirt Road (u/s) [ENG-476] 125.84 127.28 127.50 127.91 128.13 128.27 

792225 *Coronet Road (d/s) [ENG-478] [PBS&J Junction N-V] 128.39 128.64 128.87 129.14 129.31 129.51 

792250 *Coronet Road (u/s) [ENG-478] [PBS&J Junction N-S] 129.98 130.26 130.35 130.46 130.53 130.63 

792310 *[PBS&J Junction N-I2] 134.17 134.39 134.54 134.75 134.90 135.05 

792350 *[PBS&J Junction N-H] 140.22 140.46 140.65 140.90 141.05 141.19 

792360 *[PBS&J Junction N-F2] 140.34 140.57 140.75 140.98 141.13 141.26 

792370 *Alabama St (d/s) [PBS&J Junction N-F1] 140.50 140.68 140.83 141.04 141.17 141.29 

792380 *Alabama St (u/s) [PBS&J Junction N-D2 & N-P1] 140.83 141.01 141.18 141.40 141.53 141.64 

792390 *Entrance Road (u/s) [PBS&J Junction N-A1 & N-D1] 141.58 142.05 142.24 142.42 142.51 142.60 

792320 *Coronet Road (u/s) [PBS&J Junction N-J] 134.85 134.91 134.96 135.02 135.05 135.08 

792355 *Wetland [PBS&J Junction N-G] 140.53 140.74 140.92 141.16 141.31 141.46 

792365 *Park Road (u/s) [PBS&J Junction N-E] 140.35 140.57 140.75 140.99 141.13 141.26 

Tributary2148 

792148 *Jim Johnson Loop Road (d/s) [ENG-473] 119.58 119.94 120.11 120.33 120.47 120.56 

792150 *Jim Johnson Loop Road (u/s) [ENG-473] 121.73 121.87 121.97 122.09 122.15 122.21 

792158 *Retreat Lane (d/s) [ENG-472] 124.71 124.96 125.14 125.33 125.41 125.48 

792160 *Retreat Lane (u/s) [ENG-472] 125.63 125.70 125.74 125.78 125.81 125.82 

792168 *SCL RR (d/s) [ENG-471] 125.86 126.01 126.11 126.23 126.27 126.33 

792170 *SCL RR (u/s) [ENG-471] 126.40 126.77 127.09 127.52 127.79 128.03 

792178 *Jim Johnson Road (u/s) [ENG-470] 129.71 129.77 129.82 129.88 129.92 129.95 

792180 *SCL RR (u/s) [ENG-470] 130.33 130.71 131.09 131.64 131.97 132.22 


792204 *SR 574A (d/s) [ENG-468] 128.14 128.24 128.31 128.38 128.99 129.73 

792208 *SR 574A (u/s) [ENG-468] 130.07 130.59 130.95 131.40 131.61 131.73 

792215 *Mine Pond 136.04 136.54 137.04 137.70 138.07 138.38 




792240 *Wetland [PBS&J Junction N-U] 131.32 131.85 132.33 132.98 133.35 133.59 


792270 *[PBS&J Junction N-N] 131.32 131.51 131.69 131.93 132.08 132.22 

792260 *Mine Pond [PBS&J Junction N-R] 131.28 131.44 131.60 131.84 131.98 132.13 

792280 *Mine Pond [PBS&J Junction N-O] 137.25 137.34 137.43 137.56 137.65 137.74 

792290 *Mine Pond [PBS&J Junction N-Q] 132.20 132.74 133.22 133.68 133.81 133.93 

792300 *Mine Pond [PBS&J Junction N-P] 135.05 135.18 135.31 135.49 135.61 135.72 


792330 *Mine Pond [PBS&J Junction N-L] 134.15 134.36 134.50 134.70 134.85 134.99 

792400 *Mine Pond [PBS&J Junction N-K3] 137.77 138.11 138.44 138.59 138.68 138.76 



792430 *Mine Pond [PBS&J Junction N-C1] 141.63 141.85 142.08 142.43 142.62 142.81 

Tributaries 

792230 *Wetland 130.49 130.52 130.56 130.59 130.62 130.64 

792235 *Stormwater Pond 134.60 134.83 135.06 135.37 135.54 135.69 

English Creek from Howell Branch to Airport outfall 

791600 *Howell Branch Confluence 72.98 74.04 75.06 76.51 77.35 78.09 

792900 *Dirt Road Bridge Span (d/s) [ENG-431] 76.35 77.52 78.34 79.00 79.47 79.96 

793000 *Dirt Road Bridge Span (u/s) [ENG-431] 77.52 78.38 79.11 79.87 80.39 80.90 

793100 * 77.83 78.66 79.40 80.19 80.71 81.22 

793200 * 80.04 80.69 81.34 82.13 82.63 83.11

TABLE 6.8-2 






793398 *Mulberry Road (d/s) [ENG-434] 81.82 82.38 82.99 83.75 84.24 84.70 

793400 *Mulberry Road (u/s) [ENG-434] 83.32 85.05 86.02 86.71 87.15 87.52 

793600 * 85.64 86.41 87.17 87.89 88.35 88.75 

793798 *County Line Road (d/s) [ENG-484] 87.44 88.08 88.69 89.39 89.82 90.22 

793800 *County Line Road (u/s) [ENG-484] 87.57 88.24 88.93 90.24 90.99 91.78 

793802 * 88.71 89.39 90.04 91.07 91.73 92.40 

794000 *Airport Branch Confluence 95.18 95.74 96.26 96.90 97.27 97.61 




793218 *Coronet Road (d/s) [ENG-433] 104.96 105.18 105.35 105.60 105.73 105.74 

793220 *Coronet Road (u/s) [ENG-433] 106.75 106.99 107.21 107.52 107.70 107.89 

Tributary3800 







793838 *Mulberry Road (d/s) [ENG-488] 112.43 112.77 113.09 113.59 113.80 113.98 

793840 *Mulberry Road (u/s) [ENG-488] 112.61 113.18 113.68 113.90 114.00 114.10 

793850 *Trapnell Road (u/s) [ENG-464] 113.68 113.92 114.10 114.33 114.46 114.58 

Lakeland Airport coded from URS ADICPR Model 

794020 * 95.61 96.18 96.69 97.33 97.69 98.03 

794040 *Medulla Road (d/s) 106.32 106.55 106.73 106.93 107.03 107.17 

794050 *Medulla Road (u/s) [437-3] 109.12 110.12 110.81 111.76 112.40 112.87 

794104 *Private Road (d/s) [437-1] 110.15 110.33 110.95 111.85 112.47 112.93 

794108 *Private Road (u/s) [438A-3] 113.79 114.01 114.19 114.48 114.67 114.83 

794110 *[438A-2] 113.83 114.06 114.24 114.54 114.72 114.88 

794116 *Access Road (d/s) [438A-1] 114.50 114.74 114.93 115.19 115.33 115.64 

794130 *Access Road (u/s) [305A-2] 116.54 116.69 116.82 116.97 117.11 117.38 

794134 *Airport Pond [305A-1] 117.84 117.91 117.96 118.02 118.26 118.50 

794180 *Airport Storm Sewer (u/s) [304A-2] 121.61 122.03 122.37 123.10 124.32 125.42 

794186 *Drane Field Road (d/s)[306-1] 130.86 131.02 131.13 131.25 131.32 131.48 

794187 *Drane Field Road (u/s) [582-1] 132.14 132.63 133.04 133.54 133.78 133.99 

794190 *Wetland [308B-1] 133.48 133.54 133.59 133.75 133.86 133.95 

794192 *Wetland [308A-1] 133.44 133.61 133.72 133.83 133.92 134.00 

794200 *Airport Storm Sewer (u/s) [302-1] 124.92 126.09 127.02 128.11 128.48 128.71 

794230 *[116-1342] 126.70 126.99 127.25 128.13 128.51 128.75 

794231 *Drane Field Road (d/s) [116-1343] 127.40 127.56 127.77 128.13 128.52 128.76 


794252 *Airport Entrance (d/s) [111D-2] 130.89 131.00 131.08 131.21 131.32 131.42 

794260 *Drane Field Road (d/s) [111D-2] 132.26 132.64 132.89 133.37 133.82 134.23 



794400 *Private Road (u/s) [438B-2] 115.23 115.38 115.51 115.68 115.78 115.87 

794420 *[120-2] 118.50 118.69 118.85 119.05 119.16 119.27 

794429 *Airport Outfall (d/s) [120-1] 119.85 120.02 120.15 120.33 120.44 120.54 

794430 *Airport Taxiway (u/s) [136-2] 120.38 120.67 120.97 121.52 121.84 122.19 

794422 *Airport Access Road (d/s) [120-4] 120.49 120.71 120.88 121.07 121.17 121.25 

794500 *Airport Access Road (u/s) [432A-3] 124.25 125.19 125.93 126.85 127.31 127.75 

794530 *Airport Outfall Ditch [421-2] 124.79 125.28 125.99 126.88 127.33 127.76 

794569 *Access Road (d/s) [422-1] 126.27 127.05 127.63 128.42 128.66 129.01 

794570 *Access Road (u/s) [420-2] 126.34 127.21 128.07 129.71 130.43 130.82 

794600 *[127-1293] 128.49 128.90 129.32 130.18 130.77 131.20 

794660 *[407-1] 133.95 134.25 134.50 134.49 134.57 134.66 


794900 *Medulla Road Wetland (u/s) [413B-2] 127.95 128.28 128.55 128.97 129.22 129.43 


794022 *Medulla Road (d/s) 117.47 117.66 117.83 118.05 118.18 118.31 


794026 *Wetland [440-1] 128.43 128.62 128.82 129.09 129.25 129.41 

Tributaries

TABLE 6.8-2 







English Creek from airport outfall to US 92 

796200 * 100.66 101.22 101.72 102.32 102.68 103.02 


796400 * 101.29 101.85 102.37 103.02 103.45 103.92 

796600 *ENG-C120 104.00 104.48 104.87 105.24 105.52 105.77 

796798 *Wiggins Road (d/s) [ENG-459] 107.37 107.87 108.30 109.02 109.56 109.95 

796800 *Wiggins Road (u/s) [ENG-459] 107.70 108.24 108.72 109.52 110.12 110.57 





797200 *ENG-C121 116.69 117.28 117.72 118.22 118.48 118.73 

797400 * 125.79 126.40 126.93 127.53 127.83 128.10 

797598 *Dirt Road (d/s) 126.55 126.89 127.14 127.57 127.87 128.14 

797600 *Dirt Road (u/s) 128.83 129.51 130.10 130.97 131.58 132.16 

797798 *Futch Road (d/s) [ENG-490] 131.46 131.69 131.95 132.34 132.55 132.68 

797800 *Futch Road (u/s) [ENG-490] 132.96 133.57 134.38 135.30 135.79 136.11 

798000 * 133.33 133.90 134.65 135.51 135.99 136.33 

798100 *PBS&J Junction BNDY 133.75 134.28 134.96 135.77 136.22 136.57 

798200 *PBS&J Junction N-1-W 134.28 134.76 135.26 135.94 136.34 136.67 

798300 *PBS&J Junction N-1-V 134.69 135.13 135.56 136.15 136.49 136.81 

798600 *Wetland (PBS&J Junction N-1-P) 134.80 135.25 135.59 136.16 136.51 136.82 

799200 *CSX RR (d/s) (PBS&J Junction N-1-L) 136.81 137.10 137.34 137.64 137.82 137.99 

799400 *U.S. Hwy 92 (d/s) (PBS&J Junction N-1-I) 136.81 137.10 137.34 137.64 137.82 137.99 

799600 *U.S. Hwy 92 (u/s) (PBS&J Junction N-1-H) 136.80 137.08 137.31 137.58 137.74 137.88 

799800 *Wetland (PBS&J Junction N-1-Z) 136.51 136.80 137.05 137.36 137.57 137.78 

Hamilton Branch 

796210 *Drane Field Road (d/s) 119.23 119.83 120.36 121.02 121.42 121.79 

796220 *Drane Field Road (u/s) 120.79 121.83 122.36 122.98 123.35 123.71 

796230 *Combined Wetland 135.53 135.73 135.88 136.05 136.15 136.23 

796240 *County Line Road 128.51 128.84 129.14 129.50 129.72 129.89 

796212 *Hamilton Road (u/s) [442-1] 127.60 128.20 128.29 128.39 128.45 128.50 

796214 *Hamilton Road (u/s) [400-1] 127.11 127.27 127.44 127.69 127.87 128.09 


796408 *Dirt Road (d/s) [ENG-458D] 113.85 114.32 114.68 115.26 115.59 115.87 

796410 *Dirt Road (u/s) [ENG-458D] 118.02 118.20 118.31 118.48 118.58 118.67 

796420 *Medulla Road (d/s) [ENG-457] 120.13 120.32 120.48 120.84 121.05 121.21 

796430 *Medulla Road (u/s) [ENG-457] 120.90 120.97 121.03 121.12 121.17 121.22 


796440 *Wiggins Road (u/s) [ENG-465] 122.56 122.86 123.16 123.50 123.68 123.89 

796442 * 122.89 123.21 123.47 123.77 123.93 124.07 


796464 *Frank Moore Road (d/s) [ENG-466A] 127.42 127.57 127.72 127.88 127.94 128.08 

796466 *Frank Moore Road (u/s) [ENG-466A] 128.17 128.56 128.89 129.32 129.57 129.78 

796450 *Wetland 130.89 130.93 130.97 131.05 131.09 131.13 


797004 *Lexie Lane (d/s) [ENG-462] 121.22 121.33 121.46 122.64 123.02 123.25 

797008 *Lexie Lane (u/s) [ENG-462] 125.82 126.19 126.66 127.01 127.11 127.18 

797010 *Mine Pond 139.18 139.29 139.40 139.56 139.66 139.76 


797404 *Mine Pond Outfall Ditch 128.71 128.93 129.08 129.30 129.44 129.57 

797408 *Mine Pond 133.23 133.98 134.41 134.94 135.24 135.52 

797410 *Mine Pond 135.92 136.07 136.23 136.45 136.60 136.75 

797420 *Wetland 137.44 137.76 138.05 138.47 138.62 138.64 

797430 *Wetland 141.00 141.24 141.47 141.79 141.99 142.18 

797440 *Wetland 133.99 134.07 134.42 134.95 135.25 135.52 

797450 *Mine Pond 137.62 137.76 137.90 138.11 138.25 138.37 

797455 *Mine Pond 136.79 137.02 137.25 137.58 137.79 137.99 

797460 *Mine Pond 137.50 137.66 137.82 138.05 138.20 138.39 



797500 *Wiggins Road (u/s) [ENG-489] 127.71 127.95 128.17 128.44 128.60 128.76

TABLE 6.8-2 






Tributary 8800 (Section of model coded from CMI Stormwater Master Drainage Plan) 

798800 *PBS&J Junction N-1-T 134.69 135.13 135.57 136.15 136.50 136.81 

798810 *PBS&J Junction N-1-M 137.63 137.70 137.77 137.86 137.92 137.97 

798820 *PBS&J Junction N-1-M1 138.44 138.59 138.74 138.94 139.07 139.20 

798830 *PBS&J Junction N-1-S 134.68 135.12 135.56 136.14 136.49 136.80 

798840 *PBS&J Junction N-1-R 137.61 137.69 137.76 137.85 137.91 137.97 

798850 *PBS&J Junction N-1-Q 141.07 141.22 141.36 141.57 141.70 141.83 

Tributaries 

796610 *Wiggins Road (u/s) 115.25 116.48 117.66 118.47 118.53 118.56 

797205 *Mine Pond 126.57 126.66 126.78 126.96 127.08 127.20 

798400 *Wiggins Road (u/s) (PBS&J Junction N-1-U) 136.49 136.90 137.33 137.90 138.23 138.54 

799210 *Wetland (PBS&J Junction N-1-C) 138.54 138.92 139.26 139.69 139.94 140.15 

799220 *PBS&J Junction N-1-B1 139.80 140.01 140.22 140.48 140.63 140.77 

799230 *PBS&J Junction N-1-B 141.36 141.59 141.79 142.03 142.18 142.30 

799240 *Pond (PBS&J Junction N-1-A) 142.35 142.54 142.71 142.95 143.09 143.23 

799410 *Pond (PBS&J Junction N-1-F) 137.99 138.32 138.63 139.04 139.35 139.60 

799420 *Pond (PBS&J Junction N-1-E) 143.17 143.41 143.53 143.58 143.63 143.67




There are 81 locations within the English Creek Subwatershed for which the level of 

service was estimated. These are presented in Table 6.8-4. There is a minimum 

basin-wide goal of Level ‘B’ for the 25-year, 24-hour design storm event, referred to 

as the Target Level of Service, which has been adopted by the County. There are 

12 locations identified in Table 6.8-4 where the County’s minimum acceptable level 

of service is not met based on this criterion, as indicated by shaded cells in the 

table. Figure 6.8-2 shows the LOS by subbasin as required by County standards. 

These locations identified in Table 6.8-4 where the County’s minimum acceptable 

level of service criteria is not met are distributed throughout the drainage system. 

By comparison to Table 6.8-1, it can be assumed that most of the flooding 

complaint record sites not shown as a problem area in Table 6.8-4 are generally an 

indication of secondary system problems or possible maintenance problems. A 

detailed discussion of the problem areas that were identified as primary drainage 







LEGEND 


TABLE 6.8-4 


ENGLISH CREEK SUBWATERSHED EXISTING CONDITIONS LEVELS OF SERVICE ANALYSIS 




27-29-22 OLD HOPEWELL RD PUBLIC 790260 102.1 0.0 96.38 96.59 96.79 97.06 97.23 97.38 A A A A A A 

25-29-22 E STATE ROAD 60 PUBLIC 791200 76.8 0.0 72.11 73.35 74.44 75.94 76.80 77.54 A A A A A C 

25-29-22 S COUNTY LINE RD PUBLIC 791218 95.1 101.2 87.30 87.63 87.94 88.07 88.36 88.70 A A A A A A 

26-29-22 SAM HICKS RD PUBLIC 791320 97.5 102.7 92.73 93.17 93.66 94.58 95.10 95.58 A A A A A A 


26-29-22 HORTON RD PUBLIC 791340 89.3 91.4 89.55 89.68 89.79 89.93 90.02 90.11 B B B C C C 

22-29-22 SMITH RYALS RD PUBLIC 791358 107.7 106.8 105.38 106.16 106.96 107.85 108.06 108.21 A A D* D* D* D* 



23-29-22 HORTON RD PUBLIC 791390 104.5 106.6 103.05 103.39 103.67 103.94 104.08 104.20 A A A A A A 

23-29-22 HORTON RD PUBLIC 791650 106.8 106.8 102.79 104.71 105.27 105.82 106.11 106.38 A A A A A A 

23-29-22 COLSON RD PUBLIC 791650 107.1 106.8 102.79 104.71 105.27 105.82 106.11 106.38 A A A A A A 

23-29-22 NESMITH RD PUBLIC 791680 80.8 81.4 79.87 80.90 81.40 82.08 82.48 82.82 A A C D D D 

23-29-22 Nesmith Rd. PRIVATE 791682 0.0 86.1 82.85 83.47 84.01 84.76 85.19 85.58 A A A A A A 

23-29-22 HORTON RD PUBLIC 791718 88.2 90.0 88.24 88.34 88.42 88.52 88.58 88.66 A A A B B B 

11-29-22 RAYE ANN DR PUBLIC 791760 125.5 126.5 89.32 90.36 91.25 92.34 92.91 93.41 A A A A A A 

14-29-22 Brairwood Rd. PUBLIC 791798 107.2 108.5 105.90 106.34 106.83 108.06 108.13 108.17 A A A C C C 

14-29-22 Brairwood Rd. PRIVATE 791800 0.0 108.5 107.25 107.50 107.70 108.33 108.49 108.61 A A A A A D* 

14-29-22 BRIARWOOD MHP PUBLIC 791803 110.0 110.8 108.81 109.58 110.05 110.21 110.28 110.34 A A A A B B 

15-29-22 SMITH RYALS RD PUBLIC 791806 111.7 112.0 110.76 111.18 111.52 111.76 111.81 111.85 A A A A A A 

15-29-22 SMITH RYALS RD PUBLIC 791830 96.5 97.5 95.22 95.91 96.58 96.94 97.14 97.36 A A A B C C 

15-29-22 Dirt Road PUBLIC 791870 109.6 113.0 109.68 109.83 109.93 110.06 110.13 110.24 A A B B C C 

10-29-22 COWART RD PUBLIC 791880 116.7 116.2 113.37 114.00 114.56 115.56 116.58 117.05 A A A A D* D* 

10-29-22 E TRAPNELL RD PUBLIC 791880 115.6 116.6 113.37 114.00 114.56 115.56 116.58 117.05 A A A A C D 

15-29-22 RR Crossing PUBLIC 791890 121.2 119.2 118.73 119.94 120.78 121.43 121.59 121.70 A D* D* D* D* D* 

9-29-22 HOUSE NEAR E TRAPNELL RD PRIVATE 791896 121.4 121.5 120.97 121.63 121.81 122.05 122.18 122.31 A D* D* D* D* D* 

10-29-22 E TRAPNELL RD PUBLIC 792000 100.5 102.7 99.23 99.75 100.19 100.76 100.99 101.17 A A A B B C 

10-29-22 JAP TUCKER RD PUBLIC 792030 118.9 122.0 117.34 118.32 119.01 119.21 119.30 119.38 A A A B B B 

9-29-22 RR Xing PUBLIC 792040 128.1 0.0 125.54 126.04 126.42 126.89 127.15 127.38 A A A A A A 

9-29-22 SPARKMAN RD PUBLIC 792050 129.4 130.0 129.44 129.52 129.57 129.65 129.70 129.74 A A A B B B 

11-29-22 E TRAPNELL RD PUBLIC 792100 96.5 96.7 95.39 96.11 96.69 97.23 97.53 97.80 A A A D* D D 

11-29-22 Trapnell Rd. PRIVATE 792102 0.0 106.1 98.28 98.85 99.31 99.89 100.23 100.52 A A A A A A 

10-29-22 SPARKMAN RD PUBLIC 792120 105.2 103.7 104.22 105.04 105.64 106.19 106.53 106.85 D* D* D* D* D D 

2-29-22 HOUSE NEAR JIM JOHNSON RD PRIVATE 792132 126.6 126.9 125.16 126.45 126.72 126.83 126.89 126.95 A A A A B D* 

2-29-22 HOUSE NEAR CLEMONS RD PRIVATE 792134 0.0 129.3 127.73 128.13 128.24 128.35 128.42 128.48 A A A A A A 

11-29-22 CLEMONS RD PUBLIC 792135 127.7 128.1 127.78 127.88 127.95 128.05 128.11 128.16 A A B B D* D* 

3-29-22 JIM JOHNSON RD PUBLIC 792140 112.6 115.1 109.65 110.38 110.96 111.61 111.94 112.42 A A A A A A 

3-29-22 Jim Johnson Loop Road PRIVATE 792150 0.0 125.1 121.73 121.87 121.97 122.09 122.15 122.21 A A A A A A 

3-29-22 RETREAT LN PUBLIC 792160 125.5 126.8 125.63 125.70 125.74 125.78 125.81 125.82 A A A B B B 

3-29-22 SCL RR PUBLIC 792170 129.6 0.0 126.40 126.77 127.09 127.52 127.79 128.03 A A A A A A 

4-29-22 JIM JOHNSON RD PUBLIC 792178 129.5 0.0 129.71 129.77 129.82 129.88 129.92 129.95 A B B B B B 

4-29-22 SCL RR PUBLIC 792180 132.8 135.5 130.33 130.71 131.09 131.64 131.97 132.22 A A A A A A 

3-29-22 SCL RR PUBLIC 792200 126.6 0.0 118.79 120.52 122.41 125.51 126.79 126.94 A A A A A B 

2-29-22 CORONET RD PUBLIC 792208 132.0 0.0 130.07 130.59 130.95 131.40 131.61 131.73 A A A A A A 

3-29-22 IRA TAYLOR RD PUBLIC 792238 133.3 0.0 132.52 132.78 133.00 133.25 133.37 133.45 A A A A A A 

34-28-22 HOUSE NEAR ROBERTS RANCH RD PRIVATE 792240 0.0 133.2 131.32 131.85 132.33 132.98 133.35 133.59 A A A A D* D* 



33-28-22 S PARK RD PUBLIC 792365 142.9 142.9 140.35 140.57 140.75 140.99 141.13 141.26 A A A A A A 

27-28-22 E DR MARTIN LUTHER KING JR BLVD PUBLIC 792390 142.0 146.0 141.58 142.05 142.24 142.42 142.51 142.60 A A A B C C 


13-29-22 OLD MULBERRY RD PUBLIC 793400 86.5 0.0 83.32 85.05 86.02 86.71 87.15 87.52 A A A A C D 



13-29-22 Dirt Road PUBLIC 793820 107.2 0.0 107.22 107.34 107.43 107.60 107.68 107.75 A A A B B C 

13-29-22 OLD MULBERRY RD PUBLIC 793840 114.4 114.8 112.61 113.18 113.68 113.90 114.00 114.10 A A A A A A 

12-29-22 E TRAPNELL RD PUBLIC 793850 113.6 114.8 113.68 113.92 114.10 114.33 114.46 114.58 A B C C C C 


1-29-22 S COUNTY LINE RD PUBLIC 796398 105.6 100.3 100.72 101.33 101.88 102.58 103.05 103.57 D* D* D* D* D* D* 

1-29-22 Dirt Road PRIVATE 796410 0.0 118.5 118.02 118.20 118.31 118.48 118.58 118.67 A A A A D* D* 

1-29-22 MEDULLA RD PUBLIC 796430 120.7 121.3 120.90 120.97 121.03 121.12 121.17 121.22 A B B B B C 

12-29-22 S WIGGINS RD PUBLIC 796440 123.7 124.2 122.56 122.86 123.16 123.50 123.68 123.89 A A A A A A 

12-29-22 SPARKMAN RD & CORONET RD PUBLIC 796448 129.0 129.6 126.04 126.49 126.84 127.28 127.48 127.57 A A A A A A

LEGEND 


TABLE 6.8-4 


ENGLISH CREEK SUBWATERSHED EXISTING CONDITIONS LEVELS OF SERVICE ANALYSIS 




12-29-22 HOUSE NEAR CLAY TURNER RD PRIVATE 796448 127.4 126.6 126.04 126.49 126.84 127.28 127.48 127.57 A A D* D* D* D* 

12-29-22 FRANK MOORE RD PUBLIC 796466 129.7 129.6 128.17 128.56 128.89 129.32 129.57 129.78 A A A A A D* 

12-29-22 CORONET RD PUBLIC 796466 129.4 129.5 128.17 128.56 128.89 129.32 129.57 129.78 A A A A D* D* 


1-29-22 Carson Rd. PRIVATE 796998 0.0 121.1 110.90 111.43 111.88 112.57 113.04 113.38 A A A A A A 

1-29-22 LEXIE LN PUBLIC 797008 126.8 0.0 125.82 126.19 126.66 127.01 127.11 127.18 A A A A B B 


36-28-22 HOUSE NEAR KIRKLAND RD PRIVATE 797542 0.0 134.2 132.17 132.57 132.94 133.46 133.57 133.62 A A A A A A 

36-28-22 FUTCH LOOP PUBLIC 797600 136.0 136.7 128.83 129.51 130.10 130.97 131.58 132.16 A A A A A A 

36-28-22 HOUSE NEAR FUTCH RD PRIVATE 797650 0.0 137.8 135.23 135.50 135.64 135.69 135.71 135.73 A A A A A A 

36-28-22 FUTCH RD PUBLIC 797800 138.0 138.9 132.96 133.57 134.38 135.30 135.79 136.11 A A A A A A 


27-28-22 HOUSE NEAR E US HIGHWAY 92 PRIVATE 799234 0.0 146.6 141.90 142.13 142.40 142.89 143.22 143.59 A A A A A A 

26-28-22 E US HIGHWAY 92 PUBLIC 799400 144.5 0.0 136.81 137.10 137.34 137.64 137.82 137.99 A A A A A A 

26-28-22 THRASHER RD PUBLIC 799410 141.8 141.2 137.99 138.32 138.63 139.04 139.35 139.60 A A A A A A 

26-28-22 SON KEEN RD PUBLIC 799420 142.5 143.5 143.17 143.41 143.53 143.58 143.63 143.67 C C D D D D 

26-28-22 E US HIGHWAY 92 PUBLIC 799600 141.8 137.9 136.80 137.08 137.31 137.58 137.74 137.88 A A A A A A 

24-28-22 HOUSE NEAR CHARLIE TAYLOR RD PRIVATE 799750 0.0 140.5 138.59 138.95 139.22 139.57 139.76 139.93 A A A A A A

ENGLISH CREEK 


HOWELL BRANCH 

HOWELL CREEK 


Polk Co 


A 

B 

C 

D/D* 

Polk Co. 

O 

Legend 

County Line 





Suite 120 



39 

Notes: 

60 

HOWELL BRANCH 

HORTON BRANCH 

ENGLISH CREEK 

1:72,000 


0 3,000 6,000 12,000 

Feet 

0 0.5 1 2 

Miles 

60 

Filename: 

Fig6_8_ 

2.mxd 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 









6.9 North Prong Alafia River Subwatershed 


















within the North Prong Alafia River Subwatershed are listed in Table 6.9-1, and the 

locations of the individual complaints are plotted in Figure 6.9-1. There were a total 

of 3 individual flooding complaint records within the North Prong Alafia River 

Subwatershed. It can be seen from examination of Table 6.9-1 that all of these 

complaints were repetitive (i.e. same location). 




Table 6.9-1 

North Prong Alafia River Subwatershed Reported Flooding Problems 

INFORMATION 

SOURCE 

MAP REFERENCE 

NUMBER 

LOCATION 

DESCRIPTION 


Complaints 

1025 8419 Edison Road \ 8411 Edison Road No information available 




2004 Edison Rd. south of Nicholson Rd. Road flooding. Standing water in roadway. 

2024 Edison Rd. & Keysville Area (Keysville Dr. to Allen Rd.) Road flooding. No standing water. Ongoing citizen concern for years. Probably need drainage studies. 


4 


Polk Co 

POLEY CREEK 

LAKE DRAIN 

540 

Scott 

Lake 

60 

CARTER RD 

39 

POLEY CREEK 

37 


Legend 


January 1998 

County Line 



Roads 




Suite 120 


ALAFIA RIVER 

1145 



1025 

2004 

SLOMAN BRANCH 

2024 


Notes: 



1:100,000 

640 

0 3,000 6,000 12,000 

0 0.5 1 2 

Miles 

Feet 

Filename: 

Fig6_9_ 

1.mxd 

60 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 











hydrodynamic model of the North Prong Alafia River Subwatershed. These 

simulations reflect existing conditions, defined as circa 2006 land-use and drainagesystem 

conditions. Table 6.9-2 lists peak-flood elevations at junctions of interest as 

a function of recurrence interval. Table 6.9-3 summarizes simulated peak flows at 

selected locations within the subwatershed as a function of recurrence interval. 

Table 6.9-3 

North Prong Alafia River Subwatershed Peak Flows at Selected Locations 

Location 

North Prong Alafia River 

at USGS Gage (9781650) 


at County Line (9783400) 

Tributary 782000 at 

Mouth (9782006) 

Sloman Branch at Mouth 

(9782806) 

Sloman Branch at Nichols 

Rd Bridge (9782828) 

Tributary 782830 at 

Mouth (9782868) 

Thirty Mile Creek at 

Mouth (9783010) 

2.33-year 

(cfs) 

5-year 

(cfs) 

10-year 

(cfs) 

25-year 

(cfs) 

50-year 

(cfs) 

100-year 

(cfs) 

5523 7591 9821 13270 15615 17989 

2867 4042 5441 7698 8968 10425 

98 136 188 269 323 402 

353 494 639 975 1225 1496 

331 468 594 799 935 1072 

67 105 146 211 253 295 

1052 1496 1952 2604 3031 3465 






TABLE 6.9-2 


NORTH PRONG ALAFIA RIVER SUBWATERSHED EXISTING CONDITIONS FLOOD ELEVATIONS SUMMARY 




NORTH PRONG ALAFIA RIVER FROM KEYSVILLE RD TO POLEY CREEK 

781650 USGS Gaging Station (300' d/s OF KEYSVILLE ROAD BRIDGE) 50.89 52.06 53.23 54.94 56.04 57.11 

781700 KEYSVILLE RD BRIDGE SPAN (D/S) 50.95 52.12 53.28 54.99 56.09 57.16 

781800 KEYSVILLE RD BRIDGE SPAN (U/S) 51.01 52.18 53.33 55.02 56.11 57.18 

782000 FEMA J - XS-18 52.31 53.41 54.48 56.01 57.01 58.00 

782200 FEMA J - XS-18 53.93 55.04 56.03 57.43 58.33 59.23 

782400 FEMA K - XS-19 55.27 56.49 57.60 59.08 59.99 60.87 

782600 FEMA L - XS-20 55.78 57.06 58.21 59.76 60.71 61.62 

782800 FEMA M - XS-21 57.77 59.03 60.22 61.82 62.80 63.74 

783000 FEMA N - XS-22 60.43 61.78 63.07 64.81 65.85 66.85 

783200 FEMA O - XS-23 61.09 62.50 63.82 65.59 66.65 67.66 

783400 HILLSBOROUGH / POLK COUNTY LINE 61.75 63.06 64.30 66.00 67.03 68.02 

783402 64.66 65.44 66.20 67.18 68.01 68.88 

SLOMAN BRANCH 

782800 CONFLUENCE WITH NORTH PRONG ALAFIA RIVER 57.77 59.03 60.22 61.82 62.80 63.74 

782806 DIRT RD (D/S) 69.68 70.39 71.01 71.83 72.35 72.82 

782808 DIRT RD (U/S) 69.76 70.49 71.12 71.97 72.50 73.00 

782810 77.51 77.96 78.35 78.91 79.23 79.55 

782826 NICHOLS RD BRIDGE SPAN (D/S) 80.60 81.23 81.83 82.52 82.87 83.17 

782828 NICHOLS RD BRIDGE SPAN (U/S) 80.79 81.46 82.06 82.78 83.16 83.49 

782830 81.17 81.80 82.36 83.07 83.44 83.77 

782831 84.10 84.43 84.74 85.04 85.20 85.35 

782840 98.86 99.12 99.41 99.73 99.85 99.95 

782846 107.23 107.63 107.91 108.08 108.17 108.23 

782847 SCL RR (D/S) 111.45 111.59 111.74 111.82 111.85 111.88 

782848 SCL RR (U/S) 112.44 112.73 113.01 113.43 113.74 114.06 

782849 SCL RR (D/S) 109.85 110.05 110.19 110.33 110.41 110.45 

782850 SCL RR (U/S) 112.73 113.83 114.84 116.09 116.77 117.31 


783000 CONFLUENCE WITH NORTH PRONG ALAFIA RIVER 60.43 61.78 63.07 64.81 65.85 66.85 

783010 61.60 62.32 63.16 64.88 65.92 66.91 

783020 MOBIL MINING DRAGLINE CROSSING 68.97 69.57 70.15 70.89 71.31 71.70 

783030 SECTION LINE CROSSING 74.42 74.93 75.41 76.06 76.45 76.83 

783040 SCL RR BRIDGE SPAN 76.94 77.42 77.86 78.48 78.86 79.22 

783050 ROAD CROSSING (D/S) 79.68 79.98 80.21 80.52 80.69 80.86 

783060 ROAD CROSSING (U/S) 98.73 98.95 99.16 99.46 99.65 99.84 

783070 ROAD CROSSING (U/S) 100.31 100.88 101.46 102.27 102.78 103.21








There are 15 locations within the Hillsborough County portion of the North Prong 

Alafia River Subwatershed for which the level of service was estimated. These are 

presented in Table 6.9-4. There is a minimum basin-wide goal of Level ‘B’ for the 

25-year, 24-hour design storm event, referred to as the Target Level of Service, 

which has been adopted by the County. There is one location identified in Table 

6.9-4 where the County’s minimum acceptable level of service is not met based on 

this criterion, as indicated by shaded cells in the table. Figure 6.9-2 shows the LOS 

by subbasin as required by County standards. By comparison to Table 6.9-1, it can 

be assumed that most of the flooding complaint record sites not shown as a 

problem area in Table 6.9-4 are generally an indication of secondary system 

problems or possible maintenance problems. A detailed discussion of the problem 

areas that were identified as primary drainage system deficiencies is presented in 

Chapter 13 of this report. 






LEGEND 


TABLE 6.9-4 


NORTH PRONG ALAFIA RIVER SUBWATERSHED EXISTING CONDITIONS LEVELS OF SERVICE ANALYSIS 




17-30-22 PINECREST LITTLE LEAGUE FIELD PRIVATE 780100 0.0 50.7 42.41 43.78 45.05 46.73 47.86 48.82 A A A A A A 

17-30-22 SCL RAILROAD PRIVATE 780750 59.10 0.00 46.72 47.99 49.20 50.86 51.86 52.78 A A A A A A 

9-30-22 E KEYSVILLE RD PUBLIC 780825 54.60 0.00 48.40 49.92 52.18 54.81 55.14 55.38 A A A A C C 

9-30-22 LUPTON PL PUBLIC 780830 61.30 0.00 61.41 61.57 61.72 61.92 62.04 62.16 A B B C C C 

10-30-22 SCL RAILROAD PRIVATE 781600 59.00 0.00 49.96 51.34 52.65 54.51 55.67 56.78 A A A A A A 

10-30-22 E KEYSVILLE RD PUBLIC 781800 55.10 0.00 51.01 52.18 53.33 55.02 56.11 57.18 A A A A D D 

15-30-22 NICHOLS RD PUBLIC 781808 60.40 0.00 58.03 58.55 59.03 59.70 60.15 60.55 A A A A A A 

15-30-22 NICHOLS RD PUBLIC 782008 73.71 78.50 72.65 73.86 74.03 74.20 74.30 74.39 A A B B C C 

13-30-22 NICHOLS RD PUBLIC 782828 84.50 0.00 80.79 81.46 82.06 82.78 83.16 83.49 A A A A A A 

13-30-22 SCL Railroad PUBLIC 782848 119.30 0.00 112.44 112.73 113.01 113.43 113.74 114.06 A A A A A A 

24-30-22 SCL Railroad PUBLIC 782850 119.60 116.70 112.73 113.83 114.84 116.09 116.77 117.31 A A A A D* D* 

14-30-22 Edison Rd (W-E) PUBLIC 782874 111.60 113.80 111.70 111.73 111.76 111.80 111.82 111.85 A A A A A B 

14-30-22 Edison Rd (S-N) PUBLIC 782878 114.00 115.00 114.03 114.07 114.12 114.20 114.25 114.29 A A A A B B 

14-30-22 KEYSVILLE DR PUBLIC 782888 115.20 115.40 114.96 115.23 115.28 115.36 115.40 115.44 A A A A A D* 

14-30-22 SCL Railroad PUBLIC 782894 118.50 0.00 115.20 115.63 115.92 116.29 116.50 116.70 A A A A A A






Polk Co 

POLEY CREEK 

LAKE DRAIN 

540 

Scott 

Lake 

60 

CARTER RD 

39 

POLEY CREEK 

37 


A 

B 

C 

D/D* 

Polk Co. 

O 

Legend 

County Line 





Suite 120 


ALAFIA RIVER 



SLOMAN BRANCH 


Notes: 



1:100,000 

640 

0 3,000 6,000 12,000 

Feet 

0 0.5 1 2 

Miles 

Filename: 

Fig6_9_ 

2.mxd 

60 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 









6.10 South Prong Alafia River Subwatershed 



In 2001, Parsons interviewed the Hillsborough County East Service Unit, the branch 

of the County that performs maintenance of the drainage system in the South Prong 

Alafia River Subwatershed. The Unit reported 5 locations that experience recurring 

flood problems. Locations are detailed Table 6.10-1 and shown on Figure 6.10-1. 














and Hurricane Frances floods. Hillsborough County compiled a cursory digital 

database of complaints. Complaint locations in the South Prong Alafia River 

Subwatershed are listed in Table 6.10-1; locations are shown on Figure 6.10-1. 

Hillsborough County recorded four El Nino flood complaints in the South Prong 

Alafia River Subwatershed. There were a total of 6 individual flooding complaint 

records within the South Prong Alafia River Subwatershed. It can be seen from 

close examination of Table 6.10-1 that a number of these complaints were repetitive 

(i.e. same location). It is also noted that the County database does not include a 

description of the nature of the problem for those complaints that were reported 

during the February 1998 flooding event, thus limiting its interpretive usefulness. 




Table 6.10-1 

South Prong Alafia River Subwatershed Reported Flooding Problems 

INFORMATION 

SOURCE 

MAP REFERENCE 

NUMBER 

LOCATION 

DESCRIPTION 






Complaints 


Complaints 




40 East Service Unit Dam Washout 


42 East Service Unit Possible Dam Failure 


70 South Service Unit Channel Flooding - Maintenance Issue; Outfall is Overgrown 

None 

None 

693 310 Wendel No Information Available 

754 2230 Welcome Rd. No Information Available 

1030 8104 Hwy. 39 S.5811 Hwy. 39 N.13119 Hwy. 39 S No Information Available 

1034 8911 Lithia Pinecrest Road No Information Available 

2014 Porter Rd. from George Smith Rd. to Allen Rd. Yard flooding. Ditches full and hard to get in and out of driveway. 

Lithia Pinecrest Rd. south of Lyons Ave. (from Lyons Ave. to 

2025 Van Horn Ln.) 

Water standing in roadway. 



ALAFIA RIVER 




39 

1034 

2025 


754 

Serv_41 

MIZELLE CREEK 

2014 

Serv_40 

Serv_42 

640 


Legend 

January 1998 


Service Unit 


County Line 



Roads 




Suite 120 


672 

HURRAH CREEK 

CHITO BRANCH 

693 

1030 

Serv_43 

Serv_70 


674 

Notes: 


1:100,000 


Polk Co 

0 3,000 6,000 12,000 

Feet 

0 0.5 1 2 

Miles 

LAKE BRANCH 


Filename: 

Fig6_10_ 

1.mxd 

Map Date: 


37 


N/A 

Prepared By: 

Yoav 

Rappaport 

555 











hydrodynamic model of the South Prong Alafia River Subwatershed. These 

simulations reflect existing conditions, defined as circa 2006 land use and drainage 

system conditions. Table 6.10-2 (on the next page) lists peak-flood elevations at 

junctions of interest as a function of recurrence interval. Table 6.10-3 (below) 

summarizes simulated peak flows at selected locations within the subwatershed as 

a function of recurrence interval. 

Table 6.10-3 


Simulated Peak Flows at Selected Locations 

Location 

South Prong Alafia 

River below Lithia- 

Pinecrest Road Bridge 

(9770500) 


River at Owens Branch 

Outfall (9771200) 


River at Jameson Road 

Bridge (9771844) 


River at Hurrah Creek 

Outfall (9772700) 


River at Lake Branch 

Outfall (9773505) 

Chito Branch at County 

Road 39 Bridge 

(9771058) 

2.33-year 

(cfs) 

5-year 

(cfs) 

10-year 

(cfs) 

25-year 

(cfs) 

50-year 

(cfs) 

100-year 

(cfs) 

2903 4054 5252 7194 8570 9837 

1228 1669 2522 3572 4885 5841 

1123 1676 2559 3588 4894 5794 

1138 1705 2481 3447 4653 5531 

816 1176 1548 2149 2565 2997 

480 626 795 1021 1305 1567 






TABLE 6.10-2 


SOUTH PRONG SUBWATERSHED EXISTING CONDITIONS FLOOD ELEVATIONS SUMMARY 




South Prong Alafia River: Outfall to Alafia River

TABLE 6.10-2 






770553 West Branch South Prong Alafia River 90.35 90.74 91.00 91.33 91.58 91.92 

770559 D/S Side 60" RCP @ Farm Road 106.85 107.28 107.58 107.88 108.06 108.25 

770560 U/S Side 60" RCP @ Farm Road 108.37 108.58 108.71 108.85 108.97 109.08 

770569 D/S Side 2-59" x 81" CMPA @ George Smith Road 108.96 109.10 109.31 109.54 109.65 109.84 

770570 U/S Side 2-59" x 81" CMPA @ George Smith Road 109.15 109.39 109.66 110.04 110.25 110.67 

770578 D/S Side 6' x 6' RBC @ Lithia Pinecrest Road 113.21 113.48 113.66 113.90 114.26 114.64 

770580 U/S Side 6' x 6' RBC @ Lithia Pinecrest Road 113.28 113.59 113.80 114.15 114.81 115.48 



770522 D/S Side 24" CMP @ Utility Easement 60.81 61.43 62.00 62.75 63.20 63.62 

770525 U/S Side 24" CMP @ Utility Easement 60.83 61.45 62.03 62.78 63.23 63.66 


770554 D/S Side 44" x 72" CMPA @ Utility Easement 91.93 92.15 92.30 92.43 92.52 92.70 

770555 U/S Side 44" x 72" CMPA @ Utility Easement 94.03 94.57 95.16 96.11 96.71 97.04 

770560 U/S Side 60" RCP @ Farm Road 108.37 108.58 108.71 108.85 108.97 109.08 

770563 D/S Side 44" x 72" CMPA @ George Smith Road 108.39 108.60 108.75 108.98 109.24 109.34 

770565 U/S Side 44" x 72" CMPA @ George Smith Road 109.02 109.73 110.50 111.62 111.74 111.83 

770580 U/S Side 6' x 6' RBC @ Lithia Pinecrest Road 113.28 113.59 113.80 114.15 114.81 115.48 

770595 Kingsford Complex Reclaimed Mine Unit 25-30-22 132.63 132.74 132.83 133.01 133.13 133.24 

Mizelle Creek: Outfall to South Prong Alafia River

TABLE 6.10-2 






771046 U/S Side 2-5' x 14.5' RBC @ South County Road 39 91.10 91.56 91.93 92.55 92.92 93.27 

771043 Unnamed Creek at Moccasin Hollow Road 77.03 77.24 77.43 77.65 77.80 77.93 

771048 D/S Side 60" RCP @ South County Road 39 84.20 84.63 84.89 84.89 85.06 85.31 

771050 U/S Side 60" RCP @ South County Road 39 83.98 84.49 84.97 86.11 86.48 86.71 

771081 Chito Branch 87.20 87.34 87.55 87.77 88.18 88.39 

771094 D/S Side 2-27" x 43" CMPA @ Wendel Avenue 87.40 87.63 87.98 88.16 88.40 88.49 

771095 U/S Side 2-27" x 43" CMPA @ Wendel Avenue 87.42 87.66 88.05 88.31 88.85 89.21 

771040 Chito Branch 64.65 65.22 65.68 66.21 66.53 66.88 

771098 D/S Side 44" x 72" CMPA @ Jameson Road 80.01 80.53 80.92 81.34 81.54 81.94 

771100 U/S Side 44" x 72" CMPA @ Jameson Road 80.31 81.17 82.03 83.27 84.09 84.76 

771110 Kingsford Complex South Mine Unit 7-31-22 95.60 96.08 96.57 97.43 97.98 98.39 

771112 Kingsford Complex North Mine Unit 7-31-22 98.28 98.56 98.71 98.82 98.93 99.05 


771114 Kingsford Complex West Central Mine Unit 8-31-22 106.21 106.26 106.31 106.38 106.43 106.47 


771116 Kingsford Complex East Central Mine Unit 7-31-22 103.20 103.26 103.32 103.39 103.44 103.48 


771118 Kingsford Complex North Mine Unit 18-31-22 95.00 95.32 95.70 96.14 96.53 96.79 

Owens Branch: Outfall to South Prong Alafia River

TABLE 6.10-2 






772302 Kingsford Complex Mine Unit 17-31-22 94.99 95.32 95.70 96.14 96.53 96.79 

772300 South Prong Alafia River 59.02 59.68 60.43 61.18 62.01 62.53 

772314 Kingsford Complex Mine Unit 17-31-22 72.05 72.53 72.57 72.70 72.77 72.82 


772401 Kingsford Complex Southern Mine Unit 17-31-22 76.80 76.89 76.98 77.10 77.21 77.28 


772404 Kingsford Complex Northwest Mine Unit 18-31-22 91.60 91.64 91.71 91.79 91.94 92.01 

Pollard Branch: Outfall to South Prong Alafia River

TABLE 6.10-2 






772795 U/S Side 36" DIP @ Rural Creek Crossing 114.11 114.33 114.64 114.84 115.21 115.39 

772780 Lewis Branch 86.48 86.92 87.61 87.99 88.62 88.88 

772783 D/S Side 36" DIP @ Rural Creek Crossing 101.57 101.80 102.09 102.35 102.99 103.20 


772780 Lewis Branch 86.48 86.92 87.61 87.99 88.62 88.88 



772762 Hurrah Creek 76.10 76.99 77.93 78.45 79.43 79.89 




772905 Kingsford Complex Southwest Mine Unit 29-31-22 79.80 80.04 80.39 80.61 81.03 81.23 

773090 Hurrah Lake 64.31 65.08 65.85 66.74 67.48 68.07 

773094 D/S Side 2-46" CMP @ Alafia Church Road 89.75 89.84 89.97 90.04 90.19 90.26 

773095 U/S Side 2-46" CMP @ Alafia Church Road 89.89 90.08 90.39 90.59 90.97 91.16 


Boggy Branch: Outfall to South Prong Alafia River









South Prong Alafia River Subwatershed. Figure 6.10-2 shows the LOS by subbasin 

as required by County standards. Hillsborough County adopted Level of Service B 

for the 25-year, 24-hour design-storm event. There are 6 locations listed that are 

indicated to not meet this target in the subwatershed. 





The analysis does not identify cases of structural flooding on the tertiary drainage 

system, or portions of the secondary drainage system. The primary drainage 

system includes the South Prong Alafia River and all major tributaries. The 

secondary drainage system includes small creeks that drain to the primary system. 

The tertiary drainage system drains to the secondary system. 

The SWMM details the primary drainage system and portions of the secondary 

drainage system. Solutions to structural flood problems on the secondary or tertiary 

system are not complicated if the primary system has the capacity to accept 

additional runoff. 

There is little correlation between the 1997/1998 El Nino and 2004 Hurricane 

Frances flood complaints and the level-of-service problem areas identified in this 

analysis. Section 6.7.3 discusses the possible issues that can contribute to the lack 

of correlation between this level-of-service analysis and the flood complaint 

database. 

By comparison to Table 6.10-1, it can be assumed that most of the historical 

flooding complaint record sites not shown as a problem area in Table 6.10-4 are 

generally an indication of secondary system problems or possible maintenance 

problems. A detailed discussion of the problem areas that were identified as 

primary drainage system deficiencies is presented in Chapter 13 of this report. 






LEGEND 


TABLE 6.10-4 


SOUTH PRONG ALAFIA RIVER SUBWATERSHED EXISTING CONDITIONS LEVELS OF SERVICE ANALYSIS 




21-30-22 LITHIA PINECREST RD PUBLIC 770520 52.60 0.0 52.52 52.78 53.01 53.32 53.53 53.71 A A B C C D 

22-30-22 E KEYSVILLE RD PUBLIC 770540 83.50 0.0 79.20 79.79 80.20 80.74 81.09 81.42 A A A A A A 

23-30-22 DRY BRIDGE RD PRIVATE 770552 89.10 102.8 89.33 89.69 89.94 90.23 90.47 90.79 A C C D D D 

23-30-22 GEORGE SMITH RD PRIVATE 770560 0.00 112.7 108.37 108.58 108.71 108.85 108.97 109.08 A A A A A A 

23-30-22 GEORGE SMITH RD PUBLIC 770565 111.50 113.8 109.02 109.73 110.50 111.62 111.74 111.83 A A A A A B 

24-30-22 GEORGE SMITH RD PUBLIC 770570 113.30 113.2 109.15 109.39 109.66 110.04 110.25 110.67 A A A A A A 

24-30-22 LITHIA PINECREST RD PUBLIC 770580 119.00 122.3 113.28 113.59 113.80 114.15 114.81 115.48 A A A A A A 


28-30-22 WALTER HUNTER RD PUBLIC 770710 57.70 59.2 56.72 57.46 58.05 58.84 59.28 59.69 A A B D D D 

27-30-22 E KEYSVILLE RD PUBLIC 770740 75.40 0.0 76.10 76.40 76.74 77.19 77.47 77.76 C D D D D D 

29-30-22 Old Welcome Road PRIVATE 770929 0.00 79.1 75.57 75.94 76.22 76.60 76.80 76.98 A A A A A A 

29-30-22 PRIVATE DRIVE PRIVATE 770930 0.00 88.0 80.14 80.31 80.46 80.66 80.79 80.90 A A A A A A 



6-31-22 S COUNTY ROAD 39 PUBLIC 771060 73.50 0.0 71.01 71.65 72.32 73.42 74.09 74.46 A A A A C C 

12-31-21 OLD RUSTY LN PUBLIC 771080 90.70 0.0 86.80 87.11 87.55 87.77 88.18 88.39 A A A A A A 

7-31-22 Wendel Avenue PRIVATE 771081 0.00 89.1 87.20 87.34 87.55 87.77 88.18 88.39 A A A A A A 



6-31-22 JAMESON RD PUBLIC 771100 84.50 85.7 80.31 81.17 82.03 83.27 84.09 84.76 A A A A A B 

5-31-22 JAMESON RD PUBLIC 771136 88.70 0.0 88.71 88.83 88.90 88.97 89.01 89.05 A A A B B B 

4-31-22 WALTER HUNTER RD PUBLIC 771220 71.00 74.9 67.66 68.34 68.98 70.03 70.68 71.25 A A A A A B 

3-31-22 VIRGIL HALL RD PUBLIC 771226 105.20 108.5 103.98 105.36 105.69 105.99 106.16 106.32 A A B C C D 

3-31-22 Virgil Hall Road PRIVATE 771227 0.00 113.1 108.52 108.94 109.23 109.58 109.76 109.94 A A A A A A 

34-30-22 E KEYSVILLE RD PUBLIC 771240 108.50 0.0 105.40 106.51 107.77 108.73 108.86 108.95 A A A A B B 

4-31-22 WALTER HUNTER RD PUBLIC 771419 76.50 86.5 73.44 73.79 74.17 74.72 75.03 75.31 A A A A A A 

10-31-22 VIRGIL HALL RD PUBLIC 771430 81.33 0.0 80.42 81.45 81.63 81.81 81.92 82.01 A A B B C C 

16-31-22 JAMESON RD PUBLIC 771804 103.10 0.0 103.25 103.30 103.34 103.42 103.47 103.51 A A A B B B 

9-31-22 WALTER HUNTER RD PUBLIC 771806 107.90 0.0 105.92 107.50 108.09 108.25 108.33 108.40 A A A B B C 

9-31-22 JAMESON RD PUBLIC 771845 58.00 0.0 55.58 56.22 57.04 57.84 58.77 59.34 A A A A C D 

16-31-22 JAMESON RD PUBLIC 772210 75.50 0.0 71.81 73.05 74.24 75.81 76.21 76.50 A A A B C D 

19-31-22 S COUNTY ROAD 39 PUBLIC 772730 71.50 72.0 68.95 69.63 70.63 71.28 72.41 72.83 A A A A D* D 

30-31-22 COUNTY ROAD 672 PUBLIC 772740 73.50 0.0 69.26 70.06 71.22 72.01 73.61 74.22 A A A A A C 

24-31-21 COUNTY ROAD 672 PUBLIC 772748 88.30 0.0 82.55 83.14 84.90 85.92 87.86 88.61 A A A A A B 

24-31-21 ROUGH DIAMOND RANCH RD PRIVATE 772750 88.80 0.0 88.73 89.06 89.42 89.60 89.88 90.03 A B C C D D 

6-32-22 HISCOCK RD PUBLIC 772768 87.09 0.0 85.15 85.78 86.59 87.15 87.84 88.08 A A A A C C 


27-31-21 COUNTY ROAD 672 PUBLIC 772795 116.10 0.0 114.11 114.33 114.64 114.84 115.21 115.39 A A A A A A 

19-31-22 THATCHER RD PUBLIC 773000 71.30 0.0 64.26 65.00 65.75 66.60 67.32 67.88 A A A A A A 

32-31-22 Kingsford-Four Corners Mine Road Bridge PRIVATE 773200 77.70 0.0 66.79 67.45 68.04 68.90 69.50 70.03 A A A A A A 

3-32-22 FORT LONESOME PLANT RD PUBLIC 773430 97.60 0.0 96.68 96.72 96.76 96.81 96.85 96.88 A A A A A A 

2-32-22 FORT LONESOME PLANT RD PUBLIC 773500 90.00 0.0 79.50 79.84 80.13 80.51 80.91 81.16 A A A A A A 

1-32-22 Bethlehem Road Bridge PUBLIC 773600 91.60 0.0 86.38 87.35 88.14 88.98 89.45 89.78 A A A A A A



This page intentionally left blank. 



ALAFIA RIVER 





640 

MIZELLE CREEK 


A 

B 

C 

D/D* 

Polk Co. 

O 

Legend 

County Line 





Suite 120 


672 

HURRAH CREEK 

CHITO BRANCH 

39 


Notes: 


1:100,000 


Polk Co 

0 3,000 6,000 12,000 

Feet 

0 0.5 1 2 

Miles 

LAKE BRANCH 


Filename: 

Fig6_10_ 

2.mxd 

Map Date: 


37 


N/A 

Prepared By: 

Yoav 

Rappaport 









6.11 ALAFIA RIVER MAIN STEM SUBWATERSHED 


Hillsborough County Central, East and South Service Units Reported 

Problems 

In 2001, Parsons interviewed Hillsborough County Central, East, and South Service 

Units, who perform maintenance service for the drainage systems in the Alafia River 

Main Stem Subwatershed. These units reported 20 locations that experience 

recurring flood problems. The problem locations are shown in Figure 6.11-1 with 

detailed descriptions summarized in Table 6.11-1. 

















within the Alafia River Main Stem Subwatershed are listed in Table 6.11-1, and the 

locations of the individual complaints are plotted in Figure 6.11-1. There were a 

total of 136 individual flooding complaint records within the Alafia River 

Subwatershed. It can be seen from close examination of Table 6.11-1 that a 

number of these complaints were repetitive (i.e. same location). It is also noted that 

the County database does not include a description of the nature of the problem for 

those complaints that were reported during the February 1998 flooding event, thus 

limiting its interpretive usefulness. 




Table 6.11-1 

Alafia River Main Stem Subwatershed Reported Flooding Problems 

INFORMATION 

SOURCE 

MAP REFERENCE 

NUMBER 

LOCATION 

DESCRIPTION 


Central Service Unit 

Hillsborough County East 

Service Unit 



September 1997 Flood 

Complaints 


Complaints 

57 Watson Road OTHER/No Pond Outfall/ 

58 Watson Road ROAD/Road Flooding/ 

59 Providence Road ROAD/Road Flooding/ 

60 Hickory Creek drive ROAD/Flooding/Pond OCS Reconstructed 

27 Herdon Street DRAINAGE/Poorly Drained - Bad Perc Pond/ 

28 Durant road OTHER/Proposed Pump Station/ 

29 Little Road DRAINAGE/Undersized Culvert/ 

30 Sterns Road DRAINAGE/Poorly Drained/ 

31 Private Property off Lithia-Pinecrest Road CHANNEL/Channel Flooding - Maintenance Issue/ 

32 Golf Hieghts Circle ROAD/Road Flooding/ 

34 Bobcat Trail HOUSE/Houses at Low Elevations/ 

35 Pitt Road DRAINAGE/Poorly Drained/ 

37 East Keysville Rd, East of CR 39 Washout from Dam Failure 

61 McMullen Road ROAD/Road Flooding/ 

63 McMullen Road ROAD/Road Flooding/ 

64 Culver Place YARD/Yards Flding-Sheet Flow through Subs/H20 Is Eroding Thorough Way b/c High Slopes 

71 Red Bird Lane ROAD/Road Flooding/ 

73 Kenda Drive ROAD/Road Flooding / Poorly Drained/?Culvert Needs to be Replaced? 

75 Riverview Drive CHANNEL/Channel Flooding - Maintenance Issue/Ditch Blocked - Maintenance Issue 

76 Anna Ave. ROAD/Road Flooding/ 

16 Bloomingdale Road(E Of Bell Sho Flooding of Bloomingdale Road in front of the new Kash N Karry. 

40 Hesperides Street There was approximately nine blocks under water. The water depth was about 2'. 

62 Providence Road North of Crescent Lake Road. The roadway overtopping was observed to be approximately 3'. 

66 River Cove @ Ashman Street and front yard flooding caused by the construction activities. 

71 Stearns Road Flooding on Stearns Road at the beginning of Stearns Creek. 

72 Summitview Water behaves as reported, runs along west curb, west of TECO box and users driveway. 

210 Alafia Ridge Rd Overflow/runoff/having septic tank problems from this. 

240 Crescent Lake Dr Driveway damaged by water flowing over Crescent Lake Dr. 

243 Dee Circle Retention pond overflowing and flooding streets. 

259 Gulf Heights Circle Had contacted Service Unit. They told her to contact us about getting permission to set up pumps. 

272 Kanawha St. Yard flooded due to water runoff from Dyer Rd. 

286 Laurel Oak Drive Conservation pond on site and drainage easement in back is clogged causing flooding. 

288 Linda Street Citizen reported received by Bob Gordon. Flooding driveway. 

297 Mays Avenue From Bob Gordon. Ditch runs through her property to Alafia River. 

318 Providence Road Road and yard flooding. Driveway washed away. 

321 Riverview Drive Serious flooding problem in this area. Reported several times. 

346 Tomahawk Trail Flooding 

348 U.S. Highway 301 S Flooding 

369 Emerald Creek Drive Yard and road flooding. 

370 Spring Road Flooding 




Table 6.11-1 


INFORMATION 

SOURCE 

MAP REFERENCE 

NUMBER 

LOCATION 

DESCRIPTION 


Complaints 

648 8022 Alafia Ridge Road\Alafia Ridge Road No Information Available 

654 9903 Connecticut Street No Information Available 

655 2212 Cornell Drive No Information Available 

656 104 Dee. Cir No Information Available 

661 9916 Ethel Street10010 Ethel Street No Information Available 

664 10714 Hackney Dr. No Information Available 

665 7403 Hancock No Information Available 

668 721 Holly Terrace No Information Available 

674 10028 Kenda Drive No Information Available 

675 3424 Little Oak Street No Information Available 

676 840 Louis St. No Information Available 

678 10705 N. 4th St. No Information Available 

680 Palmetto Street No Information Available 

681 7806 Pleasant Lane No Information Available 

682 7409 Providence Road\11120 Providence Dr. No Information Available 

683 10612 Rivercrest Dr. No Information Available 

684 11005 Riverview Drive\7017 Riverview Dr.\11203 Riv No Information Available 

687 11111 Shady Lane No Information Available 

688 10520 St. Rose Circle No Information Available 

689 11926 Sugarberry Dr. No Information Available 

690 10431 Tara Drive No Information Available 

691 11701 Tucker Road No Information Available 

694 10738 Whitt Rd. No Information Available 

708 2112 Herndon Street\2207 Herndon Street\2208 Hernd No Information Available 

714 5104 Lithia Spring Rd No Information Available 


729 4510 Pawnee Path No Information Available 

740 1620 South Dover Road No Information Available 

755 411 Windel Ave. No Information Available 

786 2621 Stearns Road\3623 Lithia Pinecrest Rd\2621 St No Information Available 

790 9402 Pine Ridge Avenue No Information Available 

983 3816 Pine Dale Street No Information Available 

1033 2831 Lewis Rd No Information Available 

1035 2024 Martin Road No Information Available 

1040 2811 Miller Road S. No Information Available 

1052 8106 Sandcrane Lane No Information Available 

1054 2110 Siloman Springs Drive No Information Available 

1057 5201 Summerall Road No Information Available 

1070 9903 Alafia Vista No Information Available 

1071 9509 Alice Lane No Information Available 

1072 10303 Balm Riverview Road No Information Available 

1073 11837 Balm Riverview Road No Information Available 

1076 11104 Browning Rd. No Information Available 

1079 11115 Church Drive No Information Available 

1081 11211 E. Riverview Drive No Information Available 

1083 11005 Elliot Street\11017 Elliot Street No Information Available 

1087 4511 Jessi Lane No Information Available 

1090 11609 Leonard Ave. No Information Available 

1092 6111 Nundy Avenue No Information Available 

1093 8615 Parkway Circle No Information Available 

1094 8003 Revels Road No Information Available 

1095 11914 Rhodine Road No Information Available 

1097 4411 Rose Street No Information Available 

1099 11067 Scott Loop No Information Available 

1100 10129 Shadow Oaks Circle No Information Available 

1103 10714 Hwy 301 S. No Information Available 

1104 8807 Van Fleet Road No Information Available 

1105 9001 Wiggins Road No Information Available 

1135 8015 S. 78th Street No Information Available 

1136 4618 Ackerly Way No Information Available 

1138 8202 Mays Avenue No Information Available 

1139 1115 Myrtle Road No Information Available 



1145 8713 SR 39 South No information available 

1146 2102 Whitlock Place\2111 Whitlock Place\2108 Whitl No Information Available 

1088 10610 Johanna Avenue No Information Available 




Table 6.11-1 


INFORMATION 

SOURCE 

MAP REFERENCE 

NUMBER 

LOCATION 

DESCRIPTION 


Complaints 


Hurricane Frances Flood 

Complaints 

0 Park Drive Barbara Heald 

0 South Miller Road Barbara Heald 

5 Private Property near River Drive No Information Available 

7 Magnolia Street No Information Available 

8 Providence Road No Information Available 

9 Private Property near Jessi Lane No Information Available 

10 Private Property near River Drive No Information Available 

11 Apache Trail No Information Available 

14 Old Gibsonton Drive No Information Available 

17 Alafia Ridge Loop No Information Available 

21 Revels Road No Information Available 

22 Valerie Lane No Information Available 

23 River Close Blvd. No Information Available 

201 Lithia Pinecrest Road No Information Available 

202 Squirel Run Way No Information Available 

204 Cummins Road No Information Available 

205 Private Property off Myrtle Road Road No Information Available 

212 Apache Trail No Information Available 

213 Private Property off Stoner Road 1993 yard flooding of river rising 

217 McMullen Road No Information Available 

2008 10503 Sanford Street Citizen concerned about possible flooding if hurricane comes since land is lower than road. 

2019 2015 Martin Road (Camarra's Plant Nursery) Yard flooding. No standing water in road. Small pockets of water on private property. No action needed. 

2005 

2801 & 2803 Bloomingdale Ave. (from S. Saint Cloud Ave. to 

Sprawling Oaks Pl.) 

Yard flooding. Residential flooding on private property at 2801 & 2803 Bloomingdale. Some standing water on south side of Bloomingdale in 

front of these two residences. 

2812 Stearns Rd. Road and structure flooding. Water increased to 2" since pump was installed. 

2023 3707 Coppertree Circle, Brandon No flooding. 

2006 7214 Alafia Ridge Road Road flooding. Breach in bank of river. Need to close breach in levee and install pump station. 

2000 78th Street S. 

Road flooding. Overgrown ditch and trash in the ditch. Culvert rusted south of 8221 is plugged. Called Ms. York on 09/15/04 @ 10:15 A.M. 

and left a message. 

2060 Alafia Blvd. & Louise St. (from Louise St. to Center Ave.) Road flooding. 

2073 Alafia St. from Gibsonton Dr. to Nundy Ave. No Information Available 

2071 

Balm Riverview Rd. from S. U.S. Hwy 301 to Jefferson St. (Advanced 

Auto Parts) 

Balm Riverview Rd @ Hwy. 301 flooded. There is imminent roadway erosion (new Advanced Auto Parts). 

2066 Bloomingdale Ave. from Patterson Rd. to Watson Rd. No Information Available 

2029 Coconut Cove Place from Lithia Springs Rd. to dead end Road flooding. Road underwater. 

2069 Crescent Lake Dr. from Providence Rd. to Mathers Ln. Road flooding. Street flooding washing out driveway. 

2002 Dee Circle Stormwater pond overtopped its banks and flooded road. May want to review the outfall design. 

2021 Herndon Street Retention pond flooding. Pump station #29 not working. 

2061 Lake Grove Ct. from Southview Dr. to dead end Road flooding. 

2072 Lula St., Gibsonton (from S. U.S. Hwy 41 to Anna Ave.) Road flooding. The road is adjacent to coastal wetlands. This flooding may have been tidally influenced. 

2067 Mathers Lane from Crescent Lake Dr. to dead end No Information Available 

2007 McMullen Loop @ McMullen Rd. east side Road flooding. 

2012 

McMullen Loop from Dee Circle to dead end (Hidden River Travel 

Resort Park) 

Road flooding. 400 travel trailers - 40 people trapped in recreation center due to high water. 

2057 Pine Street from Williams Blvd. to dead end Road flooding. Road underwater. 

2062 Pinedale Ct. from Pinedale St. to dead end No Information Available 

2070 Providence Rd. from Bloomingdale Ave. to Kenbrook Dr. Intersection flooded. 

2068 Providence Rd. from Watson Rd. to Watermark Dr. Road flooding. 

2020 Providence Rd., Riverview (from Kenbrook Dr. to Watson Rd. 

Flow on street is fast. Citizen protected homes with sand bags, but seems to be little help. Check system and heavy street, yard & structure 

flooding. Checking system and D/S channel is OK. Problem most likely is drainage system. 

2058 Rose Street from Williams Blvd. to dead end Road flooding. 

2054 S. Miller Rd. from Greenhills Dr. To Arborwood Dr. Retention pond flooding. 

Road flooding. 

2056 Spring Rd. south of Adelaide Ave. (from Williams Blvd. to dead end) 

2076 Stearns Rd. (Pinecrest and Bloomingdale) Road and structure flooding. Water flooding over her property. 

2053 Stearns Rd. from Hillgrove Rd. to Pearson Rd. Road flooding. Underwater pump set up. 



E LUMSDEN RD 


Legend 


Service Unit 


January 1998 

December 1997 


County Line 


Suite 120 





Roads 



ALAFIA RIVER 


Serv_60 

Serv_64 

BELL CREEK 

369 

1139 

Serv_32 

Meet_205 

BOYETTE RD 

675 

Notes: 

72 

755 

Meet_23 

Meet_1 

2054 

16 

1040 

2005 

259 

Serv_27 

1146 

Meet_201 

2053 

Serv_30 

40 

71 

786 716 

Serv_31 

Meet_5 

Meet_9 

Meet_202 

Meet2_39 

Meet2_13 

Meet_10 

370 

2056 

729 


708 

Serv_29 

1143 

1097 2029 1142 

1087 


1:60,000 

0 1,500 3,000 6,000 

Feet 

0 0.25 0.5 1 

Miles 

1035 

1054 

Serv_28 

714 

740 

ALAFIA RIVER 

BOYETTE RD 

1033 

TURKEY CREEK 

Filename: 

Fig6_11_ 

1E.mxd 



Serv_34 

1057 

Map Date: 

1076 



N/A 

Serv_71 

Prepared By: 

Yoav 

Rappaport 

Serv_35 

39 


Figure: 6.11-1(E) - Historical Flood Complaint 









2070 

2066 


Legend 


Service Unit 


January 1998 

December 1997 


County Line 



Roads 




Suite 120 


41 

2069 2023 

62 

676 

2067 

983 

664 

1088 

2060 

2006 

75 

Meet2_28 

682 

Meet_17 

665 

1081 

210 Meet_21 

Meet_204 

1135 

690 

684 297 

648 

668 

680 

1138 

243 

Meet_212 

2000 

2071 

321 

2012 

1136 

Serv_75 

Meet_0 1099 

Meet2_3 Serv_63 

272 1104 

790 

Meet_217 

66 1071 Serv_73 

661 

2072 

1070 Meet_7 

Meet_14 

225 

1105 

348 BOYETTE RD 

Serv_76 

674 

1100 

288 

654 

694 

1072 

Serv_65 

2073 

681 

1092 

687 1090 

678 

691 

1103 

689 

ALAFIA RIVER 

GIBSONTON DR 

Notes: 

301 

1:60,000 

0 1,500 3,000 6,000 

Feet 

0 0.25 0.5 1 

Miles 

318 

RICE CREEK 

Meet_39 

1073 

1095 

Filename: 

Fig6_11_ 

1W.mxd 

2061 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 

Figure: 6.11-1(W) - Historical Flood Complaint 






TABLE 6.11-2 


ALAFIA RIVER MAIN STEM SUBWATERSHED EXISTING CONDITIONS 

FLOOD ELEVATIONS SUMMARY 




Alafia River from Hillsborough Bay to U.S. Highway 301 

700000 Hillsborough Bay 1.09 1.09 1.09 1.09 1.09 1.09 

700030 1.14 1.17 1.23 1.35 1.48 1.61 

700050 U.S. Highway 41 Bridge (d/s); FEMA XS No 1 1.16 1.20 1.29 1.45 1.62 1.80 

700060 U.S. Highway 41 Bridge (u/s); FEMA XS No 2B 1.16 1.21 1.30 1.46 1.64 1.82 

700100 FEMA XS No 5 (A) 1.17 1.22 1.32 1.50 1.69 1.89 

700150 FEMA XS No 6 1.19 1.26 1.38 1.60 1.82 2.05 

700200 FEMA XS No 7 (B) 1.21 1.29 1.43 1.68 1.93 2.18 

700280 FEMA XS No 8 1.23 1.31 1.47 1.74 2.01 2.28 

700350 FEMA XS No 9 1.26 1.36 1.56 1.88 2.19 2.48 

700400 FEMA XS No 10 (C) 1.36 1.52 1.80 2.25 2.66 3.04 

700500 FEMA XS No 11 1.43 1.62 1.95 2.47 2.93 3.35 

700550 FEMA XS No 12 1.46 1.66 2.02 2.56 3.04 3.48 

700600 FEMA XS No 13 (D) 1.50 1.72 2.10 2.68 3.19 3.64 

700700 I-75 Bridge (d/s) 1.51 1.74 2.13 2.72 3.23 3.69 

700750 I-75 Bridge (u/s) 1.57 1.83 2.26 2.91 3.46 3.96 

700900 FEMA XS No 14 1.68 1.99 2.49 3.22 3.84 4.39 

701000 FEMA XS No 15 (E) 1.76 2.10 2.64 3.43 4.09 4.66 

701020 FEMA XS No 16 1.84 2.22 2.80 3.64 4.34 4.94 

701100 [S-20-T30-R20] 1.91 2.32 2.94 3.82 4.54 5.16 

701180 FEMA XS No 17 1.98 2.41 3.06 3.98 4.74 5.38 

701200 FEMA XS No 18 2.04 2.49 3.17 4.12 4.90 5.56 

701250 U.S. Highway 301 Bridge (d/s); FEMA XS No 19 2.24 2.76 3.54 4.60 5.45 6.17 

Alafia River from U.S Highway 301 to Rice Creek 

701350 U.S. Highway 301 Bridge (u/s); FEMA XS No 20B (F) 2.30 2.84 3.65 4.75 5.62 6.36 

701370 FEMA XS No 21 2.34 2.91 3.74 4.87 5.76 6.51 

701380 FEMA XS No 22 2.36 2.93 3.76 4.89 5.78 6.54 

701390 FEMA XS No 23 2.40 2.98 3.82 4.96 5.86 6.62 

701400 [S17-T30-R20] 2.44 3.03 3.88 5.04 5.95 6.71 

701500 FEMA XS No 24 (G) 2.68 3.36 4.33 5.61 6.60 7.41 

701600 Rice Creek 2.80 3.51 4.53 5.87 6.90 7.74 

Alafia River from Rice Creek to Buckhorn Creek 

701700 FEMA XS No 25 2.83 3.56 4.59 5.94 6.98 7.83 

701800 FEMA XS No 26 (H) 3.05 3.85 4.95 6.39 7.49 8.39 

701900 3.25 4.11 5.26 6.75 7.88 8.81 

701950 FEMA XS No 27 3.32 4.19 5.37 6.88 8.02 8.95 

702000 3.46 4.38 5.59 7.14 8.32 9.27 

702100 FEMA XS No 28 3.71 4.70 5.95 7.54 8.73 9.71 

702200 FEMA XS No 29 (I) 3.81 4.82 6.08 7.71 8.94 9.95 

702205 4.02 5.07 6.34 7.96 9.19 10.19 

702250 FEMA XS No 30 4.19 5.27 6.54 8.17 9.40 10.41 

702400 Buckhorn Creek; FEMA XS No 31 (J) 4.77 5.99 7.37 9.11 10.40 11.44 

Alafia River from Buckhorn Creek to Bell Creek 

702450 FEMA XS No 32 5.23 6.59 8.07 9.91 11.28 12.39 

702500 FEMA XS No 33 (K) 5.27 6.69 8.22 10.07 11.45 12.57 

702600 5.34 6.77 8.29 10.16 11.54 12.66 

702650 FEMA XS No 34 5.41 6.88 8.47 10.36 11.73 12.83 

702700 FEMA XS No 35 (L) 5.49 6.98 8.60 10.58 12.02 13.18 

702800 5.65 7.20 8.85 10.83 12.33 13.53 

702880 FEMA XS No 36 5.71 7.28 8.92 10.92 12.44 13.64 

702900 5.97 7.57 9.23 11.22 12.70 13.89 

702950 FEMA XS No 37 6.43 8.15 9.77 11.71 13.17 14.34 

703000 6.60 8.33 9.95 11.89 13.34 14.50 

703050 FEMA XS No 38 6.81 8.60 10.24 12.19 13.64 14.79 

703100 FEMA XS No 39 (M) 7.26 9.21 10.97 13.02 14.53 15.73 

703200 7.33 9.32 11.13 13.23 14.78 16.01 

703300 FEMA XS No 40 (N) 7.34 9.35 11.19 13.33 14.91 16.15 

703400 FEMA XS No 41 (O) 7.62 9.77 11.68 13.83 15.40 16.64 

703500 FEMA XS No 42 8.17 10.19 12.06 14.16 15.70 16.92 

703550 FEMA XS No 43 8.28 10.30 12.15 14.26 15.79 17.01 

703600 FEMA XS No 44 (P) 9.20 11.04 12.83 14.88 16.35 17.53 

703700 Bell Creek 9.44 11.30 13.06 15.09 16.54 17.70 

Alafia River from Bell Creek to Bell Shoals Road Bridge 

703790 FEMA XS No 45 9.59 11.44 13.19 15.21 16.66 17.82 

703800 FEMA XS No 46 9.62 11.47 13.23 15.26 16.72 17.89 

703850 FEMA XS No 47 9.92 11.84 13.62 15.63 17.08 18.24 

703900 FEMA XS No 48 10.50 12.52 14.42 16.58 18.16 19.34

TABLE 6.11-2 







704000 FEMA XS No 49 (Q) 11.27 13.34 15.32 17.62 19.33 20.65 

704050 FEMA XS No 50 11.88 14.02 16.05 18.42 20.16 21.54 

704100 Bell Shoals Road Bridge (d/s); FEMA XS No 51 12.13 14.26 16.30 18.69 20.44 21.83 

Alafia River from Bell Shoals Road Bridge to Fishhawk Creek 

704105 Bell Shoals Road Bridge (u/s); FEMA XS No 52B 12.18 14.31 16.36 18.75 20.51 21.90 

704180 FEMA XS No 54 12.26 14.45 16.49 18.88 20.63 22.02 

704200 FEMA XS No 55 (R) 13.75 15.73 17.63 19.86 21.52 22.84 

704290 FEMA XS No 56 14.92 17.02 18.95 21.11 22.69 23.98 

704300 FEMA XS No 57 (S) 15.26 17.39 19.33 21.51 23.10 24.40 

704450 FEMA XS No 58 16.50 18.46 20.27 22.35 23.90 25.17 

704600 FEMA XS No 59 (T) 17.53 19.50 21.35 23.50 25.08 26.36 

704650 FEMA XS No 60 17.96 19.96 21.84 24.03 25.63 26.94 

704700 18.33 20.35 22.26 24.48 26.12 27.44 

704800 FEMA XS No 61 (U) 18.41 20.42 22.32 24.55 26.19 27.52 

704900 Fishhawk Creek; FEMA XS No 62 18.66 20.65 22.55 24.80 26.45 27.79 

Alafia River from Fishhawk Creek to Lithia Pinecrest Road Bridge 

705000 FEMA XS No 63 (V) 18.87 20.85 22.74 24.97 26.62 27.95 

705100 19.06 21.02 22.90 25.13 26.78 28.10 

705150 FEMA XS No 64 19.39 21.36 23.25 25.49 27.14 28.45 

705200 19.65 21.63 23.53 25.78 27.42 28.72 

705300 FEMA XS No 65 19.92 21.84 23.71 25.94 27.56 28.85 

705400 Lithia Springs; FEMA XS No 66 (W) 20.25 22.10 23.93 26.12 27.73 29.01 

705500 FEMA XS No 67 20.72 22.64 24.43 26.48 28.00 29.25 

705600 FEMA XS No 68 (X) 21.05 22.88 24.61 26.63 28.13 29.38 

705795 21.55 23.23 24.86 26.83 28.31 29.54 

705800 FEMA XS No 69 (Y) 21.70 23.36 24.99 26.95 28.43 29.66 

705900 FEMA XS No 70 22.12 23.74 25.32 27.26 28.71 29.92 

706000 FEMA XS No 71 (Z) 22.32 23.92 25.49 27.42 28.87 30.07 

706010 FEMA XS No 72 22.72 24.23 25.75 27.64 29.05 30.25 

706100 22.93 24.42 25.90 27.76 29.16 30.34 

706199 USGS Gaging Sta. @ Lithia Pinecrest Road Bridge (d/s); FEMA XS N 23.32 24.89 26.42 28.22 29.55 30.69 

Alafia River from Lithia Pinecrest Road Bridge to Turkey Creek 

706200 Lithia Pinecrest Road Bridge (u/s); FEMA XS No 74R-B 23.39 24.98 26.52 28.35 29.70 30.85 

706300 FEMA XS No 76 (AA) 23.86 25.37 26.85 28.63 29.96 31.08 

706400 24.03 25.52 26.98 28.76 30.08 31.20 

706500 FEMA XS No 77 24.12 25.61 27.06 28.84 30.15 31.27 

706525 24.69 26.14 27.53 29.24 30.52 31.60 

706600 FEMA XS No 78 (AB) 25.15 26.47 27.78 29.44 30.69 31.76 

706610 25.85 27.01 28.21 29.78 30.99 32.02 

706900 FEMA XS No 79 (AC) 26.36 27.45 28.56 30.06 31.23 32.23 

707000 Turkey Creek 27.08 28.12 29.12 30.51 31.63 32.59 

Alafia River from Turkey Creek to State Road 39 

707100 FEMA XS No 80 27.41 28.47 29.46 30.82 31.90 32.84 

707200 27.94 29.02 29.99 31.30 32.33 33.24 

707250 FEMA XS No 81 29.56 30.75 31.79 33.10 34.08 34.93 

707300 FEMA XS No 82 30.07 31.41 32.62 34.16 35.28 36.22 

707400 FEMA XS No 83; old SCL RR Bridge 30.15 31.51 32.76 34.34 35.48 36.44 

707450 FEMA XS No 84 30.57 32.04 33.40 35.11 36.31 37.31 

707500 30.91 32.50 33.95 35.74 36.99 38.03 

707600 FEMA XS No 85 (AD) 31.34 32.96 34.43 36.23 37.50 38.56 

707700 33.31 34.80 36.17 37.88 39.10 40.12 

707800 FEMA XS No 86 33.63 35.14 36.53 38.27 39.51 40.56 

707900 34.15 35.67 37.09 38.87 40.14 41.21 

708000 34.85 36.37 37.81 39.62 40.93 42.03 

708100 FEMA XS No 87 (AE) 35.20 36.69 38.11 39.92 41.23 42.33 

708200 35.37 36.84 38.26 40.06 41.37 42.47 

708300 35.55 37.00 38.41 40.21 41.51 42.61 

708350 FEMA XS No 88 35.74 37.18 38.58 40.38 41.68 42.78 

708400 35.88 37.31 38.70 40.50 41.79 42.89 

708500 36.33 37.71 39.08 40.86 42.15 43.24 

708570 FEMA XS No 89 36.52 37.88 39.23 40.99 42.28 43.37 

708600 36.89 38.19 39.51 41.24 42.51 43.60 

708700 FEMA XS No 90 (AF) 37.18 38.46 39.77 41.49 42.75 43.83 

708800 37.29 38.56 39.86 41.58 42.84 43.91 

708900 FEMA XS No 91 37.85 39.04 40.29 41.95 43.18 44.23 

709000 38.46 39.59 40.77 42.37 43.56 44.58 

709050 FEMA XS No 92 39.53 40.51 41.58 43.05 44.18 45.16 

709100 S.R. 39 Bridge (d/s); FEMA XS No 93 39.65 40.66 41.73 43.21 44.34 45.32

TABLE 6.11-2 







Alafia River from State Road 39 to North and South Prong Alafia River 

709150 S.R. 39 Bridge (u/s); FEMA XS No 94B 39.66 40.67 41.75 43.25 44.38 45.37 

709200 FEMA XS No 95 40.21 41.37 42.55 44.10 45.25 46.23 

709400 Confluence N. Prong and S. Prong; FEMA XS No 96 (AG) 41.22 42.63 43.96 45.64 46.81 47.76 

North Prong Alafia River from Alafia River to Keysville Road 

709400 Confluence N. Prong and S. Prong; FEMA XS No 96 (AG) 41.22 42.63 43.96 45.64 46.81 47.76 

780000 FEMA XS-1 41.92 43.29 44.58 46.26 47.40 48.36 

780100 42.41 43.78 45.05 46.73 47.86 48.82 

780200 FEMA A 42.67 44.04 45.31 47.00 48.12 49.09 

780300 43.25 44.58 45.82 47.50 48.59 49.56 

780400 FEMA B 43.51 44.84 46.08 47.76 48.85 49.82 

780500 FEMA C 43.88 45.22 46.47 48.16 49.24 50.21 

780600 FEMA D 45.97 47.15 48.30 49.88 50.82 51.69 

780700 SCL RR BRIDGE SPAN d/s 46.60 47.89 49.12 50.79 51.79 52.72 

780750 SCL RR BRIDGE u/s; FEMA E 46.72 47.99 49.20 50.86 51.86 52.78 

780800 47.78 49.27 50.67 52.59 53.73 54.79 

780900 47.99 49.49 50.89 52.82 53.96 55.03 

781000 FEMA F 48.05 49.55 50.95 52.88 54.03 55.11 

781100 48.32 49.81 51.22 53.14 54.33 55.46 

781200 FEMA G 48.80 50.22 51.57 53.46 54.63 55.75 

781300 48.92 50.31 51.64 53.52 54.68 55.80 

781400 49.37 50.77 52.10 53.98 55.14 56.26 

781500 SCL RR BRIDGE SPAN d/s 49.88 51.26 52.59 54.45 55.61 56.73 

781600 SCL RR BRIDGE SPAN u/s 49.96 51.34 52.65 54.51 55.67 56.78 

781650 USGS Gaging Station (300' d/s OF KEYSVILLE ROAD BRIDGE) 50.89 52.06 53.23 54.94 56.04 57.11 

Tributary S-1 System 

700102 Anna Ave. Crossing (d/s) 1.74 2.21 2.91 3.31 5.01 6.11 

700103 Anna Ave. Crossing (u/s) 2.76 3.32 4.00 4.34 5.60 6.51 

700105 Gibsonton Dr. crossing (d/s) 5.81 6.23 6.76 7.08 7.43 7.65 

Tributary N-2 System 

700364 Riverlachen Way (d/s) 8.08 8.22 8.37 8.43 8.57 8.62 

700370 Riverlachen Way (u/s) - Riverview Drive (d/s) 8.33 8.56 8.88 9.03 9.37 9.54 

700375 Riverview Drive (u/s) 8.89 9.41 10.00 10.30 10.69 10.89 

700387 Tomasino survey site No.38 9.06 9.46 10.03 10.32 10.69 10.89 

700389 S 78th Street (d/s) 9.10 9.47 10.03 10.32 10.68 10.88 

700390 S 78th Street (u/s) 9.11 9.48 10.03 10.32 10.61 10.80 

700392 Moore St. (d/s) 6.55 6.88 7.45 8.45 9.35 9.54 

700393 Moore St. (u/s) 6.43 6.68 7.00 7.24 7.52 7.62 

700396 N. Hickory Ln. 4.02 4.11 4.31 4.47 4.73 4.86 


701104 Wilson Miller Survey X201 3.42 3.90 4.40 4.64 4.99 5.16 

701120 Gibsonton Drive (d/s) 23.78 24.11 24.38 24.46 24.61 24.67 

701124 Gibsonton Drive (u/s) 25.01 25.88 26.76 27.21 27.87 28.18 

701128 Kenda Drive (d/s) 25.01 25.88 26.76 27.21 27.87 28.18 

701132 Kenda Drive (u/s) 25.03 25.88 26.71 27.11 27.87 28.18 

701140 Ken Lake 25.98 26.29 26.81 27.18 27.93 28.29 

701142 Eckerd Drugs Pond outfall 36.66 36.72 36.78 36.88 37.03 37.08 

701146 Eckerd Drugs Pond Control Structure 36.95 37.07 37.20 37.72 39.11 39.49 

701147 Eckerd Drugs Pond 38.30 38.61 39.06 39.25 39.46 39.57 


701252 Moody Road Bridge (d/s) 3.49 3.91 4.42 4.65 5.45 6.17 

701254 Moody Road Bridge (u/s) 3.50 3.93 4.44 4.68 5.45 6.17 

701258 Riverview Drive Crossing West of US 301 (d/s) 8.96 9.10 9.27 9.37 9.54 9.60 

701260 Riverview Drive Crossing West of US 301 (u/s) 10.32 10.54 10.83 11.00 11.34 11.47 

701284 Riverview Drive (d/s) 8.23 8.68 9.21 9.50 9.94 10.12 


701288 Krycul Avenue (d/s) 15.37 15.53 15.67 15.74 15.90 16.03 

701289 Krycul Avenue (u/s) 16.10 16.37 16.62 16.78 17.29 17.72 

701290 Ashley Oaks Pond B outfall 16.30 16.56 16.80 16.96 18.29 19.15 

701292 Ashley Oaks Pond B (combined) 18.43 18.80 19.42 19.83 20.44 20.64 

701272 Moody Road (d/s) 8.06 8.52 9.03 9.32 9.76 9.95 

701274 Moody Road (u/s) 8.09 8.56 9.06 9.35 9.81 10.01 

701276 19.11 19.33 19.57 19.69 19.91 20.01 

701277 River Vista Minor Pond pipe outfall 19.13 19.34 19.58 19.70 19.91 20.01 

701278 River Vista Minor Pond Control Structure 19.72 19.85 20.19 20.42 20.84 21.02 

701281 River Vista Minor Detention Ponds 1 & 2 20.03 20.15 20.33 20.52 20.91 21.08

TABLE 6.11-2 








701499 Manhole 2.70 3.26 3.88 5.04 5.95 6.71 

701402 Park Drive (d/s) 3.02 3.90 4.82 5.31 6.18 6.71 

701404 Park Drive (u/s) 4.69 5.10 5.54 6.51 7.98 8.69 

701406 Balm Riverview Road (d/s) 15.12 15.36 15.95 16.22 16.64 16.82 

701408 Balm Riverview Road (u/s) 17.77 17.83 17.98 18.06 18.17 18.22 

701409 Chapel Garden Drive East of US 301 17.80 17.88 18.07 18.15 18.25 18.30 

701418 Boyette Road (d/s) 36.23 36.43 36.71 36.87 37.09 37.18 

701422 Boyette Road (u/s) 39.17 39.23 39.31 39.36 39.43 39.46 

701426 Uncle Tom Road (d/s) 39.21 39.31 39.46 39.56 39.73 39.80 

701430 Uncle Tom Road (u/s) 39.25 39.34 39.49 39.59 39.76 39.83 

701447 US301 (d/s) 39.31 39.42 39.61 39.74 39.95 40.05 

701434 US301 Road Side Ditch 40.50 40.69 40.94 41.07 41.31 41.41 

701442 ASPH Drive Crossing Near Hungry Howie Pizza and Subs 42.52 42.58 42.65 42.69 42.77 42.80 

701158 Wilson Miller survey site S-203 (u/s) - Lake 41.37 41.61 41.96 42.18 42.60 42.80 

712020 US Post Office Pond 26.64 26.81 27.04 27.18 27.44 27.54 

701414 US301/Boyette Pond 27.42 27.47 27.54 27.59 27.67 27.71 

701438 Hungry Howie's Pizza and Subs Pond. 40.68 40.81 41.01 41.13 41.33 41.42 


701710 McMullen Loop Road (u/s) 6.92 6.99 7.09 7.14 7.39 7.83 

701715 Shallow Creek Lane (d/s) 12.41 12.66 12.92 13.02 13.71 13.96 

701720 Shallow Creek Lane (u/s) 16.83 19.32 20.59 20.64 20.95 21.06 

701724 Shallow Creek Lane (d/s) 23.94 24.18 24.40 24.50 25.39 25.74 

701726 Shallow Creek Lane (u/s) 31.16 34.29 39.07 42.02 43.98 44.17 

701727 Cristina Phase III Pond E outfall 47.42 47.69 48.06 48.27 48.64 48.79 

701729 Cristina Phase III Pond E 58.78 59.47 60.07 60.25 60.53 60.64 

701730 Cristina Phase III Pond B outfall 50.79 51.01 51.29 51.45 51.77 51.89 

701732 Cristina Phase III Pond B 62.22 62.70 63.38 63.80 64.05 64.13 

701733 Cristina Phase III Pond A outfall 61.42 61.65 61.95 62.13 62.41 62.54 

701736 Cristina Phase III Pond A 63.88 64.26 64.87 65.29 65.93 66.05 

701738 Manhole 67.73 67.92 68.17 68.32 68.57 68.68 

701740 Manhole 68.46 68.63 68.85 68.97 69.16 69.24 

701742 McMullen Rd. (d/s) 69.66 69.81 70.02 70.15 70.39 70.49 

701744 Manhole, McMullen Rd. (u/s) 70.34 70.52 70.76 70.91 71.19 71.32 

701748 3 Ponds (combined) 72.77 72.93 73.16 73.32 73.63 73.79 


702002 Wilson Miller survey location X202 6.89 7.47 7.82 7.98 8.32 9.27 

702005 Cummins Rd. D/S 19.47 19.67 19.90 20.01 20.24 20.36 

702010 Cummins Rd. U/S 21.55 21.74 21.97 22.10 22.38 22.53 

702015 WM survey site No.2, S-211 22.10 22.34 22.61 22.76 23.05 23.21 

702020 WM survey site No.2, S-211 23.19 23.39 23.62 23.75 24.02 24.18 

702025 McMullen Loop Rd. D/S 40.38 40.69 41.32 41.60 42.29 42.47 

702030 McMullen Loop Rd. U/S 41.05 41.71 43.37 44.31 45.44 45.58 

702031 McMullen Rd. crossing (d/s) 52.85 53.03 55.29 55.99 57.11 58.62 

702032 McMullen Rd. crossing (u/s) 56.23 56.57 59.53 60.56 61.65 61.88 

702035 Riverglen units 3,4,5,6,& 7 Lake C 59.45 59.53 59.62 59.66 59.76 59.82 

702045 Riverglen units 3,4,5,6,& 7 Lake B 62.27 62.65 63.14 63.35 63.67 63.75 

702050 Riverglen units 3,4,5,6,& 7 Lake A 66.21 66.82 67.10 67.18 67.30 67.34 


701905 Riverview Drive (d/s) 3.25 4.11 5.27 6.75 7.88 8.81 


701915 Church Steet 13.53 13.97 14.22 14.30 14.44 14.61 

701920 Providence Road (d/s) 16.80 17.08 17.35 17.44 17.60 17.77 

701925 Providence Road (u/s) 18.08 18.74 19.49 19.81 20.31 20.41 

701930 Hannaway Drive (d/s) 24.38 24.57 24.74 24.82 25.03 25.14 

701935 Hannaway Drive (u/s) 25.10 25.16 25.22 25.26 25.34 25.38 

Rice Creek from McMullen Loop Road to Boyette Road 

710010 Rice Creek McMullen Loop Road (d/s) 3.41 3.92 4.62 5.87 6.90 7.74 

710015 Rice Creek McMullen Loop Road (u/s) 3.55 4.08 4.91 5.87 6.90 7.74 

719105 RICE-FEMA B 7.38 8.20 9.25 9.78 10.78 11.25 

719106 RICE-FEMA ID 6 7.95 8.79 9.86 10.41 11.43 11.92 

719107 RICE-FEMA C 9.90 10.78 11.79 12.27 13.29 13.74 

719108 RICE-FEMA D 10.58 11.45 12.46 12.94 13.96 14.42 

719109 RICE-FEMA ID 9 11.21 12.05 13.02 13.50 14.49 14.94 

719110 RICE-FEMA E 11.65 12.47 13.42 13.91 14.91 15.37 

710028 RICE-FEMA ID 11, Balm Riverview Drive 11.85 12.66 13.61 14.10 15.11 15.57 

710032 RICE-FEMA ID 12, Balm Riverview Drive 12.01 12.92 13.98 14.57 16.08 16.79

TABLE 6.11-2 







710036 Boyette Road (d/s) 16.25 16.76 17.43 17.76 18.69 19.12 

710013 CAMP Christina YMCA North Pond 39.62 40.01 40.76 40.94 41.04 41.33 

710022 Christina YMCA South Pond 36.68 36.95 37.39 37.72 38.33 38.37 

710019 Christina Phase III Pond D & C. 59.93 60.52 61.40 61.92 62.46 62.66 

Rice Creek from Boyette Road to Balm Riverview Road West 

710040 Boyette Road (u/s) 16.66 17.36 18.43 19.05 20.94 21.96 

710045 Beyette Animal Hospital Detention Pond 23.19 23.39 23.61 23.69 23.81 23.87 

719114 RICE-FEMA ID 14 17.36 18.08 19.18 19.79 21.57 22.52 

710060 Asphalt Road Bridge (d/s) 21.60 22.22 23.07 23.53 24.48 25.00 

710070 Asphalt Road Bridge (u/s) 21.98 22.66 24.02 24.70 26.34 27.47 

719115 RICE-FEMA H 24.00 24.40 25.22 25.55 26.97 27.96 

710080 Dirt Road 32.63 32.81 33.10 33.28 33.79 34.05 

710082 Balm Riverview Road (d/s) 42.68 42.70 42.73 42.74 42.76 43.07 

710083 Balm Riverview Road (u/s) 45.85 47.04 47.20 47.26 47.36 47.41 

719118 RICE-FEMA K 43.23 43.69 44.27 44.56 45.15 45.48 

Tributary N-11 system 

702210 Cresent Lake Drive (d/s) 12.28 12.86 14.04 14.51 15.26 15.50 

702212 Cresent Lake Drive (u/s) 14.60 16.11 16.75 16.83 17.00 17.07 

702216 Providence Road (d/s) 19.49 20.22 20.88 21.11 21.51 21.68 

702220 Providence Road (u/s) 20.40 20.66 20.92 21.14 21.54 21.71 

702230 Highway 301 (d/s) 39.33 39.47 39.62 39.66 39.80 39.83 

702232 Highway 301 (u/s) 40.08 40.44 40.93 41.25 41.70 41.82 

702237 Bloomingdale Hills Pond "E" outfall 43.44 43.64 43.93 44.10 44.17 44.19 

702238 Bloomingdale Hills Pond "E" 43.44 43.65 43.94 44.11 44.17 44.19 

702278 Bloomingdale Hills Ponds "F" and "F-1" 27.68 28.36 29.36 30.02 30.63 30.86 

702262 Bloomingdale Avenue (d/s) 21.10 21.38 22.04 22.59 23.65 23.72 

702264 Bloomingdale Avenue (u/s) 32.03 32.62 33.34 33.75 34.43 34.71 


703205 John Moore Rd (d/s) 12.07 12.52 13.06 13.32 14.53 15.73 

703210 John Moore Rd (u/s) 14.20 14.92 15.84 16.30 17.38 18.02 

703215 Hickory Creek Drive (d/s) 23.21 23.50 23.77 23.89 24.13 24.22 

703220 Hickory Creek Drive (u/s) 25.20 25.89 26.80 27.38 28.39 28.86 

703225 Bloomingdale Sect F Pond Outfall 56.91 57.48 57.81 58.10 58.39 58.49 

703227 Bloomingdale Sect F Pond Control Structure 60.53 60.87 61.06 61.18 61.42 61.50 

703230 Bloomingdale Sect F Pond 61.14 61.30 61.44 61.51 61.65 61.71 

703235 Bell Shoals Rd (d/s) - Wetland 63.99 64.07 64.19 64.25 64.39 64.45 

703240 Bell Shoals Rd (u/s) - Wetland 64.19 64.32 64.52 64.65 64.92 65.05 


704202 Bell Shoals Road East 24.76 25.18 25.61 25.83 26.25 26.37 

704210 Dirt Road 28.94 29.21 29.52 29.74 30.06 30.38 

704213 Myrtle Road (d/s) 37.51 37.78 38.09 38.33 38.85 39.33 

704215 Myrtle Road (u/s) 39.32 39.59 39.90 40.22 41.60 42.48 

704226 Emerald Creek Drive (d/s) 50.81 51.00 51.32 51.55 51.98 52.28 

704227 Emerald Creek Drive (u/s) 51.89 52.14 52.66 53.14 55.14 55.30 

704228 Dirt Road crossing (d/s) 55.63 55.80 56.12 56.33 56.78 57.04 

704229 Dirt Road crossing (u/s) 56.95 58.27 59.56 59.64 59.82 59.94 

704235 Oakdale Riverview Estates Wetland 63.25 63.32 63.40 63.44 63.61 63.70 

704245 Oakdale Riverview Estates, South Pond C.S. 63.62 64.32 64.97 65.39 65.82 65.93 

704250 Oakdale Riverview Estates, South Pond 64.37 64.69 65.20 65.54 65.91 66.01 

704206 Bell Shoals Road (d/s) 25.61 25.77 25.99 26.13 26.38 26.50 

704207 Bell Shoals Road (u/s) 26.16 26.40 26.71 26.91 27.25 27.37 

704209 St. Stephens Catholic Church Pond No.1 27.24 27.27 27.32 27.34 27.40 27.44 

704217 Emerald Creek Subdivision Pond No.1 43.69 44.29 44.97 45.14 45.37 45.48 

704219 Emerald Creek Subdivision Pond No.2 45.56 46.02 46.39 47.15 47.25 47.28 

Tributary N-13, N-14, N-15, N-16, and N-18 Systems 

704476 Bloomingdale Section "W" Detention Lake "W" 63.09 63.84 65.20 65.47 65.84 66.01 

704480 Bloomingdale Section "O" Detention Lake "O" 64.73 65.15 65.33 65.47 65.85 66.02 

704456 Oakdale Riverview Estates, East Wetland 59.19 59.37 59.56 60.21 61.09 61.43 

704462 Oakdale Riverview Estates, East Pond 62.57 62.90 63.37 63.67 64.18 64.30 

704605 River Crossing Estates detention pond "A" 36.72 37.55 38.78 39.22 39.47 39.55 

704710 Bloomingdale Section "B-B" detention pond BB-3 26.93 27.82 28.43 28.84 29.60 29.89 



704740 Bloomingdale Section "AA-GG" detention pond 44.59 45.68 47.74 48.56 49.30 49.51 

704904 Bloomingdale Section "CC" Pond "CC" 26.51 27.13 28.05 28.61 28.85 28.94 

705161 Bloomingdale Section "DD" Detention Pond "C" 26.37 27.43 28.43 28.71 29.20 29.38 

705167 Bloomingdale Section "DD" Detention Pond "B" 40.47 40.95 42.92 42.98 43.08 43.13

TABLE 6.11-2 







705173 Bloomingdale Section "DD" Detention Pond "A" 42.65 42.86 43.24 43.55 44.07 44.31 

705185 Culbreath Cove detention pond 63.06 63.55 64.01 64.18 64.48 64.60 


705604 Williams Blvd. (d/s) 22.39 22.88 24.61 26.63 28.13 29.38 

705606 Williams Blvd. (u/s) 24.59 24.73 24.85 26.62 28.08 29.31 

705608 Duncan Cove Way (d/s) 24.64 24.83 25.03 26.62 28.07 29.30 

705610 Duncan Cove Way (u/s) 25.63 25.77 25.90 26.61 28.00 29.22 

705611 Dirt Road (d/s) 25.63 25.77 25.91 26.60 27.98 29.21 

705612 Dirt Road (u/s) 26.08 26.27 26.49 26.72 28.00 29.22 

705614 Lithia Pinecrest Rd. 26.14 26.35 26.61 26.90 28.01 29.25 

705616 Lithia Ridge Blvd. (d/s) 26.23 26.48 26.74 27.05 28.02 29.25 

705630 Lithia Ridge Blvd. (u/s) 26.60 27.23 28.38 28.77 29.19 29.35 

705640 Dirt Road (d/s) 38.09 38.55 38.97 39.27 39.80 40.08 

705647 Detention Pond Control Structure 38.77 38.86 39.08 39.36 39.92 40.22 

705648 Detention pond 38.79 38.88 39.09 39.37 39.92 40.22 

705650 Lithia Pinecrest Road (d/s) 46.58 46.80 47.14 47.32 47.57 47.67 

705652 Lithia Pinecrest Road (u/s) 46.60 46.86 47.37 47.74 48.37 48.67 

705664 Dirt Road (d/s) 49.23 49.39 49.79 50.14 50.95 51.32 

705666 Dirt Road (u/s) 49.58 49.97 52.07 52.29 52.56 52.66 

705740 Bloomingdale Avenue (d/s) 52.72 52.76 52.79 52.81 53.05 53.37 

705741 Bloomingdale Avenue (u/s) 54.27 54.44 54.57 54.64 56.34 56.65 

705742 Ryoal Oaks Shopping Center Detention pond Control Structure 55.66 56.04 56.33 56.47 56.70 56.77 

705743 Ryoal Oaks Shopping Center Detention Pond 55.73 56.08 56.36 56.50 56.71 56.78 

705700 River Hill Ridge retention pond 51.26 51.36 51.44 51.49 51.55 51.58 

705619 Lithia Ridge Elementary School detention pond 26.21 26.41 26.70 27.08 28.04 29.26 

705632 Lithia Ridge Elementary School "Parcel A" detention pond 4B 26.94 27.25 28.38 28.77 29.19 29.35 

705635 Lithia Ridge Elementary School "Parcel A" detention pond 4A 27.03 27.37 28.38 28.77 29.19 29.35 

705710 Lithia Ridge Unit Pond 1 40.75 41.38 42.38 43.04 44.34 44.97 

705654 Bloomingdale Section "J-J" Lake "JJ" Control Structure 46.73 47.23 47.80 48.04 48.44 48.73 

705655 Bloomingdale Section "J-J" Lake "JJ" 46.84 47.41 47.93 48.13 48.47 48.76 

705657 Bloomingdale Section "P-Q" Lake "P-Q" Control Structure 52.89 55.02 55.23 55.35 55.50 55.56 

705658 Bloomingdale Section "P-Q" Lake "P-Q" 54.91 55.24 55.39 55.46 55.59 55.64 

705662 Bloomingdale Section "U&V" Lake "U" 59.99 60.61 61.18 61.45 61.86 62.05 

705672 Bloomingdale Elementary School "C" existing Pond 52.70 53.28 53.54 53.66 53.84 53.92 

705685 Bloomingdale Section "R" Detention Lake "R" Control Structure 51.44 51.64 52.19 54.54 56.19 56.50 

705687 Bloomingdale Section "R" Detention Lake "R" 53.27 53.91 54.76 55.10 56.24 56.55 

705689 Mason Oaks Detention pond 53.55 54.34 55.37 55.52 56.24 56.54 

705705 Mason Oaks percolation pond 50.12 51.00 52.11 52.13 52.32 52.58 

705719 Canterbury Oaks Phase 1 retention pond 30.00 30.06 30.45 30.85 33.83 34.84 

705792 Lithia Pinecrest Hess Gas Station south pond 53.46 54.05 54.11 54.14 54.22 54.25 

705790 Lithia Pinecrest Albertson's pond 49.06 50.16 51.70 52.66 56.13 56.21 

705745 Lithia Pinecrest Hess Gas Station west pond 50.98 51.88 54.19 55.52 56.31 56.66 

705725 Cinnoman Trace retention pond 54.59 55.39 55.62 55.66 55.76 55.79 

705727 Sugarloaf Ridge Pond B 79.58 79.86 80.26 80.46 80.76 80.89 

705730 Country Gate Retention Pond 80.34 80.61 80.99 81.65 82.35 82.47 

705739 Sugarloaf Ridge Percolation Pond A 73.22 74.21 75.59 76.40 77.12 77.13 

705784 Buckhorn Unit 2 South/North Detention Ponds 46.91 48.65 49.70 49.80 50.20 50.37 

705788 Buckhorn percolation pond B 57.08 58.54 60.08 60.12 60.17 60.22 

705756 Buckhorn Run Pond No.1 57.51 57.56 57.60 57.63 58.23 58.75 



728340 Greenhills Pump Station Outfall (Buckhorn Creek) 70.42 71.80 72.48 72.74 73.32 73.51 

705752 Greenhills Pump Station Pond 49.73 52.32 56.11 57.69 58.23 58.75 

705760 Buckhorn Golf Course Retention Pond 54.16 55.33 56.66 57.30 58.24 58.77 

705777 Buckhorn neighborhood Park North detention pond 82.16 82.20 82.35 82.57 83.12 83.41 

705767 Buckhorn neighborhood Park South detention pond 78.13 78.31 78.56 78.72 79.01 79.15 

705779 Parkwood Manor detention pond 93.81 94.67 94.72 94.75 94.80 94.82 


706501 D/S of old railroad culvert 42.74 42.94 43.38 43.68 44.18 44.26 

706502 U/S of old railroad culvert 50.36 50.47 50.61 50.70 50.87 50.95 

706503 X-sec of Fishhawk Trails outfall creek 50.44 50.65 50.93 51.13 51.55 51.74 

706504 Pine Rocklands Avenue (d/s) 53.39 54.13 54.89 55.32 56.07 56.22 

706506 Pine Rocklands Avenue (u/s) 53.44 54.22 55.11 55.61 56.62 56.77 

706507 Manhole on X-sec D/S of Audubon Manor Blvd. Crossing 58.66 58.78 58.90 58.96 59.10 59.16 

706511 Audubon Manor Blvd. (d/s) 63.59 63.98 64.49 64.79 65.27 65.49 

706512 Audubon Manor Blvd. (u/s) 64.39 64.86 65.48 65.85 66.50 66.80 

706519 Flatwoods Manor Circle (d/s) 80.54 80.90 81.32 81.61 82.09 82.31 

706520 Fishhawk Trails Wetlands Area "A" 81.10 81.53 82.14 82.57 83.64 84.17 

706505 Fishhawk Trails Pond "T" 52.93 53.55 54.57 55.27 55.88 56.40 

706508 Fishhawk Trails Pond "U" 70.23 70.85 71.80 72.44 73.56 73.97

TABLE 6.11-2 







706509 Fishhawk Trails Pond "S" 58.65 58.72 58.78 58.81 58.86 58.88 

706510 Fishhawk Trails Pond "R" 64.43 64.93 65.69 66.20 67.21 67.35 

706516 Fishhawk Trails Wetlands Area "C" 84.93 85.04 85.20 85.30 85.62 85.84 

706518 Fishhawk Trails Wetlands Area "B" 86.20 86.28 86.42 86.50 86.68 86.76 

706521 Fishhawk Trails Pond "D" 67.09 67.27 67.48 67.59 68.36 68.84 

706522 Fishhawk Trails Pond "A" 71.13 71.68 72.56 73.13 73.90 74.14 

706524 Fishhawk Trails Pond "F" 84.01 84.35 84.86 85.18 85.80 86.01 


707905 X-sec survey location 36.15 36.58 37.49 38.87 40.14 41.21 

707910 X-sec N. of Thompson Rd. 44.29 44.63 45.26 45.74 46.52 46.91 

707920 Thompson Road (d/s) 45.92 46.18 46.68 46.95 47.42 47.71 

707925 Thompson Road (u/s) 48.23 49.42 50.45 50.68 51.10 51.32 



707955 D/S side of culvert W. of Bryant Rd. 78.84 79.07 79.28 79.61 80.20 80.50 

707960 U/S side of culvert W. of Bryant Rd. 82.01 83.61 86.23 87.31 87.73 87.97 

707965 Lithia-Pinecrest Road (d/s) 82.82 83.65 86.23 87.31 87.74 87.99 

707970 Lithia-Pinecrest Road (u/s) 84.71 85.24 86.42 87.56 88.33 88.89 


707980 D/S side of culvert E. of Browning Rd. 102.73 103.17 103.63 103.89 104.21 104.41 

707985 U/S side of culvert E. of Browning Rd. 104.69 105.11 105.20 105.27 105.36 105.41 

707990 Dorman Road (d/s) 104.82 105.24 105.59 105.82 106.02 106.13 

707993 Dorman Road (u/s) - Wetlands 105.04 105.38 105.61 105.83 106.04 106.14 

707930 Fish Hawk Trails Park Pond 78.56 78.91 79.40 79.60 79.80 79.93 


708803 Mcdonald Branch Convergence 38.35 39.04 39.86 41.58 42.84 43.91 

708805 Thompson Road (d/s) 40.50 41.02 41.38 41.84 42.84 43.91 

708810 Thompson Road (u/s) 46.95 47.84 48.07 48.35 48.52 48.68 


708820 D/S of 4-culvert dirt road crossing 59.68 60.20 60.64 61.15 61.45 61.77 

708825 U/S of 4-culvert dirt road crossing 66.13 66.39 66.62 66.91 67.09 67.27 

708830 D/S of 3-culvert dirt road crossing 68.73 69.03 69.26 69.62 69.84 69.97 

708835 U/S of 3-culvert dirt road crossing 68.79 69.10 69.36 69.73 69.96 70.11 

708840 Lithia Pinecrest Road (d/s) 103.27 103.38 103.47 103.61 103.69 103.76 

708845 Lithia Pinecrest Road (u/s) 103.50 103.73 103.98 104.39 104.73 105.00 

708870 D/S of Thompson Rd. culvert 48.15 48.50 48.76 49.20 49.67 49.97 

708875 U/S of Thompson Rd. culvert 51.44 53.49 55.48 57.65 57.88 58.03 



708895 D/S of Lithia Pinecrest Rd. crossing 95.62 95.96 96.27 96.69 96.92 97.14 

708897 U/S of Lithia Pinecrest Rd. crossing 96.98 97.57 98.11 99.20 99.97 100.65 

Riverhills: From Pond BB to Alafia River 

706130 U/S Side Lithia-Pinecrest Road 23.23 24.80 26.35 28.20 29.57 30.70 

706140 Northeasterly Side River Hills Haul Road 23.82 24.80 26.35 28.20 29.56 30.70 

706182 U/S Side River Hills Pond E Outfall Pipe 27.33 27.99 30.00 31.23 32.04 32.20 

706183 River Hills Pond E 30.66 30.85 31.18 31.36 32.09 32.25 

706184 U/S Side River Hills Pond D Outfall Pipe 34.87 35.15 36.50 38.64 39.30 39.63 

706185 River Hills Pond D 38.42 38.59 38.75 38.81 39.33 39.65 

706194 U/S Side River Hills Pond BB Outfall Pipe 38.46 38.78 40.62 40.90 41.57 41.92 

706195 River Hills Pond BB 40.33 40.48 40.65 40.91 41.58 41.93 

Riverhills: From Pond a to Lithia Pinecrest Road, Detention Ponds 

706134 U/S Side Southwesterly U/S Side of Haul Road 23.23 24.80 26.35 28.20 29.56 30.70 

706135 Southwesterly U/S Side of Haul Road 23.74 24.80 26.35 28.20 29.56 30.70 

706144 U/S Side River Hills Pond B Outfall Pipe 23.83 24.80 26.30 28.20 29.56 30.70 

706145 River Hills Pond B 25.68 25.86 26.24 28.20 29.56 30.70 

706150 River Hills Pond A 25.68 25.87 26.24 28.20 29.56 30.70 

706170 Lithia Ridge Pond 5 29.94 30.51 31.46 32.12 33.38 33.98 

706168 Lithia Ridge Pond 2 27.85 28.05 28.39 28.61 29.02 29.28 

706179 Lithia Ridge Unit 2 Dry Pond 2 39.39 39.95 40.82 41.40 42.49 43.03 

706410 River Hills Pond F 29.75 30.22 30.52 30.74 32.10 32.81 

706420 River Hills Pond JL 37.21 37.47 38.52 39.14 39.38 39.48 

706575 River Hills Pond Z 35.57 36.05 36.67 36.75 37.28 37.75 

706585 River Hills Pond H 35.66 36.29 37.41 38.19 39.00 39.07 

706590 River Hills Pond FF 41.20 41.44 41.82 42.24 43.05 43.17 

Riverhills: From Pond DD to Alafia River 

706530 River Hills Pond G 28.68 29.30 29.98 30.29 30.60 31.60 

706535 Bottom River Hills Pond GG Connector DBI 34.27 35.27 36.79 37.49 37.82 37.91

TABLE 6.11-2 







706536 Top River Hills Pond GG Connector DBI 35.97 36.07 36.86 37.56 37.89 37.98 

706550 U/S Side Pond II Outfall Ditch 40.09 40.09 40.09 40.09 40.21 40.41 

706555 River Hills Pond II 37.27 37.66 39.06 39.77 40.38 40.93 

706559 U/S Side River Hills Pond EE Outfall Pipe 38.06 38.62 40.77 41.63 43.16 43.46 

706560 River Hills Pond EE 40.50 40.83 41.28 41.80 43.19 43.49 

706561 D/S Side Ponds C-EE Connector Channel 40.51 40.85 41.33 41.85 43.25 43.55 

706564 U/S Side Ponds C-EE Connector Channel 40.55 40.93 41.42 41.90 43.27 43.60 

706565 River Hills Pond CC 40.56 40.95 41.46 41.95 43.31 43.65 

706570 River Hills Pond DD Lower 40.63 41.22 42.11 42.70 43.64 43.88 

706571 U/S Side River Hills Pond DD Upper Outfall P 40.64 41.32 42.28 42.92 43.68 43.92 

706572 River Hills Pond DD Upper 41.09 41.48 42.32 42.95 43.69 43.93 

706545 River Hills Pond GG 40.13 40.68 41.16 41.23 41.33 41.38 

Stems Ditch: U/S Side of Durant Road to Alafia River 

706613 Stern's Ditch 25.87 27.03 28.22 29.80 31.00 32.02 

706617 Stern's Ditch 31.21 31.26 31.39 31.48 31.68 32.02 

706630 Stern's Ditch 32.54 32.79 33.27 33.41 33.74 33.96 

706635 D/S Side Fairway Lane South 33.97 34.32 34.72 34.99 35.54 35.85 

706640 U/S Side Fairway Lane South 34.07 34.45 34.89 35.19 35.81 36.19 

706645 Stern's Ditch 34.14 34.52 34.96 35.27 35.90 36.27 

706660 D/S Side Golf Cart Bridge 34.32 34.72 35.18 35.48 36.12 36.49 

706665 U/S Side Golf Cart Bridge 34.43 34.84 35.35 35.66 36.37 36.84 

706670 D/S Side Fairway Lane North 34.51 34.93 35.44 35.75 36.46 36.92 

706675 U/S Side Fairway Lane North 34.58 35.01 35.54 35.86 36.62 37.17 


706685 d 34.77 35.21 35.77 36.10 36.91 37.61 


706725 U/S Side Golf Cart Bridge 35.16 35.56 36.09 36.41 37.32 38.15 

706730 Stern's Ditch 35.22 35.62 36.14 36.46 37.36 38.18 

706740 Stern's Ditch 35.42 35.82 36.31 36.62 37.53 38.30 

706770 Stern's Ditch 35.56 35.94 36.43 36.73 37.64 38.39 

706780 D/S Side Bloomingdale Avenue Extension 35.70 36.07 36.55 36.84 37.76 38.49 

706785 U/S Side Bloomingdale Avenue Extension 35.71 36.09 36.56 36.86 37.77 38.50 

706795 Stern's Lake 35.91 36.42 37.17 37.67 38.46 38.59 

706839 D/S Side Driveway 48.59 48.72 48.97 49.13 49.42 49.55 

706840 U/S Side Driveway 50.21 50.83 51.16 51.20 51.27 51.30 

706845 U/S Side Durant Road East of Memory Lane Sub 50.81 51.38 51.92 52.17 52.61 52.81 

706849 Natural Depression North of Memory Lane Subd 51.61 51.83 52.18 52.39 52.77 52.94 

706850 Natural Depression North of Hidden Forrest E 48.18 49.57 50.93 51.66 52.87 53.38 

706855 U/S Side Durant Road @ Hidden Forrest East 63.24 64.29 65.81 66.34 66.47 66.51 

Riverhills Stems Ditch Ponds 

706615 River Hills Pond T 31.21 31.26 31.39 31.48 31.68 32.02 

706620 River Hills Pond QQ 31.82 32.36 32.58 32.78 32.98 32.99 

706625 River Hills Pond KK 35.81 35.88 36.00 36.06 36.32 36.56 

706642 River Hills Ponds S-Q-I-MM 35.21 35.75 36.53 37.08 38.02 38.35 

706690 River Hills Ponds Q-J 35.21 35.76 36.54 37.08 38.03 38.38 

706655 River Hills Pond R 35.95 36.45 37.16 37.35 37.65 37.85 

706710 River Hills Pond JJ 38.39 38.62 39.30 39.80 40.26 40.32 

706715 River Hills Ponds NN-K 39.00 39.44 40.14 40.39 40.83 41.15 

706735 River Hills Pond O 35.97 36.38 36.93 37.28 37.90 38.20 

706745 River Hills Ponds N-P 36.17 36.34 36.72 37.07 37.72 38.45 

706755 River Hills Ponds M-L 36.27 36.99 37.92 38.52 39.56 39.98 

706760 River Hills Ponds CC-BB-AA 36.27 36.99 37.93 38.53 39.57 39.98 

706910 River Hills Pond U 30.86 31.01 31.18 31.28 31.47 32.23 

706912 River Hills Pond UU 31.29 31.56 31.98 32.26 32.75 32.92 

706920 River Hills Pond V 32.07 32.18 32.42 32.60 32.90 33.03




Once the existing conditions are programmed into the hydrologic/hydraulic model, 

the subwatershed can be analyzed in response to design storms statistically 

created using a Florida modified rainfall distribution. 

The design storms used in the study are 24-hour duration with recurring interval of 

2.33, 5, 10, 25, 50, and 100 years. Table 6.11-2 lists peak flood elevations at 

junctions of interest for all six design storms. Table 6.11-3 summarizes the 

simulated peak flows at the Alafia River outfall and at outfalls of a number of 

selected tributaries in the Alafia River Main Stem Subwatershed and Lower North 

Prong Alafia River Subwatershed. 

Table 6.11-3 

Alafia River Main Stem Subwatershed Peak Flows at Selected Locations 

Location 

Alafia River Outfall at 

Hillsborough Bay 

(9700030) 

Alafia River at Buckhorn 

Creek (9702400) 

Alafia River at Lithia- 

Pinecrest Road Bridge 

(9706100) 

Alafia River at Turkey 

Creek (9707000) 

Alafia River at S.R. 39 

Bridge (9709100) 


at Confluence (9780000) 

Rice Creek at McMullen 

Loop Road Bridge 

(9719105) 

Alafia River Tributary 

(9704202) 


(9705604) 


(9706501) 


(9707905) 

2.33-year 

(cfs) 

5-year 

(cfs) 

10-year 

(cfs) 

25-year 

(cfs) 

50-year 

(cfs) 

100-year 

(cfs) 

4938 6354 8509 11493 14127 16508 

4890 6490 8591 11664 14312 16705 

5014 7008 9202 12574 15208 17584 

5210 7344 9705 13434 16423 19331 

5503 7726 10324 14227 17520 20497 

4676 6513 8463 11663 13804 16097 

787 978 1264 1440 1875 2116 

34 49 71 84 116 137 

70 131 193 260 574 912 

49 67 113 150 275 358 

268 344 522 673 1085 1288 





Table 6.11-4 shows the level of service at 298 locations in the Alafia River Main 

Stem Subwatershed. Figure 6.11-2 shows the LOS by subbasin as required by 

County standards. The level-of-service matrix provides a useful means to identify 

flooding problem locations. The flood severity ratings are especially beneficial to 

the decision making process in watershed best management practices. 

The level-of-service matrix in general indicates a good correlation between the 

flooding complained records and the hydrologic/hydraulic model results. Overall, 

the model simulations captured the predominant features of the hydrologic 

characteristics of the subwatershed. 

Hillsborough County has adopted Level of Service B for the 25-year, 24-hour 

design-storm event in this watershed. There are 55 locations listed in Table 6.11-4 

that are indicated to not meet this target. 47 of these locations within the Alafia 

River Main Stem Subwatershed received a D or D* rating subject to the 25-year 

design storm. There are 8 LOS violations identified at private or dirt roads. A 

portion of the remainder are road-flooding and structure-flooding problems on 

Donnelly Road, Squirrel Run Way, Coconut Cove Place, Rose Street, Pine Street, 

Greenhills Drive, Stearns Road, Cummins Road, and Whitlock Place. 

A detailed discussion of the problem areas that were identified as primary drainage 



LEGEND 


TABLE 6.11-4 


ALAFIA RIVER MAIN CHANNEL SUBWATERSHED EXISTING CONDITIONS LEVELS OF SERVICE ANALYSIS 




23-30-19 HOUSE NEAR ANNA AVE PRIVATE 700090 0.0 7.4 7.25 7.40 7.57 7.67 7.85 7.92 A A D* D* D* D* 

8-30-20 HACKNEY DR. PRIVATE 701353 0.0 39.5 39.16 39.30 39.45 39.53 39.67 39.73 A A A D* D* D* 

16-30-20 NEAR STONER RD. PRIVATE 701800 0.0 4.3 3.05 3.85 4.95 6.39 7.49 8.39 A A D* D* D* D* 

15-30-20 REVELS RD. PRIVATE 703200 0.0 12.4 7.33 9.32 11.13 13.23 14.78 16.01 A A A D* D* D* 

17-30-21 HOUSE NEAR SPRING RD PRIVATE 705230 26.1 25.3 24.32 24.39 24.64 25.86 27.69 28.94 A A A D* D D 

5-30-21 HOUSE NEAR PEARSON RD PRIVATE 705723 0.0 40.7 42.00 42.58 43.37 43.99 44.72 44.78 D* D* D* D* D* D* 

5-30-21 DIRT RD. PRIVATE 705780 0.0 38.6 38.15 38.53 38.62 40.02 42.95 43.09 A A D* D* D* D* 

23-30-19 LULA ST PUBLIC 700027 4.0 4.1 4.10 4.12 4.15 4.16 4.19 4.21 A D* D* D* D* D* 

17-30-20 PALMETTO ST PUBLIC 701350 14.6 4.0 2.30 2.84 3.65 4.75 5.62 6.36 A A A D* D* D* 



10-30-20 S KINGS AVE PUBLIC 702625 24.8 25.0 23.65 24.42 24.89 25.01 25.16 25.22 A A A D* D* D* 

10-30-20 CENTER AVE PUBLIC 702650 9.9 7.6 5.41 6.88 8.47 10.36 11.73 12.83 A A D* D* D D 

17-30-21 WILLIAMS BLVD PUBLIC 705220 24.8 24.2 23.84 24.00 24.37 25.79 27.50 28.81 A A D* D* D D 

5-30-21 LITTLE RD PUBLIC 705729 43.6 38.7 39.75 40.65 42.02 42.75 44.01 44.59 D* D* D* D* D* D* 

32-29-21 RACHEL CT PUBLIC 705732 94.5 93.2 92.86 94.31 94.77 94.94 95.35 95.53 A D* D* D* D* D 

32-29-21 SHERBROOK DR PUBLIC 705732 94.3 93.2 92.86 94.31 94.77 94.94 95.35 95.53 A D* D* D* D D 

32-29-21 S MULRENNAN RD PUBLIC 705733 93.5 92.5 90.89 92.10 93.54 93.89 94.78 95.05 A A D* D* D D 

31-29-21 DURANT RD PUBLIC 705775 91.0 90.8 89.60 90.04 90.89 91.08 91.17 91.21 A A D* D* D* D* 

5-30-21 BLOOMINGDALE AVE PUBLIC 705780 42.6 39.0 38.15 38.53 38.62 40.02 42.95 43.09 A A A D* D* D* 

5-30-21 STEARNS RD PUBLIC 705780 42.6 39.7 38.15 38.53 38.62 40.02 42.95 43.09 A A A D* D* D* 

33-30-20 BALM RIVERVIEW RD PUBLIC 710100 73.3 73.0 72.57 72.92 73.32 73.41 73.50 73.54 A A D* D* D* D* 

16-30-21 SQUIRREL RUN WAY PRIVATE 705900 17.4 18.1 22.12 23.74 25.32 27.26 28.71 29.92 D D D D D D 

17-30-20 PARKWAY CIR PUBLIC 701400 3.1 4.1 2.44 3.03 3.88 5.04 5.95 6.71 A A C D D D 

16-30-20 CUMMINS RD PUBLIC 702010 21.1 25.0 21.55 21.74 21.97 22.10 22.38 22.53 B C C D D D 

9-30-20 WATSON RD PUBLIC 702249 29.2 34.7 28.70 29.64 30.88 31.65 32.78 33.22 A B D D D D 

10-30-20 SOUTHVIEW DR PUBLIC 702625 22.1 24.2 23.65 24.42 24.89 25.01 25.16 25.22 D D D D D D 

10-30-20 SOUTHVIEW DR PUBLIC 702640 23.3 25.4 23.99 24.79 25.17 25.30 25.50 25.59 C D D D D D 

10-30-20 ALAFIA BLVD PUBLIC 702650 8.1 7.6 5.41 6.88 8.47 10.36 11.73 12.83 A A D* D D D 

15-30-20 ALAFIA RIDGE RD PUBLIC 702810 8.6 8.9 8.74 8.89 9.10 10.58 12.02 13.18 A B D* D D D 

10-30-20 ALAFIA BLVD PUBLIC 702950 10.0 7.3 6.43 8.15 9.77 11.71 13.17 14.34 A D* D* D D D 

14-30-20 RAMBLING RIVER RD PUBLIC 703500 9.3 9.0 8.17 10.19 12.06 14.16 15.70 16.92 A D* D D D D 

14-30-20 RAMBLING RIVER RD PUBLIC 703550 9.0 9.3 8.28 10.30 12.15 14.26 15.79 17.01 A D D D D D 

17-30-21 DONNELLY RD PUBLIC 705400 20.1 19.3 20.25 22.10 23.93 26.12 27.73 29.01 D* D D D D D 

17-30-21 SPRING RD PUBLIC 705500 19.0 19.9 20.72 22.64 24.43 26.48 28.00 29.25 D D D D D D 

17-30-21 PINE ST PUBLIC 705600 20.0 18.9 21.05 22.88 24.61 26.63 28.13 29.38 D D D D D D 

17-30-21 WILLIAMS BLVD PUBLIC 705606 24.5 24.5 24.59 24.73 24.85 26.62 28.08 29.31 D* D* D* D D D 

5-30-21 PEARSON RD PUBLIC 705723 42.3 40.7 42.00 42.58 43.37 43.99 44.72 44.78 D* D* D D D D 

32-29-21 RAVENNA DR PUBLIC 705732 91.7 93.2 92.86 94.31 94.77 94.94 95.35 95.53 D D D D D D 

6-30-21 GREENHILLS DR PUBLIC 705752 53.7 58.1 49.73 52.32 56.11 57.69 58.23 58.75 A A D D D D 

6-30-21 ARBORWOOD DR PUBLIC 705760 54.8 57.3 54.16 55.33 56.66 57.30 58.24 58.77 A C D D D D 

6-30-21 BRIMHOLLOW DR PUBLIC 705788 58.4 61.2 57.08 58.54 60.08 60.12 60.17 60.22 A A D D D D 

17-30-21 ROSE ST PUBLIC 705795 22.1 21.4 21.55 23.23 24.86 26.83 28.31 29.54 D* D D D D D 

32-29-21 CHEROKEE TRL PUBLIC 705814 81.6 84.2 83.03 83.78 83.86 83.91 84.04 84.09 D D D D D D 

16-30-21 COCONUT COVE PL PUBLIC 706000 16.6 0.0 22.32 23.92 25.49 27.42 28.87 30.07 D D D D D D 

16-30-21 LITHIA PINECREST RD PUBLIC 706140 25.6 29.4 23.82 24.80 26.35 28.20 29.56 30.70 A A C D D D 

33-29-21 WHITLOCK PL PUBLIC 706850 47.6 47.6 48.18 49.57 50.93 51.66 52.87 53.38 D* D D D D D 

17-30-20 HANNAWAY DR PUBLIC 701935 25.0 26.4 25.10 25.16 25.22 25.26 25.34 25.38 A A A B B B 

8-30-20 PROVIDENCE RD PUBLIC 702220 20.5 27.5 20.40 20.66 20.92 21.14 21.54 21.71 A A B C D D 

9-30-20 WATSON RD PUBLIC 702242 20.3 21.6 20.74 20.84 20.99 21.20 21.59 21.77 B C C C D D 

23-30-20 CARR RD PUBLIC 703710 17.5 23.5 17.00 17.82 18.21 18.44 18.82 18.98 A B C C D D 

17-30-21 ADELAIDE AVE PUBLIC 705692 27.5 0.0 27.59 27.68 28.10 28.46 28.98 29.22 A A C C D D 

6-30-21 BUCKNELL DR PUBLIC 705770 62.3 63.3 59.49 61.06 62.66 62.91 63.51 63.79 A A B C D D 

14-30-21 THOMPSON RD PUBLIC 707925 50.1 58.0 48.23 49.42 50.45 50.68 51.10 51.32 A A B C D D 

26-30-21 DORMAN RD PUBLIC 707993 105.3 106.5 105.04 105.38 105.61 105.83 106.04 106.14 A A B C C C 

13-30-21 THOMPSON RD PUBLIC 708810 47.4 49.5 46.95 47.84 48.07 48.35 48.52 48.68 A B C C D D 

17-30-20 RIVERVIEW DR PUBLIC 701374 12.8 14.1 12.47 12.91 13.00 13.05 13.14 13.18 A A A B B B 

20-30-20 BALM RIVERVIEW RD PUBLIC 701408 17.7 21.2 17.77 17.83 17.98 18.06 18.17 18.22 A A B B B C 

20-30-20 BOYETTE RD PUBLIC 701422 39.1 43.2 39.17 39.23 39.31 39.36 39.43 39.46 A A A B B B 

21-30-20 MCMULLEN LOOP PUBLIC 701710 6.7 7.6 6.92 6.99 7.09 7.14 7.39 7.83 A B B B C D 

22-30-20 GLENOX LN PUBLIC 702050 66.9 67.9 66.21 66.82 67.10 67.18 67.30 67.34 A A A B B B 

22-30-20 MCMULLEN LOOP PUBLIC 702051 56.1 0.0 56.23 56.31 56.38 56.41 56.48 56.53 A A B B B B 

15-30-20 ALAFIA RIDGE LOOP PUBLIC 702827 16.8 17.4 15.66 16.85 16.99 17.09 17.25 17.36 A A A B B C 

24-30-20 BOYETTE RD PUBLIC 704135 65.9 67.1 66.08 66.14 66.22 66.28 66.40 66.45 A A B B C C 

7-30-21 CULBREATH RD PUBLIC 705670 53.2 0.0 52.70 53.28 53.53 53.64 53.82 53.90 A A B B C C 

7-30-21 LITHIA PINECREST RD PUBLIC 705680 47.2 48.0 45.82 46.15 46.90 47.45 47.89 48.02 A A A B C D*

LEGEND 


TABLE 6.11-4 






13-30-21 THOMPSON RD PUBLIC 708515 56.0 0.0 54.65 56.04 56.16 56.28 56.35 56.41 A A A B B B 

18-30-22 THOMPSON RD PUBLIC 708875 57.4 70.3 51.44 53.49 55.48 57.65 57.88 58.03 A A A B B C 

28-30-20 BALM RIVERVIEW RD PUBLIC 710083 47.0 48.0 45.85 47.04 47.20 47.26 47.36 47.41 A A A B B B 

27-30-19 HOUSE NEAR NUNDY AVE PRIVATE 700003 0.0 5.8 2.86 2.98 3.58 3.84 4.28 4.49 A A A A A A 

27-30-19 HOUSE NEAR LULA ST PRIVATE 700003 0.0 5.5 2.86 2.98 3.58 3.84 4.28 4.49 A A A A A A 

26-30-19 HOUSE NEAR LULA ST PRIVATE 700010 0.0 5.5 2.34 2.89 3.80 4.18 4.31 4.36 A A A A A A 

26-30-19 HOUSE NEAR S US HIGHWAY 41 PRIVATE 700018 0.0 7.7 4.78 5.19 5.70 6.05 6.65 6.88 A A A A A A 

23-30-19 ALAFIA VISTA DR PRIVATE 700100 0.0 4.1 1.17 1.22 1.32 1.50 1.69 1.89 A A A A A A 

26-30-19 HOUSE NEAR NUNDY AVE PRIVATE 700120 0.0 11.3 9.29 9.53 9.82 9.87 9.93 9.95 A A A A A A 

26-30-19 HOUSE NEAR ROOSEVELT ST PRIVATE 700120 0.0 11.3 9.29 9.53 9.82 9.87 9.93 9.95 A A A A A A 

23-30-19 HOUSE NEAR RIVERVIEW DR PRIVATE 700190 0.0 11.5 10.42 10.69 11.06 11.21 11.46 11.57 A A A A A D* 


19-30-20 KENDA DR. PRIVATE 701140 0.0 29.1 25.98 26.29 26.81 27.18 27.93 28.29 A A A A A A 

17-30-20 HOUSE NEAR RIVERVIEW DR PRIVATE 701380 0.0 19.1 2.36 2.93 3.76 4.89 5.78 6.54 A A A A A A 

17-30-20 ELLIOT ST PRIVATE 701400 0.0 11.6 2.44 3.03 3.88 5.04 5.95 6.71 A A A A A A 

16-30-20 CHURCH DR PRIVATE 701915 0.0 17.1 13.53 13.97 14.22 14.30 14.44 14.61 A A A A A A 

9-30-20 HOUSE NEAR ALAFIA DR PRIVATE 702204 0.0 10.0 6.80 6.94 7.32 8.17 9.40 10.41 A A A A A D* 

9-30-20 HOUSE NEAR MATHERS LN PRIVATE 702208 0.0 15.5 10.37 11.83 12.34 12.55 12.92 13.07 A A A A A A 

8-30-20 ST. ROSE CR. PRIVATE 702233 0.0 42.1 39.11 39.45 39.94 40.26 41.06 41.51 A A A A A A 

14-30-20 HICKORY CREEK DR. PRIVATE 703225 0.0 60.1 56.91 57.48 57.81 58.10 58.39 58.49 A A A A A A 

23-30-20 STRUCTURE D/S BOYETTE RD BOX CULVERT PRIVATE 703737 0.0 55.1 49.73 50.07 50.35 50.64 51.34 51.70 A A A A A A 

24-30-20 MYRTLE RD PRIVATE 704200 0.0 24.1 13.75 15.73 17.63 19.86 21.52 22.84 A A A A A A 

13-30-20 RIVER OVCERLOOK DR. PRIVATE 704605 0.0 45.8 36.72 37.55 38.78 39.22 39.47 39.55 A A A A A A 

18-30-21 POND OUTFALL @ BLOOMINGDALE CC PRIVATE 704700 0.0 37.1 18.33 20.35 22.26 24.48 26.12 27.44 A A A A A A 

18-30-21 HOUSE NEAR PORTOBELLO CIR PRIVATE 705173 0.0 46.7 42.65 42.86 43.24 43.55 44.07 44.31 A A A A A A 

8-30-21 DIRT RD. PRIVATE 705630 0.0 38.1 26.60 27.23 28.38 28.77 29.19 29.35 A A A A A A 

7-30-21 HOUSE NEAR STEARNS RD PRIVATE 705660 0.0 44.8 43.70 43.87 44.19 44.39 44.67 44.78 A A A A A A 

7-30-21 STEARNS RD. PRIVATE 705661 0.0 50.5 48.12 48.60 49.90 50.14 50.16 50.18 A A A A A A 

8-30-21 DIRT RD. PRIVATE 705721 0 45.6 42.42 42.82 43.16 43.19 43.33 43.40 A A A A A A 

5-30-21 HOUSE NEAR BOB EVANS DR PRIVATE 705727 0.0 83.3 79.58 79.86 80.26 80.46 80.76 80.89 A A A A A A 

21-30-21 LITHIA WATER TREATMENT PLANT PRIVATE 706404 0.0 81.1 73.57 73.67 73.81 73.90 74.05 74.12 A A A A A A 

33-29-21 MARTIN RD. PRIVATE 706849 0.0 54.1 51.61 51.83 52.18 52.39 52.77 52.94 A A A A A A 

19-30-22 HOUSE OFF C.R. 39 PRIVATE 708880 0.0 78.1 67.54 67.88 68.17 68.57 68.79 69.00 A A A A A A 

20-30-20 HOUSE NEAR OAK FOREST DR PRIVATE 710070 0.0 28.0 21.98 22.66 24.02 24.70 26.34 27.47 A A A A A A 

28-30-20 HOUSE NEAR MOSS ISLAND DR PRIVATE 710081 0.0 42.6 39.24 40.01 41.19 41.88 42.75 43.06 A A A A D* D* 

20-30-20 HOUSE NEAR RICE CREEK PRIVATE 719108 0.0 16.1 10.58 11.45 12.46 12.94 13.96 14.42 A A A A A A 

20-30-20 SHADY OAKS CR. PRIVATE 719114 0.0 29.1 17.36 18.08 19.18 19.79 21.57 22.52 A A A A A A 

29-30-20 SAINT JOHNS DR PRIVATE 719115 32.7 33.1 24.00 24.40 25.22 25.55 26.97 27.96 A A A A A A 

26-30-19 NUNDY AVE PUBLIC 700020 7.8 7.8 6.84 7.12 7.48 7.72 8.01 8.12 A A A A D* D* 

23-30-19 S US HIGHWAY 41 PUBLIC 700050 9.6 0.0 1.16 1.20 1.29 1.45 1.62 1.80 A A A A A A 

23-30-19 RIVERVIEW DR PUBLIC 700062 5.4 8.0 1.82 2.19 2.79 3.22 3.99 4.32 A A A A A A 

23-30-19 ETHEL ST PUBLIC 700100 9.0 7.0 1.17 1.22 1.32 1.50 1.69 1.89 A A A A A A 

23-30-19 ANNA AVE PUBLIC 700102 10.7 10.7 1.74 2.21 2.91 3.31 5.01 6.11 A A A A A A 

26-30-19 GIBSONTON DR PUBLIC 700105 9.0 7.1 5.81 6.23 6.76 7.08 7.43 7.65 A A A A D* D* 

24-30-19 MAGNOLIA ST PUBLIC 700350 4.5 5.6 1.26 1.36 1.56 1.88 2.19 2.48 A A A A A A 

24-30-19 GORDON DR PUBLIC 700350 3.6 3.6 1.26 1.36 1.56 1.88 2.19 2.48 A A A A A A 

24-30-19 RIVERLACHEN WAY PUBLIC 700370 12.0 13.4 8.33 8.56 8.88 9.03 9.37 9.54 A A A A A A 


14-30-19 S 78TH ST PUBLIC 700390 12.4 0.0 9.11 9.48 10.03 10.32 10.61 10.80 A A A A A A 

19-30-20 VAUGHN ST PUBLIC 700400 9.1 4.7 1.36 1.52 1.80 2.25 2.66 3.04 A A A A A A 

24-30-19 EAGLE WATCH DR PUBLIC 700400 9.5 9.5 1.36 1.52 1.80 2.25 2.66 3.04 A A A A A A 

19-30-20 RIVER COVE DR PUBLIC 700500 3.9 3.9 1.43 1.62 1.95 2.47 2.93 3.35 A A A A A A 

24-30-19 ALICE LN PUBLIC 700510 11.7 14.6 5.97 6.15 6.40 6.56 6.87 7.02 A A A A A A 

24-30-19 STILLWATERS LANDING DR PUBLIC 700526 20.1 21.3 17.22 17.34 17.53 17.66 17.94 18.08 A A A A A A 

18-30-20 FANTASIA PARK WAY PUBLIC 700555 23.5 24.0 21.12 21.28 21.50 21.66 21.96 22.12 A A A A A A 

19-30-20 ALICE LN PUBLIC 700600 6.1 4.9 1.50 1.72 2.10 2.68 3.19 3.64 A A A A A A 

19-30-20 OLD GIBSONTON DR PUBLIC 700651 23.1 0.0 21.07 21.17 21.33 21.71 22.91 23.17 A A A A A A 

19-30-20 I75 S-GIBSONTON RAMP PUBLIC 700658 25.7 0.0 24.68 25.05 25.48 25.71 25.77 25.80 A A A A A A 

18-30-20 FANTASIA PARK WAY PUBLIC 700766 24.6 25.6 12.76 13.10 13.43 13.63 14.07 14.35 A A A A A A 


19-30-20 GIBSONTON DR PUBLIC 700788 24.7 0.0 21.84 22.33 23.00 23.23 23.73 23.92 A A A A A A 

19-30-20 I75 N-GIBSONTON RAMP PUBLIC 700790 27.2 0.0 23.04 23.58 24.51 25.19 26.25 26.66 A A A A A A 


20-30-20 MATHOG RD PUBLIC 701108 11.6 12.1 6.15 6.71 7.81 8.61 10.29 11.17 A A A A A A 

20-30-20 GIBSONTON DR PUBLIC 701124 28.4 0.0 25.01 25.88 26.76 27.21 27.87 28.18 A A A A A A 

19-30-20 KENDA DR PUBLIC 701132 27.7 28.2 25.03 25.88 26.71 27.11 27.87 28.18 A A A A A B

LEGEND 


TABLE 6.11-4 







17-30-20 EMI ANN LN PUBLIC 701254 8.6 9.6 3.50 3.93 4.44 4.68 5.45 6.17 A A A A A A 

18-30-20 ALBYAR AVE PUBLIC 701281 22.9 21.0 20.03 20.15 20.33 20.52 20.91 21.08 A A A A A D* 


17-30-20 KRYCUL AVE PUBLIC 701289 20.4 21.1 16.10 16.37 16.62 16.78 17.29 17.72 A A A A A A 

17-30-20 TARA DR PUBLIC 701292 20.3 21.3 18.43 18.80 19.42 19.83 20.44 20.64 A A A A A B 

17-30-20 BALM RIVERVIEW RD PUBLIC 701403 17.6 16.2 13.04 13.23 13.51 14.00 14.65 14.91 A A A A A A 



21-30-20 SHALLOW CREEK LN PUBLIC 701720 20.4 23.1 16.83 19.32 20.59 20.64 20.95 21.06 A A A A C C 

21-30-20 WYDELLA ST PUBLIC 701729 61.0 62.7 58.78 59.47 60.07 60.25 60.53 60.64 A A A A A A 

22-30-20 MCMULLEN RD PUBLIC 701744 73.9 73.0 70.34 70.52 70.76 70.91 71.19 71.32 A A A A A A 


16-30-20 MAYS AVE PUBLIC 701860 10.3 10.7 9.45 10.08 10.39 10.42 10.48 10.51 A A A A A A 


17-30-20 PROVIDENCE RD PUBLIC 701925 20.2 21.1 18.08 18.74 19.49 19.81 20.31 20.41 A A A A A A 

15-30-20 VALRIE LN PUBLIC 702020 30.0 30.2 23.19 23.39 23.62 23.75 24.02 24.18 A A A A A A 

21-30-20 MCMULLEN LOOP PUBLIC 702030 45.1 47.1 41.05 41.71 43.37 44.31 45.44 45.58 A A A A B B 

22-30-20 MCMULLEN RD PUBLIC 702032 61.6 0.0 56.23 56.57 59.53 60.56 61.65 61.88 A A A A A B 

22-30-20 TIMBERHILL DR PUBLIC 702035 61.2 62.7 59.45 59.53 59.62 59.66 59.76 59.82 A A A A A A 

22-30-20 DONNEYMOOR DR PUBLIC 702035 61.4 0.0 59.45 59.53 59.62 59.66 59.76 59.82 A A A A A A 


22-30-20 TALL ELM CT PUBLIC 702045 64.1 65.1 62.27 62.65 63.14 63.35 63.67 63.75 A A A A A A 

9-30-20 CRESCENT LAKE DR PUBLIC 702212 16.6 19.1 14.60 16.11 16.75 16.83 17.00 17.07 A A A A B B 

9-30-20 CRESCENT LAKE DR PUBLIC 702214 21.1 21.6 19.26 19.44 19.65 19.74 19.91 19.99 A A A A A A 


8-30-20 PROVIDENCE RD PUBLIC 702248 25.1 0.0 24.39 24.47 24.58 24.64 24.76 24.81 A A A A A A 

10-30-20 COPPERTREE CIR PUBLIC 702605 15.0 11.8 7.59 8.24 8.85 10.16 11.54 12.66 A A A A A D* 

10-30-20 WESTFIELD DR & PINEGROVE DR PUBLIC 702615 21.5 22.5 19.71 20.04 20.42 21.25 22.28 22.67 A A A A C D 

10-30-20 S KINGS AVE PUBLIC 702630 24.8 25.8 23.64 24.06 24.52 24.76 24.94 24.96 A A A A A A 

15-30-20 ALAFIA RIDGE LOOP PUBLIC 702830 19.5 20.3 17.67 17.98 18.32 18.55 18.97 19.17 A A A A A A 

15-30-20 BASS OAK CT PUBLIC 703050 19.3 14.3 6.81 8.60 10.24 12.19 13.64 14.79 A A A A A D* 

10-30-20 EXCALIBUR CT PUBLIC 703062 26.5 30.8 23.09 23.32 23.68 23.90 24.33 24.53 A A A A A A 

14-30-20 JOHN MOORE RD PUBLIC 703210 20.5 27.2 14.20 14.92 15.84 16.30 17.38 18.02 A A A A A A 

14-30-20 HICKORY CREEK DR PUBLIC 703220 31.2 37.3 25.20 25.89 26.80 27.38 28.39 28.86 A A A A A A 


14-30-20 APACHE TRL PUBLIC 703510 16.0 15.6 11.14 11.18 12.06 14.16 15.70 16.92 A A A A D* D* 

14-30-20 TOMAHAWK TRL PUBLIC 703520 40.1 44.5 32.89 33.05 33.53 33.83 34.20 34.31 A A A A A A 

22-30-20 RIVERGLEN DR PUBLIC 703713 23.0 24.5 19.83 20.34 21.32 21.97 22.14 22.19 A A A A A A 

22-30-20 KELP LN PUBLIC 703730 67.1 68.1 65.51 66.24 66.86 67.00 67.20 67.27 A A A A A A 

22-30-20 RUNYON CR & SUNNYOAK DR PUBLIC 703730 67.1 68.1 65.51 66.24 66.86 67.00 67.20 67.27 A A A A A A 

22-30-20 GLENPOINTE DR PUBLIC 703730 70.5 73.2 65.51 66.24 66.86 67.00 67.20 67.27 A A A A A A 

22-30-20 SHADY FOREST DR PUBLIC 703735 73.6 75.4 73.04 73.13 73.21 73.27 73.36 73.39 A A A A A A 


22-30-20 TARRAGON DR PUBLIC 703760 73.6 75.2 69.29 70.09 70.78 71.00 71.34 71.50 A A A A A A 

22-30-20 WICKERWOOD DR PUBLIC 703775 73.6 75.2 69.32 70.13 70.98 71.44 72.44 72.93 A A A A A A 

22-30-20 WILDBROOK DR PUBLIC 703775 73.6 75.2 69.32 70.13 70.98 71.44 72.44 72.93 A A A A A A 

22-30-20 TARRAGON DR PUBLIC 703785 69.3 71.0 68.18 68.39 68.93 69.19 69.31 69.35 A A A A A A 

23-30-20 CULVER PL PUBLIC 703925 31.8 30.8 28.83 29.13 29.54 29.79 30.22 30.38 A A A A A A 



24-30-20 FISHHAWK BLVD PUBLIC 704160 52.5 0.0 43.51 46.87 50.50 52.34 52.81 52.88 A A A A B B 


24-30-20 MYRTLE RD PUBLIC 704215 42.4 43.1 39.32 39.59 39.90 40.22 41.60 42.48 A A A A A A 

13-30-20 EMERALD CREEK DR PUBLIC 704227 55.1 57.0 51.89 52.14 52.66 53.14 55.14 55.30 A A A A A A 

13-30-20 ROCKINGCHAIR DR PUBLIC 704250 65.7 67.1 64.37 64.69 65.20 65.54 65.91 66.01 A A A A A B 

13-30-20 PLEASANT PINE CT PUBLIC 704250 66.1 67.1 64.37 64.69 65.20 65.54 65.91 66.01 A A A A A A 

13-30-20 QUEENSBURY AVE PUBLIC 704476 65.5 66.8 63.09 63.84 65.20 65.47 65.84 66.01 A A A A B C 

13-30-20 MONTE LAKE DR PUBLIC 704476 66.3 66.8 63.09 63.84 65.20 65.47 65.84 66.01 A A A A A A 

13-30-20 LORNEWOOD DR PUBLIC 704480 66.3 67.6 64.73 65.15 65.33 65.47 65.85 66.02 A A A A A A 

13-30-20 RIVERFIELD CT PUBLIC 704605 44.3 43.1 36.72 37.55 38.78 39.22 39.47 39.55 A A A A A A 

18-30-21 OAK RIVER CIR PUBLIC 704710 34.6 35.6 26.93 27.82 28.43 28.84 29.60 29.89 A A A A A A 

18-30-21 RIVER CLOSE BLVD PUBLIC 704720 42.1 43.1 33.08 34.09 34.70 35.10 35.73 36.04 A A A A A A 

18-30-21 CULBREATH RD PUBLIC 704720 53.9 60.5 33.08 34.09 34.70 35.10 35.73 36.04 A A A A A A 

18-30-21 OAK RIVER CIR PUBLIC 704725 47.8 47.3 38.53 39.12 39.90 40.25 41.46 41.75 A A A A A A 

18-30-21 NATURES WAY BLVD PUBLIC 704740 48.9 54.3 44.59 45.68 47.74 48.56 49.30 49.51 A A A A B C

LEGEND 


TABLE 6.11-4 






13-30-20 NATURES WAY BLVD PUBLIC 704760 69.2 70.8 68.67 68.74 68.83 68.88 68.99 69.04 A A A A A A 

18-30-21 COMPASS OAKS DR PUBLIC 704904 30.1 31.1 26.51 27.13 28.05 28.61 28.85 28.94 A A A A A A 

18-30-21 PORTOBELLO CIR PUBLIC 705161 30.3 31.1 26.37 27.43 28.43 28.71 29.20 29.38 A A A A A A 

18-30-21 BROOKVILLE DR PUBLIC 705161 32.5 31.1 26.37 27.43 28.43 28.71 29.20 29.38 A A A A A A 

18-30-21 GROVEWAY DR PUBLIC 705167 43.0 44.1 40.47 40.95 42.92 42.98 43.08 43.13 A A A A A A 

18-30-21 CULBREATH COVE CT PUBLIC 705185 65.5 67.1 63.06 63.55 64.01 64.18 64.48 64.60 A A A A A A 

18-30-21 TEVALO DR PUBLIC 705235 40.5 40.3 37.66 38.43 39.09 39.74 40.56 40.64 A A A A D* D* 


8-30-21 LITHIA RIDGE BLVD PUBLIC 705630 30.1 0.0 26.60 27.23 28.38 28.77 29.19 29.35 A A A A A A 

8-30-21 COUNTRY CREEK LN PUBLIC 705635 31.6 33.4 27.03 27.37 28.38 28.77 29.19 29.35 A A A A A A 


7-30-21 COLD CREEK DR PUBLIC 705655 49.2 50.5 46.84 47.41 47.93 48.13 48.47 48.76 A A A A A A 

7-30-21 BLOOMINGDALE AVE PUBLIC 705656 56.6 57.6 50.48 51.48 52.54 52.98 53.58 53.85 A A A A A A 

7-30-21 TREELINE DR PUBLIC 705658 55.5 56.8 54.91 55.24 55.39 55.46 55.59 55.64 A A A A A A 

7-30-21 TREELINE DR PUBLIC 705658 56.0 57.8 54.91 55.24 55.39 55.46 55.59 55.64 A A A A A A 

7-30-21 BENT OAK ST PUBLIC 705670 55.6 56.1 52.70 53.28 53.53 53.64 53.82 53.90 A A A A A A 

7-30-21 WRENCREST CIR PUBLIC 705680 55.2 57.3 45.82 46.15 46.90 47.45 47.89 48.02 A A A A A A 

7-30-21 CENTENNIAL FALCON DR PUBLIC 705680 47.6 48.0 45.82 46.15 46.90 47.45 47.89 48.02 A A A A B D* 

7-30-21 ERINDALE DR PUBLIC 705682 50.6 52.0 49.32 50.02 50.69 50.80 50.94 50.99 A A A A B B 

8-30-21 REGAL RIVER RD PUBLIC 705700 54.3 54.9 51.26 51.36 51.44 51.49 51.55 51.58 A A A A A A 

8-30-21 MASON OAKS DR PUBLIC 705705 52.1 53.2 50.12 51.00 52.11 52.13 52.32 52.58 A A A A A B 

8-30-21 STEARNS PARK RD PUBLIC 705715 42.6 43.1 41.78 42.02 42.22 42.38 42.73 42.90 A A A A A B 

8-30-21 STEARNS RD PUBLIC 705715 46.5 43.1 41.78 42.02 42.22 42.38 42.73 42.90 A A A A A A 

8-30-21 PARRISH RIDGE LN PUBLIC 705717 42.9 39.1 37.29 37.29 37.29 38.02 39.56 40.06 A A A A D* D* 

9-30-21 RANCH RD PUBLIC 705719 39.9 39.0 30.00 30.06 30.45 30.85 33.83 34.84 A A A A A A 

9-30-21 SYLVAN OAKS DR PUBLIC 705719 36.5 39.0 30.00 30.06 30.45 30.85 33.83 34.84 A A A A A A 

9-30-21 SYLVAN OAKS DR PUBLIC 705719 41.0 39.0 30.00 30.06 30.45 30.85 33.83 34.84 A A A A A A 

8-30-21 STEARNS RD PUBLIC 705721 45.2 45.6 42.42 42.82 43.16 43.19 43.33 43.40 A A A A A A 

5-30-21 CINNAMON TRACE DR PUBLIC 705725 60.0 58.5 54.59 55.39 55.62 55.66 55.76 55.79 A A A A A A 

5-30-21 SPRINGDELL CIR PUBLIC 705734 64.1 64.6 60.27 63.14 63.23 63.32 63.50 63.58 A A A A A A 

5-30-21 DURANT WOODS ST PUBLIC 705736 79.8 79.6 73.70 75.01 76.67 77.64 79.34 79.95 A A A A A D* 

5-30-21 SUGARLOAF LN PUBLIC 705739 79.0 78.4 73.22 74.21 75.59 76.40 77.12 77.13 A A A A A A 

6-30-21 S MILLER RD PUBLIC 705745 55.9 57.6 50.98 51.88 54.19 55.52 56.31 56.66 A A A A B C 

6-30-21 BUCKHORN RUN DR PUBLIC 705748 61.6 62.6 60.03 60.17 60.37 60.52 60.81 60.95 A A A A A A 

6-30-21 DRAKES LANDING CT PUBLIC 705750 57.3 60.0 45.21 47.96 51.11 56.69 58.23 58.75 A A A A C D 

6-30-21 S MILLER RD PUBLIC 705754 57.1 58.1 53.11 53.93 56.66 57.28 58.23 58.76 A A A A D D 

6-30-21 BRIANHOLLY DR PUBLIC 705760 57.7 59.1 54.16 55.33 56.66 57.30 58.24 58.77 A A A A C D 

6-30-21 BERRYKNOLL PL PUBLIC 705773 64.9 66.0 61.12 63.48 63.86 64.00 64.47 64.73 A A A A A A 

31-29-21 S SAINT CLOUD AVE PUBLIC 705779 94.7 95.0 93.81 94.67 94.72 94.75 94.80 94.82 A A A A A A 

5-30-21 FALLING LEAVES DR PUBLIC 705784 51.8 52.9 46.91 48.65 49.70 49.80 50.20 50.37 A A A A A A 

5-30-21 FALLING LEAVES DR PUBLIC 705786 53.8 55.1 51.62 51.83 52.15 52.35 52.79 53.00 A A A A A A 

17-30-21 JESSI LN PUBLIC 705900 39.1 39.1 22.12 23.74 25.32 27.26 28.71 29.92 A A A A A A 

21-30-21 LITHIA SPRINGS RD PUBLIC 705912 50.5 50.1 43.50 43.93 45.07 45.87 48.04 49.02 A A A A A A 

16-30-21 LITHIA SPRINGS RD PUBLIC 706042 61.2 0.0 58.86 59.44 60.46 61.13 61.27 61.29 A A A A A A 

16-30-21 NEW RIVER HILLS PKY PUBLIC 706150 31.1 30.0 25.68 25.87 26.24 28.20 29.56 30.70 A A A A A D* 

17-30-21 LITTLE CROSSING RD PUBLIC 706166 29.5 33.4 26.21 26.42 26.70 27.09 28.06 29.28 A A A A A A 

8-30-21 CARENON LN PUBLIC 706168 32.6 34.0 27.85 28.05 28.39 28.61 29.02 29.28 A A A A A A 

8-30-21 LITHIA RIDGE BLVD PUBLIC 706170 35.6 36.7 29.94 30.51 31.46 32.12 33.38 33.98 A A A A A A 

9-30-21 CANTER CT PUBLIC 706176 47.8 48.8 37.74 38.04 38.74 39.29 40.42 40.92 A A A A A A 

9-30-21 GENTRICE DR PUBLIC 706176 46.4 47.1 37.74 38.04 38.74 39.29 40.42 40.92 A A A A A A 

9-30-21 GENTRICE DR PUBLIC 706178 48.7 49.8 45.42 45.57 45.82 46.01 46.47 46.73 A A A A A A 

9-30-21 SADDLE RIDGE ST PUBLIC 706178 49.8 49.8 45.42 45.57 45.82 46.01 46.47 46.73 A A A A A A 

9-30-21 NEW RIVER HILLS PKY PUBLIC 706183 39.8 42.1 30.66 30.85 31.18 31.36 32.09 32.25 A A A A A A 




9-30-21 SOUTH NINE DR PUBLIC 706410 36.1 37.5 29.75 30.22 30.52 30.74 32.10 32.81 A A A A A A 

15-30-21 PINE ROCKLANDS AVE PUBLIC 706506 56.0 58.1 53.44 54.22 55.11 55.61 56.62 56.77 A A A A C C 

22-30-21 AUDUBON MANOR BLVD PUBLIC 706508 75.1 76.1 70.23 70.85 71.80 72.44 73.56 73.97 A A A A A A 

22-30-21 AUDUBON MANOR BLVD PUBLIC 706512 75.6 77.1 64.39 64.86 65.48 65.85 66.50 66.80 A A A A A A 

22-30-21 FLATWOODS MANOR CIR PUBLIC 706516 86.4 86.6 84.93 85.04 85.20 85.30 85.62 85.84 A A A A A A 

22-30-21 FLATWOODS MANOR CIR PUBLIC 706520 85.1 86.1 81.10 81.53 82.14 82.57 83.64 84.17 A A A A A A 

23-30-21 HAMMOCK HILL AVE PUBLIC 706522 74.5 75.1 71.13 71.68 72.56 73.13 73.90 74.14 A A A A A A 

23-30-21 HAMMOCK HILL AVE PUBLIC 706522 86.6 86.6 71.13 71.68 72.56 73.13 73.90 74.14 A A A A A A 


9-30-21 SAND TRAP PL PUBLIC 706585 39.3 41.3 35.66 36.29 37.41 38.19 39.00 39.07 A A A A A A 

10-30-21 CORDGRASS DR PUBLIC 706620 33.0 0.0 31.82 32.36 32.58 32.78 32.98 32.99 A A A A A A

LEGEND 


TABLE 6.11-4 






10-30-21 BENT GRASS DR PUBLIC 706640 39.8 0.0 34.07 34.45 34.89 35.19 35.81 36.19 A A A A A A 

10-30-21 STONEBRIDGE TRL PUBLIC 706675 40.3 0.0 34.58 35.01 35.54 35.86 36.62 37.17 A A A A A A 

4-30-21 SMOKE HICKORY LN PUBLIC 706690 38.7 40.5 35.21 35.76 36.54 37.08 38.03 38.38 A A A A A A 



3-30-21 LEWIS RD PUBLIC 706795 52.5 40.5 35.91 36.42 37.17 37.67 38.46 38.59 A A A A A A 

4-30-21 LAKE MICHAELA BLVD PUBLIC 706798 41.1 43.5 36.02 36.60 37.49 38.16 39.56 40.14 A A A A A A 

4-30-21 BEAVER POND TRL PUBLIC 706798 40.8 43.5 36.02 36.60 37.49 38.16 39.56 40.14 A A A A A A 


33-29-21 MARTIN RD PUBLIC 706850 54.9 55.2 48.18 49.57 50.93 51.66 52.87 53.38 A A A A A A 






18-30-22 S COUNTY ROAD 39 PUBLIC 709150 44.0 0.0 39.66 40.67 41.75 43.25 44.38 45.37 A A A A B D 

21-30-20 MCMULLEN LOOP PUBLIC 710015 6.6 11.8 3.55 4.08 4.91 5.87 6.90 7.74 A A A A B D 

21-30-20 MARY ROBIN DR PUBLIC 710019 61.7 62.6 59.93 60.52 61.40 61.92 62.46 62.66 A A A A C D* 



33-30-20 SYMMES RD PUBLIC 710125 67.6 67.5 65.25 65.71 66.37 66.80 67.64 67.83 A A A A D* D* 


28-30-20 BALM RIVERVIEW RD PUBLIC 716015 50.9 52.0 47.88 48.83 50.51 51.07 51.36 51.45 A A A A B C 


27-30-20 TUCKER RD PUBLIC 716130 73.3 73.9 70.17 70.46 70.90 71.22 71.79 72.04 A A A A A A 

27-30-20 MCMULLEN RD PUBLIC 716215 72.8 73.8 71.57 71.99 72.49 72.72 72.97 73.05 A A A A A B 

27-30-20 SHADOW RUN BLVD PUBLIC 716225 73.7 76.3 72.70 73.04 73.45 73.70 73.95 74.04 A A A A B B 

34-30-20 BALM RIVERVIEW RD PUBLIC 718115 70.0 70.2 68.62 69.40 70.11 70.19 70.30 70.34 A A A A D* D* 



15-30-20 DEE CIR PUBLIC 702816 52.0 53.0 45.50 45.79 46.13 46.26 46.36 46.42 A A A A A A 

15-30-20 MCMULLEN LOOP PUBLIC 703655 26.7 50.8 24.90 24.98 25.11 25.21 25.40 25.49 A A A A A A 

27-30-20 HUCKLEBERRY CT & TARRAGON DR PUBLIC 730499 73.6 75.2 69.33 70.18 71.46 72.21 73.22 73.29 A A A A A A



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A 

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D/D* 

Polk Co. 

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Legend 

County Line 


Suite 120 






ALAFIA RIVER 


BELL CREEK 

BOYETTE RD 

Notes: 


ALAFIA RIVER 



1:60,000 

0 1,500 3,000 6,000 

Feet 

0 0.25 0.5 1 

Miles 

BOYETTE RD 

TURKEY CREEK 

Filename: 

Fig6_11_ 

2E.mxd 



Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 


39 

Figure: 6.11-2(E) - Existing Level of Service 









ALAFIA RIVER 

BOYETTE RD 


A 

B 

C 

D/D* 

Polk Co. 

O 

Legend 

County Line 





Suite 120 


GIBSONTON DR 

Notes: 

1:60,000 

0 1,500 3,000 6,000 

Feet 

0 0.25 0.5 1 

Miles 

RICE CREEK 

Filename: 

Fig6_11_ 

2W.mxd 

Map Date: 



N/A 

Prepared By: 

Yoav 

Rappaport 

Figure: 6.11-2(W) - Existing Level of Service 








6.12 Valrico Subwatershed 



In 2001, Parsons interviewed the Hillsborough County East and Central Service 

Units, the branches of the County that perform maintenance of the drainage system 

in the Valrico Subwatershed. These Units reported 4 locations that experience 


6.12-1. 














and Hurricane Frances floods. Hillsborough County compiled a cursory digital 

database of complaints. Complaint locations in the Valrico Subwatershed are listed 

in Table 6.12-1; locations are shown on Figure 6.12-1. Hillsborough County 

recorded four El Nino flood complaints in the Valrico Subwatershed. There were a 

total of 11 individual flooding complaint records within the Valrico Subwatershed. It 

can be seen from close examination of Table 6.12-1 that a number of these 

complaints were repetitive (i.e. same location). It is also noted that the County 

database does not include a description of the nature of the problem for those 

complaints that were reported during the February 1998 flooding event, thus limiting 

its interpretive usefulness. 




Table 6.12-1 

Valrico Subwatershed Reported Flooding Problems 

INFORMATION 

SOURCE 

MAP REFERENCE 

NUMBER 

LOCATION 

DESCRIPTION 


Central Service Unit 52 

East of Lithia Pinecrest Rd, north of Chickasaw Trail 

Yards Flooding-Sheet Flow From Depressional Area 




Complaints 


Complaints 

23 North of Silver Ln, West of Mulrennan Rd Poorly Drained 

24 Copper Canyon Blvd at Crest Top Trail Percolation Pond 

25 Southeast of Seaboard Coastline Railroad and Mulrennan Rd Proposed Pump Station 

329 Silver Lane Wants someone to look at flooded property. Believes Strawberry Ridge is pumping water off their trailer park. Future Project - Mulrennan Rd @ Silver 

Lane, currently on Master Priority Listing, unfunded. 

338 Strawberry Ridge Park's swimming pool is being raised out of the ground due to high groundwater levels in retention pond. Randy Stafford investigated and forwarded to 

the East Service Unit to video the pipes to see if… 

349 Valrico & SR 60 Retention pond behind McDonalds is flooding road. Bernardo Garcia, Bob Gordon and Ed Tapia analyzed the situation. They decided to temporarily 

turn off the… 

711 2205 Laurel Oak Drive\2205 Laurel Oak Dr\14714 16t No information available 

767 104 Jeffrey Dr No information available 

804 313 Benson St No information available 

1031 2108 Jelane Drive No information available 

1055 4212 Silver Lane No information available 

1056 4115 Silver Ln No information available 




2055 Valrico Forest Dr. Intersection underwater 

2065 N. Valrico Rd. Road underwater. 


804 

767 

WASHINGTON RD 

349 

1031 


Legend 


Service Unit 


January 1998 

December 1997 

County Line 



Roads 




Suite 120 




S VALRICO RD 

Serv_52 

Notes: 

2065 

60 

2055 

DURANT RD 

711 

S MILLER RD 


E LUMSDEN RD 

1:24,000 

0 600 1,200 2,400 

Feet 

0 0.125 0.25 0.5 

Miles 

Serv_23 

1056 1055 

338 

329 


Filename: 

Fig6_12_ 

1.mxd 

Serv_25 

Serv_24 

Map Date: 



N/A 

S DOVER RD 

Prepared By: 

Yoav 

Rappaport 









6.12.2 Design Storm Simulations 


hydrodynamic model of the Valrico Subwatershed. These simulations reflect 

existing conditions, defined as circa 2006 land use and drainage system conditions. 

Table 6.12-2 lists peak-flood elevations at junctions of interest as a function of 

recurrence interval. 






TABLE 6.12-2 


VALRICO SUBWATERSHED EXISTING CONDITIONS FLOOD ELEVATIONS SUMMARY 




222 Brentwood Hills 84.19 84.27 84.37 84.41 84.49 84.52 

706650 Benttree Estates Subdivision Pond 1 86.86 87.06 88.77 90.75 95.40 96.04 

706651 Valrico Pointe Development Retention Pond 4 91.86 92.03 93.32 94.80 97.62 98.42 

706652 Depression near S. St. Cloud Ave & Commonwealth Ave. 88.56 88.66 90.36 92.55 95.84 96.05 

706653 Saint Cloud Reserve Pond A 92.86 92.91 93.79 94.92 98.10 98.80 

706656 Valrico Grove Subdivision Southern Pond 89.86 90.13 91.79 93.63 96.12 97.01 

706860 Buckingham Palace/Indian Trails Pond 89.87 91.53 95.72 96.10 96.62 96.68 

706865 Lumsden Place Pond 87.00 87.01 89.02 92.03 94.57 95.75 

706870 St Cloud Landing Pond A and B 87.86 87.92 88.37 88.89 96.10 96.15 

706875 Brandon E Sub Pond 100.53 100.59 100.78 100.87 101.02 101.08 

706880 Meadow Woods Estates Pond 99.55 100.40 100.48 100.56 100.72 100.79 

759015 Valrico Forest Subdivision Pond 38.00 39.22 40.76 41.32 41.48 41.64 

759016 Valrico Forest Dr. Pond 48.12 48.18 48.62 49.13 50.58 51.49 

759017 Citrus Wood Retention Pond No. 1A and 1B OCS 58.92 58.92 58.92 58.92 58.92 58.92 

759018 Citrus Wood Retention Pond No. 1A and 1B 55.28 55.45 57.98 59.63 61.06 61.73 

759019 Citrus Wood Retention Pond No. 2 72.09 72.17 74.00 76.43 78.94 79.91 

759030 Camden Oaks Place Pond 46.64 47.76 50.25 51.40 51.93 51.95 

759058 Innergary Point Subdivision Pond No. 1 77.50 77.76 79.98 82.52 84.06 84.69 

759060 Innergary Point Subdivision Pond No. 2 81.71 81.91 83.58 85.52 87.33 88.12 

759112 Hermitage Hill Way Pond 50.61 51.22 51.26 51.31 51.39 51.41 

759122 Crosby Crossings Pond 1 & 2 OCS 50.59 55.24 56.01 56.20 57.06 57.20 

759124 Crosby Crossings Pond 1 & 2 55.04 55.64 56.01 56.21 57.08 57.22 

759130 Depression east of Crosby Crossings 50.19 50.19 54.20 55.60 56.31 56.70 

759200 NE Corner of SR60 and Oakhill Village Circle [flow N-S] 35.49 35.75 36.79 37.84 39.31 40.05 

759213 Kings Mill Tract A-1 Wetland 62.18 62.18 62.18 62.18 62.21 73.08 

759215 Kings Mill Tract A-1 Pond 10 64.33 66.14 68.66 70.15 73.04 73.84 

759227 Kings Mills Tract C-2, D & E Pond 40 60.24 61.16 62.64 63.59 65.56 66.49 

759300 East Brandon Estates Pond 61.54 61.61 61.89 62.02 62.22 62.31 

759400 SE Feather Rock MHP Pond 35.20 36.57 36.78 37.83 39.31 40.05 

759512 NW Feather Rock MHP Pond 45.11 47.57 51.07 51.12 51.35 51.56 

759514 Valrico Vista MHP Pond 57.85 59.74 60.48 60.55 60.86 60.97 

759521 Brandon Brook - Phases II, III, IV & V Pond 41.13 41.29 41.65 41.87 42.26 42.44 

759522 Florida & 2nd St Retention Pond 35.11 35.11 35.11 35.69 41.21 42.33 

759523 Summer Gate Townhomes Retention Pond A 70.00 70.00 70.00 70.00 70.00 70.10 

759524 Home Depot Pond 72.06 73.82 75.25 75.95 77.50 78.31 

759527 Valrico Manor Basin #1 Pond 37.68 38.35 39.53 43.66 48.87 49.60 

759530 Brentwood Hills Pond 63.54 64.88 65.65 66.12 66.58 66.61 

759532 SR 60 & Mt. Carmel Rd Pond 57.00 57.00 57.52 58.73 63.79 65.00 

759534 Brentwood Hills Tract D/E, Unit 2 Retention Pond 67.48 69.05 69.98 70.61 70.90 70.96 

759540 RR ditch - closed basin 58.00 58.00 58.00 58.00 58.12 58.43 

759610 Valrico Manor Basin #2 Pond 46.97 48.42 50.60 50.88 51.00 51.14 

759615 Brentwood Hills Tract A Unit 1 Pond 80 82.00 83.20 84.53 84.56 84.69 84.80 

759630 Brentwood Hills Pond 50 Tract A Unit 2 69.22 70.67 71.67 72.25 73.27 73.30 

759705 Depression SW of S. Valrico Rd and Cricket Ln 69.99 69.99 71.19 73.51 73.89 73.94 

759710 Wexford Green Pond 57.28 58.03 61.50 66.83 71.55 72.37 

759711 Travis Robert Ave Pond 78.19 78.19 79.24 81.00 83.45 84.03 


759713 Valrico Pointe Development Retention Pond 2A and 2B 98.19 98.19 98.93 100.38 102.93 103.67 

759714 Dovewood Estates Pond 75.19 75.19 76.24 78.98 82.15 82.29 

759715 Fairway Ridge Addition Pond 81.21 82.38 85.78 86.85 88.83 89.09 

759716 Welington Pond 78.28 78.28 80.95 82.76 83.91 84.57 

759717 Westminster Subdivision Retention Pond 86.86 87.08 88.01 88.98 95.39 96.04 

759718 Buckhorn Trace Detention Pond 1 78.09 80.62 82.79 84.47 86.31 86.37 

759719 SE Corner of Durant Rd. & S Miller Rd Pond 89.33 90.91 94.40 95.40 95.74 95.76 

759720 Buckhorn Elementary School Pond 1 & 2 80.83 83.59 88.39 89.79 89.97 90.01 

759721 Saint Cloud Reserve Pond B 92.19 92.19 92.65 93.38 95.71 96.41 

759723 Buckhorn Trace Detention Pond 2 84.79 86.78 88.19 88.24 88.47 88.61 

759724 Windcrest Commons Retention Pond B 90.28 90.28 90.69 91.63 94.35 95.05 

759725 Development North of Windcrest Commons 92.59 92.74 94.80 96.67 97.99 98.59 

759726 Windcrest Commons Retention Pond C 95.28 95.28 95.31 95.55 96.60 97.39 

759728 Windcrest Commons Retention Pond A 98.09 98.09 98.09 98.13 98.45 98.71 

759730 Pond [SW Corner of S Valrico Rd and E Lumsden Rd] 70.19 76.06 76.74 77.08 77.19 77.27 

759731 Lumsden Pointe Pond "D" 73.32 73.33 73.45 73.57 73.94 74.16 

759732 Legends Pass Pond 73.28 73.52 75.50 77.32 78.93 79.71 

759734 Brandon Valrico Hills Estates Pond 75.74 76.36 76.74 77.08 77.19 77.29 

759736 Lumsden Pointe Pond "C" 68.04 68.10 68.61 69.22 70.98 72.37 

759737 Ridgeland Subdivion West Pond 97.19 97.90 101.67 103.06 104.91 105.59 

759746 Oakwood Terrace Townhomes Stormwater Areas A-D OCS 48.00 48.00 48.00 48.00 48.39 49.61 

759747 Oakwood Terrace Townhomes Stormwater Areas A-D 47.84 49.17 49.80 50.18 50.66 50.83

TABLE 6.12-2 


VALRICO SUBWATERSHED EXISTING CONDITIONS FLOOD ELEVATIONS SUMMARY 




759748 Depression in Valrico Staion 46.19 46.19 46.19 46.34 47.38 48.24 

759749 Rancho Viejo Pond 37.89 37.91 42.86 43.81 45.78 46.79 

759750 Copper Rideg Tract B1 Pond 39.53 41.47 42.86 43.81 45.78 46.79 

759751 Groundwater node for percolation at S. Mulrennan Rd 35.00 35.00 35.00 35.00 35.00 35.00 

759757 Bentree Subdivision Retention Area 70.86 71.28 73.05 74.89 77.17 78.03 

759760 Copper Ridge Tract B3 Pond 76.46 77.32 78.50 79.23 80.28 80.61 

759766 St. Cloud Manor Pond 87.00 87.24 89.85 92.31 93.33 93.34 

759767 Duncan Grove Parcel A Retention Pond 95.19 95.29 96.03 96.89 99.10 99.55 


759769 Valrico Grove Subdivision Pond 89.86 90.15 92.21 94.54 96.77 97.77 

759800 Valrico Elemantary School Pond 1 77.00 77.02 77.89 79.14 82.31 83.00 

759902 Kash N' Karry West Pond 33.69 34.54 36.00 36.33 37.02 37.36 

759910 SW Corner of SR60 and Oakhill Village MHP (d/s) [flowN-S] 34.84 36.57 37.27 37.84 39.42 40.44 

759912 Kash N' Karry East Pond 36.95 38.05 39.89 40.37 41.15 41.52 

759916 BonTerra Pond OCS 37.09 37.09 37.27 37.84 39.42 40.44 

759918 BonTerra Pond 35.26 35.66 36.69 37.63 40.00 40.52 

759920 Malak Forest Subdivions Pond 44.19 44.19 44.55 45.74 48.71 49.60 

759932 Buckhorn Oaks Subdivision Pond 74.00 74.21 76.54 79.11 81.39 82.15 

759935 St. Cloud Oaks Subdivions Pond 50.00 50.00 50.00 50.28 52.35 54.06 

759937 Valrico Elemantary School Pond 2 69.00 69.00 69.00 69.18 70.72 72.43 

759939 Ridgeland Subdivision East Pond 96.19 96.49 98.79 100.46 102.55 103.40 

759975 Strawberry Ridge Subdivision Pond 72.23 72.42 73.28 73.93 74.60 74.68 

759000 SW of SR60 and Miller Road 31.24 35.13 36.78 37.83 39.31 40.05 

759010 S Miller Rd (d/s) 33.38 35.13 36.78 37.83 39.31 40.05 

759011 Dummy junction for subsurface storage 29.00 29.00 29.00 29.00 29.00 29.00 

759050 Brandon-Valrico Hills Estates 59.05 59.16 59.30 59.37 59.49 59.55 

759100 Brandon Valrico Post Office 31.26 32.96 36.78 37.83 39.31 40.05 

759110 S Miller Rd (u/s) 34.90 35.29 36.79 37.84 39.31 40.05 

759120 Depression NW of Oakhill MHP 50.43 55.24 55.95 55.99 56.31 56.70 

759140 Depression 54.29 54.29 54.29 54.34 56.12 57.87 

759150 Depression 62.58 62.58 64.00 67.21 68.88 69.34 

759205 St. Cloud Ave (d/s) [flow E-W] 46.49 46.49 46.49 46.53 46.59 46.64 

759206 St. Cloud Ave (u/s) [flow E-W] 46.59 46.59 46.60 46.81 47.09 47.36 

759210 Seaboard Coast RR @ SR60 43.28 43.28 46.91 49.42 51.70 52.44 

759225 Depression W of St. Cloud Ave 54.48 54.48 55.81 57.96 59.16 59.50 

759230 Depression N & S of Viola Ln (W of Mulrennan Rd) 48.39 48.50 51.88 54.10 55.78 56.47 

759270 Depression N of Seaboard Coastline RR, West of St. Cloud Ave 61.69 61.69 61.69 61.70 63.02 64.49 

759510 Depression W of Feather Rock MHP \ S Valrico Rd (u/s) [east] 31.27 32.02 33.35 33.93 35.64 36.73 

759519 FDOT Pond 31.04 32.77 35.19 36.60 39.34 40.23 

759520 S Valrico Rd (d/s) [west] \ SR60 (d/s) [north] 31.27 32.19 34.16 34.11 35.64 36.73 

759528 Depression 58.41 59.44 62.23 62.80 64.06 64.49 

759699 Depression [SE of S Valrico Rd and Clifton Dr] 64.98 64.98 65.99 70.34 71.55 72.37 

759700 Depression [SW of S Valrico Rd and Clifton Dr] 64.18 64.18 67.02 68.52 71.55 72.37 

759740 W of S Valrico Rd on u/s Side of Durant Rd 78.28 82.47 83.22 83.25 83.31 83.35 

759755 69.09 69.09 69.11 69.77 72.02 72.59 

759765 Mulrennan Groves Pond 76.02 77.02 78.45 79.25 80.27 80.61 

759900 Miller Rd (u/s) S of SR 60 33.99 35.20 36.78 37.83 39.31 40.05 

759930 Depression NE of St. Cloud Oaks Sub 49.09 49.09 49.09 49.27 50.86 53.66 

759940 SE Corner of SR60 and St. Cloud Ave 45.40 45.90 46.22 46.47 48.39 49.61 

759960 SE Corner of SR60 and Seaboard Coastline RR 52.66 53.06 53.28 53.45 55.44 56.91 

759969 Mulrennan Rd (d/s) 70.06 70.17 70.19 70.23 70.69 70.91 

759970 Mulrennan Rd (u/s) 71.89 72.49 73.26 73.92 74.59 74.67 

759980 Mt. Taho MHP Pond 75.07 75.32 75.75 76.00 76.47 76.70





Valrico Subwatershed. Figure 6.12-2 shows the LOS by subbasin as required by 

County standards. Hillsborough County adopted Level of Service B for the 25-year, 

24-hour design-storm event. There are 8 locations listed that are indicated to not 

meet this target in the subwatershed. 





By comparison to Table 6.12-1, it can be assumed that most of the historical 

flooding complaint record sites not shown as a problem area in Table 6.12-3 are 

generally an indication of secondary system problems or possible maintenance 

problems. A detailed discussion of the problem areas that were identified as 

primary drainage system deficiencies is presented in the Turkey Creek Watershed 

portion of Chapter 13 of this report. 




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LEGEND 


TABLE 6.12-3 


VALRICO ALAFIA RIVER SUBWATERSHED EXISTING CONDITIONS LEVELS OF SERVICE ANALYSIS 




32-29-21 PALACE CT PUBLIC 706860 95.40 97.0 89.87 91.53 95.72 96.10 96.62 96.68 A A B C D D 

31-29-21 St. Cloud Ave S of E Lumsden Rd PUBLIC 706870 96.00 96.8 87.86 87.92 88.37 88.89 96.10 96.15 A A A A A A 

31-29-21 MISTY LANDING DR PUBLIC 706870 94.80 97.0 87.86 87.92 88.37 88.89 96.10 96.15 A A A A D D 

30-29-21 SR 60 W of S Miller Rd PUBLIC 759000 37.00 38.8 31.24 35.13 36.78 37.83 39.31 40.05 A A A C D D 

30-29-21 VALRICO FOREST DR PUBLIC 759015 41.80 41.9 38.00 39.22 40.76 41.32 41.48 41.64 A A A A A A 

30-29-21 INNERGARY PL PUBLIC 759050 59.90 60.8 59.05 59.16 59.30 59.37 59.49 59.55 A A A A A A 

19-29-21 N MILLER RD PUBLIC 759110 37.40 39.8 34.90 35.29 36.79 37.84 39.31 40.05 A A A B D D 

19-29-21 OAKHILL VILLAGE CIR PUBLIC 759120 55.80 56.5 50.43 55.24 55.95 55.99 56.31 56.70 A A A A C D* 

19-29-21 WASHINGTON RD PUBLIC 759140 68.10 69.0 54.29 54.29 54.29 54.34 56.12 57.87 A A A A A A 

19-29-21 HAMLIN CT PUBLIC 759150 73.20 72.4 62.58 62.58 64.00 67.21 68.88 69.34 A A A A A A 

19-29-21 N MILLER RD PUBLIC 759150 74.50 68.3 62.58 62.58 64.00 67.21 68.88 69.34 A A A A D* D* 

19-29-21 Mobile Home Park PRIVATE 759200 0.00 43.6 35.49 35.75 36.79 37.84 39.31 40.05 A A A A A A 

19-29-21 St. Cloud Ave N of SR 60 PUBLIC 759206 49.60 51.4 46.59 46.59 46.60 46.81 47.09 47.36 A A A A A A 

19-29-21 SKYWOOD DR PUBLIC 759210 60.00 58.1 43.28 43.28 46.91 49.42 51.70 52.44 A A A A A A 

19-29-21 St. Cloud Ave @ RR PUBLIC 759210 58.10 58.1 43.28 43.28 46.91 49.42 51.70 52.44 A A A A A A 


19-29-21 MARJO LN PUBLIC 759210 60.70 60.7 43.28 43.28 46.91 49.42 51.70 52.44 A A A A A A 

19-29-21 St. Cloud Ave N @ Washington Rd PUBLIC 759225 59.70 59.7 54.48 54.48 55.81 57.96 59.16 59.50 A A A A A A 

19-29-21 St. Cloud Ave N @ Viola Ln PUBLIC 759230 61.10 62.9 48.39 48.50 51.88 54.10 55.78 56.47 A A A A A A 

19-29-21 Miller Rd N of RR PRIVATE 759270 0.00 69.6 61.69 61.69 61.69 61.70 63.02 64.49 A A A A A A 

19-29-21 N MILLER RD PUBLIC 759270 72.20 70.0 61.69 61.69 61.69 61.70 63.02 64.49 A A A A A A 


24-29-20 S Valrico Rd N of SR60 PUBLIC 759520 34.00 45.0 31.27 32.19 34.16 34.11 35.64 36.73 A A A A D D 

24-29-20 S Valrico Rd N of SR60 PUBLIC 759510 0.00 34.5 31.27 32.02 33.35 33.93 35.64 36.73 A A A A D* D* 

24-29-20 SONOMA DR PUBLIC 759521 41.80 43.5 41.13 41.29 41.65 41.87 42.26 42.44 A A A A B C 

25-29-20 MORNINGSIDE DR PUBLIC 759528 65.50 66.5 58.41 59.44 62.23 62.80 64.06 64.49 A A A A A A 

25-29-20 S MOUNT CARMEL RD PUBLIC 759530 67.50 71.8 63.54 64.88 65.65 66.12 66.58 66.61 A A A A A A 

24-29-20 N MOUNT CARMEL RD PUBLIC 759540 72.00 0.0 58.00 58.00 58.00 58.00 58.12 58.43 A A A A A A 

31-29-21 S Valrico Rd S of E Lumsden Rd PUBLIC 759699 70.30 70.6 64.98 64.98 65.99 70.34 71.55 72.37 A A A A D D 

36-29-20 WEXFORD GREEN DR PUBLIC 759710 73.90 73.5 57.28 58.03 61.50 66.83 71.55 72.37 A A A A A A 

31-29-21 Durant Rd W of Miller Rd PUBLIC 759715 89.00 91.0 81.21 82.38 85.78 86.85 88.83 89.09 A A A A A A 

31-29-21 BUCKHORN SCHOOL CT PUBLIC 759718 86.20 87.7 78.09 80.62 82.79 84.47 86.31 86.37 A A A A A A 

31-29-21 DIANE AVE PUBLIC 759730 77.00 74.0 70.19 76.06 76.74 77.08 77.19 77.27 A D* D* D* D* D* 

30-29-21 E Lumsden Rd E of S Valrico Rd PUBLIC 759734 76.30 77.0 75.74 76.36 76.74 77.08 77.19 77.29 A A B D* D* D* 

36-29-20 Durant Rd W of S Valrico Rd PUBLIC 759740 83.20 84.2 78.28 82.47 83.22 83.25 83.31 83.35 A A A A A A 

29-29-21 CROWNED EAGLE CT PUBLIC 759749 47.00 50.5 37.89 37.91 42.86 43.81 45.78 46.79 A A A A A A 

29-29-21 E Lumsden Rd W of Mulrennan Rd PUBLIC 759750 42.30 44.7 39.53 41.47 42.86 43.81 45.78 46.79 A A C D D D 

29-29-21 GRAND CANYON DR PUBLIC 759750 58.20 56.0 39.53 41.47 42.86 43.81 45.78 46.79 A A A A A A 

29-29-21 GRAND CANYON DR PUBLIC 759760 79.50 83.0 76.46 77.32 78.50 79.23 80.28 80.61 A A A A C D 

30-29-21 S MILLER RD PUBLIC 759900 37.20 39.2 33.99 35.20 36.78 37.83 39.31 40.05 A A A C D D 


30-29-21 BON VIE PL PUBLIC 759918 43.80 44.8 35.26 35.66 36.69 37.63 40.00 40.52 A A A A A A 

30-29-21 SAINT ANTHONY DR PUBLIC 759930 57.50 54.0 49.09 49.09 49.09 49.27 50.86 53.66 A A A A A A 

30-29-21 St. Cloud Ave S of SR 60 PUBLIC 759940 49.60 51.4 45.40 45.90 46.22 46.47 48.39 49.61 A A A A A A 

29-29-21 RR s of SR 60 PUBLIC 759960 59.20 61.8 52.66 53.06 53.28 53.45 55.44 56.91 A A A A A A 

29-29-21 S MULRENNAN RD PUBLIC 759970 73.30 0.0 71.89 72.49 73.26 73.92 74.59 74.67 A A A C D D 

29-29-21 TAHO CIR PUBLIC 759980 73.80 75.0 75.07 75.32 75.75 76.00 76.47 76.70 D D D D D D



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WASHINGTON RD 


A 

B 

C 

D/D* 

Polk Co. 

O 

Legend 

County Line 





Suite 120 



Notes: 

S VALRICO RD 

60 

DURANT RD 

S MILLER RD 


E LUMSDEN RD 

1:24,000 

0 600 1,200 2,400 

Feet 

0 0.125 0.25 0.5 

Miles 


Filename: 

Fig6_12_ 

2.mxd 

Map Date: 



N/A 

S DOVER RD 

Prepared By: 

Yoav 

Rappaport 







. 

Chapter 13 

parsons

CHAPTER 13 

ALTERNATIVES ANALYSIS 


Chapter 13 – Alternatives Analysis 

The major objective of the original 2001 Alafia River Watershed Management Plan 

was to develop solutions to the problems identified in the previous sections of this 

report. During this update to the WMP, each of the flood control projects developed 

under the original study was re-evaluated based on the updated existing conditions 

model. The original projects were either updated (if the project was still viable), 

reconfigured (if project was not viable anymore) or removed from the Masterplan (if 

the project was either built or the flooding problem was addressed in some other 

way). This section provides a summary of the identified problems within each 

individual subwatershed and a discussion of proposed solutions and/or improvements 

with respect to flood control. For overall discussion purposes, this section provides all 

of the original “alternatives” or possible flood solutions to the identified problem areas. 

For projects that were still viable from the original 2001 WMP study, only the 

recommended alternative was updated. The other “non-recommended” alternatives 

are included again to reiterate the information so the reader does not have to refer to 

original report for this section. 

13.1 FLOOD CONTROL ALTERNATIVES ANALYSIS METHODOLOGY 

The flooding problems that were identified in Chapter 6 are divided into the following 

four types: (1) public meeting complaints, (2) historical flood complaints, (3) 

Hillsborough County Service Unit concerns, and (4) flooding level of service 

violations. 

♦ Public Meeting Complaints. Hillsborough County held open public meetings in 

October 2000, August 2001, and November 2001 during which the attendees were 

encouraged to voice any concerns and personal knowledge with respect to 

flooding problems and issues within the Alafia River Watershed. From these 

meetings, the information obtained from the County residents was used to compile 

a geographic dataset of recurrent flood problems. The dataset includes attributes 

of the flood problem, such as location, possible cause, date of occurrence, and 

duration of inundation. 

♦ Historical Flood Complaints. Hillsborough County was inundated by a series of 

severe storms in September and December 1997, and February 1998 and 

experienced heavy rainfall due to Hurricane Frances in September 2004. The 

1997-1998 storms are collectively referred to as the El Niño Storms. The 

Hillsborough County Public Works Department received numerous complaints of 

flooding from County residents and made preliminary efforts to investigate flood 

and drainage problems during the El Niño Storms. Unfortunately, the Department 

did not develop an extensive database of these complaints and in many cases 




recorded only the address of the caller and other minor information. The 

Hillsborough County Public Works Department received numerous complaints of 

flooding from County residents after Hurricane Frances and collected detailed 

backup information required to make meaningful, defensible correlation with the 

source of the problem. Both the El Niño and Hurricane Frances data are included 

in this document and identified as historical flood complaints. 

♦ Hillsborough County Service Unit Concerns. The Hillsborough County Public 

Works Road Maintenance Division is divided into four geographically defined 

Service Units that perform operation and maintenance tasks for County-owned 

public works infrastructure, such as roads, culverts, and ditches. Many drainage 

infrastructure problems are referred to Service Unit personnel to address 

deficiencies in the drainage system. These County staff are therefore some of the 

most knowledgeable of flooding problem areas in the County. Parsons staff 

conducted extensive interviews with Service Unit staff to obtain input as to known 

flooding problems in the Alafia River Watershed. The results of service unit 

interviews are referred to in this document as Hillsborough County Service Unit 

concerns. 

♦ As previously discussed in Chapter 6, the Stormwater Management Element of 

the Hillsborough County Comprehensive Plan defines a set of flooding levels of 

service (LOS) provided by a stormwater facility in terms of the frequency/duration 

(e.g., 10-year/24-hour) of the rainfall event that a particular facility can 

accommodate without causing floodwaters to rise above an acceptable level at 

that facility. The four flood level designations, A, B, C, and D, correspond to the 

following: 

• Level A – No significant street flooding 

• Level B – No major residential yard flooding 

• Level C – No significant structure flooding 

• Level D – No limitation on flooding 

The term “significant flooding” which is used in the County’s Comprehensive Plan is 

interpreted to refer to flooding which prohibits the use of a roadway by vehicles (i.e. 

nuisance and minor flooding are not to be included in the definitions of flooding). The 

LOS definition that has been adopted by the County for use within this analysis 

establishes the assigned LOS designation based primarily on the road crown 

elevation, and relates the existence of significant street, yard and/or structure flooding 

to the depth of flooding of the street. 

Numerical criteria were adopted as a means of providing measurable depth 

definitions of “significant flooding” for determining existing LOS in the original study 

and are being used in this update. Two new LOS designations, D* and O were added 

to provide greater problem definition in assessing existing LOS. 




It should be noted that the LOS designations were redefined in updates to the 

Hillsborough County Comprehensive Plan since the original study was performed and 

are as follows: 

• Level A - No significant street flooding. All lanes are drivable*. 

• Level B - Minor street flooding. At least one lane drivable* 

• Level C - Street flooding. Flooding depth above road crown is less than one 

foot. 

• Level D - No limitation on flooding 

*The term drivable defined as less than or equal to three (3) inches of water 

above the crown of the road. 

It is assumed that while the definition of Levels B and C in the current LOS have been 

revised, that the level of protection is still the same. Note that the current level-ofservice 

for Levels B and C have been included in parentheses in the following table. 

Flooding 

Level of 

Service 




Management Plan Definition 

A No significant street flooding Street flooding is less than 3” 


B 

C 

No major residential yard flooding 

(Minor street flooding. At least 

one lane drivable) 

No significant structure flooding 

(Level C - Street flooding. 

Flooding depth above road crown 

is less than one foot.) 


above the crown of road, but 

less than 6” 


above the crown of road, but 

less than 12” 

D No limitation on flooding Street flooding is more than 

12” above the crown of road 

D* No limitation on flooding* Flood elevation is greater than 

finished floor elevation, and 

street flooding is less than 12” 


O N/A No structure and no street to 

compare with flood elevation 

The goal of the County’s Watershed Management Planning program is to develop 

a capital improvement program to improve the flooding level of service for all 

watersheds from the adopted LOS to either the target or ultimate LOS. The 




Board of County Commissioners, in the Comprehensive Plan, promulgated the 

25-year/24-hour/B flooding level of service as the target level of service for all 

watersheds within the county. The ultimate LOS standards have not been 

determined for the major stormwater conveyance systems located outside of the 

areas for which completed watershed management plans currently exist. These 

standards are to be established via the Comprehensive Stormwater Management 

Master Planning Program, of which this study is a part. 

♦ Flooding Level of Service Violations. Hillsborough County's updated 

Stormwater Management Model -- developed for this plan -- is run with a series of 

hypothetical design storms. Model development and results are described in 

Chapters 5 and 6 of this plan. Public road crown elevations are estimated from 

Southwest Florida Water Management District topographic maps or design plans. 

Finished floor elevations are estimated from District maps as one foot above the 

lowest intersected topographic contour. Finished floor elevations are also 

collected from design plans. These control elevations are compared with flood 

elevations generated by the model for the 25-year/24-hour to determine the LOS 

provided. Those locations that do not attain the County’s target level of service (B 

LOS) are referenced in this document as flooding level of service violations. 

The model and this level-of-service analysis detail the primary drainage system, and 

portions of the secondary drainage system. Constituent complaints, more often than 

not, occur in the tertiary drainage system. The analysis does not identify cases of 

structural flooding on the tertiary drainage system, or some portions of the secondary 

drainage system. The primary drainage system includes the creek or river the 

subwatershed is named for and most secondary drainage systems. The secondary 

drainage systems include stormwater management ponds and small creeks that drain 

to the primary system. The tertiary drainage system drains to the secondary system. 

As noted, flooding problems have been previously identified, mapped, and tabulated 

in Chapter 6. Unless otherwise noted, all cited water-surface elevations and flood 

depths are the result of a 25-year storm with a hypothetical rainfall distribution and 24- 

hour duration. All elevations are in feet, referenced to the North American Vertical 

Datum of 1988 (NAVD 88). The methodology adopted for this study was to consider 

all flooding problems identified from the four sources of information and evaluate 

alternatives to resolve them. The list was screened at first to eliminate those 

problems that, by Hillsborough County policy, are not the responsibility of the County 

to address. For the most part, these types of flooding problems are those that occur 

solely within private property where the County has no jurisdiction nor County-owned 

stormwater facilities. Exceptions to this are where it may be considered in the 

County’s and general public’s interest to enter onto private land to provide flood relief 

not only there but also in adjacent public and private properties. 

During the screening process, many of the locations of historical flooding complaints 

were eliminated from further consideration since it could not be determined from the 




County records what defined the problem or where it occurred. Also, those 

complaints that could be considered maintenance problems were in some cases 

referred to a list of recommended maintenance activities (see Chapter 15). 

A number of flooding level of service problem areas were identified by modeling 

results for closed drainage basins. These occurrences were evaluated on an 

individual basis to determine whether alternative mitigative measures were warranted. 

The difficulty in these instances is that the model formulation for closed basins does 

not account for any percolation that occurs over the course of the simulation within 

these ponded areas. As many of these indicated problem areas are underlain by 

highly pervious (Type A) soils, model results can be unreliable. In general, only those 

areas for which there was correlating evidence of a flooding problem (i.e. historical 

flooding problems reported from the El Nino events in 1997 and 1998, historical 

flooding problems reported from Hurricane Frances, flooding complaints, or Service 

Unit reported problems) were considered as candidates for alternatives analyses. 

Discussions of the specific problems and alternatives are provided in the following 

subsection. 


13.2 FLOOD CONTROL ALTERNATIVES 

13.2.1 Buckhorn Creek Subwatershed 



As described in Chapter 6, the County’s adopted Ultimate Level of Service for the 

Buckhorn Creek Subwatershed is a minimum goal of Level B for the 10-year, 24-hour 

design storm event. There are 13 locations identified within the Buckhorn Creek 

Subwatershed where the County’s minimum acceptable level of service criteria are 

not met (See Table 6.4-4 and Figure 6.4-2). Of these 13 locations, 7 constitute a LOS 

deficiency for a Hillsborough County improved public roadway and 5 constitute a LOS 

Deficiency for structures near Hillsborough County public Roads. One of the 

locations, however, lies within closed basins and was disregarded for reasons 

described earlier in this chapter. Two of the locations were substantiated with 

flooding complaints and alternatives were proposed. 



identified based on input received during public meetings or from Hillsborough County 

Service Unit or historical flooding complaints databases (See Figure 6.4-1). These 

problem areas were investigated where there was sufficient information provided and 

alternative measures analyzed. In some cases, further detailed study is needed. In 

many instances, the problem was related to a maintenance issue and it was added to 

a list of recommended maintenance needs provided in Chapter 15. 

The following discussion details the flooding problems identified in the Buckhorn 

Creek Subwatershed, and provides a description of the proposed solutions and 

alternatives. 

Problem Areas BUCK-1 and BUCK-2: Barkfield St. and Huntington St. 

Problem Definition: 

The flooding problems that were identified by model results for Barkfield Street, 

Huntington Street, and Princeton Street were addressed simultaneously as a 

combination of alternatives that act in concert. Barkfield Street experiences chronic 

flooding up to 2.0 feet deep in the street for the 10-year, 24-hour design storm event 

due to inadequate outfall capacity. The street (low road elevation approximately 29.0 

ft NAVD) is served by an existing 27”x43” CMPA storm sewer outfall to the 

Tanglewood Ditch, west of Kings Avenue. The capacity of this storm sewer is 

constrained by the hydraulic inefficiency of the ditch, which is extremely flat, heavily 

vegetated, and silted. It is possible that the existing pipe is also of diminished 

capacity due to sediment deposition. The problems at this location were confirmed by 

local residents who attended the public meetings, and by flood complaint records and 

Hillsborough County Service Unit staff. Over recent years, house flooding was 

reported by these sources in several instances. 




Huntington Street and Princeton Street are flooded by the backwater conditions in 

Tributary D created by an inadequately sized downstream private drive crossing 

located just downstream (south) of the storm sewer system outfall and north of 

Ronele Drive. The existing culvert at this private drive is a 27”x43” CMPA, which 

creates a head loss of over 1.5 feet across this structure for the 10-year event. The 

backwater conditions created at this structure result in flooding conditions in 

Huntington Street and Princeton Street of approximately 0.9 feet. 

Buck-1 and Buck 2 Flooding Problem Area Location Map 

Barkfield Street on September 14, 2001 (during Tropical Storm Gabrielle) 




Sediment and vegetation blocking Tanglewood Ditch west of Kings Avenue at 

Barkfield Street storm sewer system outfall 

Alternative Solutions: 

Alternative 1: 

Description: This alternative addresses the flooding problems on Barkfield 

Street through the replacement of 240 LF of the existing storm sewer with a 

new 32”x49” ERCP storm sewer that connects to the Tanglewood Ditch. For 

this to achieve an acceptable level of service, it is also required that the 

Tanglewood Ditch be cleared of the sediment deposits and vegetative growth 

that has accumulated for a distance of 5750 feet from Kings Avenue to Viola 

Drive. This is necessary to achieve an acceptable hydraulic efficiency and 

must be part of a regular maintenance program to ensure a continued 

performance standard. 

Advantages: This alternative requires no additional easement or land 

purchase and utilizes the existing drainage system to the greatest extent. 

Disadvantages: In addition to the initial capital cost of this alternative, its 

effectiveness is directly dependent on the continued maintenance of the 

Tanglewood Ditch, which has not been proven a reliable function. There are 

no additional water quality or environmental benefits. Removal of vegetative 

growth in the ditch will, to a degree, result in loss of environmental habitat and 

stormwater treatment functions. This alternative does not address the 

identified problems on Huntington Street. Environmental permitting for ditch 

maintenance could become an issue. 




Effectiveness: The effectiveness of this alternative is a reduction in the 10- 

year and 25-year flood elevation on Barkfield Street and a 25-year flooding 

LOS B. Downstream flood elevations would not be impacted as long as 

continued maintenance is accomplished. 

Estimated Cost: The initial capital cost of this alternative is estimated at a 

third of the cost of Alternative 3 This figure does not include the cost of regular 

continued maintenance of the ditch. 


Description: This alternative addresses both the flooding problems on 

Barkfield Street and Huntington Street through the abandonment of the existing 

Barkfield Street storm sewer and rerouting of street drainage via 200 LF of new 

32”x49” ERCP storm sewer that connects southward to Huntington Lake. In 

addition, the existing 12” CMP lake outfall would be replaced by 550 LF of 

19”x30” ERCP and a modified FDOT Type D inlet control structure added to 

optimize the stormwater detention and treatment capacity of this lake. The 

control structure would have a 10-foot weir notch with a crest elevation of 25.5 

ft NAVD (existing outfall control elevation). Finally, the existing private road 

culvert on Channel D would be replaced by a 34”x53” ERCP to reduce the 

flood elevation at Huntington Street to an acceptable level of service. 

Existing Huntington Lake 12” CMP Outfall (no control structure) 




Private dirt road 27”x43” CMPA crossing of Tributary D downstream of 

Huntington Lake outfall 

Advantages: This alternative addresses both the Barkfield Street and 

Huntington Street flooding problem areas. By rerouting the Barkfield Street 

drainage to Huntington Lake, the stormwater runoff from the contributing 

drainage area would receive treatment that is not currently provided, thus 

providing water quality benefits. No extreme maintenance activities are 

required for the Tanglewood Ditch, thus retaining its environmental habitat 

intact. Environmental permitting for the improvements should not be difficult. 

Disadvantages: Drainage easements will be required for the construction and 

continued maintenance of the new stormwater conveyances, thus the 

cooperation of affected property owners will be necessary. Increases flood 

elevations in Tanglewood Ditch. 

Effectiveness: The effectiveness of this alternative is reduction of the 10-year 

and 25-year flood elevations on Barkfield Street and a 25-year flooding LOS A 

condition is attained. The flood elevations on Huntington Lake are slightly 

reduced for both the 10-year and 25-year storm events. For Tributary D, at the 

Huntington Street storm sewer system outfall, the 10-year and 25-year flood 

elevations are reduced and a 25-year LOS B condition is attained for 

Huntington Street. Due to the fact that in high flow events Tanglewood Ditch 

reverses flow and discharges into Barkfield, removal of this connection 

increases flood elevations in Tanglewood Ditch to an out of bank elevation. 




Estimated Cost: The capital cost of this alternative is estimated at $220,200. 

This figure includes the cost of drainage easement purchases to construct the 

new drainage conveyances. 


Description: This alternative is the same as Alternative 2 in all respects 

except that the existing 27”x43” CMPA Barkfield Street storm sewer is kept in 

service and the lake outfall is replaced with a 34”x53” ERCP. Private road 

culvert replacements are identical to Alternative 2. 

Advantages: This alternative addresses both the Barkfield Street and 

Huntington Street flooding problem areas. By rerouting the Barkfield Street 

drainage to Huntington Lake, the stormwater runoff from the contributing 

drainage area would receive treatment that is not currently provided, thus 

providing water quality benefits. No extreme maintenance activities are 

required for the Tanglewood Ditch, thus retaining its environmental habitat 

intact. Environmental permitting for the improvements should not be difficult. 

Disadvantages: Drainage easements will be required for the construction and 

continued maintenance of the new stormwater conveyances, thus the 

cooperation of affected property owners will be necessary. 

Effectiveness: The effectiveness of this alternative is to reduce the 10-year 

flood elevation on Barkfield Street from 30.2 ft NAVD to 28.8 ft NAVD. 

Additionally, the 25-year flood elevation is reduced from 30.4 ft NAVD to 29.3 ft 

NAVD, thus attaining a 10-year LOS A and 25-year LOS B condition with this 

alternative. The flood elevations on Huntington Lake are raised approximately 

0.1 feet for the 10-year and reduced approximately 0.3 ft for the 25-year storm 

event. For Tributary D, at the Huntington Street storm sewer system outfall, 

the 10-year flood elevation is reduced by 1.1 feet, and the 25-year is reduced 

by 0.8 feet. A 10-year and 25-year LOS A condition is attained for Huntington 

Street. By retaining the connection to the Tanglewood Ditch with this 

alternative, there is actually a reversal of flow direction from the ditch to 

Huntington Lake, which detracts from the effectiveness of the improvements, 

but does not raise flood elevations in the Tanglewood Ditch as in Alternative 2. 


This figure includes the cost of drainage easement purchases to construct the 

new drainage conveyances. 

Recommendation: Because of its greater effectiveness in achieving the desired 

flooding LOS objectives, better reliability, and more desirable water quality and 

environmental benefits, the recommended alternative for the Barkfield Street and 

Huntington Street problem areas is Alternative 3. 




Problem Area BUCK-3: Craft Road Ditch between Craft Rd. and Bryan Rd. 


Excessive flooding conditions along the Craft Road Ditch system from Craft Road to 

Bryan Road were identified in the 2001 WMP and substantiated by flood complaints. 

This same location was a designated problem in the County’s original 1988 master 

plan study of the Buckhorn Creek Subwatershed. In 2005, improvements were made 

to the Craft and Bryan Street culverts. The improvements made most closely 

resemble Alternative 1 (with the exception of the Bryan Road culvert replacement): 

Alternative 1 addresses the identified flooding problem areas with conveyance 

improvements to the Craft Road Ditch system from Craft Road upstream to 

Bryan Road. The existing Craft Road 24”x38” ERCP was replaced with a 

38”x60” ERCP, and the existing Bryan Road and private church road 27”x43” 

CMPA’s are also replaced with 38”x60” ERCP’s. In addition, the ditch 

downstream of Bryan Road is regraded and enlarged for a distance of 600 feet 

to achieve a greater hydraulic capacity in this channel segment and 

accommodate the larger culvert size. 

The 2009 WMP update reflects the Hillsborough County Craft Road Culvert 

Replacement project that closely approximates Alternative 1; therefore only 

Alternative 2 and Alternative 3 were considered in this analysis. Currently, the County 

road crossings and all structures meet the 10-year level of service criterion; however, 

the New Methodist Church of Brandon on Bryan Road and numerous homes in the 

Bryan Manor subdivision and north of the Craft Road Culverts would likely experience 

structural flooding during the 25-year storm event. 

Buck-3 Flooding Problem Area Location Map 




Church property downstream (west) of Bryan Road on Craft Road Ditch 

Existing Church Road 27”x43” CMPA 




Existing Craft Road 24”x38” ERCP on Craft Road Ditch 



Description: The County’s Craft Road Culvert Improvement Project addressed 

the identified flooding problem areas with conveyance improvements to the 

Craft Road Ditch system from Craft Road upstream to Bryan Road. The 

existing Craft Road 24”x38” ERCP was replaced with a 38”x60” ERCP, and the 

existing Bryan Road and private church road 27”x43” CMPA’s were also 

replaced with 38”x60” ERCP’s. In addition, the ditch downstream of Bryan 

Road was regraded and enlarged for a distance of 600 feet to achieve a 

greater hydraulic capacity in this channel segment and accommodate the 

larger culvert size. 


Description: Alternative 2 features a 5.8-acre on-line stormwater detention 

pond located in what is currently a wet pasture just west of the New Methodist 

Church of Brandon property. The function of this pond would be to attenuate 

peak flood flows while providing additional water quality and environmental 

benefits for the downstream reaches of Craft Road Ditch and Buckhorn Creek. 

Because there is a small existing pond located within the proposed site, the 

weir control elevation of the new pond would be set at the current normal pool 

elevation, estimated at 31.6 ft NAVD, with a crest length of 5 feet. The top of 

bank of the new pond would be set at elevation 37.1 ft NAVD. 




Advantages: The alternative achieves an acceptable flooding LOS by 

attaining greater hydraulic capacity in the Craft Road Ditch and attenuating 

peak flows in downstream reaches of the ditch and Buckhorn Creek. There 

are water quality benefits provided by the treatment of stormwater runoff in the 

proposed detention pond. In addition, there is an opportunity for creation of up 

to 5.8 acres of new wetland habitat within the proposed detention pond. 

Environmental permitting for the improvements should not be difficult, and the 

County may be able to obtain wetland mitigation credits with the new pond. 

Disadvantages: The alternative requires the purchase of approximately eight 

acres of undeveloped land, including multiple parcels, for construction and 

continued maintenance of the proposed detention pond. Thus the cooperation 

of affected property owners will be necessary. 

Effectiveness: While it was predicted in the 2001 model that this alternative 

will achieve a 25-year LOS B at the Craft Road and Bryan Road crossings of 

the Craft Road Ditch, it adds very little improvement over Alternative 1 in terms 

of flood benefits. This is likely because the site of the proposed detention pond 

is already a part of the existing floodplain and there is no appreciable additional 

storage being provided since there can be no increase of flood elevation on 

upstream or adjacent properties. 

Estimated Cost: The capital cost of this alternative is estimated at over 

$750,000. This figure includes the purchase of the pond site, pond excavation, 

and construction of the new drainage conveyances. 


Description: Alternative 3 achieves effective flood attenuation in the Craft 

Road Ditch with the construction of a 3.4-acre on-line stormwater detention 

pond located in what is currently a wet pasture just east of the Southpointe 

Subdivision (west of Bell Shoals Road). The pond would be created by both 

excavation at the site and construction of a berm across the floodplain with a 

top of bank elevation of 43.1 ft NAVD. The pond outfall would consist of a 

combination structure with a 2’ weir notch at elevation 36.6 ft NAVD and 10’ 

overflow spillway weir at elevation 41.6 ft NAVD. The function of this pond 

would be to attenuate peak flood flows while providing additional water quality 

and environmental benefits for the downstream reaches of Craft Road Ditch 

and Buckhorn Creek. 

Advantages: The alternative improves LOS for roads in the area and 

removes multiple houses from the floodplain, in addition to reducing flood 

levels in Buckhorn Creek as far downstream as Bloomingdale Avenue. There 

are water quality benefits provided by the treatment of stormwater runoff in the 




proposed detention pond. In addition, there is an opportunity for creation of up 

to 3.4 acres of new wetland habitat within the proposed detention pond. 

Environmental permitting for the improvements should not be difficult, and the 

County may be able to obtain wetland mitigation credits with the new pond. 

The site is contained within a single parcel that, if purchased in whole, could be 

utilized for other purposes such as recreation, education, passive park, and 

conservation. 

Buck-3 Flooding Problem Area Alternative 3 Detention Pond Site 

Existing wet pasture at proposed Craft Road Ditch Alternative 3 Detention Pond site 




Disadvantages: The alternative requires the purchase of approximately 

sixteen acres of undeveloped land for construction and continued maintenance 

of the proposed detention pond. Thus the cooperation of the existing property 

owner will be necessary. 

Effectiveness: Model results indicate that this alternative will achieve a 25- 

year LOS A at the Craft Road crossing and 25-year LOS B for both the Bryan 

Road crossing of the Craft Road Ditch and Bryan Manor Roads. Model results 

indicate flood elevations that remove multiple homes in the Bryan Manor 

Subdivision, New Methodist Church of Brandon property west of Bryan Road, 

and homes north of Craft Road Culverts from 25-year and in some cases the 

100-year storm events. At Craft Road, the 10-year peak flow reduction is from 

112 cfs to 95 cfs, Even in Buckhorn Creek, the 25-year peak flow is reduced 

by 60 cfs. When combined with BUCK-6 Alternative Buckhorn Creek peak 

flows between John Moore Road and Bloomingdale Avenue are reduced by up 

to 80 cfs for the 25-year storm event and 76 cfs for the 100-year storm event. 

These reductions are achieved with no increase in flood elevations upstream of 

the proposed pond site. At the pond site itself, additional flood storage is being 

provided by raising the existing flood elevations by 0.87 and 1.25 feet for the 

10-year and 25-year storm events, respectively. Flood stages in the creek 

immediately downstream of the pond site are reduced by 0.64 ft and 0.40 ft for 

the 25yr/24hr and 100yr/24hr events respectively. Reductions in the creek 

further downstream average ~ 0.2-0.3 feet down all the way to John Moore Rd. 

Estimated Cost: The capital cost of this alternative is estimated at 

$1,297,500. This figure includes the costs of purchase of the pond site and 

pond excavation. 

Recommendation: Although the desired flood control objectives have been 

achieved with Alternative 1, appreciably greater effectiveness can be attained with 

Alternative 3 along with highly desirable water quality, environmental, and possibly 

additional benefits. Because of these multiple benefits that are consistent with the 

watershed plan objectives, the recommended alternative for the Craft Road Ditch 

problem areas is Alternative 3. 

Problem Area BUCK-4: 

Bloomingdale West Pond Outfalls 


The Bloomingdale West Subdivision has two stormwater detention ponds that serve 

as the primary storage facilities for this residential subdivision. The ponds do not 

appear to receive any maintenance, as the outfall structures are overgrown and 

function is impaired such that flooding problems could arise if a significant storm 

event were to occur. The entire subdivision drainage system was constructed of 

corrugated metal pipe, which is corroded and likely in need of repair in the near 




future. Model results do not indicate flooding level of service violations, but there is 

overtop of the Bloomingdale West pond bank for the 10-year storm event. 

Additionally, the existing pond outfall structures were constructed prior to Chapter 17- 

25 regulations, so no formal stormwater treatment provisions are incorporated in their 

current design. 

Alternatives were analyzed that replace the existing outfall structures for the Canoga 

Park and the Bloomingdale West ponds with modified FDOT inlet structures that will 

provide enhanced flood control and stormwater treatment function over the existing 

structures. The County Central Service Unit identified some of these problems that 

were not addressed due to lack of access and/or easements. Any action to address 

the identified problems will require easements and/or access for construction and 

continued maintenance. 





Existing Canoga Park Pond outfall structure in Bloomingdale West 

subdivision 

Existing Bloomingdale West Subdivision Pond outfall structure 






Description: Alternative 1 is to take no action. Ultimately, the structures 

would fail and either the local residents or the County would take responsibility 

for repairing any damages and replacement of the structures at that time. 

Advantages: There is no initial cost. 

Disadvantages: There is no resolution to a problem that will continue until 

action is taken or structure failure. Failure could potentially add damages to 

the cost of repair. 

Effectiveness: The “no action” alternative is not effective in resolving the 

defined problem. 

Estimated Cost: The initial capital cost of this alternative is zero. However, 

no action only postpones the cost of retrofit with the potential for additional 

costs for damage repairs. 


Description: Alternative 2 is to replace the existing pond outfall structures 

with new outfalls that mimic the exact same hydraulic performance. This would 

consist of modified FDOT Type E inlets with weir notches of the same length 

and crest elevation as the existing. The new pond outfall structures would be 

equipped with skimmer plates, per current design practice, to provide 

enhanced stormwater treatment efficiency. 

Advantages: The new structures will provide reliable performance 

comparable to the existing structures and design with enhanced water quality 

treatment function. Environmental permitting should not be an issue. 

Disadvantages: The Bloomingdale West pond bank will still be overtopped by 

the 10-year storm event. 

Effectiveness: The alternative will be an effective means of restoring and 

ensuring proper performance of the existing drainage system and reduce 

exposure to potential damages resulting from structure failure and/or lack of 

maintenance. Flooding conditions will remain the same; the Bloomingdale 

West pond bank will be overtopped by the 10-year event. 

Estimated Cost: Based on the 2001 report, the capital cost of this alternative 

is estimated to be approximately the same as Alternative 3. This figure 

includes only the cost of construction of the new pond structures. It is 




presumed that the local residents will welcome the improvements, so no cost 

of access in the form of easements is included. 


Description: Alternative 3 is to replace the existing pond outfall structures 

with new outfalls that provide enhanced hydraulic performance. This would 

consist of modified FDOT Type E inlets with weir notches of different length 

and crest elevation as the existing. For the Canoga Park pond outfall, the 

control weirs would be modified to have one 3.5’ notch at elevation 49.0 ft 

NAVD, and one 11.0’ notch at elevation 50.6 ft NAVD. The Bloomingdale 

West pond outfall would lower the pond normal pool elevation by 0.5 feet (the 

pond currently provides only 2.0 feet of storage below the top of bank). This 

new structure would have a 15.0’ weir crest at elevation 41.6 ft NAVD. The 

new pond outfall structures would be equipped with skimmer plates, per 

current design practice, to provide enhanced stormwater treatment efficiency. 

Advantages: The new structure will provide reliable performance comparable 

to the existing structures and designed with enhanced water quality treatment 

function. The Bloomingdale West pond bank will not be overtopped by the 10- 

year storm event. 

Disadvantages: Environmental permitting may be an issue with regards to 

lowering of the pond normal pool elevation, but considering that there are no 

existing permits to modify, other benefits may override concerns. 

Effectiveness: The alternative will be an effective means of restoring and 



maintenance. Flooding conditions will be slightly improved, as the 

Bloomingdale West pond bank will not be overtopped by the 10-year event. 


This figure includes the cost of construction of the new pond structures, only. It 

is presumed that the local residents will welcome the improvements, so no cost 

of access in the form of easements is included. 

Recommendation: Maintenance and structure retrofit is considered best performed 

on a proactive basis rather than reactive (i.e. after failure). Because of the added 

flood control and water quality benefits, the recommended alternative for the 

Bloomingdale West pond outfall problem area is Alternative 3. 





Lithia Oaks Pond Outfall 


The Lithia Oaks Subdivision (formerly known as Buckhorn Springs Manor) detention 

pond that serves as the primary storage facility for this residential subdivision does 

not have a functional outfall structure. The pond does not appear to receive any 

maintenance and the outfall consists of an 18" CMP pipe that is collapsed and silted. 

Function is impaired such that flooding problems could arise if a significant storm 

event was to occur, and it is possible that the pond bank has already been breached. 

Lithia Oaks flooding problems were identified in the original 1988 Buckhorn Creek 

study. The pond is contained entirely within a parcel owned by a local resident. 

Hence, any action to address the identified problems will require an easement and/or 

access for construction and continued maintenance. 





Existing Bloomingdale West Subdivision Pond outfall structure 



Description: Alternative 1 is to take no action. 

Advantages: There is no initial cost. 

Disadvantages: There is no resolution to the defined problem. Pond bank 

failure could potentially create downstream damages and add to the cost of 

repair. 


defined problem. 

Estimated Cost: The initial capital cost of this alternative is zero. However, 

no action only postpones the cost of retrofit with the potential for additional 

costs for damage repairs. 


Description: Alternative 2 is to address the defined problems with the 

replacement of the existing outfall structure for the Lithia Oaks pond by a 24" 

RCP with a modified FDOT Type C inlet structure that will provide enhanced 

flood control and stormwater treatment functions over the existing structure. 

The inlet structure would have a 3.0’ slot at elevation 60.1 ft NAVD (same 




normal pool elevation as existing) and an 8.0’ primary overflow weir at 

elevation 61.6 ft NAVD. The new pond outfall structure would be equipped 

with a skimmer plate, per current design practice, to provide enhanced 

stormwater treatment efficiency. 

Advantages: This alternative will resolve the problem of a dysfunctional 

outfall structure and provide enhanced water quality treatment for the 

subdivision stormwater drainage above that provided by the current structure. 

Environmental permitting should not be an issue. The new structure performs 

better hydraulically and lowers the downstream peak flood elevation on the 

Bloomingdale High School grounds. 

Disadvantages: Requires cooperation of local resident/property owner. 

Effectiveness: The outfall retrofit will be an effective means of restoring and 



maintenance. Downstream flooding conditions at Bloomingdale High School 

will be slightly improved for the 25-year storm event. 


This figure includes the cost of construction of the new pond structure only. It 

is presumed that the local resident/owner would welcome the improvements, 

so no cost of access in the form of easements is included. 

Recommendation: To achieve the flooding LOS goal and provide enhanced water 

quality benefits, the recommended alternative for the Lithia Oaks pond outfall problem 

area is Alternative 2. 


Buckhorn Creek between Kings Ave. and Holland Dr. 


Buckhorn Creek traverses a set of large tracts of privately owned land between 

Holland Road and the Bloomingdale Plaza shopping center south of Bloomingdale 

Avenue. Mostly unoccupied, this is the last remaining unencroached part of the 

natural floodplain of the creek upstream of the Bloomingdale Avenue bridge and 

portions of the tracts are impacted wetlands. The creek is in an unmaintained state, 

and excessive channel vegetation creates a hydraulic impediment. Current modeling 

analysis indicates a LOS deficiency at a private dirt road that floods nearly two foot 

deep during the 10-year storm event. The flood profile plots show that the structure, 

consisting of two 59”x81” CMPA’s, is inundated by tailwater conditions (i.e. from the 

downstream reach of the creek) and no flooding problems are created upstream by 

this constriction. This problem area was identified in the original 1988 master plan 

study, and a replacement structure was recommended. Local residents indicate that 

structural flooding has occurred in the past. 




Downstream from this area, the creek passes through residential developments with 

low street grades that do not meet a 25-year LOS B condition. The original 1988 

master plan study also identified problems within this area of the main stem. There 

are currently no road crossing restrictions within this portion of the Buckhorn Creek 

drainage system since a number of road improvement projects in the past twelve 

years have resulted in replacements of Buckhorn Creek culverts with larger structures 

(e.g. Kings Avenue, John Moore Road, and Bloomingdale Avenue). Flooding 

conditions along the main channel have thereby improved since the original 1988 

master plan. These past improvements have done nothing, however, to reduce peak 

flows, and the County Central Service Unit has identified channel bank erosion 

problems in this area. As new development in the subwatershed continues, it is likely 

that increased flows and velocities will exacerbate such localized erosion problems. 





Excessive vegetation growth in existing Buckhorn Creek main channel 

between Bloomingdale Plaza and Holland Road south of Bloomingdale 

Avenue 



Description: Alternative 1 is to take no action. 

Advantages: There is no cost. 

Disadvantages: There is no resolution to the defined problems. 


defined problems. The defined flooding LOS violation is a private road for 

which the County does not assume responsibility. Downstream flooding at Van 

Gogh Circle is not a problem for the 10-year event, and the County can 

continue to use this as the target LOS for the Buckhorn Creek Subwatershed. 

Estimated Cost: The initial capital cost of this alternative is zero. 


Description: This alternative consists of the purchase of the properties that 

encompass the floodplain between Bloomingdale Plaza and Holland Drive and 

conversion of the area to a compatible use that restores and preserves the 

natural floodplain. This area provides an opportunity to preserve the natural 




floodplain and restore wetland functions while providing both flood control and 

stormwater treatment benefits. 

All or portions of five land parcels along this portion of the main Buckhorn 

Creek channel would be purchased to construct a 13.5-acre on-line stormwater 

detention pond, encompassing an existing isolated 1.7-acre pond within its 

confines. The pond would be created by both excavation at the site and 

construction of a berm across the floodplain with a top of bank elevation of 

32.1 ft NAVD. The embankment would be located at the western property line 

of the parcel approximately 300 feet west (downstream) of the existing private 

road that crosses the creek. Thus the existing road crossing and much of the 

overgrown channel will be eliminated by incorporation into the pond. The pond 

outfall would consist of an 8’-long overflow spillway weir with a crest elevation 

of 26.1 ft NAVD. This normal pool elevation was approximated from 

topographic mapping with the intent of maintaining current water table and 

adjacent wetland hydroperiod conditions. 

The function of this proposed pond would be to attenuate peak flood flows in 

the downstream reaches of Buckhorn Creek while providing additional water 

quality and environmental enhancement benefits. As designed, the new 

detention pond facility will reduce the downstream peak flows by approximately 

9-14% and lower the 25-year flood elevation by as much as 0.3 feet in 

Buckhorn Creek. 

Buck-6 Flooding Problem Area Alternative 2 Detention Pond Site 




Advantages: The natural floodplain of Buckhorn Creek will be preserved 

instead of succumbing to development pressures and water quality treatment 

will be provided for ~30 acres of development that currently has no water 

quality treatment measures in place. There will be up to 13.5 acres of new 

wetlands created that will provide valuable environmental habitat and 

enhanced stormwater treatment function in the watershed. The County may 

be able to obtain wetland mitigation credits with the new pond. The proposed 

pond site uses only a portion of the five land parcels. If purchased in whole, 

the remaining upland areas could be utilized for other purposes such as 

recreation, education, passive park, and conservation. 

Disadvantages: The alternative requires the purchase of five land parcels to 

construct the proposed detention pond. Some of these properties may be 

currently on the market, but implementation would require willing sellers. 

There are some residential structures located on the properties. 

Environmental permitting for the proposed pond could be difficult, since it 

consists of impounding an existing jurisdictional waterway. 

Effectiveness: Model results show moderate downstream peak flow 

reductions. Immediately downstream of the proposed pond, the 25-year peak 

flow is decreased from 675 cfs to 641 cfs. At Kings Avenue, the reduction is 

from 1111 cfs to 1032 cfs. These reductions are achieved with no increase in 

flood elevations upstream of the proposed pond site, nor on adjacent 

properties. 

Estimated Cost: The capital cost of this alternative is estimated at 

$2,674,800. This figure includes the costs of purchase of the 5 individual land 

parcels for the pond site, pond excavation, and construction of the appurtenant 

structures. 

Recommendation: Although the County’s adopted flooding level of service for 

Buckhorn Creek is a 10-year LOS B, greater flood control objectives can be attained 

in this subwatershed with the implementation of the proposed Alternative 2, along with 

highly desirable water quality, environmental, floodplain preservation, and possibly 

additional benefits. Because of these multiple benefits that are consistent with the 

watershed plan objectives, the recommended alternative for this problem area is 

Alternative 2. 

13.2.2 Bell Creek Subwatershed 

The County’s adopted Target Level of Service for the Bell Creek Subwatershed is a 

minimum goal of Level B for the 25-year, 24-hour design storm event. There are four 

(4) locations identified within the Bell Creek Subwatershed where the County’s 

minimum acceptable level of service criteria are not met (See Table 6.5-4 and Figure 

6.5-2). Of these four locations, none are substantiated by flooding complaints. 




Therefore, no alternatives were analyzed to provide flood protection for the LOS 

deficiencies that were identified. 









The following discussion details the flooding problems identified in the Bell Creek 

Subwatershed, and provides a description of the proposed solutions and alternatives. 

Problem Area BELL-1: Hobson Simmons Road 


According to the staff at Hillsborough County South Service Unit, flooding occurs 

along Hobson Simmons Road. There are culvert crossings at two locations along this 

road that convey the stormwater discharge from the wetlands located on the east side 

of the road westerly through an existing drainage ditch. These two culverts are 

identified as the northern culvert and the southern culvert in the figure presented 

below. This tertiary drainage system is not included in the watershed 

hydraulic/hydrologic model. Therefore, evaluations are based solely upon field 

observations. 

Field investigations revealed that the roadside ditch system along Hobson Simmons 

Road is overgrown with heavy vegetation. Additionally, the southern culvert has a 

restricted conveyance capacity due to the accumulation of silt and debris. The culvert 

appears to be a 29” x 45” ERCP; however, only a 10” x 45” opening is available on 

the upstream end of the pipe. This limits its conveyance capacity underneath Hobson 

Simmons Road. The northern culvert also has a small amount of accumulated silt, 

thus restricting its ability to convey stormwater runoff. 




Bell-1 Problem Area Location Map 

Hobson Simmons Road – Southern Cross Culvert (u/s) and Roadside Ditch 




Hobson Simmons Road – Northern Cross Culvert (u/s) 


Description: The recommended solution is to provide maintenance on a 

regular basis. The roadside ditches along Hobson Simmons Road should be 

cleared of excessive vegetation and both the northern and southern culverts 

should be cleared of the accumulated silt and debris. Emphasis should be 

placed on the actual removal of mass rather than mowing and/or use of 

herbicides that leave the conveyances impaired. The ditches at the downstream 

end of the culverts should also be regraded to provide a positive outfall. 

Advantages: Regular maintaining of this roadside ditch system should provide 

the anticipated flood relief along Hobson Simmons Road. Otherwise, further 

modeling should be conducted to determine the required improvements to the 

conveyance system. This recommendation does not require additional land 

acquisition since the County owns the right-of-way along Hobson Simmons 

Road. 

Disadvantages: There are no disadvantages associated with this alternative. 

Effectiveness: This recommended alternative will provide flood relief along 

Hobson Simmons Road, but since this tertiary conveyance system was not 

included in the hydrologic and hydraulic model an accurate assessment of its 

performance cannot be evaluated at the present time. 

Estimated Cost: The estimated capital costs for this project would be $26,200 




Recommendation: This solution is the recommended alternative. No other options 

were analyzed since this problem can be resolved by maintenance. 

13.2.3 Fishhawk Creek Subwatershed 

The County’s adopted Target Level of Service for the Fishhawk Creek Subwatershed 

is a minimum goal of Level B for the 25-year, 24-hour design storm event. Two 

locations were identified that did not meet the County’s minimum Target Level of 

Service criteria based on flood stages predicted by the model (See Table 6.6-4 and 

Figure 6.6-2). The definitions given for the Hillsborough County flood level-of-service 

(LOS) are for County-owned public works infrastructure. This does not include private 

or unpaved roads, which disqualifies the seven LOS deficient locations for alternative 

analysis. Both of these locations were either dirt roads or private access roads 




Service Unit or historical flooding complaints databases (See Figure 6.6-1). There 

have been three “flood complaints” made within the Fishhawk Creek Subwatershed 

as listed in Table 6.6-1, however no information was provided to describe the nature 

of the problems. Since the flood complaint database did not record the nature of the 

flooding problem, these complaints were not addressed. There was also one 

Hillsborough County South Service Unit concern relating a road flooding problem at 

the intersection of Boyette Road and Dorman Road. The current model analysis did 

not include this intersection, as it was not a part of the primary or secondary drainage 

systems. However, field investigations have determined that there is a 24” RCP that 

conveys flow from north to south under Dorman Road but is half-buried (8”-9”) with 

sediment build-up. Flooding at this intersection is localized. Proper maintenance of 

the RCP pipe and clearing of the channel both up and downstream to realize the full 

capacity of the pipe may alleviate this localized flooding problem. (If flooding 

conditions continue, then a more detailed study will be required to determine 

necessary hydraulic/structural improvements). Maintenance issues are discussed in 

further detail in Chapter 15. 

In summary, there were no flooding problems within the Fishhawk Creek 

Subwatershed that warranted an alternatives analysis other than an identified need 

for maintenance. 

13.2.4 Turkey Creek Subwatershed 

Valrico Subwatershed has been included in the Turkey Creek Subwatershed 

alternative section. Valrico is a closed basin west of Turkey Creek. 

The County’s adopted Target Level of Service for the Turkey Creek Subwatershed 

(and Valrico Subwatershed) is a minimum goal of Level B for the 25-year, 24-hour 




design storm event. There are 29 locations identified within the Turkey Creek 


not met (See Table 6.7-4 and Figure 6.7-2). Of these 29 locations, 24 constitute a 

LOS deficiency for a Hillsborough County improved public roadway. Two of the 

fourteen locations, are substantiated with flood complaints. There are 10 locations 

identified within the Valrico Subwatershed where the County’s minimum acceptable 

level of service criteria are not met (See Table 6.12-3 and Figure 6.12-2). Of these 10 

locations, all constitute a LOS deficiency for a Hillsborough County improved public 

roadway. One of the locations, is substantiated with flood complaints. 









The following discussion details the flooding problems identified in the Turkey Creek 

and Valrico Subwatersheds, and provides a description of the proposed solutions and 

alternatives. 

Problem Area TC-1: CSX Railroad and Mulrennan Road Drainage 

Improvements 


Hillsborough County East Service Unit staff stated that standing water ponds in the 

railroad ditch northwest of Mulrennan Road due to a high point in the ditch. According 

to County staff, this ponded water percolates through the railroad gravel bed and then 

flows overland to Silver Lane, where yard and house flooding occurs. 

County CIP # 47191 was completed in ~2003 to eliminate ponding of stormwater 

within this railroad ditch. The project consisted of re-grading the railroad ditch to a 

uniform slope, thus eliminating a high point in the ditch gradeline and providing a 

positive drainage outfall to SR 60. Additionally, the County installied fabric-formed 

concrete ditch pavement from Mulrennan Road for approximately 300 feet along the 

ditch. This concrete pavement will provide further protection from water seeping 

through the railroad gravel bed. Furthermore, the railroad culvert at SR 60 was 

cleared of accumulated sediment/debris such that a positive drainage outfall was 

attained. 




TC-1 Flooding Problem Area Location Map (location of TC-1/CIP # 47191) 

Problem Area TC-2: Mud Lake Road 


A level of service deficiency has been identified on Mud Lake Road, just south of the 

intersection with Bugg Road. Downstream of Mud Lake Road is a heavily wooded 

wetland. This tributary feeds the Little Alafia River which eventually outfalls to the 

Medard Reservoir. The tributary crosses Mud Lake Road through two 27” by 43” 

CMPA culverts. Sedimentation of the channel is a severe problem, as can be seen in 

the pictures on the following page. The combination of constrictive pipes and 

sediment accumulation aggravates flooding conditions. The hydrologic/hydraulic 

model analysis predicts road flooding with a depth of 0.42 feet for the 25-year storm. 

All conduits are modeled in maintained (not silted) conditions, therefore, this is a low 

estimate of flood elevation and this crossing would likely not meet the minimum 25- 

year LOS B. 

The primary land use of the 217-acre contributing drainage basin is agricultural, 

consisting of orange groves and strawberry fields. The strawberry farmers employ 

plastic mulch that has many beneficial aspects in terms of reducing irrigation needs, 

pesticide and fertilizer application, and weed control. However, the plastic mulch has 

drawbacks with respect to stormwater runoff; acting as an impervious surface 

increasing stormwater runoff. In addition, this type of agricultural practice can also 

increase erosion of the soil during heavy rain events, aggravating sedimentation of 

downstream reaches. As mentioned, downstream of Mud Lake Road, the channel 

joins with the Little Alafia River to outfall to the Medard Reservoir. In this area, the 

river corridor is relatively undeveloped, providing a riparian corridor on both sides of 

the channel. This has tremendous beneficial aspects in terms of floodplain 

management by connecting the creek channel with the natural floodplain and by 

allowing the natural migration and meander of the creek to occur unimpeded. It is 




also beneficial for natural habitat and water quality; therefore, it is very important to 

prevent the high levels of sedimentation that have been observed in this area. 

TC-2 Flooding Problem Area Location Map 

The culvert at Mud Lake Road with evidence of high sediment loads. 






Description: The flooding predicted at Mud Lake Road can be reduced by 

replacing the twin 27” by 43” corrugated metal pipes with two precast 3’ x 7’ 

box culvert sections. Additionally, the sediment deposit artificially raising the 

channel bottom must be removed -assuming the existing culvert was originally 

installed at the tributary’s invert, 1.4 feet of sediment has accumulated at the 

exit of the culvert. Removal of this sediment and re-grading of the conveyance 

in this area would enlarge and deepen the channel to some earlier level and 

eliminate the Level of Service deficiency at this location. While this 

maintenance type of approach will provide a quick fix to the problem, a longerterm 

solution is necessary. Sediment control through improved agricultural 

practices is required. Strawberry farming is a significant land use in this region 

of Hillsborough County, and has significant impacts on stormwater 

management issues. The water quality project TC-4/WQ discusses ideas 

related to this issue 

Advantages: If this alternative is used in conjunction with TC-4WQ, flooding 

of the road for high flow events will be eliminated and large sediment loads will 

be reduced. This, in turn, helps reduce the frequency of maintenance. 

Disadvantages: There are no disadvantages to this proposed solution. 

Effectiveness: . This alternative reduces the 100-year flood water surface 

elevation from 78.41 to 77.31 feet and prevents Mud Lake Road from being 

overtopped. The road overtops at 77.80 feet NAVD. For the 25-year design 

storm, the water surface elevation is predicted to be 76.23 feet NAVD, for no 

road flooding. Water quality and natural habitat can be improved throughout 

the downstream river corridor. 

Estimated Cost: The estimated cost for this alternative is $117,500. 


Description: Roadway flooding can be reduced by removing the existing 

culverts and replacing them with two 3’ by 7’ rectangular box culverts. This will 

meet the Hillsborough County requirement for a 25-year LOS B rating. 

Advantages: Enlarging the culvert size achieves the minimum Level of 

Service criteria required by the County’s standard. 




Disadvantages: The road will still flood during heavy rain events. The culvert 

and downstream channel will continue to experience high levels of siltation and 

sediment deposition, requiring a high level of maintenance. 

Effectiveness: A 25-year LOS B condition can be met with implementation of 

this alternative. Flood elevations are not adversely effected downstream. 


Recommendation: Alternative 1 is recommended as the solution to this problem, as 

it provides a 25-year and 100-year LOS A for nearly the same cost while providing 

much needed water quality benefits. 

Problem Area TC-4: Colson Road 


Local residents and the Hillsborough County East Service Unit reported that Colson 

Road exhibited flooding conditions during the El Nino storms. The flooding occurred 

at the curve where Colson Road intersects the Seaboard Coast Line Railroad (on the 

northeast side). The flooding was such that the road was impassable. There are no 

cross drains at the intersection of the railroad and Colson Road. The nearest culvert 

under Colson Road is a 15” HDPE pipe approximately 700 feet to the east of the 

railroad. This is a localized drainage problem in the secondary system and, as such, 

it was not included in the hydrologic and hydraulic existing conditions model. The 

nearest point, junction number 757470, is southeast and downstream at the railroad 

where the model predicts a 25-year LOS A. 





Colson Road at the intersection with the CSX RR. 



Description: Installing a cross drain under Colson Road will alleviate localized 

flooding at this location by conveying runoff from the north to the south side of 

the road. A 24” RCP cross drain at the edge of the railroad property line, but 

within the County right-of-way, is recommended. A swale should be 

constructed along the north side of Colson Road to facilitate drainage to the 

cross drain location. 

Advantages: This is a simple solution where all work can be accomplished 

within the right of way, requiring no need for easement acquisition and minimal 

permitting. 

Disadvantages: There are no disadvantages. 

Effectiveness: Since this location was not modeled directly, it is not possible 

to ascertain a quantitative level of effectiveness. An independent drainage 

analysis should be performed to confirm that the project design achieves a 

minimum 25-year LOS B. This project would have to be designed such that 

downstream stages would not be adversely affected. 

Estimated Cost: This alternative will cost approximately $18,700. 


Description: With this alternative, stormwater runoff would be diverted along 

the north side of Colson Road by constructing a ditch/swale system from the 

railroad along the north side of Colson Road toward the east for approximately 




280 feet. A new 24” RCP culvert under Colson Road from north to south would 

then connect with the existing drainage system, which flows to the south. 

Advantages: This alternative would connect the stormwater runoff to an 

existing conveyance system. 

Disadvantages: This alternative requires additional excavation. 

Effectiveness: Since this location was not modeled directly, it is not possible 

to ascertain a quantitative level of effectiveness. An independent drainage 

analysis should be performed to confirm that the project design achieves a 

minimum 25-year LOS B. This project would have to be designed such that 

downstream stages would not be adversely affected. 

Estimated Cost: This alternative will cost approximately 30% more than 

alternative 1. 

Recommendation: While both alternatives will reduce flooding, the first alternative is 

the simplest and the least expensive. 

Problem Area TC-5: Jerry Smith Road Secondary Drainage System 

Maintenance 


Hillsborough County East Service Unit staff stated that localized flooding occurs along 

Jerry Smith Road between Endeavor Avenue and O’Griffin Road. One cross culvert 

conveys floodwater to the east under Jerry Smith Road. This secondary drainage 

system is not included in the watershed hydraulic/hydrologic model. Upon field 

investigation it is evident that the cross culvert at this location is completely clogged 

with silt/debris such that virtually no conveyance capacity exists. 





Jerry Smith Road (u/s) 

Jerry Smith Road (d/s) 

Alternative Solution: 

Description: The logical solution is for maintenance activities to be performed 

in this portion of the secondary drainage system. The cross culvert should be 

cleared of the accumulated silt and debris, including the structure inlets and 

outlets. The downstream ditch should be graded such that a positive drainage 

outfall exists (the purchase of a drainage system may be required). Routine 

maintenance should be performed regularly in this secondary system. 

Advantages: Maintaining this secondary system will provide relief from 

localized flooding along Jerry Smith Road. 




Disadvantages: There are no disadvantages associated with this alternative 

unless land acquisition is necessary and poses a problem. 

Effectiveness: This recommended alternative would provide flood relief along 

Jerry Smith Road. In a maintained state it, is expected that the drainage 

system will attain the required 25-year level of service. A more detailed 

analysis of this secondary system is required, including site-specific 

information, for a quantitative assessment. 


Recommendation: This is the recommended alternative. No other alternative was 

analyzed as this problem can be alleviated by maintenance. 

Problem Area TC-6: Dover Road 


Dover Road is a north-south road that extends from Durant Road to Martin Luther 

King Blvd. Inactive mines border the east side of Dover Road from Durant Road to 

the Salem Church Road and the west side from SR 60 to Sydney Road. Between SR 

60 and Salem Church Road, the Dover Road profile has a sag point, or low spot, 

where two pipes connect the drainage system and permit flow in a west to east 

direction. At this sag point, Dover Road experiences frequent road flooding. The 

hydrologic and hydraulic existing conditions model shows water elevations of 1.22 

feet over Dover Road during a 25-year design storm event. Tailwater conditions 

dominate at this locale and are caused by constricted or obstructed structures at SR 

60 and downstream through the Sydney Mine. Raising the minimum elevation of 

Dover Road is one alternative, while conducting a detailed survey of the structures 

downstream in order to determine the exact cause of observed flooding conditions 

and the most effective solution is another.. 







Description: Further information concerning the drainage system and 

structures need to be acquired, including inverts, sizes, and possible 

blockages. This will require a de-watering operation in the vicinity of the 

structures. An informed and intelligent course of action can then be 

implemented to lower upstream water elevations (Dover Road tailwater 

conditions) and reduce flooding at Dover Road. 

Advantages: Accurately defining the hydraulic system will allow the proper 

action to be taken to alleviate flooding at Dover Road while restoring the 

drainage system around the Sydney Mine. 

Disadvantages: Detailed information is not available without a de-watering 

operation. 

Effectiveness: This inspection will reveal the nature and cause of the 

observed flooding conditions so that a remedial action plan can be 

implemented. Without it, no reliable plan can be undertaken. 

Estimated Cost: The estimated cost for the implementation of this alternative 

is $60,000. 





Description: The minimum elevation of this portion of Dover Road should be 

raised to 65.0 feet NAVD. Replace two existing 34” x 53” ERCP’s with two 48” 

RCP’s. Floodplain compensation should be provided on county owned lands to 

the east of Dover Road. 

Advantages: Raising Dover Road will achieve 100-year LOS of A and does 

not require any maintenance of downstream hydraulic features to maintain this 

LOS. 

Disadvantages: This is more costly than Alternative 1. Should Alternative 1 

be carried out, raising Dover Road could be the preferred solution for 

alleviating flooding; however a less expensive alternative may be found. 

Effectiveness: This alternative will achieve 100-year LOS of A. No 

downstream impacts are realized from this alternative. 


is $1,224,600. 

Recommendation: The recommended alternative is alternative 2. It will provide a 

100-year LOS of A. 

Problem Area TC-7: Cameron Road 


Cameron Road is a north south road that extends south from Cowart Road, providing 

the only evacuation route for 11 residences. In the vicinity of 4624 Cameron Road, 

the Cameron Road profile has a sag point, or low spot, where a pipe connects the 

local drainage from the east to a storm water treatment pond on the west side of the 

road. At this sag point, Cameron Road experiences road flooding during large storm 

events when the storm water pond fills up and flow reverses, sheet flows over a 

private driveway and ultimately connects with the Medard Tributary. Road flooding 

complaints were made during Hurricane Frances in 2004 and the hydraulic and the 

hydrologic existing conditions model indicates a 25-year LOS of C, with 0.77 feet of 

road flooding. 






Description: The minimum elevation of 340 feet road in the vicinity of 4624 

Cameron Road should be raised from 119.2 feet to 120.0 feet, the culvert 

under Cameron Road should be replaced with a 30 inch RCP and, land on the 

west side of Cameron Road needs to be purchased for floodplain 

compensation. 

Advantages: This alternative alleviates road flooding, while maintaining 

existing flood elevations and with no structure flooding. 

Disadvantages: This alternative requires purchasing land for floodplain 

compensation and does not alleviate yard flooding. 

Effectiveness: A LOS of A will be achieved for both 25-year and 100-year 

storm events with no increase in flood levels. Floodplain compensation must 

be accomplished as part of this project to avoid raising flood stages. 


is $155,100. 

Recommendation: This is the only alternative proposed to alleviate Cameron Road 

flooding. 




Problem Area VAL-1: Valrico Road 


Valrico Road is a north south road that extends from Highway 574 (out of the 

watershed) to County Road 640, providing a primary north-south corridor. 

Approximately 600 feet north of State Road 60 the Valrico Road profile has a sag 

point, or low spot, where a pipe connects the FDOT detention pond on the east to a 

wetland on the west side of the road. At this sag point, Valrico Road experiences 

road flooding during large storm events when the storm water pond and wetland fill up 

and equalize over Valrico Road. Road flooding complaints were made during 

Hurricane Frances in 2004 and the hydraulic and the hydrologic existing conditions 

model indicates a 25-year LOS of C, with 0.71 feet of road flooding. Although a 

series of two pump stations currently exist, these only facilitate flood and flood 

storage recovery. These pumps will not help with flooding during any significant 

storm event. 

VAL-1 Flooding Problem Area Location Map 


Description: This alternative includes raising the minimum elevation of 760 

feet of Valrico Road between Timothy Terrace and Jelane Drive should be 

raised to 36.5 feet, replacing the culvert under Valrico Road with a 30 inch 

RCP, and providing floodplain compensation west of Valrico Road on county 

owned lands. 




Advantages: This alternative alleviates road flooding, while maintaining 

existing flood elevations and with no structure flooding. 

Disadvantages: This alternative requires raising the road elevation and may 

require a few driveways to be raised as well. 

Effectiveness: A LOS of A will be achieved for 25-year storm events and a 

LOS of C will be achieved for 100-year storm events with no increase in flood 

levels. Floodplain compensation must be accomplished as part of this project 

to avoid raising flood stages. 


is $502,400. 

Recommendation: This is the only alternative proposed to alleviate Valrico Road 

flooding. Valrico is a subwatershed of near Turkey Creek with no direct connections 

to Turkey Creek, it is a closed basin. This location is one of the lowest points in the 

closed Valrico basin and therefore alternatives cannot be proposed to redirect flow or 

move flow downstream in the system faster. Raising the road is the only way to 

alleviate road flooding and allow this road to be used during significant flood events. 

13.2.5 English Creek Subwatershed 

The County’s adopted Target Level of Service for the English Creek Subwatershed 

has a minimum goal of Level B for the 25-year, 24-hour design storm event. Twelve 

locations were identified that did not meet the County’s minimum Target Level of 

Service criteria based on flood stages predicted by the model (See Table 6.8-4 and 

Figure 6.8-2). Of these twelve, five were road flooding and seven were structure 

flooding. Road flooding was not reported for any of the locations were the model 

predicted road flooding; therefore no projects are proposed. Verified structure flood 

complaints and finished floor elevations are not currently available for the locations 

were structure flooding was predicted and no projects are proposed for those 

locations at this time. 




Service Unit or historical flooding complaints databases (See Figure 6.8-1). There 

have been 26 “flood complaints” made within the English Creek Subwatershed as 

listed in Table 6.8-1, however, in most cases limited information was provided to 

describe the nature of the problems. Since the flood complaint database did not 

record the nature of the flooding problem, these complaints were not addressed. 

There were also ten Hillsborough County South Service Unit concerns related to road 

and yard flooding problems. These problem areas were investigated where there was 

sufficient information provided and alternative measures analyzed. . Three such 




locations were identified and alternatives are proposed below In some cases, further 

detailed study is needed. In many instances, the problem was related to a 

maintenance issue and it was added to a list of recommended maintenance needs 

provided in Chapter 15. 

The following discussion details the flooding problems identified in the English Creek 

Subwatershed, and provides a description of the proposed solutions and alternatives. 

Problem Area ENG-1: Futch Road 


The East Service Unit has noted a road flooding problem in the upper region of the 

English Creek drainage basin on Futch Road. Runoff from the subbasin to the north 

collects in the ditch on the north side of Futch Road and ponds along the east end in 

the low-lying area near the intersection of Futch and South Wiggins Road. Runoff 

from the subbasin to the south collects in the depression on the south side of Futch 

Road and is connected to the south ditch by a 12” pipe. There is a small 15” 

corrugated HDPE pipe that acts as a cross drain under Futch Road from the south 

ditch to the low lying area on the north side of Futch Road. The collector ditch on the 

north side is large and is sloped towards English Creek to the west; however, the 

eastern portion of the ditch may slope to the east. The collector ditch on the south 

side of the road extends from the intersection with Wiggins Road west to the 

depression. Overflow from the depression on the south is conveyed through the 

cross drain to the north and then west through the collector ditch, ultimately to English 

Creek. 

Homes on the south side of Futch Road occasionally experience yard and structure 

flooding. During extreme rainfall events, the depression fills up and does not have 

enough outfall capacity through either the culvert to the south ditch or the cross drain 

to the north. Overflow from the depression to the south flows overland in a 

southwesterly direction towards English Creek. The topography is generally flat, 

causing a lengthy but natural flowpath. 

The location of the flooding problem on Futch Road is part of the secondary drainage 

system and as such was not specifically modeled as a part of this study. The nearest 

level of service analysis point is at the model junction 797800, the upstream end of 

the English Creek culvert at Futch Road, where a 25-year LOS A condition is 

achieved. 




ENG-1 Flooding Problem Area Location Map 



Description: This alternative solution, based on available information, is to 

clear sediment and debris from the two driveway culverts at the east end of the 

north ditch. The cross drain should be replaced with a 30” RCP, and the pipe 

connecting the depression on the south side of the road to the south ditch 

should be replaced with a 24”RCP. The north ditch may need to be re-graded 

to drain toward the west end of the ditch for a distance of approximately 450 

feet; a detailed survey and analysis of this secondary system will be required to 

ensure proper project design and implementation. The intent of this alternative 

is to have work occur on the north side of Futch Road within the County’s rightof-way 

in the existing ditch and to improve culvert connections between the 

depression on the south side of the road and the north collection ditch and to 

facilitate conveyance from high flow events to English Creek rather than across 

the properties south of Futch Road. This will provide relief to property owners 

while minimizing impacts to the wetlands on the south of Futch Road. 

Advantages: Enlarging the culverts is simple and cost effective. By using the 

existing conveyance system, work can be done in the existing right of way 

without the need to obtain drainage easements. Environmental impacts would 

be virtually nonexistent, facilitating the permitting process. 




Disadvantages: The natural grade of the northern ditch might be to the east; 

survey will be necessary to verify this. The ditch may have to be re-graded to 

promote positive drainage to the west. There is also a large tree on the west 

side of the last driveway crossing, which may require removal in order to install 

a larger pipe. 

Effectiveness: The effectiveness of this alternative solution cannot be 

predicted here. Alternatives based on the hydrology of the area can be given 

in general terms only. More detailed survey information and a hydrodynamic 

model with increased resolution will be necessary to objectively assess this 

alternative. 

Estimated Cost: This alternative will cost approximately $42,500. 


Description: To relieve the homes on the south side of Futch Road from 

flooding conditions, in this alternative a ditch system would be constructed 

along the south side of Futch Road and graded for positive drainage from 

Wiggins Road to an outfall at English Creek. In this scenario, part of the runoff 

will be diverted along the roadside channel instead of along the natural flow 

path. This alternative may work best in conjunction with Alternative 1, but 

without blocking the Futch Road cross drain. Depending on the location of the 

right-of-way boundary on the south side of Futch Road, it is assumed for this 

analysis that easements will need to be purchased. The ditch will be 

approximately 900 feet long and five driveway culverts will need to be installed. 

Advantages: This will double the capacity of the existing ditch on the north 

side of Futch Road, thus providing further relief for flooded property owners. 

Construction of a roadside ditch and three driveway culverts is a 

straightforward project. 

Disadvantages: It remains to be determined if there is sufficient right-of-way 

to construct another ditch without purchasing an additional drainage easement. 

Permitting may be more difficult and expensive as there are probably wetlands 

involved. 

Effectiveness: The effectiveness of this alternative cannot be determined 

without further data and analysis. 

Estimated Cost: The cost of this project in 2001 was estimated to be 5 times 

that of alternative 1. 

Recommendation: Alternative 1 is the recommended alternative, although a more 

detailed study is necessary to determine if it is efficacious. 




Problem Area ENG-2: Joe King Road 


The Hillsborough County East Service Unit indicated there are flooding problems 

along Joe King Road. This is supported by documented incidents of roadway flooding. 

Joe King Road did not have a completed tertiary drainage system in place. A ditch 

system was intact along a portion of the road but was not continuous and therefore 

did not relieve the localized flooding. This is a rural area with mixed low-density 

residential, undeveloped land, and agriculture land use. 

A County improvement project (CIP 41051) completed in 2004 optimized drainage 

within the right of way for this area. Since only primary and some secondary systems 

of the major tributaries of the Alafia River were modeled, the closest corresponding 

point in the existing conditions model is at Junction 791640. This is the upstream 

node of Tributary 1622, which crosses Joe King Road through a 36” CMP culvert. 

The level of service for this location is a 25-year LOS B. The road elevation is 97.9 

feet and the water surface elevation for a 25-year storm event is 98.15 feet NAVD. 


Problem Area ENG-3: Jim Johnson Loop 


Jim Johnson Loop is a small neighborhood formed by a loop ending at both ends on 

Jim Johnson Road just east of Jap Tucker Road. The tertiary drainage system in this 

neighborhood was in need of repair and re-establishment. The neighborhood is 

generally on high ground with most of Jim Johnson Loop draining to the north. 

Homes directly along Jim Johnson Road drain toward the east. This area was 




identified by the Hillsborough County East Service Unit as having localized flooding 

problems. 

The drainage system in this area was evaluated by the County’s stormwater 

management team in April of 1996. Their recommendation was to obtain a 275-foot 

easement, re-establish 275 feet of ditch, and replace 300 feet of 24” pipe from west to 

east along the north side of the road. This project (CIP # 47126) was completed in 

2003. 

It should be noted that this is a tertiary drainage system and as such is a localized 

drainage issue. It was not included specifically in the hydraulic and hydrologic 

watershed model. The nearest junction, 792160, is located at the outfall of the 

neighborhood drainage system. This location provides a 25-year LOS B according to 

model results. 


13.2.6 North Prong Alafia River Subwatershed 

The County’s adopted Target Level of Service for the North Prong Alafia River 

Subwatershed is a minimum goal of Level B for the 25-year, 24-hour design storm 

event. There are one locations within the North Prong Alafia River Subwatershed 

where the County’s minimum acceptable level of service criteria are not met (See 

Table 6.9-4 and Figure 6.9-2). No flood complaints substantiate this LOS deficiency; 

therefore, no alternatives were analyzed to provide flood protection for the LOS 

deficiencies that were identified. It should also be noted that only that portion of the 

North Prong Alafia River Subwatershed that lies within Hillsborough County was 

considered in this analysis. 





the existing hydrologic and hydraulic conditions, flooding problem areas were 


Service Unit or historical flooding complaints (See Figure 6.9-1). Only three historic 

flooding complaint in the County’s database is located within the North Prong Alafia 

River Subwatershed, However, llimited information was provided to describe the 

nature of the problem. Therefore, no flood control alternatives were considered in the 

North Prong Alafia River Subwatershed. 

13.2.7 South Prong Alafia River Subwatershed 

The County’s adopted Target Level of Service for the South Prong Alafia River 


event. There are six (6) locations within the South Prong Alafia River Subwatershed 

where the County’s minimum acceptable level of service criteria are not met (See 

Table 6.10-4 and Figure 6.10-2). Of these six (6) locations, only four constitute a LOS 

deficiency for a Hillsborough County improved public roadway and flooding may be 

alleviated without raising the road at only one of those locations. The LOS deficiency 

is located at East Keysville Road north of Welcome Road. It is characterized as Level 

D which means that the depth of flooding at this location is greater than 12 inches. 









The following discussion details the flooding problems identified in the South Prong 

Alafia River Subwatershed, and provides a description of the proposed solutions and 

alternatives. 

Problem Area S_Prong-1: George Smith Road and Lithia Pinecrest Road 


The Hillsborough County East Service Unit staff expressed maintenance concerns 

along George Smith Road north of Lithia Pinecrest Road. Two culvert crossings 

convey stormwater runoff westerly under George Smith Road, and a third culvert 

crossing conveys stormwater runoff northerly under Lithia Pinecrest Road (see figure 

below). This conveyance system was part of the existing conditions modeling effort 

and the results indicated that all three crossings met the County’s flood control LOS 

protection requirements and are listed as LOS A for the 25-year storm event. It 

should be noted that, in the existing conditions model simulation, it was assumed that 




these pipes are completely unobstructed. During field investigation, however, it was 

observed that sedimentation problems exist at these locations. 

S_PRONG-1 Flooding Problem Area Location Map 

Northern Culvert Crossing at George Smith Road: One 44” x 72” corrugated metal 

pipe conveys stormwater runoff westerly underneath George Smith Road. This 

crossing is located approximately 725 feet north of Lithia Pinecrest Road. The head 

loss through this culvert crossing is 0.5 feet for the 25-year storm event. The road 

overtop weir elevation of George Smith Road at the culvert crossing is 111.5 feet 

NAVD and the 25-year storm flood stage elevation at the upstream side of the culvert 

(Junction Number 770565) is 111.62 feet NAVD. Therefore, less than three inches of 

flood overtopping of the roadway occurs if the culvert is maintained unobstructed, and 

a 25-year LOS A is attained at this location. However, based on field investigations, it 

was observed that this pipe is nearly 50 percent silted, leaving approximately a 22” 

opening available for conveyance. 




George Smith Rd – Northern Culvert Crossing (u/s) 

George Smith Rd – Northern Culvert Crossing (d/s) 




Southern Culvert Crossing at George Smith Road: Two 59” x 81“ CMPA’s convey the 

flow in the West Branch South Prong Alafia River northwesterly at George Smith 

Road, approximately 250 feet north of Lithia Pinecrest Road. The head loss at these 

culverts is 0.5 feet for the 25-year storm event. The road overtop weir elevation of 

George Smith Road at this location is 113.31 feet NAVD and the water surface 

elevation at the upstream side of the structures (Junction Number 770570) is 110.04 

feet NAVD. Therefore, no overtopping of the roadway occurs if the culvert is 

maintained unobstructed, and a LOS A is attained at this location. However, based 

on field investigations, it was observed that these pipes are nearly 70 percent silted, 

leaving only an 18” opening available for conveyance (see figure below). 

George Smith Rd – Southern Culvert Crossing (u/s) 

George Smith Rd – Southern Culvert Crossing (d/s) 




Channel between George Smith Road and Lithia Pinecrest Road: The channel 

upstream of the southern culvert crossing is extremely silted and overgrown with 

nuisance species as can be seen in the pictures below. This ditch crosses through a 

private property where the homeowner has denied service unit personnel access for 

routine ditch maintenance activity. 

Channel between Lithia Pinecrest Road and George Smith Road Southern Culvert Crossing. 

Channel between Lithia Pinecrest Road and George Smith Road Southern Culvert Crossing. 




Lithia Pinecrest Road Culvert Crossing: The 6’ x 6’ concrete box culvert at Lithia 

Pinecrest Road, located upstream of the previously discussed ditch, has slightly 

overgrown vegetation and accumulated debris at inlet and outlet locations (see figure 

below). The existing conditions model identifies this location as a LOS A for the 25- 

year storm event. 

Lithia Pinecrest Rd 6’ x 6’ BC (d/s) 

Lithia Pinecrest Rd 6’ x 6’ BC (u/s) 






Description: This alternative solution is to provide maintenance on a regular 

basis. Specific locations of maintenance deficits are as follows: 

Northern Culvert Crossing at George Smith Road: It is recommended 

that the 44” x 72” CMPA be cleared of silt and debris. Additionally, the 

upstream and downstream channels should be graded to remove 

accumulated sediment and debris, and to provide a positive hydraulic 

gradient. 

Southern Culvert Crossing at George Smith Road: It is recommended 

that the double 59” x 81” CMPA’s be cleared of silt and debris. 

Additionally, the upstream and downstream channels should be graded, 

to remove accumulated sediment and debris, and provide a positive 

hydraulic gradient. Cleaning of the upstream channel has posed 

problems to County’s service unit staff in the past and will be addressed 

below. 

Channel between George Smith Road and Lithia Pinecrest Road: The 

Hillsborough County East Service Unit staff stated that it is useless to 

clear the southern culvert crossing since they do not have access to 

clean and re-grade the upstream channel. It is recommended that the 

County purchase a drainage easement between the southern culvert 

crossing and the Lithia Pinecrest Road culvert crossing such that routine 

maintenance can be performed. 

Lithia Pinecrest Road Culvert Crossing: It is recommended that the inlet 

and outlet of this 6’ x 6’ BC be cleared of sediment and debris. 

Additionally, any silt captured within the structure itself should be 

removed. 

Advantages: Maintenance of this primary drainage system will allow the 

system to perform as designed and a drainage easement will allow County 

staff to perform regularly scheduled maintenance. In a maintained state, these 

structures should provide the required 25-year flooding level of service 

protection. 

Disadvantages: Considering the owner’s unwillingness to allow maintenance 

access, the acquisition of a drainage easement may be difficult. 




Effectiveness: This recommended alternative will improve the conveyance 

capacity of the system to meet the 25-year level of service requirement as well 

as provide access for maintenance. 

Estimated Cost: This alternative would cost approximately $27,100 to 

implement. 

Recommendation: The recommended alternative consists of maintenance and 

additional easement acquisition. No other alternatives were analyzed. 

13.2.8 Alafia River Main Stem Subwatershed 

The County’s adopted Target Level of Service for the Alafia River Main Stem 


event. There are 55 locations identified within the Alafia River Main Stem 


not met (See Table 6.11-4 and Figure 6.11-2). 









The following discussion details the flooding problems identified in the Alafia River 

Main Stem Subwatershed, and provides a description of the proposed solutions and 

alternatives. 

Problem Area AR-1: Cummins Road 


Cummins Road is located off Valrie Lane north of McMullen Loop in Riverview. It is an 

extremely narrow paved county-owned road that will experience 1.0 feet of flooding 

during the 25-year design storm event. The Cummins Road elevation is 21.1 ft NAVD 

and the 25-year existing condition flood elevation is 22.1 ft NAVD. The tributary that 

flows through the culvert underneath Cummins Road from the south originates from a 

wetland that is now part of the Riverglen subdivision stormwater treatment system. 

This flooding problem has been clearly documented by a county constituent, whose 

property and dirt driveway also become completely inundated with floodwaters just 

upstream (south) of Cummins Road. 




Recent residential development upstream, including the Riverglen subdivision, has 

compounded the problem. The 18” RCP is no longer able to convey the resulting 

higher flows during large storm events. The hydrologic/hydraulic model indicates 

flooding at this location, which corresponds with a recent flooding complaint received 

at the first Hillsborough County Alafia Public Meeting. The constriction at this cross 

drain is accompanied with sedimentation within the downstream channel. The 

channel is now undefined, very shallow and ineffective for floodwater conveyance. 

Additionally, even more development is under construction upstream that may 

exacerbate this problem. 

AR-1 Flooding Problem Area Location Map 

Cummins Road during Tropical Storm Gabrielle 






Description: This alternative comprises the replacement of the existing 18” 

RCP with 3 - 24”x38” ERCP’s and the raising of Cummins Road to an elevation 

of 21.7 ft NAVD. 

Advantages: This alternative should be easily permittable. No easements 

should have to be purchased, and it does not raise downstream flood 

elevations. This is the least expensive alternative. 

Disadvantages: The major disadvantage of this alternative is that, without 

improving the downstream channel, the new pipes will continue to silt up and 

become clogged because the invert of the downstream channel is higher than 

the invert of the existing culvert. 

Effectiveness: This alternative achieves the 25-year LOS flood protection and 

eliminates flooding over Cummins Road. It is estimated that this alternative 

reduces the flood elevation upstream of Cummins Road from 22.10 ft NAVD to 

22.05 ft NAVD and achieves a flooding LOS B for Cummins Road. No adverse 

downstream impacts are realized in this alternative. 

Estimated Cost: This alternative would cost approximately $221,700. 


Description: This alternative is the same as Alternative 1 with the additional 

improvement of the downstream channel by clearing a 1-foot deep swale with 

an 8-foot bottom width and 6 to 1 sideslopes for the immediate downstream 

channel, and excavating a 4-foot shelf on one side of the channel to 600 LF 

downstream of Cummins Road. The immediate downstream channel must be 

improved to prevent sediment deposition that would occur in the new culverts. 

Further downstream, the channel would be improved to reduce peak flood 

elevations that would be raised by the immediate downstream channel 

improvements. 

Advantages: With this alternative, the new culverts would not silt up and 

become clogged with sediment. Peak flood elevations are reduced at Cummins 

Road and in the downstream channel. This alternative should be permittable. 

Disadvantages: An easement would have to be purchased to make the 

downstream channel improvements feasible. This alternative is more costly 

than Alternative 1. 




Effectiveness: This alternative would reduce the flood elevation at Cummins 

Road from 22.10 ft NAVD to 22.05 ft NAVD, thus achieving a 25-year flooding 

LOS B. 



Description: In this alternative, the existing 18” RCP would be replaced with 2 

- 34”x53” ERCP’s and Cummins Road raised to an elevation of 22.1 ft NAVD. 

The downstream channel improvements from Alternative 2 would be included 

with this alternative. 

Advantages: This alternative should be permittable. Downstream flood 

elevations are not increased. This alternative also keeps the culverts from 

becoming clogged with sediment. 

Disadvantages: An easement would have to be purchased to make the 

downstream channel improvements feasible. Cummins Road would have to be 

raised to elevation 22.1 ft NAVD, 0.4 feet higher than Alternative 1 and 2, to 

accommodate the larger pipe size. 

Effectiveness: This alternative achieves the 25-year LOS flood protection and 

eliminates flooding over Cummins Road. Alternative 3 reduces the flood 

elevation upstream of Cummins Road about the same as Alternative 1 and 2 

and a flooding LOS B would be achieved with this alternative. No adverse 

downstream impacts are realized in this alternative. 

Estimated Cost: Based on the cost estimates made for the 2001 report, this 

alternative would cost slightly higher than Alternative 2. 

Recommendation: Alternative 2 is the recommended alternative. This alternative is 

preferred because, although the project cost is higher than Alternative 1, it is a more 

permanent solution. By improving the downstream channel, the new culverts should 

maintain their full hydraulic capacity since the potential for clogging with sediment will 

be reduced. Also, less maintenance will be needed. Because the cost difference 

would be lower for Alternative 2 as opposed to Alternative 3 (requires raising the road 

elevation 0.4 feet higher than Alternative 3), it is preferred. 

Problem Area AR-2: Greenhills Drive 


A pond located at the Greenhills subdivision is a natural sinkhole converted to a 

permitted stormwater pond. The subdivision is located off of Miller Road directly 

across from the Buckhorn Springs Golf & Country Club. The 25-year and 100-year 




storm floodplains extend from this location east to the large Buckhorn Springs Golf & 

Country Club retention pond, therefore, the 10-year LOS is addressed rather than the 

25-year LOS as no alternative would achieve LOS protection for the 25-year event 

(based on modeling results). Flooding across Greenhills Drive from the sinkhole 

(stormwater pond), located on the north side of the street, is indicated by the flood 

control model to be in excess of one foot for the 10-year storm event. The road 

elevation is 53.7 ft NAVD and the 10-year flood elevation is 56.1 ft NAVD. This pond 

collects stormwater runoff from the Greenhills subdivision and lies within a closed 

basin, has no positive outfall, and is undersized for its drainage basin. This flooding 

problem was apparent during Tropical Storm Gabrielle in September 2001, when the 

pond overflowed and flooded the road and property to the south. No flooding 

problems were reported during Hurricane Frances in 2004 although Frances 

calibration model results do indicate flooding for this area. A pump station had been 

installed in the previous years by the County to help control the flood elevation in the 

pond. However, the pump is insufficient to control the flood elevation to a LOS 

compliant level. An 18” RCP cross drain under Greenhills Drive connects the pond to 

a smaller sinkhole on the south side of the road, but this culvert has been blocked by 

either the local property owner or the County. It should be noted that model 

simulations for this area do not account for any significant percolation or deep 

recharge for these sinkhole ponds. 





Greenhills Drive during Tropical Storm Gabrielle 



Description: Storage should be added to alleviate the flooding. Alternative 1 

is for the County to purchase a portion of the parcel south of Greenhills Drive 

that contains another sinkhole pond.. The newly acquired sinkhole pond would 

need excavation to a 1.8 acre bottom at an elevation of 42.3 NAVD and 3.43 

acre top of bank at elevation 52 NAVD. The Greenhills pond would be 

connected to the newly acquired sinkhole pond by unblocking the existing 18” 

RCP under Greenhills Drive, the water would then be routed from the small 

sinkhole pond through a Type E modified FDOT inlet with a top elevation of 

53.5 NAVD to the newly acquired sinkhole pond via 260 LF of 18” RCP. These 

connections would equalize the peak flood elevations in the three ponds, 

thereby eliminating the LOS deficiency. 

Advantages: This alternative should be easily permittable. The easement for 

the equalizer pipe should be easy to obtain since this alternative relieves 

flooding on the owner’s property. 

Disadvantages: This alternative depends on the ability to purchase the 

property and/or to purchase a drainage easement for the pond. 




Effectiveness: This alternative achieves a 10-year flood protection LOS A for 

Greenhills Drive by reducing the maximum flood elevation in the Green Hills 

pond from 56.1 ft NAVD to 53.7 ft NAVD. This alternative also relieves flooding 

on the property to the south of Greenhills Drive. Alternative 1 does not raise 

the flood elevation in the pond (sinkhole) to the south. 

Estimated Cost: The capital cost of this alternative would be $731,800. 


Description: Like Alternative 1, Alternative 2 involves the purchase of the 

west part of the property with the large sinkhole pond. Also like Alternative 1, 

water would be routed to the small pond just south of Green Hills Drive by 

unblocking the existing pipe under the road. The County would then construct 

an overflow ditch instead of an equalizer pipe to the newly acquired sinkhole 

pond. 

Advantages: This alternative should also be easily permittable, as in 

Alternative 1, to connect the three ponds. The easement for the overflow ditch 

should be easy to obtain since this alternative relieves flooding on the owner’s 

property. This alternative would not include pipe construction as in Alternative 

1. 

Disadvantages: This alternative depends on the ability to purchase the 

property and/or to purchase drainage easements. Also, since the ditch would 

be over thirty-five feet wide at one point, the size of the required drainage 

easement would be greater, as well as excavation costs. 

Effectiveness: Based on the analysis for the 2001 WMP, this alternative also 

achieves a 10-year flood protection LOS A for Greenhills Drive by reducing the 

maximum flood elevation in the Green Hills pond. This alternative also relieves 

flooding on the property to the south of Greenhills Drive. Alternative 2 raises 

the flood elevation in the large sinkhole pond to the south, but the water is still 

contained within the banks of the pond. 

Estimated Cost: Based on the cost estimates from the 2001 Report, the 

alternative would cost approximately 10% less than Alternative 1. 


Description: Alternative 3 also involves the purchase of the west part of the 

property with the large sinkhole pond to the south and then installation of an 

additional pump station. The station would pump to the larger south sinkhole 

pond. 




Advantages: This alternative should also be permittable. The easement for 

the equalizer pipe should be easy to obtain since this alternative relieves 

flooding on the owner’s property. 

Disadvantages: This alternative depends on being able to purchase the pond 

property and to purchase drainage easements. Also, the new station would 

have to pump at a rate of five cubic feet per second to solve this flooding 

problem. This large a pump station would be very costly, especially 

considering a gravity pipeline (Alternative 1) is a viable solution. 

Effectiveness: Based on the analysis for the 2001 WMP, This alternative 

reduces the maximum flood elevation by one foot and relieves flooding to 

Green Hills Drive and surrounding properties. Although Alternative 3 does raise 

the flood elevation in the large sinkhole pond to the south by two feet, the 

water is still contained within the banks of the pond. A 10-year flooding LOS A 

is achieved with Alternative 3. 

Estimated Cost: Based on the cost estimates from the 2001 Report, the 

estimated capital costs for this alternative would be approximately 120% more 

than Alternative 1. 


preferred because, although the initial cost is slightly higher than Alternative 2, it 

would require less maintenance costs. Alternative 1 would also be more desirable for 

the easement property owner because this alternative would not interfere with the use 

of his property. 

Problem Area AR-3: River Drive & Squirrel Run Way 


There are four locations south of Lithia Pinecrest Road and north of the Alafia River 

main channel where flooding LOS deficiencies are identified by model results. The 

southern ends of Pine Street and Rose Street, most of Coconut Grove Place and 

River Drive, and all of Squirrel Run Way are estimated to flood with one to seven feet 

of water during the 10-year storm event. Flooding on these roads and properties is a 

direct result of the flood elevation in the Alafia River. The 10-year peak flood 

elevation in the river in this area is 25.24 ft NAVD. Street and property flooding is 

commonplace in this area during large storm events. There are over seventy 

privately owned properties in this area that lie within the 10-year floodplain of the 

Alafia River. Several flood complaints were received from residents on Squirrel Run 

Way at the first and second Hillsborough County Alafia Public Meeting (2001) for 

severe and frequent property flooding (3-4 feet). One complaint was also reported for 

house flooding, even though the home is on eight-foot stilts. Residents commented 

that the flooding has become more severe in recent years. Two historical flood 

complaints were also received from this area. Tropical Storm Gabrielle and Hurricane 




Frances recently flooded out many residents on these streets and realistic 

alternatives to solve this problem are limited. 

Limits of 10-year 

Floodplain 




Description: Alternative 1 is for Hillsborough County to purchase (on a 

voluntary basis) 74 properties that lie within the 10-year floodplain and allow 

the homeowners to either relocate their homes or have them demolished. The 

County could possibly acquire additional funding via other agencies to help 

fund this land acquisition (i.e SWFWMD) 

Advantages: This alternative has the advantages of no permitting or 

construction costs. This alternative also benefits natural systems by expanding 

wildlife habitats along the Alafia River. 

Disadvantages: The current cost of acquiring all of the flood prone properties 

is over four million dollars. Additionally, it is likely that most property owners in 

this area would not want to sell their property. 




River Drive during Tropical Storm Gabrielle 

Effectiveness: This alternative does not relieve any flooding to the area but it 

does eliminate flood damage for home and property owners. Once all 

properties are county-owned, a 10-year flooding LOS B would be achieved by 

eliminating the roads and properties within the floodplain. 

Estimated Cost: The estimated cost of this alternative would be $4,135,600. 


Description: Alternative 2 is to build a dike that would basically encompass 

these neighborhoods and shield them from the rising Alafia River. This large 

embankment would start from just south of Lithia Pinecrest Road east of River 

Hills and extend to the Alafia River, enclosing all of the flooded streets, and 

then back to Lithia Pinecrest Road again south of River Hills. This dike would 

be well over a mile in length and more than ten feet high in some places. A 

pump station would be constructed within the diked enclosure to collect and 

discharge the local stormwater runoff from within to the river. 

Advantages: This alternative would provide 25-year LOS flooding protection 

for all of the home and property owners. 

Disadvantages: This alternative, while solving the flooding problem, would 

be costly and would be very difficult to permit, as the dike enclosure would 

create a hydraulic encroachment within the Alafia River floodplain. 




Effectiveness: This embankment, if designed properly, would be effective in 

preventing these areas from flooding and provide the 25-year LOS flood 

protection. Estimated Cost: Based on 2001 cost estimates, the estimated 

costs of this alternative is about half of Alternative 1. 


preferred because it is the only realistic solution. This alternative is costly, but a much 

more viable solution than Alternative 2. Alternative 1 also benefits natural systems by 

promoting a contiguous riparian corridor along the Alafia River. 

Problem Area AR-4: Providence Road 


In the Tributary N-11 drainage system, which drains Providence Road and Crescent 

Lake Drive, there are two flooding LOS deficiencies that were identified in the flooding 

conditions assessments. The modeling results indicate that 0.9 feet of water will 

inundate the intersection of Providence Road and Watson Road during the 25-year 

storm. This flooding problem is one of the most severe with respect to both flood 

depth and extent of inundation in the entire watershed, and was clearly evident during 

and after the Tropical Storm Gabrielle in September 2001. Not only was this 

intersection inundated by more than a foot of water, but severe road, property and 

house flooding occurred downstream of this intersection all the way to the Alafia 

River. This area was again severely flooded during Hurricane Frances (2004) with 5 

separate flooding complaint locations including; Watson Rd/Providence Rd 

intersection, 2 other Providence Rd. locations, Cresent Lake Dr and Mathers Ln. 

The entire drainage system from the Watson Road intersection to the river needs 

improvements to alleviate flooding. The existing 24” HDPE culvert under Watson 

Road that drains the area between Watson Road and Bloomingdale Drive is not only 

completely blocked, but also insufficiently sized to convey the peak discharge from 

the 25-year design storm event. Additionally, almost every driveway culvert in the 

Providence Road channel downstream of this intersection is crushed, buried or silted 

up. The problem is compounded by the extremely flat grade of the channel. A LOS 

deficiency was also identified at the cross drain under Crescent Lake Drive, which is 

part of the downstream drainage system. This 22”x36” CMPA, installed in the mid- 

1980’s, is also undersized. Further downstream is the Alafia Drive cross drain where 

a corroded 36” CMP and a badly silted 27”x43” CMPA convey floodwaters to the 

Alafia River. Both structures are unmaintained, aged and insufficient. Additionally, 

the channel downstream of the Alafia Drive crossing is undersized and needs to be 

widened to convey the higher flows resulting from removing the upstream 

constrictions in the drainage system. 





Typical Providence Road driveway culvert 

Providence Rd./Watson Rd intersection 

during Tropical Storm Gabrielle 



Description: This alternative includes the replacement of all the undersized 

culverts within the Crescent Lake Drive/Providence Road conveyance system 

with 4’ x 8’ RCBC’s. This would reduce 25-year peak flood levels to below the 

crowns of these roads. These culvert replacements would include the four 

identified roadway cross drains and approximately ten driveway culverts. 

The 10’ long sill weir in the mitigation wetland west of Providence road will be 

replaced with a 40’ long sill weir at the same control elevation of 18.09 NAVD. 

The undersized culverts under Providence Road connecting the wetland 




mitigation area to the ditch system will be replaced with three 38” x 60” 

ERCP’s. 

Upsizing the culverts under Mathers Lane and Magnolia Drive (a.k.a. Alafia 

Drive) with 5’ x 8’ RCBC’s would reduce flood levels through the downstream 

mobile home park. Minor re-shaping of the roadside and outfall ditches would 

also be necessary to accommodate the larger culverts. Although this 

alternative would increase peak flow rates within the ditch, peak flood stages 

would be reduced throughout the tributary due to more efficient conveyance. 

Peak flow rates and flood stages within the Alafia River would not be adversely 

affected by this project because the river’s peak stage occurs more than two 

days after the peak of Tributary N-11. 

To accommodate the improvements, a 10’-15’ wide drainage easement would 

be required from the properties fronting the east side of Providence Road and 

the north side of Crescent Lake Drive. In addition, acquisition of a 40’ wide 

drainage easement along the length of the existing ditch between Crescent 

Lake Road and the Alafia River would be needed for construction and 

continued maintenance. 

Advantages: This alternative does not require additional storage. This 

alternative should be permittable. 

Disadvantages: Several drainage easements would have to be purchased in 

order to make the necessary improvements to the drainage system. 

Environmental permit requirements may include wetland mitigation. 

Effectiveness: This alternative will achieve a 25-year flooding LOS A 

condition along Providence Road and Crescent Lake Drive and a 25-year 

flooding LOS B at the intersection of Providence Road and Watson Road. The 

project will also reduce peak flood elevations downstream through the mobile 

home park to the Alafia River. 

Estimated Cost: This alternative would cost approximately $1,258,784. 


Description: Alternative 2 would include raising Providence Road 

approximately 30”, to an elevation of 22.9 ft NAVD, and increasing the flood 

storage within the existing wetland mitigation area west of Providence Road. 

The mitigation area currently accepts stormwater runoff from portions of 

Bloomingdale Hills Subdivision, Bloomingdale Avenue, and several subbasins 

along U.S. 301. The existing control structure for the mitigation area would be 

modified to increase the flood storage in the mitigation area. The existing 




control weir elevation would remain at 18.09 ft NAVD, and the weir opening 

would be reduced to lower the peak discharge rate and delay the time to peak. 

Although this alternative would reduce peak flow rates and flood stages along 

Crescent Lake Drive, flood stages would increase near the intersection of 

Providence Road and Watson Road. This increase is due to raising 

Providence Road and peak stages in the mitigation area, effectively severing 

the floodplain on the east side of the Providence Road/Watson Road 

intersection from the mitigation area on the west side. The mitigation area 

currently provides flood relief for the intersection. 

Advantages: This alternative does not require the purchase of drainage 

easements and does not require replacing any culvert replacements. 

Disadvantages: This alternative increases peak flood stages at the 

intersection of Watson and Providence Road. Also, increasing flood storage in 

the existing mitigation area would require modifying the existing permit for the 

mitigation area. 

Effectiveness: This alternative provides flood relief for Crescent Lake Drive 

and the mobile home park downstream, but because this alternative increases 

flood levels upstream and does not meet the prescribed 25-year LOS in all 

locations, it is not recommended. A flooding LOS D remains for Alternative 2. 

Estimated Cost: Based on 2001 cost estimates, the estimated costs of this 

alternative is about 30% more than Alternative 1 


Description: This alternative is essentially a combination of Alternatives 1 and 

2, with the exception that the culverts would be replaced with 3’ x 8’ RCBC’s 

instead of 4’ x 8’ RCBC’s. The increased attenuation provided by the 

mitigation area would reduce the required size of the culverts along Providence 

Road and Crescent Lake Drive. The project will also reduce peak flood 

elevations downstream through the mobile home park to the Alafia River. 

Advantages: 

The advantage of this alternative is lower costs for culverts. 

Disadvantages: The costs of raising Providence Road and modifying the 

mitigation area structure would exceed the savings resulting from installing 

smaller culverts. Therefore, the total costs of this alternative would exceed the 

costs of Alternative 1 and would come without any recognizable benefits. 




Effectiveness: Alternative 3 will achieve flood LOS A for Providence Road 

and Crescent Lake Drive for the 25-year design storm. 

Estimated Cost: Based on 2001 cost estimates, the estimated cost of this 

alternative is double the cost of Alternative 1 

Recommendation: Alternative 1 is the recommended alternative. It is the most costeffective 

alternative that provides a 25-year LOS A flood protection for the majority of 

the drainage system. 

Problem Area AR-5: Stearns Road / Hillgrove Road 


The Stearns Road / Hillgrove Road intersection just east of Lithia Pinecrest Road was 

identified by modeling analysis to not meet the 25-year LOS criteria. Road, yard and 

some structure flooding is indicated in this area. In the 2001 WMP the flood elevation 

over Stearns Road is 45.27 ft NAVD and the Stearns Road crown is at 44.6 ft NAVD. 

Much of this flooding is floodwater that overtops Stearns Road from an undersized 

culvert located on the south side of the road, and then flows overland to a large 

depression north of Stearns Road. This culvert, approximately 400 feet long, is a 36” 

CMP connecting the Stearns Road roadside ditch and the Stearns Creek channel 

heading south. This 36” CMP conveys flow from three 3.5’ x 11’ box culverts a few 

hundred feet upstream at Lithia Pinecrest Road. There are numerous flood 

complaints in this area from various sources that verify this flooding problem. 

Significant road and yard flooding at the corner of Hillgrove Road and Stearns Road 

was reported by a local resident at the first Alafia River Watershed Management Plan 

Public Meeting. This intersection is directly across the street from the culvert inlet. 

Two flood complaints in the same location were reported to the County: one indicated 

that approximately nine blocks were under water and the other indicated flooding in 

the area of the pipe inlet. The County East Service Unit also reported flooding down 

the Stearns Road east of this culvert inlet. 

In addition to the LOS deficiency there are several other drainage problems in this 

area. Stearns Road does not have a drainage system and water ponds on the side of 

the road and in yards. Also, a local resident reported severe property and house 

flooding on property north of Stearns Road after Tropical Storm Gabrielle. 3 separate 

flooding locations were also reported during Hurricane Frances. A large depression 

located north of Stearns Road receives all the drainage for this closed basin. This 

depression at one time was drained by a drainage well that maintained a water 

surface elevation of approximately 30.3 ft NAVD. In recent years, this drainage well 

was plugged by the SWFWMD. Since this storage area no longer has an outfall, the 

stage in the depression is maintained higher for a longer time following a storm. With 

this reduction in available flood storage, during large events floodwater will stage up 

and flood nearby homes and/or property. The drainage system on Hillgrove Road is 

also insufficient, as road and yard flooding is commonplace during large rainfall 




events. When Stearns Creek stages up, the water that would normally drain from 

Hillgrove Road into the Stearns Road ditch under Stearns Road, backs up on 

Hillgrove and sheets eastward to the closed depression north of Stearns Road. 

Drainage improvement is being implemented in CIP 47343 and is scheduled to go to 

construction upon completion of permitting. 


Flooding on Hillgrove Road 

36” CMP culvert on Stearns Road 

Problem Area AR-6: Whitlock Place Retention Pond 


Severe street and house flooding is predicted for the north end of Whitlock Place and 

Herndon Street, both located off Durant Road. The hydrologic/hydraulic model 

indicates a flood elevation of 51.7 ft NAVD for the 25-year storm event at the subject 




pond. The elevations of the street and lowest finished floor are 47.6 ft NAVD and 

50.1 ft NAVD respectively. This retention pond was constructed at the lowest point in 

a very large closed basin and has no outfall. There are four historical flood 

complaints from the El Nino events and one complaint from the East Service Unit in 

the immediate vicinity, and flooding at this location is a recurring problem. The 

service unit reported that the Whitlock Place retention pond is a poorly drained 

percolation pond. During Tropical Storm Gabrielle in September of 2001, emergency 

pumping measures were taken to alleviate flooding from the north end of Whitlock 

Place and Herndon Street. Again in 2004 (Hurricane Frances) flooding was reported 

(although this was due to the pump station not working) on Herndon St. This pond is 

poorly designed and a permanent solution to this problem is needed. 

DOVER RD S 

DOVER WOODS 

SUBDIVISION 

EXISTING WHITLOCK PLACE 

RETENTION POND 

HERNDON ST 

WHITLOCK PL 

EXISTING DRAINAGE 

EASEMENT 

MARTIN RD 

DURANT RD 




Description: This alternative consists of the construction of a 10 cfs pump 

station at the pond location to pipe stormwater northward via a force main to 

Durant Road and then east along Durant Road to a creek that discharges into 

Stearns Lake and eventually into the Alafia River. The pump would keep the 

pond dry, provide an outfall, and provide immediate relief to the flood prone 

area. 

Advantages: This alternative allows the County to utilize the right-of-way 

along Durant Road and limits easement purchases if any. This alternative also 




gives this large closed basin an outfall. Permitting this alternative should be 

fairly simple. 

Disadvantages: This alternative will require a very large pump station and 

force main. The station would have to pump flows more than 4500 feet against 

a static head of over 20 feet. This alternative would also require continual 

operation and maintenance costs. There may be adverse impacts to Stearns 

Lake and downstream receiving waters created by the pump discharge. 

Effectiveness: According to 2001 modeling results, this pump station would 

not prevent home or street flooding for the 25-year event. It would provide 

immediate flood relief for the area, but a 25-year flooding LOS D would remain 

for Alternative 1. 


alternative is about 30% less than Alternative 2 


Description: In this alternative, the County would purchase part of the 

existing farmland property to the northeast of Whitlock Place and construct a 9- 

acre retention pond to provide additional storage for this closed basin. The 

pond bottom would be at elevation 41.49 ft NAVD. Additionally, a 30” RCP 

would be installed between the existing Whitlock retention pond and the newly 

constructed pond to equalize water surface elevations in the two facilities. The 

County would also purchase property south of Durant Road to construct a 1.4- 

acre retention pond and the existing 24” CMP draining this area to the Whitlock 

Place Detention pond would be severed. 

Advantages: This project utilizes the existing drainage easement between the 

north side of the existing pond and the proposed pond. This alternative also 

would not require any operational costs as does Alternative 1. Alternative 2 

would not raise downstream flood elevations. This project should be feasible 

and permittable. 

Disadvantages: Alternative 2 is more costly than Alternative 1 and is 

dependent on the purchase of the property north of Whitlock Place. 

Effectiveness: Alternative 2 does not achieve the desired LOS for the 25-year 

design storm. The street elevation is 47.6 ft NAVD and the 25-year peak flood 

elevation is 48.5 ft NAVD. This alternative does eliminate structure flooding on 

both Whitlock Place and Herndon Street (finished floor elevation is 50.1 ft 

NAVD). Additionally, this alternative achieves a 10-year flooding LOS A for the 

entire area (the 10-year peak elevation is 46.9 ft NAVD). A 25-year flood LOS 

C would be achieved for Alternative 2. 




Estimated Cost: This alternative would cost approximately $2,946,400 


Description: This alternative consists of all the improvements from Alternative 

2 plus purchasing additional property, possibly to the west of Durant Road for 

additional storage. Approximately 70 more acre-feet of storage would be 

required to eliminate all flooding in this area for the 25-year storm event and 

achieve a flooding LOS A. A more current detailed modeling analysis of this 

subbasin would have to be conducted to determine the amount and location of 

additional required storage. 

Advantages: This project would utilize the existing drainage easement 

between the north side of the existing pond and the proposed pond. This 

alternative would also not require any operational costs as Alternative 1 does 

with the pump station. Alternative 2 would not raise any downstream flood 

elevations. This project should be feasible and permittable. 

Disadvantages: This alternative has the same disadvantages as Alternative 

2. It also has the disadvantage of even higher costs than Alternative 2. 

Effectiveness: Provided enough available storage is created, this alternative 

could meet the 25-year LOS criteria for roads and structures in Hillsborough 

County. A 25-year LOS A could be achieved with Alternative 3. 


alternative is about 20% more than Alternative 2 

Recommendation: Alternative 2 is the recommended alternative. Although 

Alternative 2 does not achieve the 25-year flood LOS protection for county roads, it 

does achieve the 10-year LOS A, and eliminates structure flooding for the area. Also, 

the two roads that would become inundated are dead-end roads and no traffic would 

be hindered by these flooded streets except for local traffic associated with the 

residents that live at the end of Whitlock Place and Herndon Street. 

Problem Area AR-7: Dee Circle & Alafia Ridge Road 


Road and yard flooding along Alafia Ridge Loop was reported at the first Alafia River 

Watershed Management Plan Public Meeting. The flooding on Alafia Ridge Road is 

primarily due to the north pond of Dee Circle. This pond outfall discharges directly to 

Alafia Ridge Road through an undersized outfall pipe where the only means for 

conveyance is by sheet flow down Alafia Ridge Road. Street and yard flooding on 

Dee Circle was also reported by the Hillsborough County South Service Unit and in 




the Hillsborough County historical flood complaints. This flooding originates from the 

south stormwater pond on Dee Circle. The pond is undersized and floods over the 

bank onto Dee Circle and into residential yards during heavy rainfall events. Both 

Alafia Ridge Road and Dee Circle are located off McMullen Loop east of McMullen 

Road. It should be noted that these ponds are in a tertiary drainage system and were 

not included in the existing conditions hydrologic/hydraulic model analyses. 

The County addressed these problems and contracted Reynolds, Smith and Hills Inc. 

(RS&H) to do an alternative analysis (CIP # 47075 and 40021). The CIP’s were 

completed in 2003 and reflected in the WMP update. This area now meets the 25- 

year LOS A. 


Outfall pipe from the north pond (ditch) 

Dee Circle 

Undersized pond (south) on Dee Circle 




Problem Area AR-8: Revels Road 


Street and property flooding at Revels Road was reported at the first Alafia River 

Watershed Management Plan Public Meeting. During significant rainfall events, 

stormwater runoff flows across Revels Road from the south and then to the west at 

the turn in Revels Road. This drainage problem was witnessed during Tropical Storm 

Gabrielle in September 2001. During a Parsons field investigation, a deficient and 

unmaintained secondary drainage system was discovered. This tertiary drainage 

system was not included in the hydrologic/hydraulic modeling analysis, but drainage 

improvements throughout this system are needed to resolve this problem. 


Revels Road looking west during 

Tropical Storm Gabrielle 

Driveway culvert on Revels Road 






Description: Alternative 1 consists of general improvements to the entire 

drainage system. The drainage system should be extended 300 feet east on 

the south side of the road to collect road runoff and stormwater runoff from the 

south. This would require installing one driveway culvert. Additionally, two 

existing driveway culverts are in need of replacement. Also, the entire ditch 

system on Revels Road needs maintenance improvements. 

Advantages: Nearly all recommended improvements lie within the existing 

right-of –way. This project is also highly permittable. 

Disadvantages: Drainage easements must be acquired to complete all 

recommended improvements. 

Effectiveness: If engineered properly, this alternative would relieve all street 

flooding and provide flood LOS protection for Revels Road. It is assumed that 

this alternative would achieve at least a 25-year flooding LOS B. 

Estimated Cost: The approximate cost for this alternative is $63,700 


Description: Alternative 2 incorporates all improvements from Alternative 1 

but would involve only maintenance of the existing driveway culverts by 

clearing them out rather than replacing them. 

Advantages: This alternative carries the same benefits as Alternative 1 and 

has the benefit of a slightly lower cost. 

Disadvantages: Drainage easements must be acquired to complete all 

recommended improvements. Also, simply clearing the culverts may not solve 

the problem, and replacement may ultimately be necessary to achieve the 

target flooding LOS. 

Effectiveness: If engineered properly, this alternative should relieve all street 

flooding and provide a 25-year flood LOS B protection for Revels Road. 

Estimated Cost: The approximate cost of this alternative is $42,700. 

Recommendation: Alternative 1 is the recommended alternative. Although 

Alternative 1 has a slightly higher cost, the existing driveway culverts are old and in 

need of replacement. Also, replacement may still ultimately be necessary to provide 




proper conveyance of the secondary drainage system. It is anticipated that the 

recommended alternative will achieve at least a 25-year flooding LOS B. 

Problem Area AR-9: Magnolia Street 


A complaint from the first Alafia River Watershed Management Plan Public Meeting 

indicated road flooding on Magnolia Street, a small peninsula directly on the Alafia 

River. Magnolia Street is located off Riverview Drive just west of the I-75 interchange. 

After heavy rainfall events, a low spot in the road floods with up to six inches of water. 

After meeting with the complainant, it was determined that the runoff is unable to 

reach the culvert inlet at the flooded area. The shoulder in the right-of-way is much 

higher than the road or the culvert inlet, thus impeding the drainage path. 

Additionally, a county-owned drainage easement one parcel east is eroding away 

where a stormwater pipe discharges into the Alafia River. The property owner 

adjacent to the easement indicated several feet of bank has eroded over the past few 

years. 




Description: Alternative 1 consists of regarding of the drainage path from the 

road to the culvert inlet in the right-of-way on the south side of the road in front 

of 8611 Magnolia Street. This would allow the runoff to flow into the culvert 




inlet before ponding in the street. This alternative would require very little 

excavation. 

Advantages: This alternative would require very little cost to the county. The 

project is located in an existing right-of-way. 

Disadvantages: There are no disadvantages to this alternative. 

Effectiveness: This alternative would allow the water to reach the culvert inlet 

and relieve the road flooding. It is expected that this alternative would achieve 

at least a 25-year flooding LOS B for Magnolia Street. 

Estimated Cost: This alternative would cost approximately $2,000 


Description: The County should repair/replace the eroded riverbank within 

the County easement in conjunction with installing a headwall to prevent future 

bank erosion. 

Advantages: Repairing the eroded bank will help keep the existing stormwater 

pipe from being exposed and protect it from damage. This alternative will 

prevent future bank erosion. 

Disadvantages: Besides protecting the pipe, repairing the bank has no other 

functional benefit. 



Description: Alternative 3 is the combination of Alternatives 1 and 2. 

Advantages: This alternative carries the benefits of Alternative 1 and 2. 

Disadvantages: This alternative has the disadvantages of Alternatives 1 and 

2 


Recommendation: Alternative 3 is the recommended alternative. All components of 

this alternative lie within County right-of-way and this alternative has a low cost. It is 

expected that this alternative would achieve at least a 25-year flooding LOS B for 

Magnolia Street. 


Problem Area AR-10: Watson Road/Ivy Estates 




A section of Watson Road, south of the entrance to Ivy Estates Subdivision is prone 

to severe flooding. This section of Watson Road was constructed through a natural 

depressional area that has no surficial drainage outfall. A stormwater retention pond 

for the Ivy Estates subdivision was constructed east of Watson Road as part of the 

natural depressional area. A small part of the depressional area remains isolated on 

the west side of Watson Road. During significant rainfall events, the stormwater 

retention pond fills up and overtops its banks, flooding Watson Road. The retention 

pond has no outfall and typically remains flooded for extended periods of time. The 

flooding hinders access to the newly constructed Symmes Elementary School, which 

is located south of the Ivy Estates Subdivision on Watson Road. 

This flooding problem was the subject of a study conducted by Environmental 

Research and Design, Inc. (ERD), for Hillsborough County (CIP # 47299). The 

results of this study were summarized in the report “Watson Road Drainage 

Improvement Project Evaluation Phase Results”, May 2001. The report considered 

several project alternatives including; (1) construction of an additional stormwater 

retention pond, and (2) providing a gravity outfall for the existing retention pond. The 

recommended alternative from this study consists of elevating the crown of Watson 

Road to elevation 29.8 ft NAVD and regrading the existing stormwater retention pond 

in order to accommodate the higher Watson Road elevations and to provide 

additional storage. 

CIP # 47299 was completed in 2003 and includes a pump station, but did not raise 

the road. These improvements did not correct the LOS deficiency. Watson Road still 

has a 10-year and 25-year LOS D with flood stages of 30.88 ft NAVD and 31.65 ft 

NAVD, respectively. Without raising the road, road flooding will persist. 





Watson Road just south of Bloomingdale Ave. after Tropical Storm Gabrielle 


Problem Area AR-11: Riverglen Detention Pond 




Improper function of the outfall for Riverglen detention pond on the corner of 

McMullen Road and McMullen Loop causes the pond to overtop the bank and flood 

across McMullen Loop. The water also causes flooding down Valrie Lane as well as 

exacerbating the flooding on Alafia Ridge Road, as witnessed during recent storm 

events. From visual inspection during field visits, the Riverglen pond top of bank 

appeared to be at a lower elevation than the top of the control structure. It is 

uncertain whether the pond bank is not at the correct elevation or if the control 

structure was poorly designed or constructed. 





The north bank of Riverglen detention pond during Tropical Storm Gabrielle 



Description: Hillsborough County staff has referred this matter to County 

Enforcement to take action against the owner and Engineer of Record to 

correct what is perceived to be a design or construction problem of the pond 

outfall. 

Advantages: This alternative has the benefit of no capital costs to the County. 

Disadvantages: The only disadvantage to this alternative is that it may take a 

long time to actually get the owner and Engineer of Record to take the actions 

necessary to remedy this deficiency. 

Effectiveness: If the outfall for this detention pond is reconstructed and/or 

designed correctly, it is assumed that the pond should meet the County’s 25- 

year target LOS B. 

Estimated Cost: There would be no cost to the County for this alternative. 





Description: Alternative 2 is for the County to take initiative to rectify the 

problem on its own. The County would either have the problem analyzed and 

corrected internally, or hire an outside consultant to survey and conduct an 

independent analysis. 

Advantages: The only advantage to this alternative is that the problem would 

be addressed and corrected sooner than if the County waited for the 

responsible parties to do so. 

Disadvantages: This alternative has the disadvantage of having to use 

County funds. 

Effectiveness: If the outfall for this detention pond is reconstructed and/or 

designed correctly it is assumed that the pond should meet the County’s 25- 

year target LOS B. 

Estimated Cost: 

alternative. 

There would be minimal costs associated with this 

Recommendation: Alternative 1 is the recommended alternative. The County 

should be able to enjoin the owner and Engineer of Record to correct the problem. 

This would be at no capital cost to the County. 

Problem Area AR-12: Lula Street 


Lack of cross drain at low-lying area northeast of the Lula Street and Anna Avenue 

intersection results in flooding of Lula Street and possible structure flooding. Flood 

complaints were made by residents during Hurricane Francis. Hydraulic and 

hydrologic modeling confirms flooding in this area but no LOS violation. Flooding in 

this area could be tidally influenced. 





Alternative: 

Description: Install two 18” RCP cross drains under Lula Street in the vicinity 

of the depression. 

Advantages: This alternative relieves street and structure flooding. 

Disadvantages: No disadvantages. 

Effectiveness: This project eliminates road flooding for the 25-year event and 

structure flooding for the 100-year event and provides 25-year LOS A. 

Estimated Cost: This alternative would cost approximately $10,100 

Recommendation: Only one alternative was investigated and it is the recommended 

alternative. All components of this alternative lie within County right-of-way and this 

alternative has a low cost. It is expected that this alternative would achieve at least a 

25-year flooding LOS A for Lula Street. 


Problem Area AR-13: Four Winds Subdivision 




Flooding complaints have been made in the Four Winds Subdivision. For the 10-year 

storm event, the model predicts street flooding depths of over 1.8 feet and 2.8 feet for 

the south and north ponds, respectively. Water backs up in the south pond due to the 

undersized 36" x 58" arch CMP connection to the north pond and water in the north 

pond is backed up due to the undersized 22" x 36" arch CMP connecting it to the 

ditch on the west side of King Avenue and dense vegetation in the ditch. 


Alternative: 

Description: This alternative is to redirect a portion of the stormwater runoff 

currently conveyed to the south pond by severing the stormwater collection 

system at the intersection of Southview Drive and Pinedale Street and 

reconnecting it to the north pond stormwater collection system via 720' of 30" 

RCP along Pinedale Street. Replace the existing control structure in the north 

pond with a 60' sill weir at the existing control elevation of 20.4 NAVD. A 5' x 8' 

RCBC would connect the downstream side of the sill weir to the collection ditch 

on the west side of Kings Avenue. Finally, the collection ditch must be cleared 

of excessive vegetation to ensure no downstream impacts. 

Advantages: This alternative relieves street and structure flooding while not 

requiring the purchase of drainage easements. 

Disadvantages: Traffic along Pinedale Street will be disrupted while 

construction of the new stormwater drainage system is underway. 




Effectiveness: This project eliminates road flooding for the 10-year event and 

structure flooding for the 100-year event and provides 25-year LOS C. Stages 

are increased in the channel downstream of the improvements for the 

25yr/24hr event by ~ 0.5 feet but are still well within the limits of the top-ofbank 

(TOB) of the channel (25yr proposed stage at 702615 is 21.88 ft NAVD 

compared the channel TOB at ~ 24.5 ft NAVD) 

Estimated Cost: This alternative would cost approximately $1,008,500. 

Recommendation: Only one alternative was investigated and it is the recommended 

alternative. All components of this alternative lie within County right-of-way – lowering 

the cost of this alternative. It is expected that this alternative would achieve at least a 

10-year flooding LOS A for Four Winds Subdivision. 


. 

Chapter 15 

parsons


Chapter 15 – Proposed Plan and Level of Service 

CHAPTER 15 

PROPOSED PLAN AND LEVEL OF SERVICE 


As discussed previously in Chapter 13, upon the successful completion of the 

development and calibration of the detailed hydrologic and hydraulic model of the 

Alafia River Watershed primary and secondary drainage systems, the next step was 

to apply the model to assess the performance of the basin-wide drainage facilities for 

a given set of design storm events. Results of these simulations were then analyzed 

with respect to the County’s adopted flooding level of service criteria (LOS) to identify 

locations within the watershed where the LOS are not being met. Identified water 

quality and natural systems problems and issues were not reevaluated in this study. 

Alternatives were developed and evaluated to address the identified problem areas. 

This chapter presents the preferred alternatives and recommendations for the 

implementation of a watershed management plan for the Alafia River Watershed in 

Hillsborough County. 

15.2 PROPOSED PLAN AND LEVEL OF SERVICE 

15.2.1 Flood Control Projects 

The proposed alternative recommendations from Chapter 13 were analyzed and 

evaluated using the design storm events described in Chapter 4 to establish a 

proposed level of service for each subwatershed – collectively, these projects 

comprise the proposed condition “masterplan”. 

Except for the Buckhorn Creek Subwatershed, the proposed projects were designed 

with the objective of obtaining the target level of service of 25-year, LOS B condition. 

This is therefore the proposed LOS criterion for the Alafia River Watershed. For the 

Buckhorn Creek Subwatershed, the proposed flood control projects were designed 

with the goal of achieving a 25-year, LOS B condition at those locations for which 

alternatives were considered. Recall that the County’s adopted LOS for Buckhorn 

Creek is a 10-year, LOS B, and problem areas were identified based on this criterion. 

With the implementation of the proposed recommendations, there will still be 

locations where a 25-year, LOS B condition is not met. Therefore, the proposed 

flooding level of service for the Buckhorn Creek Subwatershed is a 10-year, LOS B 

condition. 

The “Project Fact Sheets” and corresponding CIP evaluation sheets for each project, 

located at the end of this chapter, provide detailed summaries of the preferred 

alternatives for the flood control projects recommended as a part of the Alafia River 

Watershed Management Plan. These sheets provide summaries of the information 

discussed in Chapter 13, and the reader is referred there for more details. On these 

sheets are the name and location of the project, a location map, problem summary, 




description of the preferred alternative solution, environmental issues, and a project 

cost estimate. These are located at the end of the chapter in alpha-numeric order. 

15.2.2 Water Quality Improvement Projects 

Water quality improvement alternatives were not evaluated for the Alafia River 

Watershed Update. Please refer to the 2002 Alafia River Watershed Management 

Plan for proposed water quality improvement projects. 

15.2.3 Natural Systems Enhancement Projects 

Natural system enhancement projects were not evaluated for the Alafia River 

Watershed Update. Please refer to the 2001 Alafia River Watershed Management 

Plan for proposed water quality improvement projects. 

15.3 PRIORITIZED LIST OF RECOMMENDED PROJECTS 

The successful implementation of the Alafia River Watershed Management Plan will 

require a logical plan or order for the construction of the recommended stormwater 

management, environmental enhancement, and water quality improvement projects 

which were developed and documented in the previous report sections. To 

accomplish this task, the County’s CIP Evaluation Matrix was completed for each 

flood control project. 

15.3.1 Flood Control Projects 

Flood control projects were evaluated using the County’s CIP Evaluation Matrix. By 

applying points, this matrix evaluates flooding conditions for the existing condition of 

a proposed project location based on: increased hazard (9), arterial road flooding (6), 

local street flooding (4), home flooding (6), and yard flooding (4). A weighted 

multiplier value of 10, 6, and 3 was applied to these flooding conditions based on the 

storm frequency during which they occur (2.33-, 5-, and 10-year, respectively). In 

addition to evaluating flooding conditions based on storm frequency these other 

factors are evaluated with points applied: number of years flooding problems have 

persisted (up to 10), erosion/siltation (20), high ground water table (20), maintenance 

problem (20), and structural failure (80). The “CIP Evaluation Matrix” for each 

proposed project is located at the end of this chapter with the corresponding “Project 

Fact Sheets” in alpha-numeric order. 

The recommended prioritization plan for the proposed Alafia River Watershed 

Management flood control capital improvement projects is presented in Table 15.3-1. 

This table presents, in an ordered ranking, the set of preferred flood control projects, 

complete with estimated capital costs and CIP evaluation prioritization rankiing 

scores. The order of ranking does not imply a rigorous preferred order of 

implementation, since many of these projects received similar ranking scores. Other 

factors such as available funding, land purchase requirements, permitting 

requirements, and socio-political issues will influence such decisions. 




TABLE 15.3.1 

FLOOD CONTROL PROJECT PRIORITIZATION PLAN 




15.4 OPERATION AND MAINTENANCE PLAN RECOMMENDATIONS 

Comprehensive, regular maintenance of stormwater management systems is 

essential to ensure the efficient function of existing stormwater conveyances and that 

new stormwater facilities, once constructed, continue to function within their original 

design parameters for many years. Maintenance is also often required for 

prevention of water quality degradation, exotic species control, aesthetics, and safety 

reasons. This section outlines recommended maintenance practices and schedules 

for the Alafia River Watershed. 

15.4.1 Routine Maintenance Activities 

Mowing and Clearing Practices 

The mowing of grass and clearing of channels is the most typical maintenance work 

performed by County Service Unit maintenance crews. Side slopes, embankments, 

emergency spillways, and other grassed areas of stormwater systems should be 

periodically mowed. This prohibits growth of woody species and controls 

herbaceous weeds. Occasional hand removal of invasive vegetation is required. 

Residue from ditch clearing is of two types, cut vegetation and the sediment and 

soils removed from structures or ditch reshaping. Remains of these activities should 

not be lost within the channel nor piled along the banks of the ditch. Otherwise, the 

next large storm event will simply wash these materials downstream to clog 

downstream structures or pollute downstream waterways. Once heavy vegetation is 

cut, it should be removed from the channel and disposed of, preferably at a 

composting facility, as it does not contain the metals or environmentally 

objectionable materials that the soils contain. The soil residue must be disposed of 

at approved landfills. 

The use of water-tolerant, pest-tolerant and slow growing grasses is recommended 

when appropriate. Planting with native wetland species is even more appropriate as 

is the creation of longitudinal wetland/sloughs to provide opportunities for stormwater 

treatment. Note that excessive vegetation, particularly exotic or invasive species 

and plants with stiff, woody stems is not the same as planting with native species 

however. This kind of growth can greatly increase the resistance to flow, reducing 

the capacity of the channel, cause blockages to culverts and bridges, and ultimately 

generate higher flood levels. 

Excessive sediment accumulation also reduces the capacity of the channel to 

convey floodwaters by reducing the cross sectional area and hydraulic radius of the 

channel, creating an effect similar to that of excessive vegetation as described 

above. 

Erosion Control Practices 

Channel degradation, embankment instability and channel bed loss are results of 

erosion and scour caused by instability in the equilibrium of the geometry of the 

stream system. Erosion and scour are a natural part of stream geomorphology. The 




stream minimizes the energy needed to move sediment and water, evenly 

distributing that energy along the reach. This creates the meander or movement of 

the stream back and forth within the floodplain over time. 

Anthropogenic activities disrupt this equilibrium, causing excessive suspended 

sediments in the streams, channel degradation, embankment instability and channel 

bed loss. Excessive suspended sediments may result in undesirable environmental 

impacts, aesthetic problems, and high maintenance costs. 

Erosion protection should be addressed during the design phase of each project 

recommended in this study. Typical erosion control standards are slope control, i.e., 

3H:1V minimum side slopes planted with native vegetation. For steeper side slopes 

there are man-made and natural materials that can be used for erosion protection of 

stream banks such as erosion control blankets, mats and grids. There are “hard” 

protection materials such as riprap, gabions, armorjacks, etc. and for the ultimate 

protection, there are walls and channel linings. 

Poor agricultural practices are a common cause of sediment transport within the 

Alafia River Watershed. Agricultural activities are not regulated in the same fashion 

as other anthropomorphic land use activities and many farmers do not incorporate 

any type of best management practices. As a result, certain agricultural activities, in 

particular the use of plastic mulch, create a variety of stormwater management 

problems, one of which is increased downstream sediment loads. This topic is 

discussed further in Chapter 15.5. 

Stormwater Management Facility Maintenance and Rehabilitation 

Qualified personnel should conduct periodic inspection of all existing and new 

stormwater management structures for structural integrity, safety, accumulated 

sediment, vegetation, and obstructions. Vegetation and accumulated sediment 

should be removed, as needed, from water level control structures to ensure proper 

functioning. These facilities should be able to function for several decades without 

requiring regular maintenance except for that described above. However, all 

infrastructure is continually deteriorating and should be inspected periodically 

(approximately every 2 years) to identify those in need of replacement. When they 

are identified for replacement, the design should be evaluated to determine the 

appropriate size for the structure to meet current design criteria for the flood 

protection level of service. 

There are many older stormwater facilities located throughout the Alafia River 

Watershed, which do not have access easements or right-of ways such that 

maintenance crews are able to perform maintenance on these facilities. This creates 

a difficult situation for the Service Units. If County access to a stormwater facility 

doesn’t exist or is insufficient, then an easement or legal agreement with adjacent 

property owners needs to be secured for maintenance access. It should not be the 




responsibility of the maintenance crews to find solutions for these situations nor 

should these situations simply be overlooked or viewed as hopeless. 

New facilities are required by the Planning and Growth Management Department’s 

Stormwater Management Technical Manual to provide drainage easements of 

sufficient size to accommodate maintenance. This is an element of the development 

review permitting process that should not be overlooked. Stormwater department 

and Service Unit review should be included as part of the review process before new 

development plans are approved. 

15.4.2 Identified Maintenance Needs 

Table 15.4-1 lists specific locations by subwatershed within the Alafia River 

Watershed with immediate maintenance requirements. These locations were 

identified in the 2002 Alafia River Watershed Management Plan over the course of 

that study during field investigations, interviews with County Service Unit personnel, 

and review of field survey records and photographs recorded by survey crews. 

Table 15.4-1 lists the location, nature of maintenance problem, and recommended 

course of action to be taken. If no maintenance measures have been taken, the 

same course of action is recommended. 

15.4.3 General Maintenance Recommendations 

Preventative, regularly scheduled maintenance is highly preferable and cost effective 

as opposed to an alternative crisis management style of maintenance. A sound 

operation and maintenance plan will have an inspection and monitoring program, 

integrated with a tracking system, to prioritize and schedule necessary maintenance. 

Hillsborough County Service Unit staff has indicated they spend a majority of their 

time responding to non-scheduled maintenance activities driven by complaints 

and/or crises. A complaint triggers an investigation and based on the investigation, a 

priority ranking is assigned. While non-scheduled activities are to be expected, they 

should be controlled such that scheduled maintenance activities are the primary 

focus during normal routines of the year. 

The most obvious need within the Alafia River Watershed for the maintenance 

department, and the Hillsborough County Service Units in general, is the need to 

develop a systematic strategy to record, assess, and respond to flood complaints. 

Documentation is a fundamental element to a good operation and maintenance plan. 

The County was prompted to start a database for recording flooding complaints due 

to the 1997 and 1998 El Nino storm events. This was and is an excellent initiative 

but did not include enough information to make it as useful as it could be. 


Table 15.4-1 


IDENTIFIED MAINTENANCE NEEDS 

Channel Segment / 

Structure Location 

Description Maintenance Needs Access Notes 

BUCKHORN CREEK SUBWATERSHED 

Buckhorn Creek main channel 

east of Kings Avenue 

Channel bank erosion is recurring problem 

where Tributary C enters Buckhorn Creek 

near Van Gogh Circle. 

Channel bank needs reinforcement with handplaced 

riprap to stabilize. 

County has no easement. Requires 

right of entry from local residents. 

County Service Unit has been performing 

repairs in the past. 


between Bloomingdale Plaza and 

Holland Drive 

Segments of channel are completely 

overgrown with heavy vegetation. 

Channel vegetation needs to be removed to 

restore channel conveyance capacity. 



Inspect annually and maintain as needed. 


west of Bell Shoals Road 

Channel is completely overgrown with 

heavy vegetation. 






Tanglewood Ditch from Viola 

Drive to Kings Avenue 

Tributary D from Buckhorn Creek 

to Ronele Drive 


heavy vegetation. Culvert crossing 

opposite Lakehurst Way function is 

impaired. 


heavy vegetation. 

Channel vegetation and sediment deposits 

need to be removed to restore channel 

conveyance capacity. Culvert crossing needs 

to be cleared of vegetation and sediment 

deposition. 



County has access. County Service Unit has been performing 

maintenance in the past. Frequency should be 

increased to annual. 




Craft Road Ditch from Bryan 

Road to Bell Shoals Road 



Western end serves as treatment/mitigation 

facility and needs periodic maintenance. 

Channel vegetation in upstream segment 

needs to be removed to restore channel 

conveyance capacity. Bell Shoals Road 

culvert needs regular cleaning. 

County has no easement for channel 

maintenance. Requires right of entry 

from local residents. Bell Shoals 

Road culvert is within County right-ofway. 


Tributary GG wetland outfall north 

of Bloomingdale Avenue 

Control structure buried among debris and 

sediment. 

Clear out accumulated debris around structure 

and clean out any sediment or blockage of 

outfall. 



Structure controls significant upstream drainage 

system. Inspect annually and maintain as 

needed. 

Tributary GG culvert at Bell 

Shoals Road 

Culvert inlet and outlet buried among 

heavy vegetation and sediment 

accumulation. 

Clean out ditches at upstream and 

downstream ends of culvert and remove any 

sediment deposits. 

Bell Shoals Road culvert is within 

County right-of-way. 


Tributary F at Rosemead Lane Segments of channel immediately 

downstream of Rosemead Lane culvert 


Clear out accumulated vegetation and debris 

around structure and clean out any sediment 

or blockage of outfall. 

Rosemead Lane culvert is within 



Bloomingdale West pond and 

wetland control structures at 

Lakes BL-1, J-1, J-2, K, and M-2 

Lake and wetland control structures 

overgrown by vegetation and design 

function impaired. 

Remove excessive vegetation growth around 

structures and clean out any sediment or 

blockage of outfall. 

County has no easement for access 

to structures. Requires right of entry 

from local residents and/or 

homeowners association. 

Structures control entire Bloomingdale West 

drainage system. Inspect annually and maintain 

as needed.

Table 15.4-1 






BUCKHORN CREEK SUBWATERSHED 

Hurley Ditch from Bloomingdale 

Avenue to Bloomingdale High 

School 

Bloomingdale High School 

drainage system 

Northeast Tributary at Bell Shoals 

Road culverts 


heavy vegetation and dirt road culverts 

blocked. Ditch at irregular grade with 


School stormwater system enclosed ditch. 

Pond interconnections silted and 

overgrown by vegetation. 

Culvert inlet and outlet affected by heavy 

vegetation and sediment accumulation. 

Channel vegetation needs to be removed and 

channel regraded to restore channel 

conveyance capacity. Culverts need to be 

cleared of blockage. 

Channel vegetation needs to be removed from 

blocking of pond/wetland outfalls and sediment 

deposits removed from within storm sewers to 

restore design function of system. 



or blockage of outfall. 


right of entry from property owner(s). 

Property owned by Hillsborough 

County School Board. Requires right 

of entry. 

Bell Shoals Road culvert is within 


County Service Unit has been performing 

maintenance in the past. Affects flooding 

conditions upstream in Bloomingdale HS 

campus. Maintenance frequency should be 

increased to annual. 

Improper performance of high school drainage 

system affects adjacent and upstream 

contributing drainage areas. Inspect annually 

and maintain as needed. 

Critical point on conveyance system; requires 

semi-annual inspection and maintenance as 

needed. 

FISHHAWK CREEK SUBWATERSHED 

Dorman & Boyette Road 

Culvert & culvert entrance clogged with 

sediment and vegetation. 

Remove sediment from pipe. Periodic removal 

of excessive vegetation at culvert entrance 

and exit. 

All work can be accomplished within 

the right-of-way. 

Inspect semi-annually. 

TURKEY CREEK SUBWATERSHED 

North of Sparkman Road and 

west of Gerald Hall Road 

Gerald Hall cross culvert clogged. Ditches 

overgrown with torpedo grass. 

Maintain roadway drainage system, including 

cross drains, culverts, and ditch system. 

Remove excess vegetation and debris from 

conveyance and culvert entrances/exits. 



Inspect semi-annually 

Little Alafia River channel just 

upstream of Holloway Road 

Excessive seasonal sediment deposition. 

Flooded overbank. Sediment removal of 

roadway drainage system including culverts, 

bridge, and ditch system. 

Easement maybe required upstream 

of right-of-way. 

See water quality projects TURK-xWQ and 

TURK-xxWQ. If these are not implemented, 

inspection should be quarterly and maintained 

as needed. 

Grassy Creek @ Murray Farms 

Road & Trapnell 

Residnets complain channel is not 

maintained. 

Clear channel. Remove exotic species. 

Permission to access and maintain 

creek must be acquired from land 

owners or easement may be 

required. 

Inspect every 2-5 years. 

Turkey Creek Tributary B at 

Charleston Avenue 

Channel is overgrown with heavy 

vegetation upstream and downstream. 



County has easement. Inspect annually and maintain as needed. 

Little Alafia River Tributary A at 

Turkey Creek Road 

CMP under road has one foot of 

accumulated sediment deposit and 

excessive vegetative growth around inlet 

and outlet. 



or blockage in structure. 



Inspect annually and maintain as needed.

Table 15.4-1 






TURKEY CREEK SUBWATERSHED 

Medard Reservoir Tributary A at 

HWY 39 and RR tracks 

Culverts have excessive accumulated 

sediment and overgrown vegetation at 

outlets. 

Clear out accumulated vegetation around 

structure and clean out any sediment or 

blockage in structure. 




Grassy Creek tributary at Drawdy 

Road and Holloway Road 

CMP under road is over half clogged with 

accumulated sediment. 

Clear out accumulated sediment in structure to 

restore proper conveyance. 




Grassy Creek tributary at Mud 

Lake Road north of Holloway 

Road 

CMPs under road are clogged with 

accumulated sediment (probably from 

strawberry fields). 

Clear out accumulated sediment in structures 

to restore proper conveyance. 



Inspect semi-annually and maintain as needed. 

Sydney Road, south of Salem 

Church Rd, (model junction 

number 753580) 

Culvert clogged with sediment deposits. Clear out accumulated sediment in structures 

to restore proper conveyance. 



Inspect quarterly and maintain as needed. May 

need more frequent maintenance. (See Project 

TURK-4WQ.) 

Structures at intersection of Jerry 

Smith Road and April Lane. April 

Lane cross drain. 

Sediment accumulation in ditch and 

structure. CMP is deteriorating. 







Railroad culvert west of N. Dover 

Road, due west of SW of Salem 

Church Road 

Culvert is clogged by sediment 

accumulation. 

Clean out accumulated sediment in structures 

to restore proper conveyance capacity. 

County has no right-of-way or 

drainage easement. Property is 

owned by the CSX Railroad. 


Private drive north of Sydney 

Road, model junction number 

754240 

Makeshift weir has been constructed 

across channel. Trash, debris and 55- 

gallon drum litter floodplain. 


downstream ends of culvert. Remove debris 

and 55-gallon drum(s). 

County has no right-of-way or 

drainage easement. Will require 

permission or right of entry from 

resident(s). 

Inspect every 2-5 years. 

Forbes Rd between Jerry Smith 

Road and Downing Street 

Driveway culverts along Forbes Road 

drainage system are partially to fully 

blocked with sediment accumulation. 

Clean out accumulated sediment in structures 


Replace deteriorated culverts as needed. 




ENGLISH CREEK SUBWATERSHED 

Frank Moore Road 

Culverts are partially blocked by trash and 

sediment accumulation. 




Frank Moore Road culvert is within 



Horton Road culvert, b/n Berry 

Road and Colson Road 

Culverts are partially blocked by trash and 

sediment accumulation. 




Horton Road culvert is within County 

right-of-way. 


The RR culvert at node 791888 is 

clogged. 

The RR culvert at node 791888 is clogged. 






Inspect annually and maintain as needed.

Table 15.4-1 






ALAFIA RIVER MAIN STEM SUBWATERSHED 

Tributary N-10 at the intersection 

of Hannaway Drive and 

Providence Road 

Tributary S-6 under Shallow 

Creek Lane south of McMullen 

Loop. 

A 36" CMP is badly corroded and clogged 

with accumulated sediment. The 

downstream channel bed is laden with 

sediment and vegetation. 

A 42" CMP is clogged with accumulated 

sediment and debris. 

Clear out accumulated sediment in corroded 

structure or replace it. Dredge out downstream 

channel of sediment and remove excess 

vegetation. 

Clear out accumulated sediment and debris in 

structure. Remove excess vegetation from 

upstream and downstream channel. 



County has no easement for channel 

maintenance. Requires right of entry 

from local residents. Culvert is within 




Tributary N-2 under Riverlachen 

Way south of Riverview Drive. 

Two 29"x44" ERCPs are partially clogged 

with sediment, limiting hydraulic capacity. 


restore proper conveyance capacity. 




Alafia Drive and Desoto Road. County constituent complained of general 

lack of maintenance of local drainage 

ditches and culverts. 

Inspect local drainage features in the area and 

clear/maintain as needed. 

All work to be accomplished should 

be within the right-of-way. 


Hillsborough Association for 

Retarded Citizens (H.A.R.C.) on 

Hackney Drive east of HWY. 301 

All culverts in drainage system are partially 

clogged with sediment. 

Clear out accumulated sediment in structures 



permission for right of entry from 

Association. 

H.A.R.C. is privately owned but indicated County 

has maintained on-site drainage in the past. 

Tributary N-15 south of River 

Oaks Circle 

Channel in County-owned drainage 

easement is overgrown with heavy 

vegetation. 



County has easement but may 

require right of entry from local 

residents. 


Tributary N-19 at Lithia Pinecrest 

and Adelaide Avenue 

CMP under road is over half clogged with 

accumulated sediment. 


restore proper conveyance capacity. 




Rice Creek Tributary under 

McMullen Road north of Shadow 

Run Blvd. 

Culvert inlet and outlet buried among 


accumulation. 




McMullen Road culvert is within 



Tributary S-9 at Lithia Springs 

Road 

CMPs under road are clogged with 

accumulated sediment and debris. 

Clear out accumulated sediment and debris in 

structure to restore proper conveyance. 




Tributary S-10 at Lithia Pinecrest 

Road 

Culvert inlets and outlets buried among 


accumulation. 

Clear out accumulated sediment deposits in 

culverts and clear excessive vegetation at 

structure and outlets. 




Tributary N-10 between 

Providence Road and Alafia Drive 








Tributary N-20 at Lithia Pinecrest 

Road 

CMP connecting box culverts to small 

pond south of Lithia Pinecrest Road is 

clogged and damaged. 

Replacement of this CMP with a new pipe is 

recommended. This will restore proper 

conveyance to the system. 


right of entry from local resident. 

Critical point on conveyance system; requires 

semi-annual inspection and maintenance as 

needed.



As a minimum, recorded information should include: 

♦ Name and address of the individual lodging the complaint 

♦ Location and nature of flooding problem 

♦ Contact information 

♦ Dates of complaint and flooding event 

The database of flooding complaints should be linked to another similar database 

consisting of recorded maintenance activities. This would include the following 

types of records: 

♦ Description of problem 

♦ Cause for investigation 

♦ Age of structure, condition, elevations, dimensions 

♦ Investigator or point of contact 

♦ Dispensation of problem 

♦ Equipment used 

♦ Hours of labor expended 

♦ Digital pictures 

The County is currently developing a GIS database that will inventory all of the 

drainage systems within the County. This will also be integrated with a maintenance 

schedule / tracking system. More specific recommendations related to these topics 

are discussed in Section 5.6. 

Other documentation necessary to a successful maintenance plan is maintenance 

standards. Maintenance standards (also being currently developed by the County) 

are essential tools that will assist in prioritizing maintenance activities by providing a 

common “basis” for determining staffing, equipment and material requirements. 

Access, right-of-ways and easements can be difficult issues for the County’s Service 

Units. The County, as a rule, does not perform maintenance activities on private 

property, yet activity (or non-activity) on those properties can impact the County’s 

drainage system. Examples of this include maintenance of facilities within railroad 

right-of-ways, FDOT facilities, and systems owned and operated by homeowners 

associations. The County should perform regular monitoring of those facilities, which 

impact the County’s ability to provide a functioning drainage system and require 

action when necessary. 

Toolkits for County residents should be distributed when a flooding complaint is 

registered. The toolkit would be an array of educational materials explaining the 

responsibilities and limitations of the stormwater department and Service Units, the 

rights and responsibilities of property owners, stormwater management techniques 

on a microscale, the hydrologic cycle, what constitutes a true flooding problem 

versus an assumed flooding problem, and appropriate fact sheets as described in 




Section 15.6.7. The intent of the toolkit would be to educate residents and ultimately 

reduce the quantity of flooding complaints. 

Wherever possible, County projects should employ the use of non-corrosive, noncrushable 

reinforced concrete pipes with headwalls. If metal or plastic pipes are 

used, concrete headwalls should be required to protect ends from damage. 

Although the County Stormwater Technical Manual allows corrugated metal and 

HDPE pipes, reinforced concrete pipes are the preferred material due to superior 

resistance to physical damage, corrosion and deterioration over time. 


VALRIE LN 

Alafia River Model Update: Preferred Alternatives 

AR-1 

WHITEHOUSE DR 

DUSTY RD 

CUMMINS ROAD 

DRAINAGE IMPROVEMENTS 

RIVER COUNTRY DR 

RAISE CUMMINS ROAD TO 

ELEV 21.7 NAVD 

REPLACE EXISTING 18" RCP 

WITH 3 - 24" x 38" ERCPs. 

GRADE AND RESHAPE 600' 

OF CHANNEL DOWNSTREAM 

OF CUMMINS ROAD. 

CUMMINS RD 

Flooding over Cummins Road on September 14, 2001 (during 

Tropical Storm Gabrielle). 

SYLVAN GREEN LN 

PROBLEM 

Local residents of Cummins Road have reported past flooding problems, 

and analyses show the road will experience one foot of flooding during 

the 25-year storm event. The existing 18" RCP under Cummins Road is 

undersized and must be replaced. This constriction in the system has 

been exacerbated by sediment build up in the channel on both sides that 

has effectively raised the streambed and eliminated the channel 

definition as well as clogging the existing culvert. 

SOLUTION 

The preferred alternative solution is for the County to replace the 

existing 18" RCP with 3 - 24" x 38" ERCPs. The road will need to be 

raised to an elevation of 21.7' NAVD to accommodate the larger culverts 

and to eliminate the 25-year LOS deficiency at the road. Additionally, the 

downstream channel must be improved to avoid sedimentation of the 

new structures, including grading and reshaping of the channel. 

PROJECT BENEFITS 

Eliminates 25-year LOS deficiency for 

Cummins Road. Resolves sedimentation 

problem in the culverts and downstream 

channel. 

COST 

Construction: 

Land Acquisition: 

Engineering and Contingency: 

Total 

LEVEL OF SERVICE 

25-YR, LOS A 

$126,500 

$57,900 

$50,600 

$235,000 

Hillsborough County, FL

STORMWATER MANAGEMENT C.I.P EVALUATION 

PROJECT NAME: AR-1 Cummins Road Drainage Improvements 

DESIGN COST: $50,600 

DATE OF SITE VISIT: 

DATE OF EVALUATION: 

LOCATION: Cummins Road west of Valrie Lane 

ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $57,900 

CONST. COST: $126,500 

TOTAL COST EST.: $235,000 

PROJECT See Project Fact Sheet AR-1 for detailed project information. 

APPARENT SOLUTION: See Project Fact Sheet AR-1 for project information. 

COMMENTS: 

PROBLEM CONSEQUENCES 

INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 

FREQUENCY OF FLOOD 

HIGH (3-YR/24-HR) 

FLOODS DURING 3 OR LESS 

10 

40 40 


MEDIUM: (5-YR/24-HR) 


LOW: (1O-YR/24-HR) OVER 

6 24 24 

3 12 12 

INCREASE (YEARLY) 

EROSION/SILTATION 20 20 

HIGH GROUNDWATER TABLE 20 

MAINTENANCE PROBLEM 20 

STRUCTURAL FAILURE 80 

GRAND TOTAL 96

S VALRICO RD 


AR-2 

FAIRWAY VIEW DR 

EXISTING PUMP STATION 

" 

S MILLER RD 

GREENHILLS DRIVE DRAINAGE 

IMPROVEMENTS 

GREENHILLS DR 

EXISTING 18" RCP 

(CURRENTLY BLOCKED) 

CONSTRUCT MODIFIED FDOT TYPE E 

CONTROL STRUCTURE WITH TOP ELEV 

53.5' NAVD 

" 

UNBLOCK 18" RCP PIPE CONNECTION 

CONSTRUCT 260' OF 18" RCP 


CHELSEA WOODS DR 

CUNARD DR 

CONSTRUCT 2.8-ACRE POND 

BOTTOM ELEV 42.3 NAVD 

TOP OF BANK ELEV 52 NAVD 

ARBORWOOD DR 

Greenhills Drive on September 14, 2001 (during Tropical 

Storm Gabrielle). 

NORRIDGE RD 

BUCKHORN RUN DR 

PROBLEM 

SOLUTION 

DOEFIELD CT 


More than one foot of flooding over Greenhills Drive is predicted for the 

10-year storm event and has been confirmed during recent storm events. 

The sinkhole stormwater pond for the Greenhills subdivision is 

undersized for the closed basin that drains to it. Runoff from the west 

portion of Buckhorn Springs G & CC as well as part of the neighborhood 

to the north drains to this pond. A pump station has been installed in 

recent years to draw the pond down after storms, but has little effect 

during the 10-year storm event. 

OAKLANE RD 

The preferred alternative is to restore the connection of the sinkhole ponds 

to the north and south of Greenhills Dr. To implement this alternative, the 

property to the south where another large sinkhole pond exists would need 

to be purchased and a 2.8 acre pond with a bottom elevation of 42.3 NAVD 

would be excavated to provide enough storage to relieve the flooding in the 

area. A Type E FDOT inlet with a top elevation of 53.3' NAVD connected to 

an 18" RCP would be installed form the sinkhole to the south of Greenhills 

Drive to the newly purchased pond property. The connection of these three 

ponds would equalize the flood elevations in the ponds without flooding 


This project eliminates road and property 

flooding on Greenhills Drive for the 10-year 

storm event and should be easily 

permittable. 

COST 

Construction: 



Total 


10-YR, LOS A 

$341,500 

$253,700 

$136,600 

$731,800 

Private property to the south of Greenhills Drive where overflow 

from Greenhills pond flows (during Tropical Storm Gabrielle). 



PROJECT NAME: AR-2 Greenhills Drive Drainage Improvements 




ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $253,700 



LOCATION: Greenhills Drive west of S. Miller Road 



COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 

3 12 12 24 


EROSION/SILTATION 20 




GRAND TOTAL 24

JESSI LN 


PROPOSED PARCEL 

PURCHASES 

ROSE ST 

10-YEAR 

FLOODPLAIN 

RIVER DR 


JEAN RD 

RIVER DR 

COCONUT COVE PL 

OTHER ELAPP LAND 

PRESERVATION 

AR-3 

RIVER DRIVE & COCONUT 

COVE PLACE FLOODPRONE 

PROPERTY ACQUISITION 

SQUIRREL RUN WAY 

APPROVED ELAPP SITE 

ACQUISITION AREA 

LITHIA SPRINGS PARK 

(PUBLIC OWNED LAND) 

River Drive on September 14, 2001 (during Tropical 


PROBLEM 

Approximately seventy private parcels of land lie within the 10-year 

floodplain of the Alafia River. Extensive flooding will occur on River 

Drive, Coconut Cove Place and Squirrel Run Way. Current modeling 

analysis indicates these properties to be inundated from 1 to 7 feet of 

floodwater. Although most of the homes are elevated, the streets to the 

homes will be underwater and access to and from the homes would be 

impossible. These conditions have occurred to a varying degree several 

times in recent years. 

SOLUTION 

The preferred alternative solution is for the County to purchase, on a 

voluntary basis, the selected properties that are within the 10-year 

floodplain and relocate the existing residents. Any structural alternative 

to prevent this flooding would not be feasible nor permitable. The 

purchase of these parcels would promote a contiguous riparian corridor 

for migration of native species down the Alafia River that conforms with 

adjacent public land tracts. 


By effectively removing all roads and structures 

from the riverine floodplain, this project meets 

the 10-year flooding LOS requirement for County 

streets and homes and promotes a contiguous 

corridor of publicly-owned riparian habitat. 

COST 

Construction: 



Total 


10-YR, LOS A 

$578,400 

$3,557,200 

$0 

$4,135,600 

Coconut Cove Place on September 14, 2001 (during Tropical 




PROJECT NAME: AR-3 Flood Prone Property Acquisition 

DESIGN COST: $0 



ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $3,557,200 


TOTAL COST EST.: $4,135,600 

LOCATION: River Drive, Coconut Cove , and Squirrel Run Way 



COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 

3 

40 60 40 140 

24 36 24 84 

12 18 12 42 

INCREASE (YEARLY) 10 10 





GRAND TOTAL 276

MATHERS LN 


AR-4 

WATSON RD 

PROVIDENCE ROAD 


MITIGATION 

WETLAND 

REPLACE 24" CULVERTS 

WITH 4' x 8' RCBCs AND 

REGRADE ROADSIDE DITCH 

" 

ARLENE AVE 

REPLACE CULVERTS WITH 

5' x 8' RCBCs 

REPLACE 10' WEIR WITH 

40' WEIR AT ELEV 18.1 NAVD. 

REPLACE CULVERTS 

UNDER PROVIDENCE ROAD 

WITH 3- 38" x 60" ERCPs. 

PROVIDENCE RD 

CRESCENT LAKE DR 

ROBERTS LN 

STAFFORD LN 

MAHIN LN 

REGRADE DITCH 

MONETTE RD 

Flooding on Providence Road between Crescent 

Lake Drive and Watson Road. 

PROBLEM 

HAPPY ACRES LN 

During significant rainfall events, Crescent Lake Drive and Providence 

Road between Crescent Lake Drive and Watson Road are prone to 

flooding. The flooding is due to inadequate conveyance capacity within 

the Providence Road/Crescent Lake Drive roadside ditches. The existing 

18" and 24" culverts within the ditches are undersized. 

ALAFIA DR 


FERNANDEZ DR 

The project will achieve flood protection LOS on 

Providence Road and Crescent Lake Drive, for the 

25-year design storm. The project will also reduce 

peak flood elevation downstream through the mobile 

home park, to the Alafia River. 

SOLUTION 

Replace all undersized culverts within the Crescent Lake 

Drive/Providence Road conveyance system with 4' x 8' RCBCs and 

perform re-shaping of the roadside and outfall ditches to accommodate 

the larger culverts. To accommodate the improvements, a 10'-15' 

drainage easement would be required from the properties fronting 

Providence Road and Crescent Lake Drive. Install 5' x 8' RCBCs under 

Mathers Lane and Alafia Drive. In addition, purchasing a 40' drainage 

easement over the existing outfall ditch between Crescent Lake Road 

and the Alafia River is recommended. 

COST 

Construction: 



Total 


25-YR, LOS A 

$844,800 

$76,000 

$338,000 

$1,258,800 

Undersized driveway culvert in drainage ditch 

along the north side of Crescent Lake Drive. 



PROJECT NAME: AR-4 Providence Road Drainage Improvements 




ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $76,000 



LOCATION: Providence Road and Crescent Lake Drive 



COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 

3 

60 40 40 230 

36 24 24 138 

18 12 12 69 

INCREASE (YEARLY) 5 





GRAND TOTAL 271


AR-6 

CHEROKEE TRL 

CHEROKEE TRL 

MOHICAN TRL 

S DOVER RD 

WHITE CLIFF PL 

CONSTRUCT 400' OF 

30" RCP EQUALIZER PIPE 

IN EXISTING DRAINAGE 

EASEMENT 

EXISTING WHITLOCK PLACE 


SEVER EXISTING 24" CMP 

UNDER DURANT ROAD AND 

REGRADE DRAINAGE TO 

NEW 1.4-ACRE POND 

HERNDON ST 

" 

WHITLOCK PL 

EXISTING PUMP STATION 

CONSTRUCTED PER 

CIP 41046 

ARCH MCDONALD DR 

PURCHASE PROPERTY 

TO CONSTRUCT 9-ACRE 

RETENTION POND WITH 


MARTIN RD 


WITH BOTTOM ELEV 59 NAVD 

TO HOLD STORMWATER RUNOFF 

SOUTH OF DURANT ROAD 

COLEWOOD LN 

WHITLOCK PLACE AND HERNDON 

STREET FLOODING RELIEF 

Retention pond between Whitlock Place and Herndon Street. 

DURANT RD 

BISMARK DR 

LITTLE RD 

RANCH RD 

WILLIE LN 

PROBLEM 

Severe street and house flooding is predicted for the north end of 

Whitlock Place and Herndon Street from an undersized retention pond. 

The Hillsborough County Service Unit and local residents have 

confirmed this flooding problem. The pond was constructed at the 

lowest point in a large closed basin and has no positive outfall. The 

predicted 25-year flood elevation of 51.6 feet NAVD will inundate both 

street and structures (47.6 feet NAVD and 50.1 feet NAVD, respectively). 

SOLUTION 

The preferred alternative solution is for the County to create additional 

storage by constructing a 9-acre detention pond on the property 

northwest of Whitlock Place. The new pond would be connected to the 

existing one by an equalizer pipe through the existing drainage 

easement between the ponds. The new pond would have enough 

storage to achieve 10-year LOS protection for the road and 25-year LOS 

protection for the homes. 


This project eliminates road flooding for the 10-year 

event and structure flooding for the 25-year event. 

Utilizes existing drainage easement. 

COST 

Construction: 



Total 


10-YR, LOS A 

$1,861,900 

$339,700 

$744,800 

$2,946,400 

Retention pond between Whitlock Place and Herndon Street. 



PROJECT NAME: AR-6 Whitlock Place and Herndon Street Flooding Relief 




ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $339,700 

CONST. COST: $1,861,900 


LOCATION: Whitlock Place and Herndond Street north of Durant Road 



COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 




10 

40 40 





6 24 24 

3 12 18 30 






GRAND TOTAL 99


AR-8 

REVELS ROAD SECONDARY 

DRAINAGE SYSTEM IMPROVEMENTS 

ALAFIA RIDGE LOOP 

EXISTING CHANNEL 

REVELS RD 

REVELS RD 

IMPROVE EXISTING DRAINAGE 

DITCH AND REPLACE CULVERTS. 

EXTEND DITCH EAST ALONG 

REVELS ROAD. 

Revels Road on September 14, 2001 looking west 

(during Tropical Storm Gabrielle). 

PROBLEM 

Street and property flooding at the Revels Road turn has been reported 

by local residents at the first Hillsborough County public meeting. 

Parsons field investigation confirmed the flood reports and determined 

the floodwaters to be sheeting over the road from the south due to a 

poorly maintained and insufficient secondary drainage system. 


This project will eliminate flooding on Revels Road 

and adjacent property flooding. There is little 

easement to acquire as most of the project 

improvements lie within the right-of-way. 

SOLUTION 

The preferred alternative solution is for the County to improve the 

existing drainage system, including grading and/or reshaping ditches 

and replacing the existing culverts. Additionally, the rainage system 

should be extended to the east along the south side of levels Road to 

catch road runoff and sheeting water from the south. 

COST 

Construction: 



Total 


25-YR, LOS B 

$32,500 

$18,200 

$13,000 

$63,700 

Clogged culvert on Revels Road hindering proper floodwater 

conveyance. 



PROJECT NAME: AR-8 Revels Road Secondary Drainage System Improvements 




ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $18,200 



LOCATION: Revels Road bend south of Alafia Ridge Loop 



COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 

3 27 12 12 51 




MAINTENANCE PROBLEM 20 20 


GRAND TOTAL 71


AR-9 

ALAFIA RIVER 

CLEAR DRAINAGE PATH FROM 

STREET TO CULVERT INLET 

THROUGH PROPERTY WITH 

HIGHER ELEVATIONS 

MAGNOLIA ST DRAINAGE 

IMPROVEMENTS 

AND BANK STABALIZATION 

MAGNOLIA ST 

ALAFIA RIVER 

REPAIR ERODED RIVERBANK ON 

COUNTY-OWNED DRAINAGE 

EASEMENT. INSTALL HEADWALL 

AT PIPE OUTFALL. 

VAUGHN ST 

WIGGINS RD 

Low area on Magnolia Street where runoff collects and cannot 

reach culvert inlet effectively (inlet located between mailboxes). 

HIRSCH CT 

PROBLEM 

A complaint from the first Hillsborough County public meeting indicated 

after heavy rainfall events a low spot on Magnolia Street floods with up 

to six inches of water. Field investigation determined that runoff is 

unable to reach the culvert inlet because the shoulder in the right-of-way 

is higher than the road or the culvert inlet, impeding proper drainage. 

Additionally, a county-owned drainage easement is eroding away where 

the stormwater pipe discharges into the river. The adjacent property 

owner indicated several feet of bank has eroded over the past few years. 

SOLUTION 

The preferred alternative solution is for the County to clear a drainage 

path from the road to the culvert inlet through the higher elevation 

shoulder in the right-of-way. Also, the county should replace/repair the 

eroded riverbank on the county-owned drainage easement in addition to 

installing a headwall to prevent future bank erosion. 


This project eliminates localized road and property 

flooding on Magnolia Street. Project improvements 

lie within the existing right-of-way. 

COST 

Construction: 



Total 


25-YR, LOS B 

$9,100 

$0 

$3,700 

$12,800 

Erosion of County owned drainage easement on the bank of the 

Alafia River. The erosion is effecting adjacent properties. 



PROJECT NAME: AR-9 Magnolia Street Drainage Improvements 




ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $0 



LOCATION: Magnolia Street west of Vaughn Street 



COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 24 24 48 

3 12 12 24 





STRUCTURAL FAILURE 80 80 

GRAND TOTAL 182

WICKLINE DR 

VALRIE LN 

RACINE PL 


AR-11 

ALAFIA RIDGE RD 

RIVERGLEN SUBDIVISION 

DETENTION POND OUTFALL 

IMPROVEMENTS 

MCMULLEN LOOP 

ENJOIN OWNER AND ENGINEER 

OF RECORD TO CORRECT THE 

FAULTY DESIGN AND/OR CONSTRUCTION 

OF THE DETENTION POND OUTFALL 

MCMULLEN RD 

EXISTING RIVERGLEN 


RIVERGLEN 

SUBDIVISION 

TIMBERHILL DR 

MELLOWOOD DR 

ABERDEEN CREEK CIR 

LAUREL LEDGE DR 

" 

DONNEYMOOR DR 

DRESDEN PL 

SUNNYOAK DR 

Riverglen detention pond at the intersection of McMullen Loop 

and 

PROBLEM 

Improper function of the outfall for Riverglen detention pond on the 

corner of McMullen Rd. and McMullen Loop causes the pond to overtop 

the bank and flood across McMullen Loop. The water also causes 

flooding down Valrie Lane as well as exacerbating the flooding on Alafia 

Ridge Road, as witnessed during recent storm events. 


This flooding problem should be resolved through 

very little cost to the County assuming the owner 

and Engineer of record are enjoined to correct the 

deficiency. 

SOLUTION 

Hillsborough County staff has referred this matter to County 

Enforcement to take action against the owner and Engineer of record to 

correct what is perceived to be a design or construction problem of the 

pond outfall. 

COST 

Construction: 



Total 

$0 

$0 

$0 

$0 

The corner of Valrie Lane and McMullen Loop. Overflow from 

the Riverglen pond floods down Valrie Lane. 


25-YR, LOS B 



PROJECT NAME: AR-11 Riverglen Detention Pond Outfall Improvements 

DESIGN COST: $0 



ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $0 

CONST. COST: $0 

TOTAL COST EST.: $0 

LOCATION: Southeast corner of McMullen Loop and McMullen Road 



COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 24 24 

3 12 12 






GRAND TOTAL 116


AR-12 

MICHIGAN AVE 

OHIO AVE 

LULA STREET SECONDARY 

DRAINAGE SYSTEM IMPROVEMENTS 

INDIANA ST 

PENNSYLVANIA AVE 

INSTALL 2-18" RCP 

UNDER LULA STREET 

LULA ST 


ANNA AVE 

ANNA AVE 

CONNECTICUT ST 

MAGGIE ST 

LAZELLA ST 

INDIANA ST 

ESTELLE AVE 

N/A 

MARILLA AVE 

PROBLEM 

Lack of cross drain at low-lying area northeast of the Lula Street and 

Anna Avenue intersection results in flooding of Lula Street and possible 

structure flooding. Flood complaints were made by residents during 

Hurricane Frances. Modeling confirms flooding in this area but no LOS 

violation. Flooding in this area could be tidally influenced. 



event and structure flooding for the 100-year event 

and provides 25-year LOS A. 

SOLUTION 

Install two 18” RCP cross drains under Lula Street in the vicinity of the 

depression. 

COST 

Construction: 



Total 

$7,200 

$0 

$2,900 

$10,100 

N/A 


25-YR, LOS A 



PROJECT NAME: AR-12 Lula Street Localized Flooding Relief 




LOCATION: Lula Street west of US Highway 41 

ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $0 





COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 24 24 48 

3 12 12 24 






GRAND TOTAL 72

RUTH AVE 


CLEAR OVER- 

GROWN 

VEGETATION 

FROM DITCH 

COPPERTREE CIR 

REPLACE EXISTING 22" x 36" 

ARCH CMP WITH PROPOSED 

300 LF OF 5' x 8' RCBC 

CROSSWINDS DR 

PEBBLEWOOD DR 

CENTERWOOD CT 

SCENIC HEIGHTS DR 

OAK BARK LN 

CONSTRUCT 720 LF OF 30" RCP 

AND TIE INTO NORTH FOUR 

WINDS POND STORMWATER 

COLLECTION SYSTEM 

S KINGS AVE 

CONSTRUCT 60' SILL WEIR AT ELEV 20.4 NAVD 

(EXISTING CONTROL ELEVATION) 

" 

NORTH POND 

SOUTHVIEW CT 

PINEDALE ST 

WOODHILL CT 

LAKE GROVE CT 

SOUTH 

POND 

WOODHILL DR 

WINDY CIR 

EXISTING 36" x 58" ARCH CMP 

WINDY PL 

AR-13 

FOUR WINDS SUBDIVISION 

FLOODING ALLEVIATION 

SOUTHVIEW DR 

SEVER EXISTING 

DRAINAGE TO SOUTH 

FOUR WINDS POND AT 

THIS JUNCTION 

KING DR 

OAK HAMMOCK DR 

WILD OAK DR 

N/A 

PROBLEM 

Flooding complaints have been made in the Four Winds subdivision. 

For the 10-year storm event, the model predicts street flooding depths of 

over 1.8 feet and 2.8 feet for the south and north ponds, respectively. 

Water backs up in the south pond due to the undersized 36" x 58" arch 

CMP connection to the north pond and water in the north pond is backed 

up due to the undersized 22" x 36" arch CMP connecting it to the ditch 

on the west side of King Avenue and dense vegetation in the ditch. 



event and structure flooding for the 100-year event 

and provides 25-year LOS C. 

SOLUTION 

The preferred alternative is to redirect a portion of the stormwater runoff 

currently conveyed to the south pond by severing the stormwater 

collection system at the intersection of Southview Drive and Pinedale 

Street and connecting it to the north pond stormwater collection system via 

720' of 30" RCP along Pinedale Street. Replace the existing control 

structure in the north pond with a 60' sill weir at the existing control 

elevation of 20.4 NAVD. 5' x 8' RCBC would connect the downstream side 

of the sill weir to the collection ditch on the west side of Kings Avenue. 

Finally, the collection ditch must be cleared of excessive vegetation. 

COST 

Construction: 



Total 


10-YR, LOS A 

$720,300 

$,0 

$288,200 

$1,008,500 

N/A 



PROJECT NAME: AR-13 Four Winds Subdivision Flooding Alleviation 




ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $0 



LOCATION: Four Winds Subdivision west of South Kings Avenue 



COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 




10 

40 40 80 





6 24 36 24 84 

3 18 12 18 12 60 






GRAND TOTAL 224


BELL-1 

HOBSON SIMMONS ROAD 

MAINTENANCE 

HOBSON SIMMONS RD 

CLEAR ROADSIDE 

DITCH OF EXCESSIVE 

VEGETATION ALONG 

THE ENTIRE ROADWAY 

CLEAR CROSS CULVERTS 

OF ACCUMULATED 

SEDIMENT 

Hobson Simmons Road northern cross-culvert. Picture shows 

semi-obstructed inlet. 

PROBLEM 

The Hillsborough County South Service Unit staff reported flooding along 

Hobson Simmons Road. Upon field investigation, it is evident that the 

roadside ditch is extremely overgrown with vegetation and the southern 

cross culvert has a restricted conveyance capacity due to accumulation of 

silt and debris. The culvert appears to be a 29" x 45" ERCP; however, only 

a 10" x 45" opening was available on the upstream side of the structure to 

convey floodwater to the west under Hobson Simmons Road. The 

northern cross culvert also has a small amount of accumulated silt. 

SOLUTION 

The recommendation is to clean the roadside ditch, including the 

structure inlets and outlets, of excessive vegetation. Both cross culverts 

should be cleared of the accumulated silt and debris and the outfall 

ditches should be graded such that a positive drainage outfall exists. 

Routine maintenance should be performed regularly in this roadside 

ditch system. In a maintained state it is expected that the drainage 

system will attain the required 25-year flooding level of service. 


This project will provide flood relief along Hobson 

Simmons Road. 

COST 

Construction: 



Total 


25-YR, LOS B 

$18,700 

$0 

$7,500 

$26,200 

Hobson Simmons Road southern cross-culvert in vicinty of southern 

cross-culvert. Roadside ditch is overgrown with vegetation. 



PROJECT NAME: BELL-1 Hobson Simmons Road Maintenance 




LOCATION: Hobson Simmons Road 

ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $0 



PROJECT See Project Fact Sheet BELL-1 for detailed project 

information. 

APPARENT SOLUTION: See Project Fact Sheet BELL-1 for project information. 

COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 

3 12 12 






GRAND TOTAL 37

LAKEHURST WAY 


TANGLEWOOD DITCH 

EXISTING 

29" x 46" ERCP 

" 

" 

SOUTHWOOD CV 

EXISTING 

27" x 43" ERCP 

" 

CONSTRUCT 200' 

OF 32" x 49" ERCP 

BARKFIELD ST 

BUCK-1 & 

BUCK-2 

BARKFIELD STREET AND 

HUNTINGTON STREET 


CONCH HOLLOW DR 

PROVIDENCE LAKES BLVD 

VISTA CAY CT 

MILANO CIR 

KINGS CV 

HUNTINGTON ST 

HUNTINGTON 

LAKE 

" 

" " 

" 

PRINCETON ST 

REPLACE EXISTING 12" CMP 

W/ 550' OF 34" x 53" ERCP 

& MODIFIED FDOT TYPE D 

CONTROL STRUCTURE 

S KINGS AVE 

RONELE DR 

REPLACE EXISTING 27" x 43" 

CMPA CULVERT AT PRIVATE 

DRIVE WITH A 34" x 53" ERCP 

EL GRECO DR 

Barkfield Street on September 14, 2001 (during Tropical 


PROBLEM 

Barkfield Street experiences chronic flooding up to 2 feet deep in the 

street with multiple structures flooded due to inadequate outfall 

capacity. The existing outfall to the Tanglewood Ditch is constrained by 

the hydraulic inefficiency of this ditch. Huntington Street is flooded by 

the backwater conditions in Tributary D created by an inadequately sized 

downstream private drive crossing. 


The project will achieve 25-year flooding LOS 

protection and reduces peak flows downstream in 

Tributary D. Provides stormwater treatment for 35- 

acre residential area that currently has no treatment. 

SOLUTION 

Construct a new 32"x49" ERCP outfall from Barkfield to Huntington 

Lake. Replace the existing 12" CMP outfall for Huntington Lake with a 

new 34" x 53" ERCP and modified FDOT Type D inlet control structure to 

fully optimize the stormwater detention and treatment capacity of this 

lake. Replace existing 27" x 43" CMPA culvert at private drive with 34" x 

53" ERCP. Project will require purchase of drainage easements from 

local residents to construct the new outfalls. Environmental permitting 

should be fairly simple. 

COST 

Construction: 



Total 


25-YR, LOS A 

$147,300 

$14,000 

$58,900 

$220,200 

Existing Huntington Lake 12" CMP Outfall (no control structure). 



PROJECT NAME: BUCK 1 & BUCK-2 Barkfield & Huntington Street Drainage Improvements DESIGN COST: $58,900 



ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $14,000 



LOCATION: Barkfield & Huntington Streets west of South Kings Avenue 

PROJECT See Project Fact Sheet BUCK-1 & BUCK-2 for detailed 

project information. 

APPARENT SOLUTION: See Project Fact Sheet BUCK-1 & BUCK-2 for project 

information. 

COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 24 24 48 

3 12 18 12 42 






GRAND TOTAL 95


TAMMARRON LN 

MANOR HILL DR 

TIMBERWAY PL 

RAPID FALLS DR 

BUCK-3 

CRAFT ROAD DITCH STORMWATER 

DETETNTION FACILITY 

MINUTEMAN LN 

NEW METHODIST 

CHURCH OF BRANDON 

BRYAN RD 

ANNADALE CIR 

ROSEBUD LN 

BRYAN VALLEY CT 

POND EMBANKMENT 

OAK CREEK DR 

SOUTH POINTS 

SUBDIVISION 

CONSTRUCT POND 

SPILLWAY @ 


BELLE TIMBRE AVE 



NORMAL POOL ELEV 36.6 NAVD 

TOP OF BANK ELEV 43.1 NAVD 


JOHN HUNTER CT 

GUILES RD 

BELL SHOALS LN 

N/A 

KNOWLES RD 

CRAFT RD 

PROBLEM 

Currently, the County road crossings and all structures meet the 10-year 

level of service criterion, however, the New Methodist Church of Brandon 

on Bryan Road and numerous homes in the Bryan Manor subdivision and 

north of the Craft Road Culverts would likely experience structural 

flooding during the 25-year storm event. 


The project improves LOS for roads in the area and 

removes multiple houses from the floodplain, in 

addition to reducing flood levels in Buckhorn Creek 

as far downstream as Bloomingdale Avenue. Water 

quality benefits are provided by the treatment of 

stormwater runoff in the proposed detention pond. 

SOLUTION 

The reccomendation is to construct a 3.4-acre on-line stormwater 

detention pond located in what is currently a wet pasture just east of the 

Southpointe Subdivision (west of Bell Shoals Road). The pond would be 

created by both excavation at the site and construction of a berm across 

the floodplain with a top of bank elevation of 43.1 ft NAVD with a notch at 

elevation 36.6 ft NAVD and 10’ overflow spillway weir at elevation 41.6 ft 

NAVD. The function of this pond would be to attenuate peak flood flows 

while providing additional water quality and environmental benefits for 

the downstream reaches of Craft Road Ditch and Buckhorn Creek. 

COST 

Construction: 



Total 


25-YR, LOS A 

$817,800 

$439,000 

$40,700 

$1,297,500 

N/A 



PROJECT NAME: BUCK -3 Craft Road Ditch Stormwater Detention Facility 




ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $439,000 



LOCATION: Detention Facility west of South Points Subdivision 

PROJECT See Project Fact Sheet BUCK-3 for detailed project 

information. 

APPARENT SOLUTION: See Project Fact Sheet BUCK-3 for project information. 

COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 

3 12 12 24 






GRAND TOTAL 34

HOLLISTER PL 


EXISTING 

36" CMP 

REDONDO DR 

BUCK-4 

BLOOMINGDALE WEST POND 

" 

BLOOMINGDALE WEST POND 

OUTFALL RETROFITS 

" 

" 

" 

BLOOMINGFIELD DR 

" 

" 

CANOGA PARK DR 

SHADY NOOK DR 

PADDLEWHEEL CT 

WINDTREE CT 

CLOVERHILL CT 

EXISTING 

36" CMP 

OAKMOSS DR 

REPLACE EXISTING 

CONTROL STRUCTURES 

WITH MODIFIED 

FDOT TYPE E INLETS 

HERLONG CT 


VAN REED MANOR DR 

PADDLEWHEEL DR 

SWEETLEAF DR 

CANOGA 

PARK 

POND 

ISLETON DR 

Existing Canoga Park Pond outfall structure in Bloomingdale West 

subdivision. 

PROBLEM 

The Bloomingdale West Subdivision has two stormwater detention ponds 

that serve as the primary storage facilities for this residential subdivision. 

The ponds do not appear to receive any maintenance and the outfall 

structures are overgrown and function is impaired such that flooding 

problems could arise if a significant storm event were to occur. 


The new structures are needed to replace the 

dysfunctional existing pond outlets. With the new 

proposed weir configurations, the FDOT structures 

will provide better treatment functions that are 

currently absent. 

SOLUTION 

The entire subdivision drainage system was constructed of corrugated 

metal pipe, which is corroded and likely in need of repair in the near 

future. It is recommended that the existing outfall structures for the 

Canoga Park and the Bloomingdale West ponds be replaced with 

modified FDOT inlet structures that will provide enhanced flood control 

and stormwater treatment function over the existing structures. 

COST 

Construction: 



Total 


25-YR, LOS B 

$21,200 

$0 

$8,500 

$29,700 

Bloomingdale West Subdivision Pond existing pond outfall 

structure. 



PROJECT NAME: BUCK -4 Bloomingdale West and Canoga Park Pond Outfall Retrofits 




ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $0 



LOCATION: Bloomingdale West and Canoga Park Subdivisions 


information. 


COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 

3 






GRAND TOTAL 100

HIA PINECREST RD 

CUNARD DR 


GUILES RD 

CHELSEA WO 

BUCK-5 

WAYLON LN 

NORRIDGE RD 

LITHIA OAKS POND 

OUTFALL RETROFIT 


DOEFIELD CT 

OAKLANE RD 

" 

LITHIA OAKS 

SUBDIVISION 

BLOOMINGDALE 

HIGH SCHOOL 

WISTER CIR 

BLOOMINGDALE HIGH 

REPLACE EXISTING 18" 

CMP POND OUTFALL 

WITH 24" RCP & ADD 

MODIFIED FDOT TYPE D 

CONTROL STRUCTURE 

Existing Lithia Oak Pond 18" CMP outfall (no control structure). 

PROBLEM 

The Lithia Oaks Subdivision detention pond that serves as the primary 

storage facility for this residential subdivision does not have a functional 

outfall structure. The pond does not appear to receive any maintenance 

and the outfall consists of an 18" CMP pipe that is collapsed and silted. 

Function is impaired such that flooding problems could arise if a 

significant storm event was to occur, and it is possible that the pond bank 

has been breached. 

SOLUTION 

It is recommended that the existing outfall structure for the Lithia Oaks 

pond be replaced by a 24" RCP with a modified FDOT inlet structure that 

will provide enhanced flood control and stormwater treatment functions 

over the existing structure. 


The new structure is needed to replace the 

dysfunctional exiting pond outlet. The new modified 

FDOT inlet structure will provide better flood control 

benefits and a stormwater treatment function that is 

currently absent. 

COST 

Construction: 



Total 

$11,000 

$0 

$4,400 

$15,400 


10-YR, LOS A 



PROJECT NAME: BUCK -5 Lithia Oaks Pond Outfall Retrofit 




LOCATION: Lithia Oaks Subdivisions 

ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $0 




information. 


COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 

3 






GRAND TOTAL 100



BRYAN RD 

12-ACRE ON SITE 

STORMWATER 

DETENTION POND 

BUCK-6 

BUCKHORN CREEK STORMWATER 

DETENTION POND AND WETLAND 

RESTORATION/ENHANCEMENT 

JOHN MOORE RD 

SPILLWAY 


NORMAL POOL 


LITTORAL SHELF 

HOLLAND DR 

POND EMBANKMENT 

TOP OF BANK ELEV 32.1 NAVD 

SEDIMENT 

SUMP 

Buckhorn Creek at proposed 12-acre detention pond site 

overgrown with excessive channel vegetation. 

BALLYBAWN LN 

CAGLE RD 

STONE LAKE PL 

PROBLEM 

Buckhorn Creek traverses a set of large tracts between Holland Road and 

the Bloomingdale Plaza shopping center south of Bloomingdale Avenue. 

Mostly unoccupied, this is the last remaining unencroached part of the 

natural floodplain of the creek upstream of the Bloomingdale Avenue 

bridge and portions of the tracts are impacted wetlands. The creek is in an 

unmaintained state, and excessive vegetation creates a hydraulic 

impediment. Downstream from this area, the creek passes through 

residential areas where street grades barely meet a 10-year level of service. 

SOLUTION 

This area provides an opportunity to preserve the natural floodplain and 

restore wetland function while providing both flood control and 

stormwater treatment benefits. It is recommended that all or portions of 

five land parcels be purchased to construct a 12.0-acre on-line 

stormwater detention pond. As designed, the facility will reduce the 

downstream peak flows by approximately 15%. 


While preserving the natural floodplain of Buckhorn 

Creek from future development pressure, the project 

provides downstream flood protection up to a 10- 

year level of service, restores/enhances existing 

wetlands, and provides treatment of stormwater 

runoff. 

COST 

Construction: 



Total 


10-YR, LOS B 

$1,058,900 

$1,192,300 

$423,600 

$2,674,800 



PROJECT NAME: BUCK -6 Buckhorn Creek Stormwater Detention Pond 




ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $1,192,300 

CONST. COST: $1,058,900 


LOCATION: Undeveloped land south of E. Bloomingdale Avenue, west of Holland Drive 


information. 


COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 

3 12 






GRAND TOTAL 22


ENG-1 

CLEAR AND REGRADE 

DITCH IF NECCESARY 

S WIGGINS RD 

FUTCH ROAD DRAINAGE 

IMPROVEMENTS 

FUTCH RD 

REPLACE EXISTING 15" PIPE 

WITH 30" RCP 

ENGLISH CREEK 

REPLACE EXISTING 12" PIPE 

WITH 24" RCP, CLEAR DITCH 

OF OVERGROWN VEGETATION 

N/A 

FUTCH LOOP KIRKLAND RD 

PROBLEM 

Homes on the south side of Futch Road occasionally experience yard and 

structure flooding. During extreme rainfall events, the depression fills up 

and does not have enough outfall capacity through either the culvert to 

the south ditch or the cross drain to the north. Overflow from the 

depression to the south flows overland in a southwesterly direction 

towards English Creek. The topography is generally flat, causing a 

lengthy but natural flowpath. 


This should alleviate property flooding to the south. 

Work can be done in the existing right of way without 

the need to obtain drainage easements. 

SOLUTION 

The cross drain should be replaced with a 30” RCP, and the pipe 

connecting the depression on the south side of the road to the south 

ditch should be replaced with a 24”RCP. The north ditch may need to be 

re-graded to drain toward the west end of the ditch for a distance of 

approximately 450 feet; a detailed survey and analysis of this secondary 

system will be required to ensure proper project design and 

implementation. 

COST 

Construction: 



Total 


25-YR, LOS B 

$30,300 

$0 

$12,200 

$42,500 

N/A 



PROJECT NAME: ENG-1 Futch Road Drainage Improvements 




ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $0 



LOCATION: Futch Road between English Creek and South Wiggins Road 

PROJECT See Project Fact Sheet ENG-1 for detailed project 

information. 

APPARENT SOLUTION: See Project Fact Sheet ENG-1 for project information. 

COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 24 24 48 

3 12 12 24 






GRAND TOTAL 92

ALBRITTON RD 


LINK RD 

SP-1 

GEORGE SMITH RD 

GEORGE SMITH ROAD AND 

LITHIA PINECREST ROAD 

MAINTENANCE 

CLEAR STRUCTURES OF 

ACCUMULATED 

SEDIMENT & DEBRIS 

PURCHASE DRAINAGE 

EASEMENT AND REGRADE 

EXISTING DITCH AND REMOVE 

EXCESS VEGETATION 


George Smith Road southern culvert crossing. Only 17 inches 

are available out of the 59 inch pipe depth to convey floodwater. 

PROBLEM 

The Hillsborough County East Service Unit staff expressed maintenance 

concerns along George Smith Road. The two culvert crossings are 

extremely silted (the northern crossing is approximately 50% silted and 

the southern crossing is approximately 70% silted). Service Unit staff 

stated that it is useless to clear the southern crossing since they have no 

access to clean and re-grade the upstream channel. 


This project will improve the conveyance capacity of 

the system to meet the 25-year level of service 

requirements as well as provide access such that 

routing maintenance can be performed by the 

Hillsborough County East Service Unit. 

SOLUTION 

The recommendation is for the County to purchase a drainage easement 

upstream of the southern culvert crossing. The two culvert crossings 

along George Smith Road, as well as the box culvert on Lithia Pinecrest 

Road, should be cleared of accumulated silt and debris. Additionally, 

the upstream and downstream channels should be re-graded such that a 

positive hydraulic gradient exists for all storm events. Routine 

maintenance should be performed at these locations. In a maintained 

state, these structures will provide the required 25-year flooding level of 

service. 

COST 

Construction: 



Total 


25-YR, LOS A 

$9,300 

$14,000 

$3,800 

$27,100 

George Smith Road overgrown unmaintained ditch where a 

drainage easement should be acquired. 



PROJECT NAME: SP-1 George Smith Road & Lithia Pinecrest Road Maintenance 




ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $14,000 



LOCATION: George Smith Road & Lithia Pinecrest Road 

PROJECT See Project Fact Sheet SP-1 for detailed project information. 

APPARENT SOLUTION: See Project Fact Sheet SP-1 for project information. 

COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 

3 






GRAND TOTAL 45


BUGG RD 

TC-2 

REPLACE TWIN 27" x 43" CMP 

CULVERTS WITH TWO 3' x 7' 

PRECAST BOX CULVERTS. 

REMOVE SEDIMENT AND RESTORE 

CHANNEL INVERTS. 

MUD LAKE ROAD 


MUD LAKE RD 

PROVIDE SEDIMENT 

MANAGMENT TECHNIQUES 

The downstream side of the culvert at Mud Lake Road. 

Sedimentation is evident at the outlet of this pipe. 

PROBLEM 

Excessive road flooding, with depths of 0.42 feet for the 25-year storm, is 

predicted for this location by the existing conditions model. Channel 

sedimentation is a severe problem at this location, as can be seen in the 

following pictures. The combination of undersized pipes and sediment 

build-up aggravates flooding conditions. 


Road flooding hazards during large storm events will 

be eliminated. By removal and control of sediment 

deposits and sources, water quality and natural 

habitats will be restored throughout the remainder of 

the stream corridor. 

SOLUTION 

The recommended alternative is to replace the twin 27" by 43" CMPs 

with two 3' by 7' box culvert sections and remove the sediment deposit 

that is artificially raising the invert of the channel. This is only a 

temporary solution, however, if the root cause of the sedimentation 

problem is not resolved. See water quality project, TC-4WQ. 

COST 

Construction: 



Total 


100-YR, LOS A 

$83,900 

$0 

$33,600 

$117,500 

Looking west at the downstream side of the channel at Mud Lake 

Road. Evidence of severe sediment deposition is clearly shown. 



PROJECT NAME: TC-2 Mud Lake Road Drainage Improvements 




ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $0 



LOCATION: Mud Lake Road between Bugg Road and West State Road 60 

PROJECT See Project Fact Sheet TC-2 for detailed project information. 

APPARENT SOLUTION: See Project Fact Sheet TC-2 for project information. 

COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 24 24 

3 12 12 






GRAND TOTAL 76


TC-4 

COLSON ROAD SECONDARY 

DRAINAGE SYSTEM 

IMPROVEMENTS 

C S X RR TRANS SYSTEM 

INSTALL 20' OF 24" RCP 

AND CONSTRUCT 80' SWALE 

TO DRAIN TOWARD 

CROSS CULVERT 

NA 

COLSON RD 

PROBLEM 

Localized road flooding of Colson Road, east of the CSX Railroad 

crossing, has been reported by residents and cited by the Hillsborough 

County East Service Unit Staff. The topography of the area indicates this 

is a localized problem of the secondary drainage system. Cross culverts 

exist 675 feet to the east of the railroad but not at the problem area. 


Flooding conditions will be allieviated with the 

construction of a cross drain under Colson Road. 

SOLUTION 

Installation of a 24" RCP as a cross culvert within the right of way will 

alleviate future road flooding. A shallow ditch system 80 feet in length 

which drains to this culvert along the north curve of Colson Road should 

also be constructed. 

COST 

Construction: 



Total 

$13,300 

$0 

$5,400 

$18,700 

NA 


25-YR, LOS B 



PROJECT NAME: TC-4 Colson Road Secondary Drainage System Improvements 




ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $0 



LOCATION: Colson Road just east of CSX Railroad Tracks 



COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 54 24 78 

3 27 12 39 






GRAND TOTAL 117


W O GRIFFIN RD 

TC-5 

SUGAR OAK LN 

JERRY SMITH ROAD SECONDARY 

DRAINAGE SYSTEM - MAINTENANCE 

CLEAR CROSS CULVERT 

OF ACCUMULATED SEDIMENT 

PALM GROVE LN 

BLANKENSHIP RD 

JERRY SMITH RD 

RE-GRADE DITCH TO 

PROVIDE POSITIVE 

DRAINAGE OUTFALL 

Accumulated silt on the west side of the structure under Jerry 

Smith Road. Culvert is almost completely blocked. 

PALM CREEK DR 

PROBLEM 

The Hillsborough County East Service Unit staff stated that localized 

flooding occurs along Jerry Smith Road between Endeavor Avenue and O' 

Griffin Road. This secondary drainage system is not included in the 

watershed model. Upon field investigation, it is evident that the cross 

culvert is completely clogged with silt and debris, such that no positive 

drainage outfall exists. 


This project will provide flood relief along Jerry 

Smith Road. 

SOLUTION 

The recommendation is to clear the cross culvert of the accumulated silt 

and debris. The downstream ditch should be graded such that a positive 

drainage outfall exists. The purchase of a drainage easement may be 

required. Routine maintenance should be performed regularly in this 

secondary system. In a maintained state it is expected that the drainage 

system will attain the required 25-year level of service. 

COST 

Construction: 



Total 


$8,300 

$0 

$3,400 

$11,700 

Buried pipe outfall on the east side of Jerry Smith Road. Outfall 

ditch does not provide a positive gradient. 

25-YR, LOS B 



PROJECT NAME: TC-5 Jerry Smith Road Secondary Drainage System Maintenance 




ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $0 



LOCATION: Jerry Smith Road South of West O’Griffin Road 



COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 24 24 

3 12 12 






GRAND TOTAL 56

N DOVER RD 

SYDNEY DOVER RD 


TC-6 

DOVER RANCH RD 

SALEM CHURCH RD 

DOVER ROAD DRAINAGE 

IMPROVEMENTS 

CONSTRUCT PONDS FOR 

FLOODPLAIN COMPENSATION 

REPLACE TWO EXISTING 

34" x 53" ERCPs WITH 

TWO 48" RCPs UNDER 

DOVER ROAD 

RAISE MINIMUM ELEVATION OF 

DOVER ROAD TO ELEV 65.0 NAVD 

FOR THIS 1650' PORTION OF 

DOVER ROAD 

The west side of Dover Road looking at the upstream side of the 

cross drainage culvert. 

MEADOW EDGE LN 

THOMAS COOPER LN 

PROBLEM 

The portion of Dover Road south of Salem Church Road experiences 

frequent road flooding with the model predicting a depth of 1.22 feet for a 

25-year event. In significant storm events, floodwaters back up all the 

way from SR 60 (downstream) over Dover Rd. SR 60 roadtop elevation is 

much higher than this upstream arterial. No structures are present in the 

area and roadway flooding is the only concern. 



protection and make this arterial road passable while 

not increasing flood elevations. 

SOLUTION 

The minimum elevation of this portion of Dover Road should be raised to 

65.0 feet. Floodplain compensation should be provided on county 

owned lands to the east of Dover Road. In a maintained state it is 

expected that the drainage system will attain the required 25-year 

flooding level of service. 

COST 

Construction: 



Total 


100-YR, LOS A 

$874,700 

$0 

$349,900 

$1,224,600 



PROJECT NAME: TC-6 Dover Road Drainage Improvements 




ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $0 



LOCATION: Dover Road between Salem Church Road and Highway 



COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 36 24 60 

3 18 12 30 






GRAND TOTAL 100

SMITH RYALS RD 


COWART RD 

TC-7 

GULF SIERRA LN 

CAMERON ROAD FLOOD 

ALLEVIATION 

ROBERT PORTER LN 

RAISE THIS 250' PORTION OF 

CAMERON ROAD TO MINIMUM 

ELEV 120 NAVD AND PROVIDE 

FLOODPLAIN COMPENSATION 

AVONDALE GROVES ST 


WITH 30" RCP 

PEANUT DR 

CAMERON RD 

N/A 

EVACUATION ROUTE FLOODED 

FOR THESE 11 RESIDENCES 

PROBLEM 

During 25-year storm events, Cameron Road is flooded by more than 0.6 

feet. This road is the only evacuation route to Cowart Rd for 11 

residences south of the flooding on Cameron Road. 



protection and make this evacuation route passable 

while not increasing flood elevations. 

SOLUTION 

Raise the elevation of Cameron Road to a minimum elevation of 120.0 

NAVD. Purchase portions of two properties on the west side of Cameron 

Road to allow for floodplain compensation. 

COST 

Construction: 



Total 

$103,600 

$10,000 

$41,500 

$155,100 

N/A 


100-YR, LOS A 



PROJECT NAME: TC-7 Cameron Road Flood Alleviation 




LOCATION: Cameron Road south of Cowart Road 

ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $0 





COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 24 24 48 

3 27 12 12 51 






GRAND TOTAL 99


ELLINGTON CT 

BRANDON BROOK RD 

N VALRICO RD 

RICKY CIR 

MIRAMONT CIR 

TIMOTHY TER 

VAL-1 

VALRICO ROAD 


BELFORT PL 

SACRAMENTO ST 


WITH 30" RCP 

FDOT POND 

CHARDONNAY PL 

WETLAND 

ROBERT JAMES DR 

JASON DR 

SUSAN PL 

DANNY DR 

JELANE DR 

RANDY DR 

RAISE THIS 750' PORTION 

OF DOVER ROAD TO 

ELEV 36.5 NAVD AND 

PROVIDE FLOODPLAIN 

COMPENSATION 

N/A 

E STATE ROAD 60 

PROBLEM 

This portion of Valrico Road north of State Road 60 experiences frequent 

road flooding with the model predicting a depth of 0.7 feet, for a 25-year 

event. Although a series of two pump stations already exist at this 

location, these only facilitate flood recovery. These pumps do not prevent 

any flooding from occuring. 



protection and make this evacuation route passable 

while not increasing flood elevations. 

SOLUTION 

The minimum elevation of this portion of Valrico Road would be raised to 

36.5 feet. Floodplain compensation would be provided on county owned 

land to the west of Valrico Road. The existing 18" RCP pipe connecting 

the FDOT pond on the west side of Valrico Road to the wetland on the 

east side of Valrico road should be replaced with a 30" RCP. It is 

expected that the drainage system will attain a 100-year flooding level of 

service. 

COST 

Construction: 



Total 


100-YR, LOS A 

$358,800 

$0 

$143,600 

$502,400 

N/A 



PROJECT NAME: VAL-1 Valrico Road Drainage Improvements 




ENGINEER: 

CHECKED BY: 

DESIGN HOURS: 

R/W COST: $0 



LOCATION: Valrico Road North of E. State Road 60 

PROJECT See Project Fact Sheet VAL-1 for detailed project 

information. 

APPARENT SOLUTION: See Project Fact Sheet VAL-1 for project information. 

COMMENTS: 


INCREASE 

D HAZARD 

ARTERIAL 

ROAD FLOODING 

LOCAL 

STREET 

FLOODING 

HOME 

FLOODING 

YARD 

FLOODING 

INCREASE 

PTS/YEAR 

TOTAL 

PTS 9 6 4 6 4 10 








10 

6 

3 27 18 12 57 






GRAND TOTAL 67

. 

Appendix A 

parsons

DRAFT 

DETERMINATION OF GREEN-AMPT PARAMETERS 

FOR HYDROLOGY COMPUTATIONS IN ICPR TM 

SWFWMD AUGUST 2008 

Purpose 

The purposed of this paper is to discuss the determination of Green-Ampt parameters used 

in the ESRI TM Arc Hydro Tools and how they are used to parameterize ICPR's new Perc 

Pack module for determining soil infiltration capacity. Unit conversions and parameter 

adjustments required when transferring the parameters from Arc Hydro to ICPR are 

discussed in the following narrative so that the user of the ArcHydro Tools will have a better 

understanding of the process. In addition to the Green-Ampt parameterization, land use 

characterization (percent impervious and DCIA percentage) will also be discussed since 

they are important components of the runoff computations. 

Sources of Green-Ampt Parameters 

Primary parameters required for the Green-Ampt computation based upon the literature 

include: soil porosity, saturated vertical hydraulic conductivity, and soil suction. Total soil 

column storage capacity is an added parameter to determine when a soil would become 

saturated as a result of a near surface water table. Sources for these Green-Ampt 

parameters come primarily from the Natural Resources Soil Conservation Service (NRCS) 

as provided in their Soil Survey Geodatabase (SSURGO) and the Institute of Food and 

Agricultural Services (IFAS) Soil Characterization data from the University of Florida Soil 

Science Department. 

SSURGO data was used to obtain the soil infiltration capacity and the depth annual 

minimum to the water table or what has been termed the "Seasonal High Groundwater 

Table" (SHGT). Soil data for a soil series comes from the predominant soil component 

assigned. For example, if the soil series was Astatula fine sand, associated components of 

the series includes: Astatula, Paola, Candler, Lake and Tavares fine sands. Since Astatula 

was the single major soil component identified, only characteristics of the Astatula 

component were used for the soil series identified by the MUKEY (Exhibit 1). The 

SSURGO indicates that there is no water table present to a depth of at least 203 cm (6'- 8"), 

that the representative saturated hydraulic conductivity for the A and C horizons is 247 

micrometers per second or 35 feet per day, and that the soil is classified as a sand. Exhibit 

2 demonstrates the database set up for the SSURGO. Related look-up tables provided 

within the SSURGO are used for determining the soil parameters. The indicated depth of 

the deepest bore is assumed as the water table location for the soil if a water table depth is 

not indicated. In this case 203 cm is used as the assumed water table.

Exhibit 1: Astatula Soil Polygon 

Exhibit 2: Database Example

Exhibit 2 Cont'd: 

Remainder of Page Intentionally left blank.

Exhibit 2 Cont'd: 

IFAS Soil Characterization Data is used to determine the porosity and the soil storage 

potential at the indicated or assumed water table depth from the SSURGO. Determining 

soil storage potential is not part of the Green-Ampt computation as originally conceived by 

its developers in the early 1900s. This is an added component based on current research 

indicating that Florida soils do not typically exhibit significant runoff until the soil becomes 

saturated. This is considered as a bucket filling process. ICPR's Green-Ampt calculation 

process accounts for the available soil storage. 

For most soils, the IFAS Characterization data provides sufficient moisture content 

information at various tensions whereby a soil moisture curve can be developed. Soil 

information (Exhibit 3) with the same component name were used to develop an averaged 

soil moisture retention curve. For example, if the component name was Astatula, all soil 

moisture information with that name were used to develop a soil moisture curve for the 

indicated water table depth. Field capacity at 1/10 bar was the lowest soil moisture content 

used in developing the curve. The assumed soil condition prior to a major event is a gravity 

drained soil with no moisture extraction from evapotranspiration, and a water table at the 

seasonal high groundwater level (indicated or assumed). Soil moisture content will be the 

highest at or near the water table. A relative high moisture content will extend above the 

water table for some distance due to soil capillarity. Above the capillary zone the soil 

moisture content will begin to rapidly decrease to field capacity. This is the moisture 

content at which gravity drainage would cease. 

Remainder of Page Intentionally left blank.

Exhibit 3: IFAS Soil Characterization Data 

Exhibit 4 provides an illustration of the soil moisture curve for a soil with a water table at 

200 cm (6.5' ) below the surface. The area in purple illustrates the resultant soil moisture 

retention curve derived from the IFAS data. From this data the soil storage potential can be 

determined by subtracting the soil moisture retention results from the soil porosity and 

integrating by depth. The soil moisture potential is in percent volume. Porosity of the soil is 

determined either by the smallest of the highest soil moisture content determined by the 

IFAS soil test results or the porosity calculation from the soil bulk density and an assumed 

soil particle density ( Porosity = 1- { Bulk Density / 2.65 } ). The area in green represents the 

soil storage capacity. Soil storage potential was determined by subdividing the soil column 

into 1cm intervals and then adding the incremental volume between the soil porosity and the 

soil moisture content for each interval. 

Literature information from available test data indicates that about 90% of the total soil 

porosity is available for water storage. The remaining 5-10% is not available due to 

entrapped air. This was not considered in the Green-Ampt computations, since most 

hydrologic 'A' soil water tables extend below the deepest bore depths yielding conservative 

estimates of soil storage. 

Exhibit 5 demonstrates the resulting storage curves for Candler soils which have a 

hydrologic "A" classification. The curves in black indicate the total soil storage on the y-axis 

as a function of the depth to the water table on the x-axis. Each curve indicates a different 

soil bore test. The vertical red lines indicate the total depth of the test bore in inches. For 

an 80-inch depth to a water table, the soil storage calculated varied between 17- to 28- 

inches. The average soil storage (SSt) for this series was used in the soil look-up table. It 

was assumed that if a water table depth annual minimum was not provided for the soil that

the bottom of the test bore would be the assumed water table or seasonal high even though 

evidence may exists indicating that the water table could be deeper. 

Exhibit 4: Soil Moisture Curve at Water Table Depth of 200 cm 

Soil Moisture for 200 cm Depth to WT 

Height Above Water Table Centimeters 

Field Capacity 

Soil Moisture 

Saturation / Soil Porosity 

Soil Moisture Content % 

Remainder of Page Intentionally Left Blank

Exhibit 5: Candler Soil Storage vs. Depth to Water Table 

Soil suction is the remaining parameter which is not directly available from the SSURGO or 

the IFAS Characterization data. The District and ICPR use literature values based on the 

descriptive soil texture classification. It has been determined that the soil suction is only 

significant during the initial entry of rainfall into the soil after which an exponential decay in 

infiltration occurs. Literature values for soil suction are available from Rawls, Brakensiek, 

and Miller (1983). 

ICPR Green-Ampt Parameterization 

Soil vertical infiltration rates are based on the SSURGO and are converted to the units 

needed for incorporation into the ICPR data framework. The upper horizon representative 

saturated hydraulic conductivities values are used for the soil infiltration rates. In most 

hydrologic "A" soils, the hydraulic conductivities do not vary with horizon or soil depth. For 

soils where hydraulic conductivities did vary, it was generally observed that the lower 

hydraulic conductivities were encountered at or below the seasonal high water table 

therefore they were not used. It is recommended that the soil SSURGO data be reviewed in

the event that unreasonable flood elevations are being generated or conflicts arise across 

county lines to determine whether adjustments in hydraulic conductivity values (Ksat) are 

warranted. 

In the soil look-up table provided with the ArcHydro Tools, the infiltration rate (Ksat) is 

expressed in inches per hour, in the SSURGO the infiltration or saturated hydraulic 

conductivities are expressed in micrometers per second, and in ICPR requires feet per day 

units. A factor of safety of 2 or a multiplier of 0.5 is recommended for the vertical hydraulic 

conductivity (Ksat) to account for air purging that occurs during infiltration. This is the 

default factor of safety value applied in the ArcHydro tools for exporting to ICPR. ICPR 

uses the Green-Ampt equation as documented in (Chow / Maidment 1988). 

Soil storage potential (SSt) in the look-up table provided with the Arc Hydro Tools is in 

inches of water stored within the column for the water depth annual minimum provided 

(WTDAnnMin) in centimeters. This is the storage calculated using the procedures 

described above using the IFAS characterization data. ICPR does not use this storage 

value, but a functional relationship between effective or fillable uniform porosity and a cutoff 

depth. The following discusses the computations required to generate equivalency between 

the ArcHydro look-up value and the ICPR parameterization for soil storage which is already 

incorporated into the ArcHydro tool. 

In the look-up table (Exhibit 6) for a Candler soil (MUKEY 1414120), the soil porosity is 

0.434, the calculated soil storage (SSt) is 24.1 inches, and the water table is assumed to be 

203 cm or approximately 80 inches from the surface. These are the data that will be 

transformed into ICPR parameters. 

Exhibit 6: Look-up Table Example 

Fillable or effective porosity is the average available pore space that infiltrated water can be 

stored within a soil and is based on the difference between soil porosity and soil moisture 

retention curve (Exhibit 4). A fillable or effective porosity can be calculated by dividing the 

SSt value by the depth to the water table, 24.1" / 80" yielding a value of 0.30. From a 

review of the above table, the total soil porosity of 0.434 is significantly different from the 

calculated effective porosity of 0.30. 

For ICPR, the effective porosity value of 0.391 is assigned by the ArcHydro Tools which is 

equal to 90% of the porosity value of 0.434 from the look-up table. The literature indicates 

that the total porosity is not available for water storage due to air entrapment (reference) To 

render the fillable storage calculated in ICPR equal to the storage value (SSt) of 24.1" 

provided in the look-up table, a cut-off depth different from the WTDAnnMin is calculated.

The cut-off depth to render the storage equivalent is 24.1" / 0.391 or 61.63" or 5.14 feet for 

the units required by ICPR (Exhibit 7). ArcHydro makes these calculations for the user. 

Exhibit 7: Adjusted Cut-off Depth to Generate Equivalent Storage 

The 5.14 feet used in ICPR is less than the SSURGO depth of 6.66 feet (203 cm) listed in 

the look-up table because of the larger uniform porosity used in ICPR. Exhibit 8 provides a 

visual representation of the difference. The primary difference in the cut-off depths is due to 

the capillary fringe area that is located at the bottom of the graphs. It is in this area that the 

soil remains fairly saturated for about a foot above the water table. The area in green in the 

left graph represents the non-uniform porosity distribution of effective porosity developed 

from the IFAS Characterization data for the depth to the water table indicated in the 

SSURGO. The area in blue in the right graph is the uniform porosity assigned for ICPR, 

which appears to be a good representation of the fillable voids. 

Exhibit 8: Comparison Of Non-Uniform and Uniform Effective Porosity

Suction head (SSu) is the only remaining parameter required for ICPR which is left in the 

units of inches. No conversion is required. 

ICPR Land Use Parameterization 

The purpose of the following discussion is to provide a process that has been developed by 

the District for assigning percent impervious and DCIA areas. Typically the Florida 

Department of Transportation (FDOT) FLUCCS Code is used to assign land use categories 

for a study area. With the use of the Green-Ampt method for calculating runoff, it is now 

necessary to have a more exact determination of the percent impervious and the percent 

directly connected impervious areas (DCIA) which are not readily available from currently 

available GIS land use layers. Runoff generated from the DCIAs is routed directly to a point 

of interest while the difference between the percent impervious and DCIA is routed over the 

pervious areas within a given subarea. This is the procedure used in ArcHydro and by 

ICPR. 

Percent impervious areas can be determined spatially using GIS, but it is not currently 

incorporated into the ArcHydro Tools as a database at this time. To obtain accurate percent 

impervious areas, tremendous effort was employed. For example, in Hernando County, 

detailed tax assessor's information was used to determine percent impervious on a lot-by-lot 

basis. The available information includes: parking areas, driveways, sidewalks, buildings, 

pools, etc. whereby impervious area computations could be made. Aggregation of data for 

commercial and industrial areas was necessary to render a usable database. Road 

information is not available from the county information, so roadway impervious areas were 

computed by taking one-half of the perimeter length of the right-of-way and multiplying it by 

the pavement width. Rights-of-way polygons in GIS were developed where uniform 

pavement widths were encountered. 

Determination of DCIAs were based on the general land use category of the parcels. Land 

use categories were based on whether the parcel was considered as residential, 

commercial / industrial, open space, roadways, agricultural or nonagricultural area. 

Typically commercial / industrial areas contain the highest percentage of impervious areas, 

70-80 percent. Exhibit 9 below illustrates the range and the level of detail for the percent 

imperviousness found within a study area. The green areas represent low impervious areas 

while the progression toward lighter colors represents areas with higher percentages of 

impervious areas. Red, purple, and lighter colored areas indicate roadways and residential 

areas. 

Remainder of Page Intentionally Left Blank

Exhibit 9: Land Use Level of Detail 

Literature research was conducted to determine methods for calculating DCIA percentages 

based on the percentage of imperviousness for an area and land use categories. 

Equations used were of the general form: DCIA percentage = Coefficient x Total 

Impervious Area Percentage^ Power , which came from work conducted by Laenen 1983, 

Alley and Veehuis 1983, and Sutherland 1995. 

The ArcHydro tools are used to integrate the soils information, and the land use data for 

each unique subarea of a catchment. Green-Ampt parameters along with the percent 

imperviousness and DCIA for each unique soil / landuse polygon area for a sub-basin is 

processed individually and loaded into ICPR using XML. As a result several thousand soil 

land use polygons are typically parameterized to represent runoff from a watershed.

The End

. 

Appendix B 

parsons

COST ESTIMATE 

ALAFIA RIVER WATERSHED MANAGEMENT PLAN 

AR-1 Alternate 2 

CUMMINS ROAD DRAINAGE IMPROVEMENTS 

Item Unit Quantity Unit Price Total Price 

Storm Structures & Pipes 

Triple 24"x38" ERCP LF 30 $500 $15,000 

Concrete Headwall EA 2 $2,750 $5,500 

Riprap TN 30 $100 $3,000 

$23,500 

Miscellaneous 

Roadway Fill/Earthwork CY 275 $10 $2,800 

Paving & Grading SY 833 $70 $58,400 

Channel Excavation CY 700 $17 $11,900 

Sodding SY 2,500 $1.75 $4,400 

$77,500 

Subtotal $101,000 

Overhead & Profit (10%) $10,100 

Mobilization & Demobilization (5%) $5,100 

Bond and Insurance (2.0%) $2,100 

Materials sales Tax (7%) $7,100 

Permits (1%) $1,100 

Estimated Construction Cost $126,500 

Miscellaneous 

Drainage Easement Acquisition LS 1 $57,852 $57,900 

Engineering and Contingency (40% of Construction) $50,600 

ESTIMATED TOTAL COST = $235,000

COST ESTIMATE 


TC-7 

CAMERON ROAD FLOOD ALLEVIATION 


Item Unit Quantity Unit Price Total Price* 

30" RCP LF 50 $86 $4,300 


$8,300 

Grading & Earthwork 

Road Fill/Earthwork CY 150 $10 $1,500 

Paving & Grading SY 1,000 $70 $70,000 

Sodding SY 867 $1.75 $1,600 

$73,100 






Permits $2,500 


Miscellaneous 

Partial Property Purchase LS 1 $10,000 $10,000 


*Rounded to the nearest $100 


COST ESTIMATE 


TC-6 Alternate 2 

DOVER ROAD/ S.R. 60 DRAINAGE IMPROVEMENTS 

Site Demolition/Removal 



Clearing/Vegetation Removal AC 1.8 $2,000 $3,600 

$3,600 

48" RCP LF 60 $143 $8,600 


$18,200 


Excavation and Grading CY 7,500 $10 $75,000 

Road Fill CY 5,000 $16 $80,000 

Pavement SY 7,450 $70 $521,500 

$676,500 









ESTIMATED TOTAL COST = $1,224,600 

*Rounded to the nearest $100

COST ESTIMATE 



JERRY SMITH ROAD SECONDARY DRAINAGE SYSTEM MAINTENANCE 



Culvert Clearing & Sediment Removal LS 1 $2,000 $2,000 

$2,000 


Excavation & Grading CY 250 $10 $2,500 

Sodding SY 300 $1.75 $600 

$3,100 


Overhead & Profit (10%) $600 

Mobilization & Demobilization (5%) $300 

Bond and Insurance (2.0%) $200 

Materials sales Tax (7%) $400 






COST ESTIMATE 



COLSON ROAD 



Clearing/Vegetation Removal LS 1 $2,000 $2,000 

$2,000 


24" RCP LF 20 $65 $1,300 

24" Mitered End Section EA 2 $1,200 $2,400 

$3,700 


Asphalt Replacement SY 22 $70 $1,600 

Excavation and Grading CY 130 $10 $1,300 

Sodding SY 140 $1.75 $300 

Mulch SY 60 $4 $300 

$3,500 











COST ESTIMATE 



MUD LAKE ROAD DRAINAGE IMPROVEMENTS 



Clearing/Sediment Removal LS 1 $5,000 $5,000 

$5,000 


Twin 3'x7' Concrete Box Culvert CY 58 $550 $31,900 

Concrete Endwall EA 2 $5,800 $11,600 

$43,500 


Grading LS 1 $10,000 $10,000 


Sodding SY 60 $1.75 $200 

$17,200 






Permits (1.0%) $2,300 




COST ESTIMATE 


S-PRONG-1 Alternate 1 

GEORGE SMITH ROAD AND LITHIA PINECREST ROAD MAINTENANCE 



Clearing & Grubbing LS 1 $2,000 $2,000 

Clear Silt & Debris from Culverts CY 50 $25 $1,300 

$3,300 


Excavation and Grading CY 185 $10 $1,900 

Sodding SY 450 $1.75 $800 

$2,700 






Permits (1.0%) $1,700 


Miscellaneous 

25' Drainage Easement LS 1 $14,000 $14,000 



COST ESTIMATE 


ENG-1 Alternate 1 

FUTCH ROAD DRAINAGE IMPROVEMENTS 



30" RCP LF 24 $86 $2,100 


24" RCP LF 40 $65 $2,600 


$13,900 

Paving and Roadway 

Driveway Restoration SY 22 $70 $1,600 

Roadway Restoration SY 35 $70 $2,500 

$4,100 


Misc. Ditch Grading LS 1 $2,500 $2,500 

Sodding SY 1,283 $1.75 $2,300 

$4,800 










COST ESTIMATE 


BUCK-6 Alternate 1 

BUCKHORN CREEK STORMWATER DETENTION POND 

AND WETLAND RESTORATION/ ENHANCEMENT 



Land Clearing & Grubbing AC 1 $2,000 $1,200 

Miscellaneous Demolition LS 1 $10,000 $10,000 

$11,200 

Storm Structure & Pipes 

Concrete Spillway LS 1 $15,000 $15,000 

$15,000 


Excavation and Grading CY 80,795 $10 $808,000 

Riprap TN 27 $100 $2,700 

Sodding SY 5,000 $1.75 $8,800 

$819,500 

Miscellaneous 

Littoral Shelf Planting AC 3.00 $15,000 $45,000 







Estimated Construction Cost $1,058,900 

Land Acquisition MARKET MARKET 

PARCEL #74698-0000 N/A $245,100 $245,100 

PARCEL #74698-0100 N/A $129,500 $129,500 

PARCEL #74703-0100 N/A $231,600 $231,600 

PARCEL #74703-0000 N/A $329,500 $329,500 

PARCEL #74699-0000 N/A $256,600 $256,600 

Estimated land Acquisition $1,192,300 



ESTIMATED TOTAL COST = $2,674,800

COST ESTIMATE 



LITHIA OAKS POND OUTFALL RETROFIT 



FDOT Type 'C' Inlet Modified EA 1 $3,000 $3,000 

24" RCP LF 30 $65 $2,000 


$6,200 


Grading LS 1 $1,000 $1,000 

Sodding SY 30 $1.75 $100 

$1,100 










COST ESTIMATE 



BLOOMINGDALE WEST POND OUTFALL RETROFITS 



Metal Pipe Weir EA 2 $250 $500 

$500 


FDOT Type 'E' Inlet-Modified EA 2 $3,500 $7,000 

$7,000 


Grading LS 1 $1,000 $1,000 

Sodding SY 30 $1.75 $100 

$1,100 











COST ESTIMATE 



CRAFT ROAD DITCH CULVERT REPLACEMENTS AND STORMWATER DETENTION FACILITY 



Concrete Spillway LS 1 $16,000 $16,000 

Riprap TN 27 $100 $2,700 

$18,700 


Pond Excavation CY 61,673 $10 $616,700 

Sodding SY 3,000 $1.75 $5,300 

$622,000 

Miscellaneous 

Wetland Planting AC 0.81 $15,000 $12,100 








Land Acquisition 

Drainage Easement LS 1 $19,000 $19,000 

Parcel Acquisition #73296-0100 N/A $420,000 $420,000 

Land Cost Total $439,000 




COST ESTIMATE 


BUCK-1&2 Alternate 3 

BARKFIELD STREET AND HUNTINGTON STREET DRAINAGE IMPROVEMENTS 



Clearing and Grubbing AC 0.1 $7,000 $700 

$700 


32"x49" ERCP LF 200 $100 $20,000 

32"x49" Mitered End Section EA 1 $2,600 $2,600 

34"x53" ERCP LF 575 $160 $92,000 

32"x49" Mitered End Section EA 1 $2,600 $2,600 

FDOT Type 'D' Inlet Modified EA 1 $3,500 $3,500 

Connect to Existing Structure EA 1 $1,000 $1,000 

$121,700 

Paving and Roadway 


$19,600 


Grading LS 1 $5,000 $5,000 

Sodding SY 156 $1.75 $300 

$5,300 


Miscellaneous 

Drainage Easements ls 1 $14,000.00 $14,000 

$14,000 



COST ESTIMATE 


BELL-1 

HOBSON SIMMONS ROAD MAINTENANCE 



Clearing & Grubbing Ditch LF 4,000 $1.50 $6,000 

Clear Silt & Debris from Culverts CY 50 $25 $1,300 

$7,300 


Grading LS 1 $7,500 $7,500 

$7,500 






Permits (1.0%) $200 




COST ESTIMATE 


AR-13 

FOUR WINDS SUBDIVISION FLOODING ALLEVIATION 



Clear and Snag Ditch LS 1 $25,000 $25,000 

$25,000 


60-foot Concrete Weir LS 1 $55,000 $55,000 

5' x 8' RCBC CY 350 $600 $210,000 


30"RCP LF 720 $86 $62,000 

Connection to Existing Structures EA 2 $1,500 $3,000 

Flowable Fill CY 1 $190 $200 

$335,200 


Road Fill/Earthwork CY 150 $10 $1,500 


Sodding SY 2,811 $1.75 $5,000 

$214,600 









ESTIMATED TOTAL COST = $1,008,500 


COST ESTIMATE 


AR-12 

LULA STREET DRAINAGE IMPROVEMENT 



2-18" RCP LF 22 $45.00 $1,000.00 

Headwalls EA 2 $1,400.00 $2,800.00 

$3,800.00 


Grading LS 1 $1,600.00 $1,600.00 

Sodding SY 100 $1.75 $200.00 

$1,800.00 






Permits (1.0%) $100 




COST ESTIMATE 



MAGNOLIA STREET LOCAL DRAINAGE IMPROVEMENTS AND BANK PROTECTION 


Storm Structure & Pipes 575 

Concrete Headwall at Outfall LS 1 $5,000 $5,000 

$5,000 

Paving, Grading & Earthwork 575 

Grading Swale & Embankment LS 1 $2,000 $2,000 

Sodding SY 30 $1.75 $100 

$2,100 






Permits (1.0%) $100 




COST ESTIMATE 



REVELS ROAD SECONDARY DRAINAGE IMPROVEMENTS 



Ditch Clearing & Grubbing LS 1 $2,500 $2,500 

$2,500 


24"RCP LF 72 $65 $4,700 

24"Mitered End Section EA 6 $1,200 $7,200 

$11,900 

Paving, Grading & Earthwork 

Driveway Restoration SY 20 $70 $1,400 

Channel Excavation CY 520 $17 $8,900 

Sodding SY 622 $1.75 $1,100 

$11,400 






Permits (1.0%) $300 


Miscellaneous 

Drainage Easement Acquisition N/A - $18,271 $18,200 



COST ESTIMATE 



WHITLOCK PLACE AND HERNDON STREET FLOODING RELIEF 



Clearing & Grubbing AC 9.15 $2,000 $18,300 

$18,300 



30"RCP LF 400 $86 $34,400 

$38,800 


Pond Excavation CY 135,000 $10 $1,350,000 

Sodding SY 47,000 $1.75 $82,300 

$1,432,300 

Subtotal $1,489,400 





Permits (1.0%) $14,900 

Estimated Construction Cost $1,861,900 

Land Acquisition 

Partial Property Acquisition N/A - $339,615 $339,700 



COST ESTIMATE 



PROVIDENCE ROAD DRAINAGE IMPROVEMENTS 



4’ x 8’ Box Culvert (750') CY 800 $500 $400,000 

5’ x 8’ RCBC (50') CY 55 $500 $27,664 

38” x 60” ERCP LF 144 $205 $29,520 

48" x 76" ERCP LF 50 $300 $15,000 

End Treatment LS 1 $20,000 $20,000 

40' Weir Structure EA 1 $40,000 $40,000 

$532,184 



Channel Excavation CY 5,020 $17 $85,400 

Sodding SY 1,852 $1.75 $3,300 

$103,500 






Permits (1.0%) $6,400 


Miscellaneous 

Drainage Easement Acquisition NA - $76,000 $76,000 



COST ESTIMATE 



RIVER DRIVE AND COCONUT COVE PLACE FLOODPRONE PROPERTY ACQUISITION 


Item Quantity Unit Price Total Price* 

Land Clearing & Grubbing Per Lot 57 $2,500 $142,500 

House Demo 40 $8,000 $320,000 

$462,500 


Overhead & Profit (10%) 575.00 $46,300 




Permits (1.0%) $4,700 


Property Acquisition Cost (based on 12/2009 Market Value ) $3,557,200 


COST ESTIMATE 



GREENHILLS DRIVE DRAINAGE IMPROVEMENTS 



Clearing and Grubbing AC 3 $2,000 $5,000 

$5,000 


18" RCP LF 540 $45 $24,300 


Type E Modified Inlet Control Structure EA 1 $3,500 $3,500 

$32,200 


Sodding SY 20,517 $1.75 $36,000 

Pond Excavation CY 20,000 $10 $200,000 

$236,000 






Permits (1.0%) $2,732 


Miscellaneous 

Partial Parcel Acquisition N/A 1 $45,671 $45,700 

Drainage Easement N/A 1 $208,000 $208,000 



COST ESTIMATE 


VAL-1 

VALRICO ROAD DRAINAGE IMPROVEMENTS 



30" RCP LF 50 $86 $4,300 


$8,300 


Road Fill/Earthwork CY 2,210 $10 $22,100 


Sodding SY 1,800 $1.75 $3,200 

$277,300 









ESTIMATED TOTAL COST = $502,400

Alafia WMP Update Nov 2010

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