Stormwater Modeling in the Many Mind Watershed - Rutgers ...

Stormwater Modeling
in the Many Mind
Watershed
April 19, 2005
Sandra M. Goodrow
Program Associate
Water Resources
Rutgers Cooperative Extension
Phone: 732-932
932-90119011
E-mail:
sgoodrow@envsci.rutgers.edu

Overview of Presentation
• Brief introduction to the project
• Brief overview of modeling
approach
• Model results
• Model analysis
• Conclusions and next steps

Role of Rutgers
• Review and evaluate available data
• Utilize GIS databases to delineate
drainage area
• Develop model describing hydrologic and
hydraulic conditions of the watershed
• Comment on alterations to land use and
changes in stream bank elevation

2-Step Modeling Approach
Hydrologic
Hydraulic

Many Mind Modeling Process
• Estimate the volume of surface
runoff from various design storms
(2, 10, and 100-year storms)
• Route the flow of water in the
streams
• Determine the water surface
elevation, flow and velocity for
various design storms

Modeled Scenarios
• Existing
Conditions
• Anticipated Land
Use Alterations
• High Tide
• Changes to Curve
Numbers

HEC-RAS Output
Floodplain delineations

2-Year Floodplain Delineation

10-Year Floodplain Delineation

100-Year Floodplain Delineation

Q3 Floodplain Delineation

Route 36 Bridge

Grand Avenue

Seventh Avenue Bridge

HydroCAD: : Basins 7 & 8

HydroCAD: : Basins 7 & 8

Area for Potential Retention

Anticipated Land Use Changes
1. Creek Bend Park
2. Wetlands Creation
between Center and
Bay
3. Expanding Salt Marsh

Creek Bend Park
Downstream of Highland Avenue
• Creation of wetlands
• Retrofit of detention basin
Model Representation
•Change in grading of streambanks
•Increase in Mannings n

Center Avenue Bridge

Results of Center Ave Bridge Analysis
• Geometric and roughness alterations show little
effect on modeled water surface elevation and
velocity.
• Reducing slope of banks and increasing soil
retention with native vegetation will serve to
reduce total suspended solids input into the
stream, and therefore Sandy Hook Bay.
• A more detailed analysis of the mechanics of the
detention basin may find options to create a
better functioning storage area. This may include
a tidal gate.

Wetlands Between Center and Bay
Presently, this area has approximately
270 feet adjacent to the Many Mind
Creek, with steep banks, heavy
phragmites, , and little access to the
flood plain.
Model Representation
•Change in grading of streambanks
•Increase in Mannings n

Results: Wetlands Between Center
and Bay
• No significant effect on water surface elevation or
stream velocity was found.
• This area lies well within the effects of the tidal zone.
The tidal influence will be a controlling factor in the
water surface elevation of the stream.
• Re-grading the steep banks would allow better
access to the floodplain. This would serve to
moderate quick fluctuations in water surface
elevations and reduce the potential for erosion.
• Reducing slope of banks and increasing soil retention
with native vegetation will serve to reduce total
suspended solids input into the stream, and therefore
Sandy Hook Bay.

Expanding Salt Marsh
Analysis:
• The results of the model runs show that this project
will have little effect on stream flow, water surface
elevation or water velocity due to its proximity to the
bay and the tidal influence of the bay.
• This proposed restoration will create a more diverse
habitat, including a fishery habitat, within the
watershed.
• Overland flow should result in increased filtration and
improved water quality for the area.
Recommendations:
• This project provides a variety of benefits to the
ecosystem and is therefore a recommended land use
change.

Curve Number Changes
2yr-low 2yr_exist 2yr_high 10% 10%
Station W.S. Elev W.S. Elev W.S. Elev decrease CN increase CN
(ft) (ft) (ft) diff(ft) diff(ft)
Pour Point: 8-headwaters 49.14 49.2 49.26 -0.06 0.06
Grand Ave Br: upstream 20.17 20.21 20.25 -0.04 0.04
7th Ave: upstream br & pr pt 7 20.08 20.13 20.17 -0.05 0.04
First Ave: upstream of bridge 9.11 9.74 10.57 -0.63 0.83
Pour Point: 3_west south 5.61 5.89 6.22 -0.28 0.33
Rt 36 at Foodtown: upstream 5.56 5.83 6.14 -0.27 0.31
Pour Point: 1 southwest 20.5 20.53 20.55 -0.03 0.02
Area next to Fireman's Field 4.42 4.68 4.98 -0.26 0.3
Highlands Ave Brdg, upstream 3.76 4.12 4.57 -0.36 0.45
Center Ave Brdg, upstream 2.1 2.47 2.92 -0.37 0.45
Bay Ave Brdg, upstream 0.4 0.87 1.48 -0.47 0.61
outlet -1.01 -0.68 -0.29 -0.33 0.39

Curve Number Changes
2yr_low 2yr_existing 2yr_high
Station Q Total Q Total Q Total % change w/ % change w/
(cfs) (cfs) (cfs) decrease in CN increase in CN
Pour Point: 8-headwaters 16.39 20.7 26.37 -20.82 27.39
Grand Ave Br: upstream 16.38 20.69 26.36 -20.83 27.40
7th Ave: upstream br & pr pt 7 62.01 79.2 102.51 -21.70 29.43
First Ave: upstream of bridge 61.97 79.16 102.45 -21.72 29.42
Pour Point: 3_west south 104.55 133.93 173.9 -21.94 29.84
Rt 36 at Foodtown: upstream 104.55 133.93 173.9 -21.94 29.84
Pour Point: 1 southwest 6.71 8.35 10.43 -19.64 24.91
Area next to Fireman's Field 140.74 180.59 234.53 -22.07 29.87
Highlands Ave Brdg, upstream 140.64 180.46 234.34 -22.07 29.86
Center Ave Brdg, upstream 181.16 233.62 305.04 -22.46 30.57
Bay Ave Brdg, upstream 181.16 233.62 305.04 -22.46 30.57
outlet 166.57 216.62 285.27 -23.10 31.69

Recommendations
• Address additional runoff that leads
to flooding in area of Seventh and
Grand Avenues.
• Mitigate erosion
• Clean debris from streams regularly

Conclusions
• The Many Mind Regional Stormwater
Management Planning Committee can
use the model output to evaluate the
conditions that lead to flooding and
erosion, and identify where changes
can be made to make the most
significant impact.
• Intended to be a regional study, this
project provides a good preliminary
base. Enhancements to the dataset
were made in the field at a large scale,
but if detailed localized calculations are
required for future analyses, further
refinement of the input data would be
necessary.

Questions
Contact Information:
Sandra M. Goodrow
Program Associate, Rutgers Water Resources
Rutgers Cooperative Research and Extension
sgoodrow@envsci.rutgers.edu
(732)932-9011
9011
www.water.rutgers.edu