Conduit Outlet & Grassed Waterway Software Tools PowerPoint ...

Software Tools
1. Conduit Outlet Protection
2. Grassed Waterway
Bill Brash, CPESC, #3570
December 4, 2008

Conduit Outlet Protection
• “Conditions Where Practice Applies”
– Where a conduit restricts design flow
• Design Criteria
– Allowable velocity of soil type is exceeded (Table 12-1)
– 25 year or design storm whichever is greater
• Excel Spreadsheet Provides Easy Design Checks for
These Outlet Scenarios.
– Flat Apron: No defined waterway downstream.
– Scour Hole: No defined waterway, length of apron
restricted.
– Existing channel: Discharge to defined waterway or ditch. *

Definitions
• Do: Maximum inside
culvert height in
feet.
• Tw: Tailwater, depth
of receiving water
above invert.
– Not known or not
provided = (.2) Do.

Flat Apron-Design Apron Design Equations-Length
Equations Length
For Conduit of 15” (1.25 ‘) and a Q of 10 cfs
Tw < ½ Do……….. length = 21.63 feet where Tw is .25’
Tw > ½ Do……….. length = 21.47 feet where Tw is 1.25’
•Two separate equations for
determining length for a flat
apron.
Tw < ½
Do
Tw > ½
Do
Why do we
calculate
length first?

Flat Apron-Design Apron Design Equations-Width
Equations Width
For Conduit of 15” (1.25 ‘) and a Q of 10 cfs and Wo’ = inside width of pipe
Tw < ½ Do……….. width = 25.38 feet where Tw is 0.25’ Width at the
end of apron
Tw > ½ Do……….. length = 12.34 feet where Tw is 1.25’
Width at Outlet = 3 Wo

Flat Apron-Design Apron Design Equation-d50
Equation d50
For Conduit of 15” (1.25 ‘) and a Q of 10 cfs
Where Tw is .25’………. d50 = 1.02 feet
Where Tw is 1.25’……... d50 = 0.20 feet or 2.5”

Flat Apron-Design Apron Design Criteria
Special Circumstances
S < ¼ Wo d50 and length
as per 1 pipe.
S > ¼ Wo d50 and length
and increase values by
1.25.
For varying diameter
outlets use largest values.
If S >1/4 Wo…… increase
values by 1.25.

Flat Apron-Design Apron Design Criteria
• Thickness of Apron
– 2 times d50 with filter fabric
– 3 times d50 w/o filter fabric
• Apron is constructed at 0.0% slope
• There can be no “overfall” from the end of
apron to existing grade
• For Discharges into Detention Basins
–25 year storm Q
– Tw is equal to 2-year storm elevation in basin

COP Flat Apron Design Check
PROJECT NAME: ANALYSIS PERFORMED BY:
PROJECT NUMBER: DATE:
Conduit Conduit Conduit Depth of Apron Apron Apron Median Apron Apron
FES / Height Width Flow Tailwater Length Width Width at Stone Thickness Thickness
HEADWALL (D O ) (W O ) (Q) (Tw) (La) (Wa) Outlet Diameter (Ta) in FT. (Ta) in FT.
No. in FT. in FT. in CFS in FT. in FT. in FT. (Wa1) in FT. (d 50 ) in FT. w/o Filter w/ Filter
#DIV/0! #DIV/0! 0.00 #DIV/0! #DIV/0! #DIV/0!
#DIV/0! #DIV/0! 0.00 #DIV/0! #DIV/0! #DIV/0!
#DIV/0! #DIV/0! 0.00 #DIV/0! #DIV/0! #DIV/0!
#DIV/0! #DIV/0! 0.00 #DIV/0! #DIV/0! #DIV/0!
#DIV/0! #DIV/0! 0.00 #DIV/0! #DIV/0! #DIV/0!
#DIV/0! #DIV/0! 0.00 #DIV/0! #DIV/0! #DIV/0!
#DIV/0! #DIV/0! 0.00 #DIV/0! #DIV/0! #DIV/0!
#DIV/0! #DIV/0! 0.00 #DIV/0! #DIV/0! #DIV/0!
#DIV/0! #DIV/0! 0.00 #DIV/0! #DIV/0! #DIV/0!
#DIV/0! #DIV/0! 0.00 #DIV/0! #DIV/0! #DIV/0!
#DIV/0! #DIV/0! 0.00 #DIV/0! #DIV/0! #DIV/0!
#DIV/0! #DIV/0! 0.00 #DIV/0! #DIV/0! #DIV/0!
•Input data from COP
calculations in the table
provided.
•Will calculate length, width,
d50, and thickness with or
without filter fabric.
•Will calculate COP for
elliptical pipe.

Scour Hole Design Check
PREFORMED SCOUR HOLE CALCULATION SPREADSHEET
PROJECT NAME: 0 ANALYSIS PERFORMED BY: 0
PROJECT NUMBER: 0 DATE: 1/0/1900
Conduit Conduit Conduit Depth Depth of Scour Hole Dimensions Median Apron Apron
FES / Height Width Flow to Scour Stone Thickness Thickness
HEADWALL (D O ) (W O ) (Q) Tailwater Hole "A" "B" "C" Diameter (Ta) in FT. (Ta) in FT.
No. in FT. in FT. in CFS in FT. in FT. in FT. in FT. in FT. (d 50 ) in FT. w/o Filter w/ Filter
0.00 0.00 0.00 #DIV/0! #DIV/0! #DIV/0!
0.00 0.00 0.00 #DIV/0! #DIV/0! #DIV/0!
0.00 0.00 0.00 #DIV/0! #DIV/0! #DIV/0!
0.00 0.00 0.00 #DIV/0! #DIV/0! #DIV/0!
0.00 0.00 0.00 #DIV/0! #DIV/0! #DIV/0!
0.00 0.00 0.00 #DIV/0! #DIV/0! #DIV/0!
0.00 0.00 0.00 #DIV/0! #DIV/0! #DIV/0!
0.00 0.00 0.00 #DIV/0! #DIV/0! #DIV/0!
0.00 0.00 0.00 #DIV/0! #DIV/0! #DIV/0!
0.00 0.00 0.00 #DIV/0! #DIV/0! #DIV/0!
0.00 0.00 0.00 #DIV/0! #DIV/0! #DIV/0!
• Will check scour hole design
for Y=Do or Y= 1/2Do,
where Y is the depth of the
scour hole desired.
•Will provide design check for
length, width, d50 and thickness
with or without filter fabric.
•Will calculate scour hole
dimensions for elliptical pipe.

Existing Channel COP Design Check
CHANNEL CONDUIT OUTLET PROTECTION CALCULATION SPREADSHEET
PROJECT NAME: 0 ANALYSIS PERFORMED BY: 0
PROJECT NUMBER: 0 DATE: 1/0/1900
Conduit Conduit Conduit Depth Depth Apron Median Apron Apron Greater of Min. Depth
FES / Height Width Flow From of Length Stone Thickness Thickness 2 / 3 D O or of Riprap
HEADWALL (D O ) (W O ) (Q) T.O.B. to Tailwater (La) Diameter (Ta) in FT. (Ta) in FT. 1 ft.+ Tw Above
No. in FT. in FT. in CFS Invert in FT. (Tw) in FT. in FT. (D 50 ) in FT. w/o Filter w/ Filter in FT. Invert in FT.
#DIV/0! #DIV/0! #DIV/0! #DIV/0! 1.00 0.00
#DIV/0! #DIV/0! #DIV/0! #DIV/0! 1.00 0.00
#DIV/0! #DIV/0! #DIV/0! #DIV/0! 1.00 0.00
#DIV/0! #DIV/0! #DIV/0! #DIV/0! 1.00 0.00
#DIV/0! #DIV/0! #DIV/0! #DIV/0! 1.00 0.00
#DIV/0! #DIV/0! #DIV/0! #DIV/0! 1.00 0.00
#DIV/0! #DIV/0! #DIV/0! #DIV/0! 1.00 0.00
#DIV/0! #DIV/0! #DIV/0! #DIV/0! 1.00 0.00
#DIV/0! #DIV/0! #DIV/0! #DIV/0! 1.00 0.00
#DIV/0! #DIV/0! #DIV/0! #DIV/0! 1.00 0.00
#DIV/0! #DIV/0! #DIV/0! #DIV/0! 1.00 0.00
#DIV/0! #DIV/0! #DIV/0! #DIV/0! 1.00 0.00
•Will provide design check
for proposed outlets
discharging into existing
channels
•Will provide Length, d50,
Thickness with or without
filter fabric.
•Will provide the height of
the armor protection in
the channel in lieu of
width.

Grass Waterways
• Conditions Where Practice Applies
– Drainage areas < 200 acres
– The slope of the waterway cannot exceed 10%
– Do not apply this Standard if grass cannot be
maintained.
• Design Criteria
– 10 year frequency storm for capacity and
stability

Design Criteria
“as as Brought Down From the Mountain”
Mountain

The 2nd Stone Tablet
Website for Texas DOT
http://www.txdot.gov/publications/maintenance/approved_products_list_08.pdf

Grass Waterways Design Check
Project Name: Prepared By: Developed by: Paul Schiariti, P.E.
Project Number: Date: Mercer County Soil Conservation District
Grassed Waterway Calculator - Version 1.0 Beta Test For use by NJ Soil Conservation Districts
1. Choose the Soil Texture: 2 Choose the Stabilization Method: Seeded Max
Silt Loam, Sandy Loam, Loamy Sand, Muck
1
Seeded
Sod Allowable
Velocity
Sand Allowable Velocity: 2.00
Silt Loam, Sandy Loam, Loamy Sand, Muck Soil Texture: Silt Loam, Sandy Loam, Loamy Sand, Muck 1.12 1.77 5.00
Silty Clay Loam, Sandy Clay Loam Stabilization Method: Seeded 5.50
Clay, Clay Loam, Sandy Clay, Silty Clay Allowable Velocity: 2.00 FPS (No Channel Liner) 6.00
Note: The allowable velocity given above does not consider the 3.00
installation of a flexible channel liner. However, the computations 3.00
below do consider the installation of flexible channel liners. 4.00
5.00
Veg. Ret. 4 5
2. Choose Vegetal Retardance for Capacity: Choose Vegetal Retardance for Stability: Comp V 1.119385 1.765529
Vegetal Retardance D
Vegetal Retardance A
Vegetal Retardance E
Max All V
Froude No.
5.00
0.32
5.00
0.58
Vegetal Retardance B Vegetal
Vegetal Retardance C Retardance Retardance Description:
Vegetal Retardance D A Very High Vegetal Retardance
Vegetal Retardance E 4 5 B High Vegetal Retardance
Note: The values required for the analysis of Grassed C Moderate Vegetal Retardance
Waterways per The STANDARDS are: D for Capacity D Capacity- Low Vegetal Retardance
and E for Retardance. E Stability- Very Low Vegetal Retardance
Channel Data Input
3. Enter the Channel Cross-Section:
Trapezoidal
Triangular
Parabolic
Parabolic
3
• Input Soil Texture
• Input Stabilization
method
Seed
Sod
• Input Retardance
Factor for Capacity
• Input Retardance
Factor for Stability
• Input Channel
Cross Section Type:
P
ar
a
b
oli
c

6. Input Parabolic Channel Geometry Parameters: 0
0
H Swale ID H Swale No.:
15.00 Top Width in Feet ( T ) 15.00
2.00 Depth in Feet ( d ) 2.00
0.0100 Longitudinal Slope in Ft / Ft
10.00 Design Flow Q in CFS
D E 0 #REF!
Vegetal Q 10.02 10.00
RetardanceTW 9.88 8.81
Y 0.88 0.70
V 1.73 2.43
Analysis Results: 2 2
Vegetal Retardance: D
The Computed Depth is not within 10% of Crit. Depth
The Computed Vel. is less than the Allowable Vel. - Design is O.K.
Vegetal Retardance: E
The Computed Depth is not within 10% of Crit. Depth
However, the Computed Vel. is greater than the Allowable Vel.
a Type E min. classification of flexible channel liner is required
Warning! Potential for a Hydraulic Jump Exists! Consider revising the Design.
Vegetal
Retardance
D
Swale No.:
H
Vegetal
Retardance
E
Swale No.:
Parabolic Cross section data input includes:
•Top width in feet
•Depth of Channel in Feet
•Slope of grass waterway
•Design Q
PARABOLIC SECTION
(Not To Scale)
Design Top Width "T" = 15.00
CHANNEL WIDTH ( t )
Design Depth "D" = 2.00
AT WATER SURFACE IN FT. = 9.88
0
FLOW DEPTH ( Y ) IN FT. = 0.88
At 10.02 cfs
0
V avg = 1.73
PARABOLIC SECTION
(Not To Scale)
Design Top Width "T" = 15.00
CHANNEL WIDTH ( t )
Design Depth "D" = 2.00
AT WATER SURFACE IN FT. = 8.81
FLOW DEPTH ( Y ) IN FT. = 0.70
At 10.00 cfs
V avg = 2.43
H 0
0

Project Name: KNF Neuberger Prepared By: WFB
Project Number: 0 Date: 3/10/08
Output Screens
Detailed Hydraulic Analysis
Channel Geometry: Parabolic Cross Section
Swale No.: H
Top Width in Feet - T 15.00
Depth in Feet - D 1.00
Longitudinal Slope in Ft / Ft 0.0150
Longitudinal Slope in Percent (%) 1.50%
Soil Texture Silt Loam, Sandy Loam, Loamy Sand, Muck
Allowable Velocity in FPS (No Liner) 2.00 3
a Type E Even with Even with Even with
Hydraulic Computations:
CAPACITY STABILITY
Vegetal Retardance D E
Computed Q in CFS 5.012 5.015
Flow Depth "Y" in Feet 0.59 0.43 Design "Y" is within 10% of Critical Depth!
Top Width "TW" in Feet at the water surface 11.42 9.81 Less than min. top width of 10 ft.
Cross Sectional Flow Area "A" in FT 2
4.477 2.840
Wetted Perimeter "WP" in Feet 11.55 9.91
Hydraulic Radius "R" 0.387 0.287
Manning's Roughness Coefficient "n" 0.0864 0.0448 5.00 5.00
Average Velocity "V" in FPS 1.12 1.77 Exceeds Maximum Allowable Velocity of: 5.00 FPS
Froude Number "F" 0.315 0.578 Warning! Potential for Hydraulic Jump Exists!
Critical Velocity "V crit" 2.66 2.66 Consider Revising the Design.
10% of "Y crit" 0.033 0.033 0.361 2 2
Critical Depth "Y crit" 0.328 0.328 0.296
Flow Regime Sub-Critical Sub-Critical 0.361
0.30
Design Summary: 1
• Basic data input
information repeated
• Design Check output
information
Channel geometry
• Manning’s n
pursuant to D & E
Retardance factors.
• Key factors
Depth of flow for
“Capacity”. D
• Velocity in channel
for “Stability”. E

Stability:
Retardance:
Capacity:
Retardance:
E
D
Program Warnings
The Computed Depth is not within 10% of Crit. Depth
The Computed Vel. is less than the Allowable Vel. - Design is O.K.
The Computed Depth is not within 10% of Crit. Depth
The Computed Vel. is less than the Allowable Vel. - Design is O.K.
The program has two default warning messages….
1. Critical Depth within 10% of computed depth may result in a hydraulic
jump which cannot be stabilized with vegetation and the warning is to
“avoid this design”.
2. Computed velocity is greater than allowable velocity. May recommend a
Texas DOT approved erosion control blanket for stabilization.

E F G H
Bells and Whistles
• Calculated velocities are
graphically illustrated along a
horizontal bar graph to clearly
show what type “flexible
channel liner” or erosion
control blanket is necessary to
meet the Standards.
• Liners are pursuant to
Texas DOT specifications.
http://www.txdot.gov/publications/maintenance/approved_products_list_08.pdf