SW5221201_Design Calculations_20221220

APPENDIX D
CALCULATIONS
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Town of Princeville Roadside Ditch: Farmer's Market
TWC No.; 2849-J peak Flow: Rational Method
Time of Concentration (Kirpich Method)
Tc = 0.0078 * (L^0.77/s^0.385)
Length of Watershed (L) 200 feet
Delta H 0.5 feet
Slope of Watershed (s) 0.25 %
Time of Concentration (Tc) 5.00 mins
Predevelopment Runoff Volume Generated by the I -Year 24 Hour Design Storm
Runoff Coefficient Calculations (C)
Runoff Coefficient (C)
0.15
Watershed Area (A)
Watershed Area (A)
0.17
acres
Design Rainfall Intensity (I)
Design Intensity (1)
1.250
inches/hour
Pre -Developed Runoff Volume Calculations (cfs)
Runoff Coefficient (C)
Design Intensity (1)
Watershed Area (A)
Peak Flow (Q)
Q = C*1*A
0.15
1.25
0.17
0.0326
inches/hour
acres
cfs
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Area
acres
Coefficient
Pervious Area
0.160
0.20
Parking Lot
0.000
0.95
Pervious Pavement
0.000
0.60
Impervious Area
0.010
1.00
Impervious Area
0.000
1.00
Runoff Coefficient Calculations (C)
Composite Curve Number
Runoff Coefficient (C)
0.25
-
_ Post -Developed Runoff Volume Calculations (cfs)
Q = C*i*A
Runoff Coefficient (C)
0.25
-
Design Intensity (1)
1.250
inch/hour
Watershed Area (A)
0.17
acres
Peak Flow (Q)
0.0537
cfs
Percent increase In Discharge:
60.71%

Town of Princeville Roadside Ditch: Farmer's Market
TWC No.: 2849-3
Swale Calcs
Mannin 's Equation: 1-Year 24 Hour Storm for Roadside Ditch
Qp = (1.49/n)*A*RA(0.667)*S^(0.5)
Qp 0.0537 cfs A (ft^2)
Grass Turf Mat Gravel/Rip-Rap Concrete Bare Soil
Max Velocity 4 12 11 100 2.5
S 0.1 0.1 0.1 0.1 0.1
n 0.035 0.030 0.033 0.013 0.022
Minimum Depth for Side Slope of 3
Grass
Turf Mat
Gravel/Rip-Rap
Concrete
Bare Soil
n
Swale Depth, ft
0.10
0.10
0.10
0.07
0.09
o
Width, ft
0.61
0.57
0.59
0.42
0.51
n
Area, ft^2
0.03
0.03
0.03
0.01
0.02
:2
Velocity, ft/s
1.76
1.97
1.84
3.69
2.46
Ln
Check
Passes
Passes
Passes
Passes
Passes
Minimum Depth
for Side Slope of 4
Grass
Turf Mat
Gravel/Rip-Rap
Concrete
Bare Soil
.14
It
a
Swale Depth, ft
0.09
0.09
0.09
0.06
0.08
ro
o
Width, ft
0.72
0.68
0.71
0.50
0.61
C
Area, ft^2
0.03
0.03
0.03
0.02
0.02
Velocity, ft/s
1.65
1.86
1.73
3.47
2.32
Fn
Check
Passes
Passes
Passes
Passes
Passes
Minimum Depth for Side Slope of 5
Grass
Turf Mat
Gravel/Rip-Rap
Concrete
Bare Soil
Ln
Swale Depth, ft
0.12
0.12
0.12
0.09
0.11
a
o
Width, ft
1.24
1.17
1.22
0.86
1.05
N
Area, ft^2
0.08
0.07
0.07
0.04
0.06
LO
Velocity, ft/s
0.69
0.78
0.72
1.46
0.97
Check
Passes
Passes
Passes
Passes
Passes
Designed Depth
for Side Slope of 5, Depth set at 1 feet
Grass Turf Mat
Gravel/Rip-Rap
Concrete
Bare Soil
,c
N
Swale Depth, ft
2.00 2.00
2.00
2.00
2.00
(U
Width, ft
8.00 8.00
8.00
8.00
8.00
Q
V)
Area, ft"2
8.00 8.00
8.00
8.00
8.00
aU
Velocity, ft/s
0.0067 0.0067
0.0067
0.0067
0.0067
72
Ln
Check
Passes Passes
Passes
Passes
Passes
Design using existing slope of 2:1