HomeMy WebLinkAboutSW1190901_Calcs (Swale)_20200306APPENDIX F - Swale Segment Calculations
CrossWetted
Swale
10-year
Long.
Hydraulic
10-year
Length*
Upstream inlets
Sectional
Flow Depth
Segment
flow
Slope
Perimeter
Radius
Velocity
Area
ft
cfs
ft/ft
sq ft
ft
ft
fps
A
35
A3.4
1.24
0.028
0.6
4.11
0.15
0.17
2.30
B
85
A3.4 + A3.1
4.03
0.010
1.81
5.74
0.32
0.34
2.30
C
80
A3.3
3.23
0.005
1.98
5.93
0.33
0.45
1.69
D
25
A3.4 + A3.1 + A3.2
7.19
0.040
1.64
5.54
0.30
0.49
4.41
E
100
A3.1 - A3.4
10.43
0.014
3.12
7.1
0.44
0.6
3.40
*Length does not include riprap or rockdams located between curb cuts and swale outlet. Includes grassed areas only.
Flow
Curb Cut
Area
i
C
Flow Rate
Total Length
Segments
to outfall
(Ac)
in/hr
cfs
3.1
0.44
7.04
0.9
2.79
B + E + D
210
3.2
1 0.50
1 7.04
0.9
1 3.17
1 E + D
125
3.3
0.51
7.04
0.9
3.23
C + E
180
3.4
0.22
7.04
0.8
1.24
A + B + D + E
245
uiagram
A3.4
• A3.2
A3.1
D
Out. E
A3.3
�H CAR
:1Q,
AL r
04019
D
Common Parameters for all Segments
Side Slopes = 3H : 1V
Bottom Width = 3'
Maximum Allowable Velocity:
Vmax = 4.5 fps for tall Fesque in sands and silts
n = 0.03 for Grass Lined Channels
Calculations
Mannings Equation
V = 1.489/n * R^(2/3) * S^(1/2)
n = Mannings Number
R = Hydraulic Radius
R = Cross Sectional Area/Wetted Perimeter
S = Channel Slope (ft/ft)
Rational Method: Q = CiA
C = runoff coefficient
I = flow intensity
A = Drainage Area