SW4211201_Design Calculations (Swale)_20220113

Page 1 of 4
CHANNEL ANALYSIS WORKSHEET
Date: 10/8/2021 Computed: JFO Checked:
Project: The Grove - Forsyth County, NC
Q............ Discharge (cfs) A ............. Flow Area (sf)
Zreq......... (Q x n)/(1.49 x Slope A0.5) P............. Wetted Perimeter (ft)
B............. Base Width (ft) R............. Hydraulic Radius (ft)
Y............. Normal Depth (ft) V............. Velocity (fps)
M1........... Left Side Slope Zay.......... A'R12/3
M2........... Right Side Slope T............. Shear Stress (psf) 62.4 x Y x Slope
n............. Manning's Roughness Coefficient (Reference 1; Table 3, Charts 5 thru 9)
Tp........... Permissable Shear Stress (Reference 1; Table 2)
Reference 1: FHWA Hydraulic Engineering Circular No. 15, Publication No. FHWA-IP-87-7, 1988
Station: 0+34 to 1+50 GROVE Left
Description: Lateral "V" Ditch
Q = 0.7 cfs 2-YR
Slope = 0.0344 ft/ft
n = 0.121 Class D Vegetation
Zreq = 0.3 ft
B Y M1 M2 A P R V Zav T Tp Remarks
0.0 0.6 3.0 3.0 0.9 3.5 0.26 0.9 0.4 1.18 0.60 Unstable
Q = 0.9 cfs 10-YR
Slope = 0.0344 ft/ft
n = 0.114 Class D Vegetation
Zreq = 0.4 ft
B Y M1 M2 A P R V Zav T Tp Remarks
0.0 0.6 3.0 3.0 1.0 3.6 0.27 1.0 0.4 1.22 0.60 Unstable
Station: 0+34 to 1+50 GROVE Right
Description: Lateral "V" Ditch
Q = 3.4 cfs 2-YR
Slope = 0.0344 ft/ft
n = 0.076 Class D Vegetation
Zreq = 0.9 ft
B Y M1 M2 A P R V Zav T Tp Remarks
0.0 0.8 3.0 3.0 1.9 5.1 0.38 1.9 1.0 1.72 0.60 Unstable
Q = 4.0 cfs 10-YR
Slope = 0.0344 ft/ft
n = 0.072 Class D Vegetation
Zreq = 1.0 ft
B Y M1 M2 A P R V Zav T Tp Remarks
0.0 0.9 3.0 3.0 2.2 5.4 0.40 2.1 1.2 1.82 0.60 Unstable

Page 2 of 4
CHANNEL ANALYSIS WORKSHEET
Date: 10/8/2021 Computed: JFO Checked:
Project: The Grove - Forsyth County, NC
Q............ Discharge (cfs) A ............. Flow Area (sf)
Zreq......... (Q x n)/(1.49 x Slope A0.5) P............. Wetted Perimeter (ft)
B............. Base Width (ft) R............. Hydraulic Radius (ft)
Y............. Normal Depth (ft) V............. Velocity (fps)
M1........... Left Side Slope Zay.......... A'R12/3
M2........... Right Side Slope T............. Shear Stress (psf) 62.4 x Y x Slope
n............. Manning's Roughness Coefficient (Reference 1; Table 3, Charts 5 thru 9)
Tp........... Permissable Shear Stress (Reference 1; Table 2)
Reference 1: FHWA Hydraulic Engineering Circular No. 15, Publication No. FHWA-IP-87-7, 1988
Station: 1+50 to 4+25 GROVE Right & Left
Description: Lateral "V" Ditch
Q = 0.7 cfs 2-YR
Slope = 0.0101 ft/ft
n = 0.158 Class D Vegetation
Zreq = 0.7 ft
B Y I M1 M2 A P R V Zav T Tp I Remarks
0.0 0.7 3.0 3.0 1.5 4.4 0.33 0.5 0.7 0.44 0.60 Stable
Q = 0.9 cfs 10-YR
Slope = 0.0101 ft/ft
n = 0.138 Class D Vegetation
Zreq = 0.8 ft
B Y I M1 M2 A P R V Zav T Tp I Remarks
0.0 0.8 3.0 3.0 1.7 4.7 0.36 0.5 0.8 0.47 0.60 Stable
Station: 4+50 to 6+00 GROVE Left
Description: Lateral "V" Ditch
Q = 0.8 cfs 2-YR DA = 0.3 C = 0.6 1 = 5.32
Slope = 0.0100 ft/ft
n = 0.159 Class D Vegetation
Zreq = 0.8 ft
B Y I M1 M2 A P R V Zav T Tp I Remarks
0.0 0.7 3.0 3.0 1.5 4.4 0.33 0.4 0.7 0.44 0.60 Stable
Q = 1.0 cfs 10-YR DA = 0.3 C = 0.6 1 = 6.83
Slope = 0.0100 ft/ft
n = 0.132 Class D Vegetation
Zreq = 0.9 ft
B Y I M1 M2 A P R V Zav T Tp I Remarks
0.0 0.8 3.0 3.0 1.8 4.9 0.37 0.6 0.9 0.48 0.60 Stable

Page 3 of 4
CHANNEL ANALYSIS WORKSHEET
Date: 10/8/2021 Computed: JFO Checked:
Project: The Grove - Forsyth County, NC
Q............ Discharge (cfs) A ............. Flow Area (sf)
Zreq......... (Q x n)/(1.49 x Slope A0.5) P............. Wetted Perimeter (ft)
B............. Base Width (ft) R............. Hydraulic Radius (ft)
Y............. Normal Depth (ft) V............. Velocity (fps)
M1........... Left Side Slope Zay.......... A'R12/3
M2........... Right Side Slope T............. Shear Stress (psf) 62.4 x Y x Slope
n............. Manning's Roughness Coefficient (Reference 1; Table 3, Charts 5 thru 9)
Tp........... Permissable Shear Stress (Reference 1; Table 2)
Reference 1: FHWA Hydraulic Engineering Circular No. 15, Publication No. FHWA-IP-87-7, 1988
Station: 6+00 to 6+93 GROVE Left
Description: Lateral "V" Ditch
Q = 1.6 cfs 2-YR DA = 0.5 C = 0.6 1 = 5.32
Slope = 0.0450 ft/ft
n = 0.094 Class D Vegetation
Zreq = 0.5 ft
B Y M1 M2 A P R V Zav T Tp Remarks
0.0 0.6 3.0 3.0 1.1 3.8 0.28 1.4 0.5 1.68 0.60 Unstable
Q = 2.0 cfs 10-YR DA = 0.5 C = 0.6 1 = 6.83
Slope = 0.0450 ft/ft
n = 0.086 Class D Vegetation
Zreq = 0.6 ft
B Y M1 M2 A P R V Zav T Tp Remarks
0.0 0.7 3.0 3.0 1.3 4.1 0.31 1.7 0.6 1.83 0.60 Unstable
Station: 6+93 to 8+10GROVE Left
Description: Lateral "V" Ditch
Q = 2.0 cfs 2-YR DA = 0.7 C = 0.6 1 = 5.32
Slope = 0.0460 ft/ft
n = 0.085 Class D Vegetation
Zreq = 0.5 ft
B Y M1 M2 A P R V Zav T Tp Remarks
0.0 0.7 3.0 3.0 1.3 4.1 0.31 1.7 0.6 1.87 0.60 Unstable
Q = 2.5 cfs 10-YR DA = 0.7 C = 0.6 1 = 6.83
Slope = 0.0460 ft/ft
n = 0.079 Class D Vegetation
Zreq = 0.6 ft
B Y M1 M2 A P R V Zav T Tp Remarks
0.0 0.7 3.0 3.0 1.5 4.4 0.33 1.9 0.7 2.01 0.60 Unstable

Page 4 of 4
CHANNEL ANALYSIS WORKSHEET
Date: 10/8/2021 Computed: JFO Checked:
Project: The Grove - Forsyth County, NC
Q............ Discharge (cfs) A ............. Flow Area (sf)
Zreq......... (Q x n)/(1.49 x Slope A0.5) P............. Wetted Perimeter (ft)
B............. Base Width (ft) R............. Hydraulic Radius (ft)
Y............. Normal Depth (ft) V............. Velocity (fps)
M1........... Left Side Slope Zay.......... A'R12/3
M2........... Right Side Slope T............. Shear Stress (psf) 62.4 x Y x Slope
n............. Manning's Roughness Coefficient (Reference 1; Table 3, Charts 5 thru 9)
Tp........... Permissable Shear Stress (Reference 1; Table 2)
Reference 1: FHWA Hydraulic Engineering Circular No. 15, Publication No. FHWA-IP-87-7, 1988
Station: 8+50 GROVE Left & Right
Description: Lateral "V" Ditch
Q =
0.8 cfs
2-YR
DA = 0.3
C = 0.6
1 = 5.32
Slope =
0.0558 ft/ft
n =
0.132
Class D Vegetation
Zreq =
0.3 ft
B
Y
M1
M2
A
P
R
V
Zav
T
Tp
Remarks
0.0
0.5
3.0
3.0
0.6
2.8
0.21
0.9
0.2
1.57
0.60
Unstable
Q =
1.0 cfs
10-YR
DA = 0.3
C = 0.6
1 = 6.83
Slope =
0.0558 ft/ft
n =
0.097
Class D Vegetation
Zreq =
0.3 ft
B
Y
M1
M2
A
P
R
V
Zav
T
Tp
Remarks
0.0
0.6
3.0
3.0
0.9
3.5
0.26
1.5
0.4
1.92
0.60
Unstable