SW4240203_Design Calculations_20240515

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Project: Hidden Woods Village
Project#: 23-201
Submitted: 2/14/2024
Existing Side Ditch Calculations
The enclosed calculations are for the existing side ditches as shown on C-4.0. Calculations are
performed using NOAA data for a 10Yr storm event with side ditches in a mature,vegetated condition
using 4:1 fore slope and 3:1 back slope "V" shaped road side ditch.
o• • -aSS �,/o••
038574
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2/14/2024

DocuSign Envelope ID: DA5D1C67-465D-4E34-BA89-9BA558AB234F
NOAA Atlas 14,Volume 2,Version 3
0"`"'`°4, Location name: Rural Hall,North Carolina, USA* ''
i. Y Latitude: 36.2117°, Longitude: -80.2673° none
�, Y Elevation:903 ft** I
',on 4
.+� i
source:ESRI Maps 1111
* 0 '
**source:USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M.Bonnin,D.Martin,B.Lin,T.Parzybok,M.Yekta,and D.Riley
NOAA,National Weather Service,Silver Spring,Maryland
PF_tabular I PF_graphical I Maps_&_aerials
PF tabular
AMS-based point precipitation frequency estimates with 90% confidence intervals (in
inches/hour)1
Annual exceedance probability(1/years)
Duration
1/2 1/5 1/10 i 1/25 1/50 1/100 I 1/200 1/500 1/1000
5-min 4.86 6.08 6.80 7.61 8.12 8.60 9.01 9.50 9.84
(4.49-5.29) (5.60-6.61) (6.25-7.38) (6.96-8.26) (7.38-8.83) (7.76-9.35) (8.09-9.84) (8.42-10.4) (8.63-10.8)
10-min 3.89 4.87 5.44 6.05 6.46 6.83 7.15 7.51 7.75
(3.59-4.24) _(4.49-5.30) (5.00-5.91) (5.54-6.58) (5.88-7.03) (6.16-7.44) (6.41-7.81) (6.66-8.24) (6.80-8.54)
15-min 3.26 4.11 4.59 5.12 5.46 5.76 6.01 6.31 6.49
(3.01-3.55) (3.78-4.47) (4.22-4.98) (4.69-5.56) (4.96-5.94) (5.20-6.26) (5.39-6.57) (5.59-6.92) (5.69-7.14)
30-min 2.25 2.92 3.32 3.79 4.11 4.41 4.68 5.02 5.25
(2.08-2.45) (2.69-3.18) (3.06-3.61) (3.47-4.12) (3.74-4.47) (3.98-4.80) (4.20-5.11) (4.45-5.50) (4.61-5.79)
60-min 1.41 1.87 2.16 2.52 2.78 3.04 3.28 3.60 3.84
(1.30-1.54) (1.72-2.04) _(1.99-2.35) (2.31-2.74) (2.53-3.03) (2.74-3.30) (2.94-3.58) (3.19-3.95) (3.36-4.22)
2-hr 0.836 1.12 1.30 1.54 1.72 1.90 2.08 2.32 2.51
(0.769-0.913) (1.02-1.22) (1.19-1.42) (1.40-1.68) (1.56-1.88) (1.70-2.08) (1.85-2.28) (2.03-2.55) (2.17-2.77)
3-hr 0.600 0.802 0.938 1.11 1.24 1.38 1.51 1.69 1.83
(0.554-0.656) (0.738-0.874) (0.860-1.02) (1.01-1.21) (1.12-1.35) (1.23-1.50) (1.34-1.65) (1.48-1.85) (1.58-2.01)
6-hr 0.369 0.492 0.578 0.690 0.778 0.868 0.960 1.09 1.19
(0.340-0.403) (0.453-0.538) (0.529-0.630) (0.627-0.752) (0.701-0.847) (0.775-0.944) (0.847-1.04) (0.943-1.19) (1.02-1.30)
12-hr 0.221 0.295 0.349 0.420 0.477 0.537 0.599 0.688 0.760
(0.203-0.242) (0.271-0.323)1(0.319-0.380) (0.381-0.456) (0.429-0.516) (0.477-0.581)1(0.526-0.648) (0.593-0.746)1(0.644-0.825)
24-hr 0.132 0.177 0.209 0.252 0.286 0.321 0.359 0.412 0.455
(0.123-0.143) (0.164-0.192) (0.193-0.226) (0.231-0.272) (0.261-0.309) (0.292-0.347) (0.324-0.388) (0.368-0.446) (0.404-0.493)
2-day 0.077 0.102 0.120 0.143 0.161 0.180 0.199 0.226 0.248
(0.072-0.083) (0.095-0.110) (0.111-0.129) (0.132-0.154) (0.148-0.173) (0.165-0.193) (0.181-0.215) (0.204-0.244) (0.223-0.269)
3-day 0.054 0.072 0.084 0.100 0.113 0.126 0.140 0.159 0.174
(0.051-0.058) (0.067-0.077) (0.078-0.090) (0.093-0.108) (0.104-0.121) (0.116-0.136) (0.128-0.151) (0.144-0.172) (0.156-0.189)
4-day 0.043 0.057 0.066 0.079 0.089 0.099 0.110 0.125 0.137
(0.040-0.046) (0.053-0.061) (0.062-0.071) (0.073-0.085) (0.082-0.095) (0.091-0.107) (0.101-0.118) (0.113-0.135) (0.123-0.149)
7-day 0.028 0.036 0.042 0.050 0.055 I 0.062 0.068 0.077 I 0.084
(0.026-0.030) (0.034-0.038) (0.039-0.045) (0.046-0.053) (0.051-0.059) (0.057-0.066) (0.062-0.073) (0.070-0.083) (0.076-0.091)
10-day 0.022 0.028 I 0.032 I 0.038 0.043 0.047 0.052 I 0.058 0.063
(0.020-0.023) (0.026-0.030) (0.030-0.035) (0.036-0.041) (0.039-0.045) (0.043-0.050) (0.047-0.055) (0.053-0.062) (0.057-0.068)
20-day 0.014 0.018 0.021 0.024 0.027 0.030 0.032 0.036 0.039
(0.014-0.015) (0.017-0.019) (0.020-0.022) (0.023-0.026) (0.025-0.029) (0.028-0.031) (0.030-0.034) (0.033-0.038) (0.035-0.042)
30-day 0.012 0.015 0.017 0.019 0.021 0.022 0.024 0.026 0.028
(0.011-0.012) (0.014-0.015) (0.016-0.017) (0.018-0.020) (0.019-0.022)1(0.021-0.023) (0.022-0.025) (0.024-0.028) (0.026-0.029)
45-day 0.010 0.012 0.013 0.015 0.016 0.018 0.019 0.020 0.022
(0.009-0.010) (0.011-0.013) (0.013-0.014) (0.014-0.016) (0.016-0.017) (0.017-0.019) (0.018-0.020) (0.019-0.022) (0.020-0.023)
60-day 0.009 0.011 0.012 0.013 0.014 0.015 0.016 0.017 0.018
(0.008-0.009) (0.010-0.011) (0.011-0.012)1(0.012-0.014) (0.013-0.015) (0.014-0.016) (0.015-0.017)1(0.016-0.018)1(0.017-0.019)
1 Precipitation frequency(PF)estimates in this table are based on frequency analysis of annual maxima series(AMS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90%confidence interval.The probability that precipitation
frequency estimates(for a given duration and annual exceedance probability)will be greater than the upper bound(or less than the lower
bound)is 5%.Estimates at upper bounds are not checked against probable maximum precipitation(PMP)estimates and may be higher than
currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information. _
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PF graphical

DocuSign Envelope ID: DA5D1C67-465D-4E34-BA89-9BA558AB234F
AMS-based intensity-duration-frequency (IDF) curves
Latitude: 36.2117°, Longitude: -80.2673°
101 . Annual exceedance
probability
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vi
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o �� — 100
y 10-1 - ���. — 200
a 500
L_ — 1000
a.
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a
10 5-min — 2-day
2 — 10{rnn — 3-day
•- 15-mon — 4-day
o — 30-min — 7-day
a 10-1 - — 60-min — 10-day
'v
— 2fir — 20-day
aa. — 3fir — 30 day
6fir — 45-day
10-z — 12fir — 60-day
I 1 1 I I I I — 24-hr
1/2 1/5 1/10 1/2 5 1/50 1/100 1/200 1/500 1/1000
Annual exceedance probability(1/years)
NOAA Atlas 14,Volume 2,Version 3 Created(GMT):Wed Feb 14 19:49:22 2024
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Maps & aerials
Small scale terrain

DocuSign Envelope ID: DA5D1C67-465D-4E34-BA89-9BA558AB234F
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DocuSign Envelope ID: DA5D1C67-465D-4E34-BA89-9BA558AB234F
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100km
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60mi •
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US Department of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
National Water Center
1325 East West Highway
Silver Spring,MD 20910
Questions?:HDSC.Questions(a)noaa.gov
Disclaimer

DocuSign Envelope ID: DA5D1C67-465D-4E34-BA89-9BA558AB234F
Hydrology Report
Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday, Feb 14 2024
DL#1
Hydrograph type = Rational Peak discharge (cfs) = 0.547
Storm frequency (yrs) = 10 Time interval (min) = 1
Drainage area (ac) = 0.230 Runoff coeff. (C) = 0.35
Rainfall Inten (in/hr) = 6.790 Tc by User (min) = 5
IDF Curve = Hidden Woods Village NOAA.IDFRec limb factor = 1.00
Hydrograph Volume=164(cult);0.004(acft)
Runoff Hydrograph
Q (cfs) 10-yr frequency Q (cfs)
1.00 1.00
0.90 0.90
0.80 0.80
0.70 0.70
0.60 0.60
0.50 0.50
0.40 0.40
0.30 0.30
0.20 0.20
0.10 0.10
0.00 0.00
0 5 10
Time (min)
Runoff Hyd - Qp = 0.55 (cfs)

DocuSign Envelope ID: DA5D1C67-465D-4E34-BA89-9BA558AB234F
Channel Report
Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday, Feb 14 2024
DL#1
Triangular Highlighted
Side Slopes (z:1) = 4.00, 3.00 Depth (ft) = 0.31
Total Depth (ft) = 1.50 Q (cfs) = 0.550
Area (sqft) = 0.34
Invert Elev (ft) = 100.00 Velocity (ft/s) = 1.64
Slope (%) = 2.00 Wetted Perim (ft) = 2.26
N-Value = 0.035 Crit Depth, Yc (ft) = 0.28
Top Width (ft) = 2.17
Calculations EGL (ft) = 0.35
Compute by: Known Q
Known Q (cfs) = 0.55
Elev (ft) Section Depth (ft)
102.00 2.00
101.50 - 1.50
101.00 1.00
100.50 0.50
v
100.00 0.00
99.50 -0.50
0 2 4 6 8 10 12 14 16
Reach (ft)

DocuSign Envelope ID: DA5D1C67-465D-4E34-BA89-9BA558AB234F
Hydrology Report
Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday, Feb 14 2024
D L#2
Hydrograph type = Rational Peak discharge (cfs) = 0.452
Storm frequency (yrs) = 10 Time interval (min) = 1
Drainage area (ac) = 0.190 Runoff coeff. (C) = 0.35
Rainfall Inten (in/hr) = 6.790 Tc by User (min) = 5
IDF Curve = Hidden Woods Village NOAA.IDFRec limb factor = 1.00
Hydrograph Volume=135(cuft);0.003(acft)
Runoff Hydrograph
Q (cfs) 10-yr frequency Q (cfs)
0.50 0.50
0.45 0.45
0.40 0.40
0.35 0.35
0.30 0.30
0.25 0.25
0.20 0.20
0.15 0.15
0.10 0.10
0.05 0.05
0.00 0.00
0 5 10
Time (min)
Runoff Hyd - Qp = 0.45 (cfs)

DocuSign Envelope ID: DA5D1C67-465D-4E34-BA89-9BA558AB234F
Channel Report
Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday, Feb 14 2024
D L#2
Triangular Highlighted
Side Slopes (z:1) = 4.00, 3.00 Depth (ft) = 0.29
Total Depth (ft) = 1.50 Q (cfs) = 0.440
Area (sqft) = 0.29
Invert Elev (ft) = 100.00 Velocity (ft/s) = 1.49
Slope (%) = 2.00 Wetted Perim (ft) = 2.11
N-Value = 0.035 Crit Depth, Yc (ft) = 0.26
Top Width (ft) = 2.03
Calculations EGL (ft) = 0.32
Compute by: Known Q
Known Q (cfs) = 0.44
Elev (ft) Section Depth (ft)
102.00 2.00
101.50 - 1.50
101.00 1.00
100.50 0.50
100.00 0.00
99.50 -0.50
0 2 4 6 8 10 12 14 16
Reach (ft)

DocuSign Envelope ID: DA5D1C67-465D-4E34-BA89-9BA558AB234F
Hydrology Report
Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday, Feb 14 2024
DL#3
Hydrograph type = Rational Peak discharge (cfs) = 0.618
Storm frequency (yrs) = 10 Time interval (min) = 1
Drainage area (ac) = 0.260 Runoff coeff. (C) = 0.35
Rainfall Inten (in/hr) = 6.790 Tc by User (min) = 5
IDF Curve = Hidden Woods Village NOAA.IDFRec limb factor = 1.00
Hydrograph Volume=185(cult);0.004(acft)
Runoff Hydrograph
Q (cfs) 10-yr frequency Q (cfs)
1.00 1.00
0.90 0.90
0.80 0.80
0.70 0.70
0.60 0.60
0.50 0.50
0.40 0.40
0.30 0.30
0.20 0.20
0.10 0.10
0.00 0.00
0 5 10
Time (min)
Runoff Hyd - Qp = 0.62 (cfs)

DocuSign Envelope ID: DA5D1C67-465D-4E34-BA89-9BA558AB234F
Channel Report
Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday, Feb 14 2024
DL#3
Triangular Highlighted
Side Slopes (z:1) = 4.00, 3.00 Depth (ft) = 0.23
Total Depth (ft) = 1.50 Q (cfs) = 0.620
Area (sqft) = 0.19
Invert Elev (ft) = 100.00 Velocity (ft/s) = 3.35
Slope (%) = 12.00 Wetted Perim (ft) = 1.68
N-Value = 0.035 Crit Depth, Yc (ft) = 0.29
Top Width (ft) = 1.61
Calculations EGL (ft) = 0.40
Compute by: Known Q
Known Q (cfs) = 0.62
Elev (ft) Section Depth (ft)
102.00 2.00
101.50 - 1.50
101.00 1.00
100.50 0.50
100.00 0.00
99.50 -0.50
0 2 4 6 8 10 12 14 16
Reach (ft)

DocuSign Envelope ID: DA5D1C67-465D-4E34-BA89-9BA558AB234F
Hydrology Report
Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday, Feb 14 2024
D L#4
Hydrograph type = Rational Peak discharge (cfs) = 1.412
Storm frequency (yrs) = 10 Time interval (min) = 1
Drainage area (ac) = 0.594 Runoff coeff. (C) = 0.35
Rainfall Inten (in/hr) = 6.790 Tc by User (min) = 5
IDF Curve = Hidden Woods Village NOAA.IDFRec limb factor = 1.00
Hydrograph Volume=424(cult);0.010(acft)
Runoff Hydrograph
Q (cfs) 10-yr frequency Q (cfs)
2.00 2.00
1.00 1.00
0.00 0.00
0 5 10
Time (min)
Runoff Hyd - Qp = 1.41 (cfs)

DocuSign Envelope ID: DA5D1C67-465D-4E34-BA89-9BA558AB234F
Channel Report
Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday, Feb 14 2024
D L#4
Triangular Highlighted
Side Slopes (z:1) = 4.00, 3.00 Depth (ft) = 0.32
Total Depth (ft) = 1.50 Q (cfs) = 1.410
Area (sqft) = 0.36
Invert Elev (ft) = 100.00 Velocity (ft/s) = 3.93
Slope (%) = 12.00 Wetted Perim (ft) = 2.33
N-Value = 0.035 Crit Depth, Yc (ft) = 0.40
Top Width (ft) = 2.24
Calculations EGL (ft) = 0.56
Compute by: Known Q
Known Q (cfs) = 1.41
Elev (ft) Section Depth (ft)
102.00 2.00
101.50 1.50
101.00 1.00
100.50 0.50
100.00 0.00
99.50 -0.50
0 2 4 6 8 10 12 14 16
Reach (ft)