HomeMy WebLinkAboutDrainage Study-R2Stormwater Calcs -Camila Addition
using Rational Method
Time of Concentration
Tc =56 * L^.6 * n^.6 seconds Drainage Basin-1
i^.4 * S^.3
L =925.000 feet
n =0.030
S =0.025 ft/ft
Iassumed =6.8 inches / hour
Tccalculated 577.78 seconds
Tccalculated 9.63 minutes
0.16 hours
Tc =10 minutes Tc for 25-yr Storm from exhibit 2-5 city of Little Rock Drainage Manual
I =6.8 inches I for 25-yr Storm from exhibit 2-5 city of Little Rock Drainage Manual
Use Tc =10 minutes
Tc =56 * L^.6 * n^.6 seconds Drainage Basin-2
i^.4 * S^.3
L =500.000 feet
n =0.030
S =0.056 ft/ft
Iassumed =8.4 inches / hour
Tccalculated 288.19 seconds
Tccalculated 4.80 minutes
0.08 hours
Tc =5 minutes Tc for 25-yr Storm from exhibit 2-5 city of Little Rock Drainage Manual
I =8.4 inches I for 25-yr Storm from exhibit 2-5 city of Little Rock Drainage Manual
Use Tc =5 minutes
Tc =56 * L^.6 * n^.6 seconds Drainage Basin-3
i^.4 * S^.3
L =245.000 feet
n =0.030
S =0.068 ft/ft
Iassumed =8.4 inches / hour
Tccalculated 177.21 seconds
Tccalculated 2.95 minutes
0.05 hours
Tc =3 minutes Tc for 25-yr Storm from exhibit 2-5 city of Little Rock Drainage Manual
I =8.4 inches I for 25-yr Storm from exhibit 2-5 city of Little Rock Drainage Manual
Use Tc =5 minutes
Stormwater Calcs -Camila Addition
using Rational Method
Runoff Coefficient
Pre Development
Calculated C values - Drainage Basin 1
Area C10 C25 C100 (C values taken from Table 2-1 of City of Little Rock Drainage Manual)
Natural Vegetation 4.94 0.4 0.44 0.5 Clay Soil, Average 2-7%
Total Area =4.94 0.40 0.44 0.50
Calculated C values - Drainage Basin 2
Area C10 C25 C100 (C values taken from Table 2-1 of City of Little Rock Drainage Manual)
Natural Vegetation 2.06 0.4 0.44 0.5 Clay Soil, Average 2-7%
Total Area =2.06 0.40 0.44 0.50
Calculated C values - Drainage Basin 3
Area C10 C25 C100 (C values taken from Table 2-1 of City of Little Rock Drainage Manual)
Natural Vegetation 2.54 0.4 0.44 0.5 Clay Soil, Average 2-7%
Total Area =2.54 0.40 0.44 0.50
Stormwater Calcs -Camila Addition
using Rational Method
Runoff Coefficient
Post Development
Calculated C values - Drainage Basin 1
Area C10 C25 C100 (C values taken from Table 2-1 of City of Little Rock Drainage Manual)
Residential 4.94 0.4 0.45 0.65 Residential, 1/2 Ac Lots or Larger
Total Area =4.94 0.40 0.45 0.65
Calculated C values - Drainage Basin 2
Area C10 C25 C100 (C values taken from Table 2-1 of City of Little Rock Drainage Manual)
Residential 2.06 0.4 0.45 0.65 Residential, 1/2 Ac Lots or Larger
Total Area =2.06 0.40 0.45 0.65
Calculated C values - Drainage Basin 3
Area C10 C25 C100 (C values taken from Table 2-1 of City of Little Rock Drainage Manual)
Residential 2.54 0.4 0.45 0.65 Residential, 1/2 Ac Lots or Larger
Total Area =2.54 0.40 0.45 0.65
Stormwater Calcs -Camila Addition
using Rational Method
Discharge
Pre Development
Drainage Basin 1
Q10 =11.86 CFS Q25 =14.78 CFS Q100 =20.25 CFS
c =0.40 c =0.44 c =0.50
i=6.00 in/hr i=6.80 in/hr i=8.20 in/hr
A=4.94 acres A=4.94 acres A=4.94 acres
Drainage Basin 2
Q10 =6.26 CFS Q25 =7.61 CFS Q100 =10.30 CFS
c =0.40 c =0.44 c =0.50
i=7.60 in/hr i=8.40 in/hr i=10.00 in/hr
A=2.06 acres A=2.06 acres A=2.06 acres
Drainage Basin 3
Q10 =7.72 CFS Q25 =9.39 CFS Q100 =12.70 CFS
c =0.40 c =0.44 c =0.50
i=7.60 in/hr i=8.40 in/hr i=10.00 in/hr
A=2.54 acres A=2.54 acres A=2.54 acres
Stormwater Calcs -Camila Addition
using Rational Method
Discharge
Pre Development
Drainage Basin 1
Q10 =11.86 CFS Q25 =15.12 CFS Q100 =26.33 CFS
c =0.40 c =0.45 c =0.65
i=6.00 in/hr i=6.80 in/hr i=8.20 in/hr
A=4.94 acres A=4.94 acres A=4.94 acres
Drainage Basin 2
Q10 =6.26 CFS Q25 =7.79 CFS Q100 =13.39 CFS
c =0.40 c =0.45 c =0.65
i=7.60 in/hr i=8.40 in/hr i=10.00 in/hr
A=2.06 acres A=2.06 acres A=2.06 acres
Drainage Basin 3
Q10 =7.72 CFS Q25 =9.60 CFS Q100 =16.51 CFS
c =0.40 c =0.45 c =0.65
i=7.60 in/hr i=8.40 in/hr i=10.00 in/hr
A=2.54 acres A=2.54 acres A=2.54 acres
Stormwater Calcs -Camila Addition
Existing Ditch Capacity
Mannings equation for Ditch @ S-N of Dreher Road
n =0.03 based on n for earth, grass and some weeds
Depth Side Slopes Bottom Top area rH slope Velocity Q
(ft)(ft)(ft)(ft)(ft^2)(ft/ft)(ft/s)(cfs)
1.5 3.00 2.00 11.00 9.75 0.85 1.000%4.45 43.41
Mannings equation for Ditch @ E-W of Dreher Road
n =0.03 based on n for earth, grass and some weeds
Depth Side Slopes Bottom Top area rH slope Velocity Q
(ft)(ft)(ft)(ft)(ft^2)(ft/ft)(ft/s)(cfs)
1.8 3.00 2.00 12.80 13.32 1.00 1.000%4.95 65.94
Width
Width
Stormwater Calcs -Camila Addition
Proposed Ditch Capacity
Mannings equation for Ditch @ S-N of Dreher Road
Q100 =10.13 CFS
n =0.03 based on n for earth, grass and some weeds
Depth Side Slopes Bottom Top area rH slope Velocity Q
(ft)(ft)(ft)(ft)(ft^2)(ft/ft)(ft/s)(cfs)
1.5 3.00 2.00 11.00 9.75 0.85 1.000%4.45 43.41
Mannings equation for Ditch @ E-W of Dreher Road
Q100 =20.25 CFS
n =0.03 based on n for earth, grass and some weeds
Depth Side Slopes Bottom Top area rH slope Velocity Q
(ft)(ft)(ft)(ft)(ft^2)(ft/ft)(ft/s)(cfs)
1.8 3.00 2.00 12.80 13.32 1.00 1.000%4.95 65.94
Width
Width
Stormwater Calcs -Camila Addition
using Rational Method
Proposed Culvert Capacity
From To Design Flow (cfs):Slope (ft/ft):Diameter (inches)No. Pipes Manning's Area Full (sf)Wetted Perimeter Full (ft)Hydraulic Radius Full (ft)Flow Capacity (cfs)Yes/No Qd/Qc % Capacity
East West 26.33 0.012 24 1 0.012 3.14 6.28 0.5 26.85 Yes 0.98
290295300305310315320300
305
310
315
320
325
305
31
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3
1
5
320
325 Designing our client's successGNEgarnatengineering@gmail.comBryant, AR 720223825 Mt Carmel RdPh (501) 408-4650P.O. Box 116Benton, AR 72018GarNat Engineering, LLC23036CAMILA ADDITIONCITY OF LITTLE ROCKPULASKI COUNTY, ARKANSAS1.0
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BA6,1
MARCH 2024
BASIN-1
C=0.50
I=8.2 IN/HR
A=4.94 AC
Q100=20.25 CFS
PRELIMINARY
EXISTING 1.5-FT HEIGHT,
11-FT TOP DITCH
EXISTING 1.8-FT HEIGHT,
13-FT TOP DITCH
PROPOSED 24 INCH CULVERT
BASIN-2
C=0.50
I=10.0 IN/HR
A=2.03 AC
Q100=10.30 CFS
BASIN-2B
BASIN-3
C=0.50
I=10.0 IN/HR
A=2.54 AC
Q100=12.70 CFS
BASIN-2A