HomeMy WebLinkAboutMaverik Country Store - Storm Runoff CalculationsStorm Runoff Calculations
Maverik Country Store - Meridian, ID
6/14/2013 TJH
The following runoff calculations are based on the Rainfall - Intensity - Duration
Frequency Curve for the Meridian, ID area taken from data compiled by
NOAA Atlas 2, using a 100 year storm.
Runoff st water has been calculated fo erent sets of conditions, one
being the xisting undeveloped land and other w land fully improved. The
difference b een the two quantities will be retained in a seepage bed and
will percolate in natural ground at a historical rate of minutes
ations are as follows:
from the undeveloped existing land.
C*i*A =
2. Runoff from developed land
Runoff Coefficients
Paved Area
Landscaped Area
Roof
Weighted Runoff Coefficient
Rainfall Intensity
Runoff Quantity
3. Detention Basin
Volume in
Volume out
1.1
0.14 CFS
(calc. release rate per perc. rate)
37,749
C = 0.90
8,920
C = 0.20
4,630
C = 0.90
i = varies with time
Q= CIA
Q *t
0.14 *t
The capacity of the retention basin is calculated as the maximum difference
between the volume flowing in and the volume flowing out.
The outflow from the retention basin is limited to outflow if undeveloped.
Use 0.14 cfs for Q outflow
The required volume of the detention basin is 3,203 cubic feet
7
Oj
o0 1y
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Retention Basin Required Capacity
Area of Sidewalls of Basin
Length
60 ft
Width
34 ft
Void Volume of Sump
Depth
4 ft
Void Raitio
0.4
Percolation out
Perc. Rate 20 min
Check 3264 cubic feet
9
Equation
(Length x Width)
Equation
Area x Depth x Void Ratio
2040 s.f.
3264 c.f.
Equation
(1/Perc. Rate)x(1ft/12in)x(1min/60sec)xArea
0.14 cfs
3,203 cubic feet OK
4386
F Of