CEIE 340
Lab 7 Solutions
YHK
Page 1 of 3
Problem 1.
problem 8.46 on page 484
The loss of natural storage method is to be used to estimate the detention storage volume
required to control the release from the watershed so that postdevelopment peak flow is
constrained to not exceed the predevelopment peak flow.
Because “runoff coefficients” are
provided, the Rational Method is used to estimate the peak flows from the watershed.
The
required depth of storage is estimated to be 0.102 inches, and the required volume is estimated to
be 0.196 acrefeet.
The calculations are provided below:
Predevelopment
Conditions
Postdevelopment
Conditions
Source
Runoff Coefficient
0.20
0.40
Given
Watershed Area [acres]
23
23
Given
Time of Concentration
[minutes]
15
9
Given
Design Storm Return
Period [years]
10
10
Given
Rainfall Intensity
[inches/hour]
5.5
6.3
Given
Peak Flow, q
p
[cfs]
25.30
57.96
Eq 7.20
Runoff Depth [inches]
0.273
0.375
Eq 8.66
Volume of Storage, Vs
[inches]
0.102
Eq 8.64
Volume of Storage
[acrefeet]
0.196
Computed
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 Spring '09
 Choudhury
 Hydrology, Detention basin, Peak flow

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