Rainfall data for the design of sewer detention basins

where
t = time
T = total duration chosen equal to 720 minutes
r relationship between the time prior to peak intensity
and the total duration T.
11
The value of r was evaluated from the local data for Lundby and
is given in Table 2.2. An example of the local Chicago design
storm is given in Fig. 2.4.
Table 2.2 Average values of the relationship_, r_, between the
time prior to peak intensity and the total duration
of 720 minutes. Lundby_, Goteborg_, 1921-1939.
F
r
1/5 ~ F ~ l/2
1 ~ F ~ 10
0.43
0.35
Rainfall
inte2nsity , i
mm/h
b )2
+ c (before the peak)
= __ _:;,__ __
2
+ c ( after the
(-......__+b)
a, b, c = c on stan obtai ned from Fig. 1
0
0
r · T
T
Time, t
Figure 2.4 Design rainfall_, suggested by Keifer and Chu
(1957)_, derived from the Intensity-Duration-Frequency
relationship for Lundby_, Goteborg_, 1921-
1939. Return period one year. After Arnell (1982).