# CE 372 Engineering Hydrology and Hydraulics Fall 2006 Homework 4 Due September 25

CE 372 Engineering Hydrology and Hydraulics
Fall 2006
Homework 4
Due September 25
16. A soil has Horton infiltration parameters f0 = 110 mm/h, fc = 20 mm/h, and k =
1.8 h−1 .
a. Compute the total infiltration and runoff from a storm with an intensity of 15
mm/h and a duration of 2 hours.
b. Compute the total infiltration and runoff from a storm with an intensity of 115
mm/h and a duration of 2 hours.
c. Suppose the intensity is i = 90 mm/h. One of your group members (not you)
computes the ponding time tp by setting the infiltration capacity to the intensity
and solving for tp ; that is, your teammate obtained tp from
i = fc + (f0 + fc )e−ktp .
Explain why this approach is wrong.
d. Compute the total infiltration and runoff from a storm with an intensity of 90
mm/h and a duration of 2 hours.
e. A bumbling but observant professor computed a total infiltration of about 98 mm
for part d. Why did he question this result?
17. A soil has Horton infiltration parameters f0 = 110 mm/h, fc = 30 mm/h, and k =
1.8 h−1 . The storm can be divided into four 30-minute periods. The intensities are
30, 50, 70, and 40 mm/h, respectively. Plot the infiltration capacity, the infiltration
rate, the cumulative infiltration, and the runoff as a function of time.
18. Carnegie sandy loam has Horton parameters f0 = 375 mm/h, fc = 45 mm/h, and
k = 20 h−1 . For a two-hour storm in Ames, what is the probability that delayed
ponding will occur on Carnegie sandy loam?