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CE 3354 Engineering Hydrology
Fall 2022 Exercise Set 10

LAST NAME, FIRST NAME

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Purpose :

Unit hydrograph implementation (by-hand).

Assessment Criteria :

Completion, plausible solutions, use of Jupyter Notebook as a calculator/documentation method

An agricultural watershed was urbanized over a 20 year interval. A triangular one-hour unit hydrograph was developed for this watershed for an excess rainfall duration of one hour. Before urbanization, the average infiltration rate and other losses was 0.30 in/hr. Figure 1 is the unit hydrograph had a peak discharge of 400 cfs/in occurring at 3 hours, and a base time of 9 hours.

After urbanization the loss rate was reduced to 0.15 in/hr and the peak discharge of the unit hydrograph was increased to 600 cfs/in occurring at 1 hour, and the base time was reduced to 6 hours. Figure 2 is the unit hydrograph with a peak discharge of 600 cfs occurring at 1 hours, and a time base of 6 hours.

Exercise 1:

For a two hour storm in which 1 inch of rain fell in the first hour and 0.5 inch in the second hour, determine the direct runoff hydrographs before and after urbanization.

Note This exercise is the same as problem 7.5.7, pg. 238 in Chow, Maidment, Mays

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