Using the runoff volume found in Problem 2, determine the depth of storage in a retention...

Using the runoff volume found in Problem 2, determine the depth of storage in a retention basin that has vertical walls and a base area of 500 m2.

Problem 2

A small, 2-ha, mostly impervious urban catchment has an average slope of 1.5% and the following average Horton infiltration parameters: f0 = 4 mm/hr, fc = 1 mm/hr, k = 2.2 hr-1 (infiltration occurs through cracks in the paving). Consider the rainfall hyetograph in Figure.1

(a) Determine the depression storage using Figure 2.

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(b) Determine the time of beginning of runoff.

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(c) Calculate and sketch the hyetograph of rainfall excess. Use the same time intervals as for the rainfall hyetograph, and average the first nonzero rainfall excess over the whole time interval.

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(d) Determine the runoff coefficient.

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(e) Compute the volume of runoff, in m3.

Figure 1

Figure 2

Depression storage vs. catchment slope. (After Kidd, 1978; Viessman and Lewis, 1996.)