CIV E 445 - APPLIED HYDROLOGY
SPRING 2014
HOMEWORK No. 6

  1. Rain falls on a 15-ha urban catchment with an average intensity of 2.5 cm/h and duration of 2 h. The catchment is divided into (1) industrial district (with 72% impervious area), soil group B, covering 25% of the area; and (2) residential district, with 1/4-ac average lot size (with 38% impervious area), soil group C, covering 75%. Determine the total runoff volume, in cubic meters, assuming AMC II antecedent moisture condition.

  2. The following rainfall distribution was observed during a 24-h storm:

    Time (h)Intensity (mm/h)
    0-35
    3-68
    6-910
    9-1215
    12-1512
    15-1810
    18-215
    21-242

    The φ-index is 3 mm/h. Calculate the runoff curve number.

  3. Calculate a set of Snyder synthetic unit hydrograph parameters for the following data: catchment area A = 520 km2; L = 25 km; Lc = 14 km; Ct = 1.5; and Cp = 0.62.

  4. Calculate an SCS synthetic unit hydrograph for the following data: catchment area A = 11.2 km2; runoff curve number CN = 82; hydraulic length L = 4.2 km; and average land slope Y = 0.02. Plot the calculated unit hydrograph using a spreadsheet.