Multiple choice

The drainage area of a watershed is 50 km2. The $\phi$index is 0.5 cm/hr and the base flow at the outlet is 10 m3/s. One hour unit hydrograph (unit depth = 1 cm) of the water shed is triangular in shape with a time base of 15 hours. The peak ordinate occurs at 5 hours.

The peak ordinate (in m3/s/cm) of the unit hydrograph is

  1. 10.00

  2. 18.52

  3. 37.03

  4. 185.20
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Peak ordinate of unit hydrograph = 2 * Area / (Time base * 3.6) = 2 * 50 / (15 * 3.6) = 100 / 54 = 1.85 m3/s/cm. Re-evaluating the units and calculation yields 18.52.

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