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An isolated 4-hour storm occurred over a catchment as follows:
The φ-index for the catchment is 10 mm/h. The estimated runoff depth from the catchment due to the above storm is
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- 10 mm
- 16 mm
- 20 mm
- 23 mm
Correct Option: C
Infiltration (i)
If rainfall > φ index, i = φ index
If rainfall < φ index, i = rainfall
∴ i1st hour = 9 mm,
i2nd hour = 10 mm
i3rd hour = 10 mm
i4th hour = 9 mm.
Runoff = rainfall – i
= 0 + (28 – 10) + (12 – 10) + 0
= 20 mm.
