Question

The peak of a flood hydrograph due to 2 hour duration isolated storm in a catchment area is $135m^3/s.$ The total depth of rainfall is 54 mm. Assume a constant base flow of $10m^3/s$ and $\varphi -index$ to be equal to 4 mm/hr, then peak of 2-hr UH for the catchment in $m^3/s$ is

• A. 25.0
• B. 29.23
• C. 23.15
• D. 27.17

Answer 1

The correct option is D 27.17

Peak of 2 hr DRH
$=135-10=125m^3/s$

Effective rainfall
$=54-4\times 2$
$=46mm=4.6cm$

Peak of 2 hr UH
$=\frac{125}{4.6}=27.17m^3/s$