Question

A rainfall with an intensity of 1.5 cm/h occurred over a catchment area in a 3 hour storm, resulting in a peak discharge of $210m^3/s$ in the river. The base flow and average storm loss $\varphi -index$ were $25m^3/s$ and 8 mm/hour respectively. The peak of the 3-hour unit hydrograph is ______ $m^3/s$. (Upto two decimal places).

• A. 88.095

Answer 1

The correct option is A 88.095
$P=i\times t=1.5\times 3=4.5cm$

$R=P-\varphi t$
$=4.5-(0.8\times 3)=2.1cm$

$\text{Peak of UH}=\frac{\text{Peak of FH - Base Flow}}{R_{cm}}\times 1cm$

$\text{Peak of UH}=\frac{210-25}{2.1}\times 1$

$\text{Peak of UH}=88.095m^3/s$