Question

A direct-runoff hydrograph due to isolated storm was triangular in shape with a base of 80 h and peak of $200m^3/s$. If the catchment area is $1440k{m}^2$, the effective rainfall of the storm is

• A. 20 cm
• B. 10 cm
• C. 5 cm
• D. 2 cm

Answer 1

The correct option is D 2 cm

Total runoff = Area of triangle
$=\frac{1}{2}\times 80\times 3600\times 200$
$=28.8\times {10}^6{m}^3$

$\text{Area of catchment}=1440k{m}^2$

$\therefore \text{Effective rainfall}=\frac{\text{Total runoff}}{\text{Area of catchment}}$
$=\frac{28.8\times {10}^6}{1440\times {10}^6}$

= 0.02 m = 2 cm