Question

The direct runoff hydrograph of a storm obtained from a catchment is triangular in shape and has a base period of 80 hours. The peak flow rate is 30 $m^3/sec$ and catchment area is 86.4 $k{m}^2$. The rainfall excess that has resulted the above hydrograph is

• A. 5 cm
• B. 8 cm
• C. 10 cm
• D. 16 cm

Answer 1

The correct option is A 5 cm



$(\frac{\text{Area of runoff}}{\text{hydrograph}})=(\frac{\text{Area of}}{\text{catchment}})\times (\frac{\text{Effective rainfall}}{\text{depth}})$

$\frac{1}{2}\times 80\times 3600\times 30=86.4\times {10}^6\times \text{effective rainfall depth}$

$\text{Effective rainfall depth}=0.05m=5cm$