Question

A direct runoff hydrograph due to a storm idealized into a triangular shape has a peak flow rate of $60m^3/s$ occuring at 25 hours from its start. if the base width of this hydrograph is 72 hours, and the catchment area is $777.6k{m}^2$, the run-off from the storm is

• A. 1 cm
• B. 2 cm
• C. 5 cm
• D. 10 cm

Answer 1

The correct option is A 1 cm

$\text{Total runoff}=\frac{1}{2}\times 60\times 72\times 3600$
$=77776000m^3$

Depth of runoff
$=\frac{\text{Total runoff}}{\text{Catchment area}}$

$=\frac{7776000}{777.6\times {10}^6}m=\frac{1}{100}m$
$=0.01m=1cm$