Question

Ordinates of a 1-hour unit hydrograph at 1 hour intervals, starting from time t = 0 , are 0, 2, 6, 4, 2, 1 and 0 $m^3/s$

Catchment area represented by this unit hydrograph is

• A. 1.0 $k{m}^2$
• B. 2.0 $k{m}^2$
• C. 4.0 $k{m}^2$
• D. 5.4 $k{m}^2$

Answer 1

The correct option is D 5.4 $k{m}^2$

Excess rainfall x catchment area = Area under unit hydrogaph

$0.01\times A=\left[\frac{1}{2}\right(0+1)\times 1+\frac{1}{2}(2+6)\times 1+\frac{1}{2}(6+4)\times 1+\frac{1}{2}(4+2)\times 1+\frac{1}{2}(2+1)\times 1+\frac{1}{2}(1+0)\times 1]\times 3600$
$0.01\times A=15\times 3600m^3$
$\Rightarrow A=\frac{15\times 3600}{0.01}{m}^2$
$=5.4\times {10}^6{m}^2=5.4k{m}^2$