Question

A 3 hour triangular unit hydrograph (UH) has a time base of 30 hours with peak discharge of $90m^3/s$. For the same catchment 9 hour unit hydrograph was derived using 3 hour UH. The peak of 9 hour UH will

• A. $75m^3/s$
• B. $50m^3/s$
• C. $90m^3/s$
• D. $30m^3/s$

Answer 1

The correct option is A $75m^3/s$


For same catchment area,

$\therefore {\text{Area of UH}}_1={\text{Area of UH}}_2$
$\frac{1}{2}\times 30\times 90=\frac{1}{2}\times 36\times Q_P$
$Q_P=75m^3/s$