Question

A rectangular open channel carries a discharge of $15m^3/s$ .when the depth of flow is 1.5 m and the bed slope is 1: 1440. What will be the discharge through the channel at the same depth if the slope would have been 1: 1000?

• A. $18m^3/S$
• B. $14.4m^3/S$
• C. $21.6m^3/S$
• D. $12.5m^3/S$

Answer 1

The correct option is A $18m^3/S$

Area, perimeter, and hydraulics radius will not change

$\frac{Q_2}{Q_1}=\sqrt{\frac{S_2}{S_1}}$

$\Rightarrow Q_2=15\sqrt{\frac{1}{1000}\times \frac{1440}{1}}=18m^3/s$