Question

Flow happens at a critical depth of 0.5 m in a rectangular channel of 4 m width. What is the value of discharge?

• A. $4.9m^3/s$
• B. $5.1m^3/s$
• C. $5.4m^3/s$
• D. $4.4m^3/s$

Answer 1

The correct option is D $4.4m^3/s$

(d) For a rectangular channel, critical depth is given by

$y_c^3=\frac{q^2}{g}$

$\Rightarrow q^2=y_c^{3}g$

$\Rightarrow q^2={\left(0.5\right)}^3\times 9.81$

$\Rightarrow q=1.107m^2/s$

But discharge,

$Q=q\times B=1.107\times 4$

$=4.4m^3/s$