Question

A hydraulically efficient trapezoidal section of open channel flow carries water at the optimal depth of 0.6m. Chezy coefficient is 75 and bed slope is 1 in 250. what is the discharge through the channel?

• A. $2.24m^3/s$
• B. $1.62m^3/s$
• C. $1.92m^3/s$
• D. $1.44m^3/s$

Answer 1

The correct option is B

$1.62m^3/s$

$Q=CA\sqrt{RS}$

For hydraulically efficient trapezoidal section,

$A=\sqrt{3}{y}_e^2=\sqrt{3}\times {\left(0.6\right)}^2=0.624m$

$R=\frac{y_e}{2}=\frac{0.6}{2}=0.3m$

$\therefore Q=75\times 0.624\times \sqrt{0.3\times \frac{1}{250}}=1.62m^3/s$