A natural river is conveying a flow of 2500 cumec. What is the expected wetted perimeter of the river cross-section?

Question

Question

This question was previously asked in

BPSC AE Paper 6 (Civil) 25 March 2022 Official Paper

Answer 1

Explanation:

According to Lacey's theory, following formulae has been given below:

Hydraulic mean depth, \(R = \frac{5}{2}\frac{{{V^2}}}{f}\)
Area of the channel section, \(A = \frac{Q}{V}\)
Wetted perimeter, \(P = 4.75\sqrt Q \)
Regime mean velocity, \(V = {\left( {\frac{{Q{f^2}}}{{140}}} \right)^{1/6}}\)
Bed Slope, \(S = \frac{{{f^{5/3}}}}{{3340{Q^{1/6}}}}\)

Calculation:

Q = 2500 cumec

\(P = 4.75\sqrt Q =4.75\sqrt {2500 }\) = 237.5 m