Civil Engineering MCQJE Level Civil Engineering

According to Lacey's regime theory, the hydraulic mean radius R of a stable alluvial channel is related to the discharge Q as:

Irrigation EngineeringRegime ChannelsHARD

Choose the correct answer

A

R ∝ Q^(1/6)

B

R ∝ Q^(1/3)

C

R ∝ Q^(1/2)

D

R ∝ Q^(2/3)

Correct Answer

B. R ∝ Q^(1/3)

Why is this the answer?

Lacey's regime formula: R = 0.47 (Q/f)^(1/3), where f is Lacey's silt factor. Thus R ∝ Q^(1/3). Velocity V ∝ Q^(1/6) and area A ∝ Q^(5/6) in Lacey's regime, which differ from Kennedy's approach.

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