Lacey's Regime Theory MCQ with answer and solution

Concept

Lacey regime channel bed slope formula

Formula

NONE

Step-by-step solution

1. Lacey's regime theory provides empirical relationships for designing stable channels in alluvial soils. 2. The regime bed slope equation relates the slope S to the silt factor f and discharge Q in m3/s. 3. The exact formula proposed by Lacey is S = f^5/3 / (3340 Q^1/6). Answer: B

Explanation

In Lacey's regime theory for alluvial channels, the hydraulic bed slope S is derived using the silt factor f and total discharge Q. The standard governing equation for bed slope is expressed as S = f^5/3 / (3340 Q^1/6). This relationship balances sediment transport capacity with channel slope in stable regime channels.

Why the other options are wrong

A) The exponent of the silt factor f should be 5/3 and discharge Q should be 1/6 in Lacey's bed slope formula. C) The power of discharge Q in Lacey's bed slope formula is 1/6, not 1/2. D) This formula misstates the exponent of the silt factor and the numerical constant.

Shortcut

Lacey bed slope formula: S = f^5/3 / (3340 × Q^1/6).

Common mistake

Confusing the exponents for silt factor and discharge in the slope formula with other Lacey regime equations.