Section 4: Soil and Water Conservation Engineering
Soil and Water Erosion
Subtopic: Mechanics of soil erosion – wind and water erosion
Question Statement:
In wind erosion process, the rate of soil movement (S) depends on wind speed (v), threshold limit of wind speed required to move the soil (vm) and average soil particle size (d). This interrelationship is expressed as
Options:
(A) S ∝ (v−vm)² d^(1/2)
(B) S ∝ (v−vm)² d
(C) S ∝ (v−vm)³ d^(1/2)
(D) S ∝ (v−vm)³ d
Official Answer Key:
D
Step-by-Step Solution & Explanation
The standard empirical relationship for wind-driven soil (sediment) transport rate, following Bagnold-type sand-transport theory, expresses the rate of soil movement as proportional to the cube of the excess wind shear velocity above threshold, (v − vm)³, and directly proportional to particle size d (coarser particles move in higher, more energetic saltation trajectories that increase the transport rate per unit width). This matches option (D), S ∝ (v−vm)³·d.
Practice This in Real CBT Exam Interface
Test yourself with the official TCS-iON palette, virtual calculator, and immediate performance analytics.