Section 4: Soil and Water Conservation Engineering
Water Erosion Mechanics & USLE
Subtopic: USLE parameters and units
Question Statement:
Which of the following statements regarding the Universal Soil Loss Equation (USLE) parameters is/are TRUE?
Options:
(A) The topographic factor $LS$ is dimensionless, representing the ratio of soil loss to that from a unit plot of length $22.13\text{ m}$ on a $9\%$ slope
(B) The cropping management factor $C$ ranges from near $0$ for dense virgin forest to $1.0$ for clean-tilled continuous fallow
(C) The support practice factor $P$ for up-and-down slope tillage without conservation measures equals $1.0$
(D) USLE predicts both sheet/rill erosion and deep gully channel erosion
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
1. $LS$ is normalized relative to the standard unit plot ($22.13\text{ m}$ length, $9\%$ gradient) (A is true).
2. $C = 1.0$ for bare fallow and approaches $0.001$ for undisturbed mulch/canopy (B is true).
3. $P = 1.0$ for straight up-and-down slope cultivation (C is true).
4. USLE only predicts sheet and rill erosion; it does NOT account for gully erosion, stream bank erosion, or mass wasting (D is false).