Section 4: Soil and Water Conservation Engineering
Soil and Water Erosion
Subtopic: Biological and engineering measures to control erosion
Question Statement:
Hilly areas receiving heavy rainfall, where a major portion of the rainfall is to be drained as surface runoff, are suggested to adopt bench terraces with __________.
Options:
(A) sloping inward
(B) level tops
(C) sloping outward
(D) narrow width
Official Answer Key:
A
Step-by-Step Solution & Explanation
The three standard bench-terrace types are selected by rainfall regime:
Sloping inward — the bench is graded towards the hillside, where a drainage channel runs along the inner edge to intercept and safely convey excess runoff to a protected outlet. This is prescribed for heavy-rainfall regions where surplus water must be drained away. ✔
Level (level tops) — used in medium-rainfall areas with permeable soils, where the intent is to retain and infiltrate the rainfall.
Sloping outward — used in low-rainfall regions with mild slopes, where a small amount of runoff is disposed of over the outer edge (protected by a shoulder bund).
Since the question specifies heavy rainfall with a major portion to be drained as surface runoff, the inward-sloping bench with an inner drain is correct.
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