Section 4: Soil and Water Conservation Engineering
Soil Conservation Structures
Subtopic: Soil Conservation Structures
Question Statement:
Graded bunding (channel terraces) is preferred over contour bunding when annual rainfall exceeds:
Options:
(A) $600 - 800\text{ mm}$ on soils of low permeability, to safely drain surplus runoff
(B) $100\text{ mm}$ in desert dunes
(C) Zero rainfall
(D) $2000\text{ mm}$ on rocky cliffs
Answer Key:
A
Step-by-Step Solution & Explanation
In higher rainfall areas (gt; 600-800\text{ mm}$) and poorly drained soils, graded bunds provide a channel with longitudinal gradient ($0.1-0.3\%$) to discharge runoff safely without waterlogging.