Subtopic: Planning, design and layout of surface and sub-surface drainage systems
Question Statement:
Which of the following field layout patterns are standard configurations for agricultural subsurface relief tile drain systems?
Options:
(A) Gridiron layout, where parallel lateral drains enter a sub-main or main collector from one side only across flat, uniform topography
(B) Herringbone layout, where parallel lateral drains enter the main collector from both sides at acute angles along a natural depression or swale
(C) Random layout, where individual isolated drains connect scattered localized wet spots and depressions across undulating terrain
(D) Interceptor (cut-off) drain layout, aligned along the toe of an adjacent hillside to capture lateral seepage before it infiltrates valley farmland
Answer Key:
A, B, C, D
Step-by-Step Solution & Explanation
All four layouts are standard subsurface drainage configurations described in ILRI (Ritzema) and Michael:
- Gridiron: Most economical for uniform slopes, minimizing main line duplication.
- Herringbone: Lateral branches join central collector like fish bones in natural drainage draws.
- Random: Targets isolated wet pockets.
- Interceptor: Placed along geological boundaries or hill toes to intercept foreign seepage flow.