Question Bank • QB_IDE_ADV_078 MCQ • 1 Mark

Section 5: Irrigation and Drainage Engineering

Agricultural Drainage

Subtopic: Non-conventional drainage system

Question Statement:

Mole drainage is an unlined subsurface drainage method specifically suited to which type of agricultural soil?

Options:

  • (A) Dense, cohesive clay soils with low hydraulic conductivity (
    gt; 30\% \text{ to } 35\%$ clay content) and high structural stability
  • (B) Coarse sandy soils with high gravel fractions
  • (C) Loose peat soils and organic muck
  • (D) Fractured granite bedrock formations

Answer Key:

A

Step-by-Step Solution & Explanation

Mole drains are unlined cylindrical channels pulled through the subsoil by a torpedo-shaped mole plow. They rely entirely on the cohesion and plasticity of the clay to prevent channel collapse. Consequently, mole drains are feasible only in dense, uniform, stone-free clay soils with
gt; 30 - 35\%$ clay content. In sandy or gravelly soils, the unlined walls collapse immediately. Option A is correct.
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