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Lining of drains

Short answer

Lining of drains is covering the bed and sides with stone, masonry, concrete, or precast blocks. It is necessary when velocity exceeds the non-scouring value, soil is erodible or sandy, seepage could weaken the road, space is narrow, or in urban areas. Lining reduces roughness and maintenance.

What is lining of drains and when is it necessary?

Lining of drains means covering the bed and sides of an earth drain with a durable, smooth material such as stone pitching, brick or stone masonry, plain or reinforced concrete, or precast blocks, so that it can carry water without erosion or seepage.

Necessity of lining

Lining is required when:

  • the flow velocity is more than the non-scouring velocity of the soil, for example, on steep gradients (more than about 3 to 4%) in erodible soil;
  • the drain runs through erodible, sandy or loose soil, or dispersive soil;
  • water seeping from the drain could weaken the subgrade or slope (drain close to the pavement or in an unstable hill slope);
  • the drain is narrow because of lack of space (rectangular lined section carries more flow);
  • the drain is in an urban or built-up area, or needs to be cleaned easily.

Lining also improves the flow capacity, because of the lower roughness, which reduces the section needed and the cost of maintenance.

✓ Answer checked by Claude Opus 5.5 (high effort)

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