---
title: "Lining of drains"
subject: "Transportation Engineering I"
chapter: 4
key: "semester_6/transportation_engineering_i:lining-of-drains"
source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/lining-of-drains
site: BCT Engineering
---

# Lining of drains

Transportation Engineering I · Chapter 4: Highway Drainage

- Asked in: 2065 Chaitra (old course), 2 marks
- Video: [Types of Road Drains l Line Drain l Unlined Drain l Drawing Reading | Reinforce QST](https://www.youtube.com/watch?v=p45GUrjBRgw) — REINFORCE
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/lining-of-drains
- Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-4

## Question

What is lining of drains and when is it necessary?

## 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.

## Answer

**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.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Lining of drains means:
   A. Adding plants only
   B. Covering with soil
   C. Digging deeper
   D. Covering bed and sides with durable smooth material
   Answer: D. Stone pitching, masonry, concrete or precast blocks prevent erosion and seepage. (Key point: Definition)

2. Lining is needed when:
   A. Velocity is very low
   B. Flow is nil
   C. Velocity exceeds non-scouring velocity of the soil
   D. Soil is rock
   Answer: C. For example on steep gradients in erodible soil. (Key point: When necessary)

3. Lining also:
   A. Raises seepage
   B. Improves flow capacity through lower roughness
   C. Increases roughness
   D. Reduces capacity
   Answer: B. Lower roughness means smaller section and maintenance cost. (Key point: Extra benefit)

## Related in Transportation Engineering I

- [Catch water drains in hill roads](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Acatch-water-drain-hill) — Transportation Engineering I, chapter 5, asked 2×