---
title: "Canal escape structures with sketch"
subject: "Irrigation and Drainage Engineering"
chapter: 7
key: "semester_6/irrigation_and_drainage_engineering:escape-structure-sketch"
source: https://www.bctengineer.com/q/semester_6/irrigation_and_drainage_engineering/escape-structure-sketch
site: BCT Engineering
---

# Canal escape structures with sketch

Irrigation and Drainage Engineering · Chapter 7: Regulating Structures

- Asked in: 2076 Bhadra, 3 marks; 2065 Kartik (old course), 4 marks (asked 2 times)
- Video: [Canal Escapes It's Types - Canal Structures - Water Resource Engineering 2](https://www.youtube.com/watch?v=kFW-cMll7f4) — Ekeeda
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/irrigation_and_drainage_engineering/escape-structure-sketch
- Whole chapter: https://www.bctengineer.com/md/semester_6/irrigation_and_drainage_engineering/chapter-7

## Question

Describe escape structures (canal escape) with neat sketch.

## Short answer

An escape is a side structure that discharges surplus water into a natural drain to safeguard the canal, allow emptying for repairs, and flush silt. Weir-type escapes with crest at full supply level spill automatically; sluice-gate escapes drain the canal quickly. A stilling basin and protection works dissipate energy.

## Answer

An **escape** is a structure built in the side of a canal to release surplus water into a natural drain or stream. It protects the canal from damage, allows it to be emptied for repair, and removes silt.

#### Functions
1. Remove excess water caused by heavy rainfall, sudden closure of outlets or faulty operation of the head regulator.
2. Empty the canal quickly in an emergency (breach) or for maintenance.
3. Scour out silt deposited at the head of the canal (scouring escape).

#### Types
1. **Weir type escape** (surplus escape): a fixed weir wall with its crest at FSL, which automatically spills the excess water over its crest. Used where the excess flow comes from rain.
2. **Escape with sluice gates**: gates at bed level that can be opened to empty the canal quickly or to flush silt. Used at the tail of the canal or at silted reaches.
3. **Syphon escape** (a syphon spillway type): works automatically when the water level exceeds FSL.

#### Neat sketch
```text
 Plan                          Section through escape
  canal ==>===+===>==            FSL ~~~~~|
              | escape                 ___|__ crest = FSL
              v                  bed __|    |
        ====== escape                floor, gates
        ====== channel to drain      d/s protection
```
- The head wall has its crest at the full supply level of the canal.
- A scour sluice at canal bed level discharges silt and drains the canal.
- A stilling basin and protection works are provided at the toe.
- The escape is located upstream of major structures, near natural drains, and upstream of the cross regulator.

## Check yourself

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

1. What is an escape?
   A. A structure that raises canal level
   B. A gate that feeds the water course
   C. A fall that drops the bed
   D. A structure in a canal side that releases surplus water to a natural drain
   Answer: D. It protects the canal and helps emptying. (Key point: Escape definition)

2. How does a weir type (surplus) escape work?
   A. Its fixed crest at FSL spills excess water automatically
   B. Gates must be opened manually at bed level
   C. It sucks water by siphon only
   D. It measures discharge
   Answer: A. Water above FSL spills over the crest automatically. (Key point: Weir type escape)

3. What is a sluice-gated escape used for?
   A. Passing flood over the crest
   B. Gates at bed level emptying the canal quickly or flushing silt
   C. Raising upstream level
   D. Measuring discharge
   Answer: B. The scour sluice at bed level also flushes silt. (Key point: Sluice escape)

## Related in Irrigation and Drainage Engineering

- [Drop structures: need and types with sketches](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Adrop-structures-types-sketch) — Irrigation and Drainage Engineering, chapter 7, asked 6×
- [Head regulator; outlets and escapes](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Ahead-regulator-outlet-escape-importance) — Irrigation and Drainage Engineering, chapter 7, asked 2×