---
title: "Functions of divide wall, undersluice, silt devices"
subject: "Irrigation and Drainage Engineering"
chapter: 5
key: "semester_6/irrigation_and_drainage_engineering:divide-wall-undersluice-silt-devices-functions"
source: https://www.bctengineer.com/q/semester_6/irrigation_and_drainage_engineering/divide-wall-undersluice-silt-devices-functions
site: BCT Engineering
---

# Functions of divide wall, undersluice, silt devices

Irrigation and Drainage Engineering · Chapter 5: Diversion Headworks

- Asked in: 2079 Jestha, 4 marks
- Video: [Diversion Headwork's / Canal headworks's (components of canal headwork's)](https://www.youtube.com/watch?v=3qgUbYbi6lg) — 𝐁𝐥𝐨𝐨𝐦 𝐰𝐢𝐭𝐡 𝐀𝐧𝐚𝐦𝐢𝐤𝐚
- 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/divide-wall-undersluice-silt-devices-functions
- Whole chapter: https://www.bctengineer.com/md/semester_6/irrigation_and_drainage_engineering/chapter-5

## Question

Explain the functions of the divide wall, under sluices, silt excluder, and silt ejector at the diversion headworks.

## Short answer

Divide wall separates the quiet pocket from weir flow, prevents cross currents, and protects sluices. Under sluices scour silt from the pocket and pass low floods. Silt excluder diverts silty bottom water through tunnels to the river, keeping canal water clear. Silt ejector extracts silt from the canal downstream and returns it to the river.

## Answer

- **Divide wall.** A wall between the weir and the undersluices (on the head regulator side). It separates the quiet pocket in front of the regulator from the weir, prevents cross currents, protects the sluices from high-velocity flood flow, and also forms one side of the fish ladder.
- **Undersluices.** Low-level gated bays beside the head regulator. They scour the silt that settles in the pocket, keep a clear channel in front of the regulator, and pass the low floods.
- **Silt excluder.** Tunnels built in the pocket in front of the head regulator. They let the clear upper water go into the canal and pass the silty bottom layer through the undersluices to the river, so the canal water carries less bed load.
- **Silt ejector (extractor).** A device on the canal, a little below the regulator, which removes the silt that has entered the canal. Tunnels carry the bottom layer to an escape channel and back to the river.

## Check yourself

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

1. What does the silt excluder do?
   A. Removes silt from the canal downstream
   B. Passes the silty bottom layer to the river so the canal gets clearer upper water
   C. Raises the pond
   D. Lets fish pass
   Answer: B. Tunnels under the regulator send the bottom layer to the river. (Key point: Silt excluder)

2. Where does the silt ejector act?
   A. Upstream of the weir
   B. In the pocket
   C. On the canal below the regulator, removing silt already entered
   D. On the divide wall
   Answer: C. It removes silt that has entered the canal and returns it to the river by an escape channel. (Key point: Silt ejector)

3. What does the divide wall prevent?
   A. Cross currents and flood damage to the sluices
   B. Fish migration
   C. Canal flow
   D. Seepage
   Answer: A. It protects the sluices from cross currents and high-velocity flow. (Key point: Divide wall)

## Related in Irrigation and Drainage Engineering

- [Divide wall, under sluice, fish ladder functions](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Adivide-wall-undersluice-fish-ladder) — Irrigation and Drainage Engineering, chapter 5, asked 2×
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