--- title: "Methods of river training with sketches" subject: "Irrigation and Drainage Engineering" chapter: 6 key: "semester_6/irrigation_and_drainage_engineering:river-training-methods-sketch" source: https://www.bctengineer.com/q/semester_6/irrigation_and_drainage_engineering/river-training-methods-sketch site: BCT Engineering --- # Methods of river training with sketches Irrigation and Drainage Engineering · Chapter 6: River Training Works - Asked in: 2073 Magh, 8 marks; 2079 Jestha, 4 marks; 2080 Chaitra, 6 marks; 2073 Bhadra, 2×4 marks; 2063 Baisakh (old course), 8 marks; 2078 Poush, 3 marks (asked 6 times) - Video: [DHS- River Training Works](https://www.youtube.com/watch?v=bunhpRmoyxI) — Chandrakant Jejurkar - 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/river-training-methods-sketch - Whole chapter: https://www.bctengineer.com/md/semester_6/irrigation_and_drainage_engineering/chapter-6 ## Question What is river training works? Explain with sketches the different methods (types) of river training works normally adopted in Nepalese rivers (Terai region). ## Short answer River training works guide and confine flow to protect banks and structures. In Nepalese Terai methods include guide bunds, spurs or groynes, marginal embankments, revetment with launching apron, cut-offs, check dams/bed sills, and bio-engineering; usually a combination is used. ## Answer **River training works** are structures built on or along a river to guide and confine the flow, control its erosion and deposition, and keep it in a stable course so that bridges, headworks, towns and farmland are protected. Rivers of the Nepal Terai (Koshi, Narayani, Bagmati, Karnali) are steep, braided and carry heavy bed load from the Churia hills, so they need training works. #### Objectives - Prevent floods and spilling over the banks. - Protect banks from erosion and the river from shifting its course (flanking a bridge or barrage). - Give a steady, axial approach flow to a structure. - Control silt entry and maintain a navigable or regular channel. #### Methods normally adopted in the Terai **1. Guide bunds (guide banks)** are embankments built on both sides of the river upstream (and a short length downstream) of a bridge or barrage, to guide flow centrally through the opening. ```text flow ---> ____ guide bund (curved head) ______________/ \______ waterway W = bridge/barrage ______________ ______/ \____/ ``` **2. Spurs (groynes)** project from the bank into the river to push the current away from the bank, create slack water and cause silt to settle between them. They protect concave banks. ```text bank ======+==+==+==+==== | | | | spurs (L) v v v v current deflected away ``` **3. Marginal (flood) embankments** are earth levees along the river, set back from the bank, which confine the flood within the river corridor. **4. Bank protection (revetment / pitching)** covers the bank with stone pitching, concrete blocks or gabion mattresses over a filter, with a launching apron at the toe. **5. Cut-offs** are artificial channels across the neck of a meander that straighten the river and lower flood levels. **6. Check dams / bed sills and gabion crate walls** control bed degradation in steep tributaries. **7. Bio-engineering** (vegetative spurs, bamboo piles, planting of grass and trees) is used as a cheap supplement along banks. **8. Pitched islands and training walls** are used where the river must be held in one channel. Selection depends on river slope, bed material, flood discharge and cost; in practice a combination (embankment, spurs and gabion revetment) is used. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is the purpose of river training works? A. To store water for irrigation only B. To increase sediment load C. To make the river steeper D. To guide and confine flow, control erosion and deposition and keep the river in a stable course Answer: D. Training works protect bridges, headworks, towns and farmland by holding the river in a stable course. (Key point: Definition) 2. Where are guide bunds built and what do they do? A. Only downstream of a structure B. Along the bank in the middle of a reach to induce silt C. On both sides upstream of a bridge or barrage to guide flow centrally through the opening D. Across the river as a dam Answer: C. Guide bunds are embankments upstream (and a short length downstream) of a structure, giving axial flow through the waterway. (Key point: Guide bunds) 3. How do spurs protect a bank? A. They straighten the river B. They speed up flow along the bank C. They store flood water D. They push the current away and create slack water so silt settles between them Answer: D. Spurs project into the river, deflect the current and create slack water that builds silt. (Key point: Spurs) 4. Why do Terai rivers need training works? A. They are very narrow and deep B. They have no floods C. They are flat and clear D. They are steep, braided and carry heavy bed load from the Churia hills Answer: D. Steep braided rivers with heavy bed load shift their course and erode banks. (Key point: Terai conditions) 5. What is a cut-off, and what does revetment do? A. Cut-off: a pile under a weir; revetment: a spur B. Both are bed sills C. Cut-off: a channel across a meander neck; revetment: armouring of the bank with stone, blocks or gabions D. Cut-off: a type of embankment; revetment: a cut-off Answer: C. Cut-offs straighten the river across a meander neck, and revetment covers the bank with pitching over a filter with a launching apron. 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