--- title: "Merits and demerits of river and ridge routes" subject: "Transportation Engineering I" chapter: 5 key: "semester_6/transportation_engineering_i:river-ridge" source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/river-ridge site: BCT Engineering --- # Merits and demerits of river and ridge routes Transportation Engineering I · Chapter 5: Hill Roads - Asked in: 2081 Chaitra, 4 marks; 2080 Chaitra, 3 marks; 2078 Chaitra, 5 marks; 2074 Bhadra; 2073 Magh; 2072 Ashwin; 2063 Kartik (old course), 4 marks (asked 7 times) - Video: [U6L5- Factor which affecting selection of hill road alingment](https://www.youtube.com/watch?v=EexvHIh81os) — GPC Online Learning - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/river-ridge - Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-5 ## Question List the merits and demerits (characteristics) of River Route and Ridge Route in hill road location. ## Short answer River route offers easy gradient, water, materials and settlement access but suffers many cross-drainage works, flood and scour risk, landslides and costly protection. Ridge route has few cross-drainage structures, stable well-drained ground and low maintenance, yet has poor access to water and villages, steep saddle climbs and scarce construction materials. ## Answer In hill road location, the alignment may follow a **river (valley) route** along the stream or a **ridge route** along the crest of the ridge. | Aspect | River (valley) route | Ridge route | |---|---|---| | Gradient | Gentle, follows the river slope; easy gradients | Fairly steady along the ridge, but steep rises into and out of saddles | | Cross-section | Side-hill cut and fill, often on steep banks | Mostly gentle ground, little earthwork | | Cross-drainage | Many tributaries and side streams, so many culverts and bridges | Few drainage crossings, since water drains away from the ridge | | Stability | Landslides, flood and scour damage at the river bank, high water table | Generally stable, firmer soil/rock, well drained | | Construction cost | High, because of bridges, protection walls and spoil | Lower, with less drainage and earthwork | | Length | Often long, with many loops | Shorter, but may be indirect or have ups and downs | | Access to settlements | Serves villages and farmland in the valley, fertile areas | Settlements lie below the ridge; poor access to water and markets | | Materials and water | Water, sand and gravel at hand | Water and aggregates are scarce | | Flood risk | Floods above HFL and undercutting of banks | Not affected | | Maintenance | High, due to floods and slides | Lower | #### Merits and demerits in brief **River route**: *merits*: easy gradient, direct access to water, materials and settlements; *demerits*: many cross-drainage works, flood and scour risk, landslides on the bank, unstable slopes and costly protection. **Ridge route**: *merits*: few cross-drainage structures, stable and well-drained ground, low earthwork and maintenance cost, wide view; *demerits*: poor access to water and settlements, long detours to reach villages, steep climbs at saddles, exposure to wind, and scarcity of construction water and material. In practice a combination is used, following the river at lower levels and climbing to a ridge by gradual hairpin bends or switch-backs. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. How does cross-drainage compare between river and ridge routes? A. Ridge route has many tributary crossings B. Both have the same number C. River route has many tributaries and so many culverts and bridges; ridge route has few D. River route has none Answer: C. A valley route meets many side streams, while water drains away from a ridge so few crossings are needed. (Key point: Cross drainage) 2. Which is a merit of the river route? A. Easy gradient and access to water, materials and settlements B. Free from flood risk C. Lowest construction cost D. Few drainage structures Answer: A. The river route follows the gentle river slope and has water, sand and gravel and villages nearby, though it faces flood and slide problems. (Key point: River route merits) 3. Which is a demerit of the ridge route? A. Many culverts are needed B. Poor access to water, materials and settlements, and steep climbs at saddles C. High flood risk D. Unstable, waterlogged ground Answer: B. Settlements and water lie below the ridge, and saddles bring steep rises, although the ground is stable and well drained. (Key point: Ridge route demerits) 4. How is the route chosen in practice? A. Always the ridge only B. Always the river only C. A combination: follow the river at lower levels and climb to the ridge by gradual hairpins or switchbacks D. A straight line ignoring terrain Answer: C. Combining both uses the merits of each. (Key point: Practical combination) ## Related in Transportation Engineering I - [Route location in hill road design](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Ahill-route-location) — Transportation Engineering I, chapter 5 - [River route location considerations](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Ariver-route-considerations) — Transportation Engineering I, chapter 5, asked 2× - [Structure of route location process](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Astructure-route-location) — Transportation Engineering I, chapter 2, asked 5× - [Principle and complexities of route location](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Alocation-principle-complexities) — Transportation Engineering I, chapter 2 - [Special considerations in hill road design](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Ahill-special-considerations) — Transportation Engineering I, chapter 5, asked 5× - [Hill road drainage structures](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Ahill-drainage-structures) — Transportation Engineering I, chapter 5, asked 4× ## Related in other subjects - [Cofferdam types, uses, merits and demerits](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Acofferdam-types-merits) — Foundation Engineering, chapter 5, asked 7× - [Incineration: merits and demerits](https://www.bctengineer.com/question.md?key=semester_6%2Fsanitary_engineering%3Asolid-waste-incineration) — Sanitary Engineering, chapter 10, asked 7× - [Distribution layouts, merits and demerits](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Adistribution-layouts-merits-demerits) — Water Supply Engineering, chapter 7, asked 6× - [Composting: methods, merits, demerits](https://www.bctengineer.com/question.md?key=semester_6%2Fsanitary_engineering%3Asolid-waste-composting) — Sanitary Engineering, chapter 10, asked 5×