Irrigation engineering — provision of berms in canals: Under which site conditions are berms provided along canals to improve stability, access, and maintenance?
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AWhen the canal is fully in excavation (in cutting)
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BWhen the canal is partly in excavation and partly in embankment
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CWhen the canal is fully in embankment
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DAll the above
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E—
Answer
Correct Answer: All the above
Explanation
Introduction / Context:Berms are horizontal strips or shelves provided along canals between the toe and the spoil or between water edge and bank to improve stability, reduce erosion, and facilitate inspection and maintenance. Their need arises under a variety of ground conditions.
Given Data / Assumptions:
- Canal alignment may pass through cuttings, fills, or mixed profiles.
- Design aims to control side slope erosion and provide access.
Concept / Approach:
Whether the canal section is in cutting, filling, or mixed, berms can stabilize slopes, separate spoil banks, permit drainage, and serve as inspection paths. Hence, they are employed broadly across all typical site conditions, with width and level chosen per design manuals and soil conditions.
Step-by-Step Solution:
1) In excavation: berm isolates canal bank from spoil and reduces erosion.2) In embankment: berm flattens the profile and improves stability against slips.3) In mixed sections: berms handle transitions and provide uniform maintenance access.Verification / Alternative check:
Design guides specify berms as a common feature; their absence is exceptional and must be justified by site conditions.
Why Other Options Are Wrong:
- (a)–(c) are each valid conditions; therefore the inclusive answer is “All the above”.
Common Pitfalls:
- Confusing berms with service roads; although sometimes coincident, design intents differ.
- Omitting berms on dispersive or erodible soils where they significantly reduce maintenance.
Final Answer:
All the above.