Question

The permanent irrigation channels should not usually have side slopes steeper than

• A. 0.5 to 1
• B. 1 to 1
• C. 2 to 1
• D. 3 to 1

Hint:

Steeper than 1:1 is usually asking for a landslide!

Answer 1

The Correct Option is B

Step 1: Concept
Side slopes of unlined (earthen) channels are designed based on the "angle of repose" of the soil to prevent the banks from collapsing.

Step 2: Meaning
A "1 to 1" slope means for every 1 meter of horizontal distance, there is 1 meter of vertical rise ($45^{\circ}$ angle).

Step 3: Analysis
Most stable soils can hold a 1:1 slope. Steeper slopes (like 0.5:1) are too vertical and will cause the soil to cave into the canal, blocking the flow.

Step 4: Conclusion
For permanent unlined channels, 1:1 is the standard safe limit.
Final Answer: (B)