Question

What is the return period generally adopted for design of a cross drainage works?

• A. 15 years
• B. 25 years
• C. 40 years
• D. 50 years

Hint:

Cross drainage works: Bridges, culverts, siphons.
Return period: 50 years (standard).
Risk factor: Higher return period means higher safety but higher cost.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Return period is the average interval between occurrences of a flood of a given magnitude.

Step 2: Detailed Explanation:
For the design of cross drainage works (culverts, bridges, etc.), a return period of 50 years is generally adopted.
This is considered sufficient for the economic design of cross drainage structures.
Other return periods:
- 15 years (A): Used for minor drainage works.
- 25 years (B): Used for smaller structures.
- 40 years (C): Used for medium structures.
- 50 years (D): Standard for major cross drainage works.
For dams and major hydraulic structures, return periods of 100-1000 years are used.
Thus, 50 years is the standard return period for cross drainage works.

Step 3: Final Answer:
Thus, the return period generally adopted for design of a cross drainage works is 50 years.
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