Cross Drainage Works MCQ with answer and solution

Concept

Cross drainage works are required whenever a canal and a natural drainage channel intersect each other at different or same elevations, making natural flow impossible without artificial structures.

Step-by-step solution

1. Understand that a canal alignment often crosses natural streams and rivers. 2. When a canal and a river intersect, their natural flow paths conflict, necessitating a Cross Drainage (CD) work. 3. Depending on the relative bed levels and discharge, different types of CD works are used (e.g., Aqueduct when canal crosses over river). 4. Therefore, cross drainage works are needed when a canal crosses over a river or vice versa.

Explanation

Cross drainage works are structures constructed at the intersection of a canal and a natural drainage (like a river or stream) to safely dispose of drainage water or convey canal water across the obstruction, such as when a canal crosses over a river (aqueduct).

Why the other options are wrong

A: When they meet at the same elevation, a level crossing is used, but it's not the general definition for all CD works. C: Parallel running streams/canals do not require cross drainage works. D: When the canal is below the river, a siphon aqueduct or superpassage is used, but option B represents the classic primary case of a canal crossing over a river (Aqueduct).

Shortcut

Whenever a canal and river intersect, a cross drainage work is required.

Common mistake

Confusing parallel flow or meeting at the same elevation with intersection points requiring structural intervention.