Question

What type of cross drainage work is provided when the canal runs below the drain, with FSL of canal well below the bed of the drain?

• A. Aqueduct
• B. Super passage
• C. Level crossing
• D. Siphon aqueduct

Answer 1

The correct option is B Super passage

If bed level of canal is sufficiently above the HFL of the drain, an aqueduct is the right choice. Sometimes bed level of canal may be little below the HFL of drain so that water flows under syphonic action. This structure is known as aqueduct syphon.
If bed level of the drain is sufficiently above the canal FSL, a super passage may be constructed. If the canal FSL is little above bed level of drain to allow syphonic action, the structure is called Canal Syphon. Aqueduct or super-passage type of drainage works are used when high flood discharge is large and continues for a sufficient time.
A level crossing is used when the canal water and drain water are allowed to intermingle with each other. This is adopted when high flood drainage discharge is short lived.