Components at a canal–drain level crossing — identify the correct set of provisions typically adopted in a level crossing arrangement.

Introduction / Context:
When a canal and a natural drain intersect at approximately the same bed level, a level crossing is adopted. Proper appurtenances are required to manage relative water levels and prevent undesirable backflows or sediment entry, while maintaining canal supply reliability.

Given Data / Assumptions:

• Canal and drain cross at similar elevations.
• No superpassage or aqueduct (i.e., no vertical separation).
• Operational need to control flows on both channels near the junction.

Concept / Approach:

Standard practice provides (i) a crest/weir in the drain upstream of the junction to maintain adequate water level for controlled exchange, (ii) a regulator in the drain downstream to modulate outflows and prevent drawdown issues, and (iii) a cross-regulator on the canal downstream of the crossing to maintain canal F.S.L. and safeguard distribution.

Step-by-Step Solution:

Verification / Alternative check (if short method exists):

Operational simulations show that absence of any one element can cause level instability, reverse flows, or sediment ingress; the trio ensures robust control.

Why Other Options Are Wrong:

Any subset omits an essential control element; therefore, only “All the above” reflects the complete, typical provision set.

Common Pitfalls (misconceptions, mistakes):

Confusing level crossing with superpassage/aqueduct; forgetting the canal cross-regulator below the junction; ignoring sediment management after events.

Final Answer:

All the above