Understanding Canal Structures Parallel to Roads

The question describes a situation where a canal runs parallel to a road, and there is a natural drain located along the edges of this road. This scenario requires a specific type of hydraulic structure to manage the crossing or proximity of the canal and the drain.

Identifying the Appropriate Structure

Let's consider the definitions of the given options:

• Aqueduct: This is a structure designed to carry water, typically a canal, across an obstacle such as a valley, road, railway, or another stream or drain. In an aqueduct, the canal water level is usually higher than the level of the obstacle being crossed.
• Syphon: A syphon uses a pipe or conduit system to carry water under an obstacle, relying on pressure differences. The water flows under pressure.
• Syphon Aqueduct: This structure is similar to an aqueduct in that it carries water over an obstacle, but it uses inverted syphon principles, often through pipes, when the level difference is not sufficient for a simple gravity flow aqueduct. It functions like an aqueduct but under pressure like a syphon.
• Super passage: This is a structure where a natural drain or stream is carried over a canal. It is the opposite of an aqueduct, where the canal is carried over the drain.

Analyzing the Scenario

The question states that the canal runs parallel to the road and there is a natural drain along the road's edge. This setup means the canal needs to somehow cross or maintain its course while the drain is present alongside it. Given they are parallel, the drain is likely below or at a similar level to the road. For the canal to maintain its flow alongside the road and drain, if it needs to cross over the drain's path or elevated presence, a structure to carry the canal water over the drain is required.

Comparing this need with the definitions:

• An Aqueduct carries the canal over the drain. This fits the description where the canal needs to pass while the drain is along the road's edge, implying the canal must maintain its level above the drain.
• A Syphon carries water under the obstruction. This is not what is needed for the canal to run parallel and potentially cross or coexist with the drain along the road's edge; the canal needs to be above.
• A Syphon Aqueduct also carries the canal over, but specifically uses siphonic action, usually for specific hydraulic conditions not mentioned. The general term for carrying water over is Aqueduct.
• A Super passage carries the drain over the canal. This is the reverse of the situation described.

Therefore, the structure required to carry the canal over the natural drain along the road's edge is defined as an Aqueduct.

Based on the scenario described in the question, where the canal runs parallel to the road with a natural drain along its edges, an Aqueduct is the structure that fits the description of carrying the canal's water course over the path or presence of the drain.