What are the different method of cross drainage

A cross drainage work is created where a canal and a natural drain meet to keep the drain water from combining with the canal water. This is a more costly structure that should be avoided to the greatest extent possible. To avoid cross-drainage works, there are two approaches:

 By altering the canal’s waterway alignment
 The structure can be developed by merging two or three streams into a single, cost-effective cross drainage system.

Cross Drainage works:

Type 1: Cross-drainage work including the crossing of a canal across a drain.

This category includes the following structures: 1. Aqueduct and 2. Syphon Aqueduct

Type 2: Cross-drainage work that carries drainage across a canal.

• Super passage • Canal Syphon are examples of this type of structure.

Type –3: Cross-drainage works that allow canal water to flow back into the canal.
• Level crossings • Canal inlets are examples of this type of building.

Type – 1: Canal over drainage [HFL FSL)

Super Passage:

The super passage construction conveys drainage over the canal because the canal bed level is lower than the drainage bed level. Drainage water will flow through the drainage trough from upstream to downstream, while canal water will flow through the piers that will be placed below it as support.

Canal Syphon:

A canal syphon, similar to a super passage, transports drainage over the canal, with the canal’s full supply level above the drainage troughs a result, syphonic action causes the canal water to flow, and the canal is devoid of air pressure. The super passage is generally favoured over canal Syphon because canal water lies under a drainage trough in a canal Syphon, making any faulty minerals or silt deposited harder to remove, as in the case of a Syphon Aqueduct. The canal’s floor is lowered, and a ramp-like structure is erected upstream and downstream to induce syphonic motion. In this design, the Syphon aqueduct is reversed.

Type –3: Drainage admitted into canal (HFL = FSL)

The drainage water is combined with canal water in this instance; the cost of construction is lower, but silt clearance and canal water maintenance become extremely challenging. As a result, these structures are constructed with extraordinary caution.

Level Crossing:

When the canal and drainage bed levels are equal, a level crossing will be built.
The procedure entails the following steps:
• Construction of a weir to prevent drainage water from flowing behind it
• Providing a canal regulator that spans multiple canals.
• Installing a head regulator throughout a drainage system

A level crossing’s operation is as follows:

At the peak supply of canal water parallel to drainage, both regulators are opened at the same time to clear the drainage water from the canal for a predetermined time interval. The head regulator is turned off once the drainage has been cleaned. Regardless, the cross regulator is kept open all year to ensure that canal water is always available.

Canal inlets:

A canal entrance construction allows only a minimal amount of drainage water to be let into the canal. At the inlet, the canal’s banks are used to channel drainage. The drainage combined with canal then goes a given length of the canal, after which an outlet is supplied to create suction pressure and remove all the drainage solids, disposing them to a nearby watershed area. The use of a canal inlet structure has several disadvantages, including the possibility for drainage to pollute canal water and bank erosion, both of which can cause the canal structure to deteriorate and result in high maintenance costs. As a result, this form of structure isn’t seen very often.