STANDARDS OF CANAL CROSS-SECTION

  • Usual dimensions of canal cross-section elements have been given here and there inappropriate articles.
  • The standards as suggest by CWPC are given as follows.
Indian standard criteria for design of unlined canals in alluvial soil (IS: 7112—1973)
Indian standard criteria for design of unlined canals in alluvial soil (IS: 7112—1973)

 

1. General.

  • A trapezoidal section is recommended for the canal.
  • The longitudinal slope of the canal is determined depending upon the average slope.
  • The natural ground along the proposed alignment.
  • This is the maximum average slope that can be provided on the canal.

2. Side Slopes.

  • These are dependent on the local soil characteristics and are designed to withstand.
  • The following conditions during the operation of the canal.

(a) The sudden drawdown condition for inner slopes.

(b) The canal running full with banks saturated due to rainfall.

  • Canal in the filling will generally have side slopes of 1.5: 1.
  • For canals in cutting, the side slope should be between 1: 1 and 1.5: 1 depending upon the type of soil.

3. Free Board.

  • Freeboard in a canal is governed by consideration of the canal size and location, rainwater inflow, water surface.
  • Fluctuations caused by regulators, wind action, soil characteristics, hydraulic gradients.
  • Service road requirements, and availability of excavated material.
  • A minimum freeboard of 0.5 m for discharge less than 10 cumecs and 0.75 m for discharge greater than 10 cumecs is recommend.
  • The freeboard shall be measured from the FSL to the level of the top of the bank.
  • The height of the dowel portion should not be used for freeboard purposes.

4. Bank Top Width.

The minimum values recommended for top width of the bank are as follows.

Bank Top Width.
Bank Top Width.