Canal Cross section | Irrigation Engineering in Hindi | Water Resources

CROSS SECTION OFCANAL

* A typical and most desirable section of a canal is partly in cutting and partly in filling and aims at

balancing the quantity of earthwork.

* Berm is a narrow strip of land at the ground level between the inner toe and top edge of the cutting.

* Counter berm (or back berm) is provided on the outside of the canal bank to contain the hydraulic

gradient line within the bank.

* Minimum free board required in any canal is 0.5 m. With increase in discharge, minimum free

board specified is increased for a canal with discharge more than 30 cumec free board of 0.90 m

is enough.

Lining of Canal

* Advantages of lining a canal are

1. Seepage is controlled

2. Waterlogging can be prevented

3. Channel capacity is increased

4. Command area is increased

5. Maintenance cost is reduced

6. Danger of flood is eliminated.

* Maximum permissible velocities in different types of lining are:

1. Cement concrete lining – 2.0 to 2.5 m/sec

2. Burnt clay tile lining – 1.8 m/sec

3. Boulder lining – 1.5 m/sec

* As per IS : 10300 – 1982, free board for lined canal are

1. Main and branch canal 0.75 m

2. Branch and distributaries

(a) Q = 5 to 10 cumecs 0.6 m

(b) Q = 1 to 5 cumecs 0.5 m

3. Water courses 0.1 to 0.15 m

* Types of Lining

1. Hard surface lining:

(a) Cast in situ cement concrete lining

(b) Shotcrete or plaster lining

(d) Asphaltic concrete lining

(e) Boulder lining

2. Earth type lining

(a) Compacted earth lining

(b) Solid cement lining

* For lining a canal in black cotton soil a layer of cohesive non-swelling soil (CNS) like murram is

required.

* Safety ladders are to be provided on both banks of canal alternatively at 300 m staggered distance.