Table of Contents
- 1 DESIGN CONSIDERATION OF INUNDATION CANALS
DESIGN CONSIDERATION OF INUNDATION CANALS
- The head regulator should be installed a few kilometers D/S of the off-take point.
- This measure would eliminate the risk of the head regulator being washed away.
- As escape should be located D/S of the head regulator and escape channel should be joined to the river D/S.
- If more water enters the canal at the off-take point it can be taken out through the escape.
- In order to reduce the chances of silting of the canal.
- The flood regulator should be provided with vertical lift gates that could be lifted in stages.
- The full supply level of the canal should be fixed at a level at which the river water is more or less steady for a period of 40—50 days.
- which the canal can be run full to irrigate the lands.
- This steady level of water in the river is called fair irrigation level.
- The bed of the canal should be as low as possible.
- The low bed level of the canal can draw some river water even when the river is in lower stage.
- The section of the canal should be kept liberal to carry the entire required discharge as quickly as possible within the limited time factor.
- The longitudinal slope should be such that scouring velocities are not developed longitudinal.
- The slope of the canal may be 0.25 m per kilometre length.
- The slope of the canal depends upon the general slope of the area also.
- The floodwater is heavily charged with silt. So these canals are more likely to be silted.
- Silt clearance must be done after every season.
- The canals may be aligned with a number of bends so as to trap the silt at intervals.
Advantages of Inundation Canals Following are the advantages of foundation canals.
- It is cheap, as no head work and other works have to be constructed.
- Water being rich in silt has good manurial qualities.
- The area is less liable to be waterlogged.
Disadvantages of Inundation Canals Disadvantages of foundation canals are as following.
- As there is no headworks structure the head of the canal is liable to be washed away during floods.
- The duty of water is very low.
- Since the availability of water is dependent upon floods, the scarcity of water is always felt.
- Irrigation water may be badly required and the floodwater in the river may not be available.
- Due to a lack of assured supply, the farmers take little interest in their work.
- Canals will have to be frequently cleared from silt.
- The bigger size of the canal is generally adopted.
- This is done to get as much floodwater as possible within a limited time.
- The alignment of the canal is not very precise.
- It may be silting at some sections and scouring at other sections.
Maintenance of inundation canals.
- Inundation canals always suffer from the difficulty of silting, scouring and scarcity.
- In order to maintain these canals in fine shape, the following provisions should be necessarily made.
- Besides the main off-take point, subsidiary off-take points should be constructed.
- In case, main off-take point is closed somehow, water could be admitted in the canal from subsidiary off-take points.
- A feeder canal should be constructed linking several foundation canals, taking-off from the same river.
- This measure avoids the necessity of constructing several subsidiary heads.
- By this method, a good head of water can be availed for a considerable length of time.
- Provision of a pucca head regulator, attached with an escape, a few km D/S of the off-take point, also enables the exercise of good control on the inundation canal.