Canal fall structure may be defined as :
Canal fall structure
A vertical drop which is provided to step down the canal bed and then it is continued with permissible slope is called canal fall structure or simply canal fall.
The structure built to safe guard the drop is called canal fall structure. This structure is an integral part of an irrigation system.
Why canal fall structures are required ?
The longitudinal slopes of canals are fixed as per sediment transport capacity, i.e, for non silting and non scouring velocity. It may happen that the ground on which the canal is to be laid is steeper than the designed bed slope. This results in excessive filling. This excessive filling will increase the cost of construction.
If there is a difference between ground water table and the water level in the canal, then it may causes excessive seepage which results in water logging. To avoid this, the bed of canal is given a sudden drop or fall at a suitable place, so that it may run partly in excavation and partly in filling, depending upon the command areas.
When the slope of the ground is more or less uniform and the slope is greater than the permissible slope of the canal. Then canal falls are necessary.