If available natural slope is steeper than bed slope of canal, n this is adjusted by construction of vertical falls or drops in canal bed at suitable intervals. But such a drop will not be stable, refore in order to maintain this drop a masonry structure is constructed. This is known as canal fall or canal drop.

The main does not irrigate any area directly, so refore site of fall is based on considerations of economy in cost of excavation and filling versus cost of fall. The excavation and filling on both sides of fall should be balanced because unbalanced work causes extra cost.

By considering commanded area of a branch canal or a distributary canal location for falls is decided. The procedure is to fix FSL needed at head of off taking channels and outlets. Thus FSL can be marked at all commanded points and hence deciding appropriate locations for falls in canal FSL and refore in canal beds.

Since idea of construction of falls various types of falls have been designed. Some important falls are ogee falls, rapids, trapezoidal notch falls, simple vertical drop type and sarda type falls, straight glacis falls, Montague type falls and inglis falls.

The diagram gives clear image that in this fall a high crested fall takes place into water cushion below. There is no clear hydraulic jump or energy dissipation, as velocity jet enters deep pool of downstream. Hence it is a simple vertical drop type fall.

The diagram shows that water is gradually led down convex and concave curves. It also shows draw down on upstream side which results in lower depths, higher velocities and subsequent soil erosion. The curves provide smooth surfaces which results in less energy dissipation, which again causes soil erosion. Hence diagram is ogee fall type.

Ogee fall has two major defects. Heavy drawdown occurs on upstream side, which results in lower depths, higher velocities and bed erosion. The kinetic energy of flow will not be dissipated due to smooth transition, causing erosion on downstream bed and banks.

In this fall notches could be designed to maintain normal water depth in upstream channel at any two discharges, as intermediate values do not vary much. Therefore depth discharge relationship of channel is not affected by introduction of fall.

In this type of modern fall, a straight glacis is provided after raised crest. The hydraulic jump is made to happen on this glacis causing sufficient energy dissipation. If not flumed this fall gives good performance. This fall is suitable for 60 cumecs discharge and 1.5 m drop.

The baffle wall is provided at a calculated height and a calculated distance from toe of glacis to ensure proper formation of jump on baffle platform. This type of fall is suitable for all discharges and for drops which are more than 1.5 m.