10.3. HISTORICAL DEVELOPMENT OF FALLS There was no theory or established practice for the design and construction of falls in the nineteenth century. Falls were usually avoided by providing sinuous curves in the canal alignment. This alternative increased the length of the canal. Obviously, this approach was uneconomical and resulted in an inefficient irrigation system.
The ogee fall (Fig. 10.1) was first constructed by Cautley on the Upper Ganga canal with a view to providing a smooth transition between the upstream and the downstream bed levels so that flow disturbances could be reduced as far as practicable. The smooth transition of the ogee fall preserved the kinetic energy and also resulted in large drawdown which caused heavy erosion of bed and banks on the downstream as well as upstream of the fall. Later, this type of fall was converted into a vertical impact type so as to cause more energy dissipation downstream of the fall.
