*Paper presented at the 26th Annual Research Committee Meeting held in July 1956 at Colombo.
A series of investigations of a basic nature were conducted on a 1/60 scale model of the Kaddam Spillyiay with a view to find out whether the increase of the width or depth of a stilling basin, without any friction blocks in it, would encourage the formation of a hydraulic jump in the basin and improve the dissipation of energy. Stilling basins 10 to 18 ft. deep and 30 to 60 ft. wide were tried in these series. The effects of low obstructions within the basin at various positions, and a stepped end cill were also studied. A stable hydraulic jump was not formed either with these devices or by the increase of depth or width of the stilling basin. Further basic experiments, on such stilling basins without blocks in them are proposed to be taken up.
