Local scour downstream of stilling basins

In this study some results on local scour downstream of stilling basins for low-head structures are presented. A number of laboratory experiments were conducted in a 1 m wide and 20 m long rectangular straight channel in which an ogee-crest spillway followed by a stilling basin type USBR IV (without chute blocks) was positioned. Two nearly uniform bed sediments were tested. The runs were of long durations, typically 3 days, to achieve conditions of quasi-equilibrium scour hole. Based on the data collected, a new relationship was conjectured relating the quasi-equilibrium scour depth to the tail water densimetric Froude number.