Scour volumes downstream of positive-step stilling basins

The paper deals with temporal and spatial evolution of local scour downstream of low-head stilling basins. In this aim, experiments were carried out in a 1 m wide and 20 m long rectangular channel. The jet was caused by an ogee-crested spillway with a positive-step stilling basin. Nearly uniform sandy beds were generally used, but additional tests were also made with a special bed of lead spheres. Tests were of long durations mainly to get conditions of quasi-equilibrium. Flow depths and bed levels were normally recorded at 2, 24, 48 hours from the start and at the end of the run. The volume of scour hole was estimated by kriging gridding method for each survey. Thus, based on the data collected empirical models were identified for the scour volume as a function of the time and at the quasi-equilibrium stage.