Experimental study of scouring downstream of USBR Type I stilling basin aligned with or below the erodible bed.

The bed elevation of the stilling basins is most often located below the river bed in order to provide the required tail water depth. Both basins located in alignment with the erodible bed or below it are studied. To this end, the scoured hole dimensions under various circumstances and the sediment transport process within the scour hole were thoroughly examined. Results revealed that the upstream slopes of the dimensionless scour profiles are approximately identical at different times. According to the results, the basin located below the erodible bed was of a greater maximum scour depth and a lower scour depth at the beginning of the erodible bed. Moreover, a simple generalized equation correlating the temporal development of the maximum scour depth and the scour depth at the beginning of the erodible bed at equilibrium time was derived for the USBR Type I basin aligned with or below the erodible bed. [ABSTRACT FROM AUTHOR]