Experimental evaluation of energy dissipation in modified USBR-IV stilling basins with downstream abrupt drops

This study presents an investigation on the effects of introducing an abrupt drop immediately downstream of a modified USBR Type IV stilling basin. Conducted on 1:60 scaled model, this study explored various abrupt drop heights to assess their effects on energy dissipation and hydraulic performance. The discharge and Froude number ranged from 8.5 to 16 litre per second and 2.5 to 3.7 respectively. Results showed the energy dissipation enhanced by up to 19% compared to traditional configurations for relative drop heights of 0.5 to 1.5 and then reduced with increase in drop height. The presence of a drop downstream of the stilling basin reduced the sequent depth ratios, and compensated tailwater deficits by 20% to 37% compared to horizontal bed hydraulic jumps. Thus, an abrupt drop downstream of a stilling basin has shown to offer a promising solution for improving energy dissipation and addressing insufficient tailwater levels.