Reclamation Information Sharing Environment (RISE)

The purpose of this research project was to develop a methodology to determine the presence of dangerous submerged hydraulic jumps at low-head hydraulic structures. Even when low-head dams are operating as intended, strong currents, hydraulic forces, and other hazardous conditions may exist in localized areas downstream from the dam and may trap persons who pass over the dam or approach the dangerous zone. After reviewing related literature, a spreadsheet was created to examine the hydraulic conditions downstream of a given structure over a wide range of flows. The calculations show the range over which a submerged hydraulic jump occurs and whether the surface velocity is directed upstream or downstream based on the tailwater depth at which the surface velocity “flips” direction. The calculations also show estimated surface velocities which can be compared to human swimming capability. Results of this research can be used by federal, state, and private dam owners to properly identify structures of concern and institute appropriate short-term and long-term mitigation strategies. Proper classification of low-head hydraulic structures will assist nationwide efforts to improve public safety.