Submerged Hydraulic Jump Remediation at Low-Head Dams: Partial Width Deflector Design

Abstract

Low-head dams are capable of creating dangerous countercurrents just downstream from the structure. These dangerous countercurrents are known as submerged hydraulic jumps and are responsible for hundreds of fatalities at numerous low-head dams across the United States. The countercurrent creates high upstream-directed surface velocities across the width of the channel, making it nearly impossible for a trapped individual to escape. This submerged jump can occur for a range of upstream and downstream conditions. A multiple partial width deflector design for the downstream side of the dam was tested in the laboratory to determine effectiveness in completely or partially eliminating the submerged hydraulic jump. The results demonstrate that a dramatic reduction in upstream-directed surface velocities over a wide range of headwater and tailwater conditions is possible. The dam modification is relatively inexpensive, simple to install, and designed such that an individual will likely escape the submerged jump without severe injury or harm. The design is ready for prototype testing.