Saving Lives While Improving Fish Passage at "Killer Dams"

During the 19th and 20th centuries, many low-head dams were constructed on rivers for water supply, ice harvesting, recreation, navigation, power generation (mills), and flow measurement. Little consideration was given to fish passage and public safety when most of these structures were designed and constructed. With significant development occurring in the vicinity of these structures, growing interest in river recreation, and the recent movement to restore river and stream environments to a more natural condition, many of these dams are now subject to intense pressures for their removal. When it is necessary to keep the structure in service, the dam owner is often faced with the difficult problems of addressing public safety concerns and providing effective fish passage. This paper presents the author’s experience rehabilitating low head dams to improve public safety and provide effective fish passage. Lessons learned from experience with litigation related to drownings at low head dams are discussed with an emphasis on design concepts for modifying low head dams to eliminate the hazardous submerged hydraulic jump. A state-of-the-art design for fish passage for low head dams, recently developed by Dr. Luther Aadland of the Minnesota Department of Natural Resources, is also presented that not only provides fish passage for all species of fish, but also effectively eliminates the hazardous hydraulic roller. 9 pp., 11 references.