Facilitating Sustainable Fishery in the Potomac River with Innovative Hydraulics

Restoration of migratory fish populations to maintain a sustainable fishery often is a function of the effectiveness of fish passage systems at manmade river obstructions. This paper presents a novel design of a fish passage structure for low head dams where conventional type fishways are undesirable or impractical. The hydraulic physical modeling yielded a unique design of a notch in the dam crest combined with three labyrinth (W-shaped) weirs. The notch provides adequate water depth, and the weirs dissipate the flow energy to provide fish with low velocities for passage. For American shad (Alosa sapidissima), the water depth is adequate at minimum river flows, and water velocities are less than the fish burst speeds. The structure complies with the maximum allowable withdrawal at no flow condition over the dam. Weirs provide side openings and center attraction flow. This design is suitable for other low head dams with similar characteristics.