Simple Design of a Safer Low Head Dam

We present a straight-forward procedure for the design of low head dams (LHDs) that eliminates the submerged hydraulic jump (SHJ) or “drowning machine” condition. The design procedure is based on empirical equations delineating the conditions under which SHJs occur, derived from a series of flume studies [1]. The empirical equations are used to design a stepped LHD that minimizes both cost and design uncertainties and is effective as a sea lamprey barrier. We discuss how input uncertainties can be reflected in design performance uncertainty and methods to mitigate this effect. Use of a flume study to confirm the design is also suggested. Finally, we present example calculations for a new low head dam designed and constructed in Harpersfield, Ohio and discuss how the approach could be applied to mitigate hazards at existing LHDs. The design procedure is straight-forward and has potential as a least-cost alternative for both design of new dams, and mitigation of risks at existing dams.