Stream Slope Map to Predict Drowning Potential at Low-Head Dams

Every year an estimated 50 people drown downstream from low-head dams. The purpose of this paper is to develop a quick way to identify potentially dangerous low-head dam sites using stream slope as an indicator. The current that causes deaths at low-head dams is created by a submerged hydraulic jump. A hydraulic jump becomes submerged when tailwater is high. For a simplified approach based on the Manning equation, a flat slope can be a predictor of high tailwater. Stream slope values of low-head dams in Colorado, Utah, Indiana, Wyoming, and Idaho were tested against dams with recorded fatalities in those states to see if they were statistically significantly different. Bias in the data prevented a conclusion, but stream slope maps created from the National Hydrography Dataset will allow individual testing of low-head dams to establish the dangerous flow regimes that might cause a submerged hydraulic jump.