Wetlands / Environmental Permitting
Aquatic Terrestrial Species
Wetlands & Waters of the U.S.
Low Head Dams
Low head dams are called “drowning machines” because they often have a submerged hydraulic jump. A submerged hydraulic jump is an energy dissipating underwater jet that can often maintain enough kinetic energy to cause a current to travel downstream and then rise to the surface as a "boil," with a portion of the water of the jet flowing back to the dam. This is known as the reverse roller effect. Hydraulic engineering analyses can define the approximate location of the boil and the likely velocity of the reverse flow. It is this reverse flow that carries a victim back to the base of the dam, where he or she can become trapped in a vicious cycle.
Low head dams across the United States, from New Jersey to Oregon, continue to needlessly take lives as victims are lured into the seemingly placid water flow over the dams. WWE has analyzed numerous submerged hydraulic jumps and resulting reverse rollers across the United States and designed various types of dam retrofits. WWE engineers serve as experts for evaluations and testimony in depositions and court hearings. Our work has included scientific analyses of currents, hydraulics and hazards.