Hydraulic at Low-Head Dam

The Warning Signs

Proper signage is critical to protecting the public from the dangers of low-head dams.

Video of Low-Head Dam Hydraulic

The video shows a low-head dam hydraulic created in lab flume. Notice the reverse current created on the down stream side of the dam. The object caught in the hydraulic is continuously circulated in the current. Although the net water flow is down stream a cyclic flow pattern, known as a hydraulic or roller, is present.

Hydraulics of Low-Head Dams

The dam is an obstruction to the downstream flow of the water, causing the water level to increase upstream and to flow overtop of the dam. The water cresting the dam flows downward over the face of the dam into the downstream pool. 

The water continues to the bottom of the generally shallow downstream pool. The flow is then deflected upwards and downstream.

Definition of a Low-Head Dam

A low-head dam is an engineered structure traversing the full width of a stream that creates a pool of backwater that flows downstream over the face of the dam. Low-head dams are usually less than fifteen feet high although there is not regulatory distinction for the height of a low-head dam.

Low-head dams are considered extremely dangerous structures because of the hydraulic condition at the downstream face of the dam.

Low-head dams are frequently referred to as drowning machines.

Websites to visit: Boat Safe.com  Ohio DNR  American Canoe Association