Low-head dams don’t look particularly menacing. Thousands of these dams were built on American rivers and streams in the 1800s and early 1900s to power gristmills and small industries.
With a short drop of up to 5 feet, low-head dams can seem like a minor inconvenience – or even a thrill – for paddlers and swimmers. However, the churning waters at the base of these dams present a high level of danger.
Often referred to as “drowning machines,” low-head dams produce dangerous recirculating currents, large hydraulic forces, low buoyancy and other hazardous conditions sufficient to trap and drown victims.
Since 1960, more than 350 fatalities have occurred at low-head dams in the United States, according to Dr. Bruce Tschantz, former professor emeritus at the University of Tennessee and low-head dam expert. Two-thirds of these fatalities occurred in the past 15 years, and most occurred on weekends between April and August.
Upon entering the churning water at the base of the dam, the victim is pounded by a never-ending wave of water that forces them to the bottom. If they can bob up to the surface, the recirculating current carries them back to the dam and the nightmare begins again.
“Most people underestimate or are ignorant of the forces and currents that surround these low-head dams, and they overestimate their abilities to overcome these forces,” said Tschantz, who maintained the website www.SafeDam.com to help inform the public about dam safety and the dangers of low-head dams.
There are no reliable inventories of how many low-head dams exist in the U.S. today, but a study by the Association of State Dam Safety Officials estimates there may be as many as 5,000 low-head dams on small waterways across the country.
Know Before You Go
Public safety experts urge all swimmers, anglers, boaters, paddlers and tubers to check river maps and ask locals for locations of dangerous low-head dam structures before setting out on any waterway.
One of the best ways to look for low-head dams on a waterway is to look in Satellite Mode on Google Maps (see below). If you see a white line of water across a river, it is most likely a low head dam.
Be aware of all upstream and downstream public safety warning signs, takeout portages, and boat barrier buoys; and always wear appropriate personal flotation vests.
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