If your first interaction with low head dams is the title of this post, then you may think I was being hyperbolic by adding aka “Drowning Machines.” Believe it or not, the dangers of low head dams are so well-established among those in natural resources and in dam safety that low head dams are routinely referred to as “drowning machines” throughout the nation. With ease, I found examples from the Iowa DNR, the National Weather Service, a Virginia news channel, the Minnesota DNR, Montana Fish Wildlife & Parks, the North Dakota State Water Commission, an engineering blog, and the Indianapolis Star. For perspective, according to the National Weather Service, there were 111 deaths due to drowning at low head dams between 2018 and 2020.
I must admit, prior to handling my first case resulting from a life lost to a low head dam, despite years of fishing on various waterways, I was generally unfamiliar with the dangers low head dams pose. But I’m not alone. A recent trivia episode of The MeatEater Podcast (ep. 422) asked a room full of devout outdoorsman, “What type of manmade structure is often referred to as a ‘drowning machine?’” Only one got the answer correct, which, as you now know, was “low head dam.”
While the danger of behemoths such as the Grand Coulee Dam or the Hoover Dam can be self-evident, the true danger of low head dams arises from what you can’t readily see. As the water rolls over the top of the dam and plunges down, it creates a recirculating current that can trap objects or people. While standing on a bridge overlooking a low head dam in Indianapolis, I watched a broken away floating dock get caught in the recirculating current and bob laterally across the river stream for many minutes unable to break free and continue its escape down river. I doubt the dock’s owner would have imagined such a fate for the dock.
Another major danger with low head dams is that many were erected over a century ago and have remained in place long after their intended purposes ceased. Indeed, after such a long period of time, it can often be difficult to locate an owner for the dam, let alone task anyone with maintaining it. While some dams may be safely removed or otherwise augmented with designs to help avoid recirculating currents, the inability to locate responsible parties for low head dams often lead to drowning machines remaining in place, wholly unchanged.
Even more astonishing is how many exist with no advance warning signs of the danger that lies ahead. That is particularly problematic with low head dams because they are usually not readily apparent from boat or kayak height on approach. That you could be floating a river and have no advance warning that you were approaching a manmade drowning machine was beyond my comprehension before seeing multiple instances of it.
One step currently being taken to help fight against the dangers of low head dams is the use of AI technology scanning Google Earth to try and create an inventory of low head dams. Until that inventory is completed and some concerted effort is taken to remove or otherwise make these kinds of dams safer, the best you can do is to familiarize yourself in advance with any waterway you get on, read and memorize advice on what to do if trapped in a recirculating current—I had a client who survived such an encounter because he had previously heard advice on how to free himself from the current—and bring awareness to others about the dangers of low head dams.
A couple additional resources you may want to check out are: this video providing an engineering explanation of low head dams and possible solutions; and this documentary helping to show the true human cost of these drowning machines.
Knowing and understanding the dangers posed by low head dams will go a long way to helping ensure that you or a loved one are not injured or worse. Ultimately, it will not be until these low head dams are removed, made safer, or at a minimum marked by appropriate warning devices that their dangers can truly be mitigated.