Low-head dams create a barrier across the width of a river to alter the flow of the water and change the level of a river. Unlike other dams, low-head dams are difficult to notice upstream since the water flows over the barrier across the entire river, making the water appear continuous.

Across the nation, from 2018-2021, there were 149 reported deaths due to incidents caused by low-head dams, according to the National Weather Service.

“I would guess that most people don’t even know they’re going to go over a low-head dam until it’s too late. When you approach a low-head dam from the upstream side, everything looks tranquil and just fine,” said Brigham Young University professor Rollin Hotchkiss.

While not all low-head dams are dangerous, Hotchkiss said those that have a reverse current are often fatal. A reverse current is a result of the water in the river downstream rising and drowning out the whitewater at the dam. He explained when someone jumps or falls into the dam, the water rushing over the barrier pushes them down, and the water coming upstream creates a cycle that keeps them trapped under the water, causing them to drown.

He compared this to people who are whitewater rafting getting stuck behind a rock. In that situation, they can get out of the current by going sideways. However, low-barrier dams are across the entire river, meaning the current pushing the person down cannot be escaped by going to the side, making it very difficult to escape.

The dangerous nature of these dams inspired Hotchkiss to create, with the help of dozens of others, an inventory with the locations of over 13,000 low-head dams across the nation.

Inspiration from students

Hotchkiss is a professor of civil engineering at BYU, and years ago he was looking for an experiment students could do that involved design, when he came across an article about drownings at low-head dams. Working with the students, they attempted to design something that could go next to low-head dams to eliminate the “killer current.”

They could not find a design that fixed the problem, but later Hotchkiss did research with graduate students and developed a design that eliminated the “killer current” and then published their work.

Later, one of Hotchkiss’ students created a database of fatalities caused by low-head dams in the U.S. The website allows a visitor to learn about the deaths that occurred at any low-head dam in the nation. The work of this student inspired Hotchkiss to try to locate all low-head dams in the country.

After the student’s work was published online, Hotchkiss received two phone calls. One was from a first responder who was standing outside next to a low-head dam where someone had just drowned. He said to Hotchkiss, “‘Why does this have to happen?'”

Hotchkiss continued, “Another phone call I got from a mother who had just lost her son in his early 20s. He and a buddy went over a low-head dam and drowned. And she too, wondered, ‘Why does this have to happen?'”

After speaking with these people who had experienced such tragedy, he realized many people did not know where low-head dams were located, so he enlisted the help of around 25 people from across several professional societies to begin the work of locating each low-head dam in the U.S.

When he received those two phone calls, Hotchkiss said, “It was heartbreaking, heart-rending, not only for the loss of life, which was tragic, but the nature of these fatalities is very emotional. You can actually see the deceased lose their life, and there’s nothing you can do about it. It’s just heartbreaking, especially when I know it doesn’t have to happen.”

How the inventory was created

Over the course of three years, Hotchkiss and the national task force of professionals he had recruited worked with students each semester to locate over 13,000 low-head dams across the U.S. Over 100 people in total volunteered their time to create the inventory of low-head dams.

The volunteers were split into subcommittees to work on different ways of locating the dams, including contacting state dam safety offices, creating cellphone apps for people to upload a picture of a low-head dam they see while recreating, looking at satellite photography and looking at Google Earth Pro.

Students were assigned to the last subcommittee and located low-head dams by looking for the whitewater associated with a current downstream on Google Earth Pro. All of their work was verified by a professional, Hotchkiss said. Students from three universities — BYU, the University of Kentucky and Utah State University — found low-head dams in about a dozen states. “It’s quite tedious work. They did a great job,” Hotchkiss said.

Hotchkiss said students who participated in the research have shared how the project impacted them. “From what they tell me, it’s a sense of contributing to something very positive, that is to save lives, and they played a real role in creating this inventory,” he said.

The role of the national task force and their research was to create the inventory, and now the action that will be taken according to their data is the decision of each state. The inventory map of each low-head dam across the U.S. will be distributed to each state’s dam safety office in the next six weeks. Hotchkiss explained that those doing the research are not advocating, but they do hope each state does something with the information.

“We provide the information to the state dam safety officers and they don’t have any funding to do anything, but perhaps they would approach the state legislature,” Hotchkiss said. He suggests solutions such as placing warning signs around the low-head dams and evaluating if the dams are still serving a useful purpose or if they could be removed.

Hotchkiss said, “We don’t want this inventory for states to be a noun, we want it to be a verb. We want it to inspire people to do things.”

“This inventory, it’s a bunch of latitude and longitude numbers. By themselves, they don’t do anything,” he added. “We hope that the locations inspire states and citizens, recreation groups, those who rent rafts and things. We hope it inspires them to do things to increase safety.”

While their research was extensive, Hotchkiss said they know there are more low-head dams in the U.S. that are not on their map. They hope for the research to continue with funding from a federal or state agency. For now, the work of the national task force that created the inventory “will be rather limited now to distributing the inventory to all the states and a few follow-up things, but this really was our major goal,” he said.

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