To look at, the low-head dam that crosses the Great Miami River a short distance north of downtown Sidney in western Ohio is a stunning combination of natural beauty and human engineering. The water pours over its edge in a calm and constant movement. When the sun shines on it, the colors of the rainbow shine on the glassy form of the water. It is one of tens of thousands of such dams built in the United States in the early 20th century to manage waterways for various reasons.

But it was here, in April 2020, that an engaged couple drowned after paddling the seemingly benign river barrier. The tragedy shocked the city, but such incidents are becoming more common.

Flotation devices such as life jackets fail due to the large amount of oxygen bubbles present in the water which counter their buoyancy

Here in the heartland of the United States, low-head concrete dams are found on nearly every major river. Mostly built in the late 19th and early 20th centuries, they served as flood management devices for towns and cities as well as providing farmers with a constant supply of water for irrigation.

They are dangerous because the hydrodynamics caused by the rapid flow of the dam cornice results in a reverse upstream movement of water between the dam wall and the “boiling point” or countercurrent of the water. Any human, animal or object unlucky enough to get caught in the circular current is pushed underwater, flipped over and pushed back again in an endless cycle. Flotation devices such as life jackets fail due to the large amount of oxygen bubbles present in the water which counter their buoyancy.

Nearly impossible to see by boaters and paddlers upstream due to their drop, low-head dams have caused untold carnage, drowning hundreds of swimmers, paddlers, and fishing enthusiasts across the United States over the years. . The Dock Street Dam in Harrisburg, Pennsylvania drowned nearly 30 people. Further west in Iowa, about 200 people died after crossing and struggling in low-head dams. Along with Minnesota, those two states are responsible for a third of all drownings nationwide, according to a 2015 study by researchers at Brigham Young University in Utah.

Now, as more people take to the rivers and canals for entertainment, especially in the coming months, and outdoor activities continue their popular run as the pandemic lingers, the threat posed by dams – many of which have long since been abandoned by their owners – is increasing. Last April was proclaimed the first-ever Low Head Dams Public Safety Month.

But a new effort in the United States to locate and map dangerous dams is underway, mirroring a similar effort that has been developed in Ireland in recent years.

The Brigham Young University study authors are developing AI software that would find and identify all low-head dams in the country using Google Earth Pro.

“Through collaborative actions, we are able to solve problems that no one agency can handle. Although originally formed as a flood-based program, our team is more focused on an all-hazards approach,” says Manuela Johnson, who leads a task force called the Indiana Silver Jackets, which is collaborating with the effort. US National Dam Database.

“We are made up of state, federal, and regional agencies and organizations as well as higher education.”

Dams are a problem that affects many countries, adds Johnson. “It’s a global challenge that puts our young men and women who enjoy rivers and streams at risk.”

These dangers are increasingly prompting local and state authorities across the United States to work to alter or remove structures entirely.

Low-head dams present more than just a danger to human life. The dams have been particularly damaging to migrating fish and other riverine species that must move up and down the river to reproduce, survive and thrive. In the United States, organizations such as American Rivers have supported river restoration efforts that have seen 69 dams removed in 2020 alone.

dodder

In Ireland, efforts by researchers at University College Dublin have charted a similar course. Funded by the Environmental Protection Agency, the Reconnect initiative based at the university’s School of Biology and Environmental Sciences ran from 2016 to 2020, working to locate and map barriers such as weirs and dams.

“Obstacles associated with road-river crossings (eg, culverts and fords) were the most common and most evenly distributed across the 10 study watersheds. After the crossings there were weirs, 117 in the Dodder alone. Many of the weirs are structures that have been used for power generation for milling in the past,” says Dr Mary Kelly-Quinn, who served as the Reconnect Project Coordinator.

“In addition to detailed barrier mapping in 10 catchments, fish, macroinvertebrate, macrophyte, hydromorphology and eDNA surveys were carried out in four main study areas on the Duag (Co Tipperary ), Brown’s Beck Brook (Co Wicklow), Dalligan (Co Waterford) and Burren (Co Carlow), which each contained a significant barrier.

The River Obstacles app, created by a group of UK-based environmental organisations, found that between July 2016 and October 2017 there were 98 downloads of river obstacle recordings across 16 counties in Ireland.

“The research included monitoring responses to ford removal on Brown’s Beck Creek. Specific surveys were conducted at 35 other locations across 12 river and river systems,” Kelly-Quinn adds. A report detailing the results of the mapping and the potential impacts on ecology and sediment dynamics will be published this spring (copies can be obtained from: [email protected]).

She adds that it is estimated that there are at least 1.2 million barriers in waterways across Europe, 68% of which are low-head structures.

Some members of the public oppose the removal of the low-head dams as they attract visitors and tourists eager to view and photograph the beautiful sight

While the Reconnect project focused on effects on riverine flora and fauna, the presence of low-head dams and weirs has resulted in multiple drownings and near-death experiences across Ireland. In April 2010, two kayakers drowned after becoming trapped in a weir on the Clodagh River in Co Waterford.

Several months later, a kayaker attempting to paddle over a weir on the River Bannon in County Derry drowned when his Canadian canoe got stuck in the eddy. In August 2020 a man drowned trying to rescue his brother who had fallen into the River Lee at a low head weir in Ballincollig, Co Cork while fishing.

In the United States, some members of the public oppose the removal of low-head dams because they attract visitors and tourists eager to observe and photograph the beautiful sight. Some fishermen claim that removing the dams would harm their access to the fish that congregate in the pools at the base of the dam, although research suggests this is not the case.

A growing number of communities are working to convert dams into safe river waves that can be used for surfing and as whitewater drops for paddlers. Cities such as Dayton and Springfield in Ohio and Grand Rapids in Michigan have spent or are investing millions of dollars to convert dangerous low-head dams into features that will attract water enthusiasts. In some cases, businesses such as surf schools and shops selling kayaks and other watercraft have sprung up in neighborhoods surrounding converted dams, adding to a sense of renewal around waterways that for decades had been feared or ignored. It shows that behind every barrier is an opportunity.