Low-head dams pose public safety threat

VALLEY CITY, N.D. – The Little Dam, a squat structure that spans the Sheyenne River, doesn't look treacherous. But in reality, the churning tailwater below this Valley City dam is a drowning machine that's killed two people since 2012.

Mickey Kvien knows just how powerful that tailwater is. Every day for three years, he's been missing his daughter, 38-year-old Jodi Kvien Opatz, who drowned trying to save her dog from the dam's undercurrents.

"We have experienced firsthand what a low-head dam like that can do," Kvien said. "The dangers are definitely there."

View North Dakota low head dams in a full screen map

View Minn. low head dams in a full screen map

Low-head dams, named for their low profiles, usually stand about 15 feet tall or less, cover the width of a river and are made of brick, stone or concrete. While there's no exact count of such dams in the U.S., estimates put the number between 2,700 and 4,400.

Many of these dams were built decades ago to power mills, irrigate farms, impound drinking water or-as in the case of the Little Dam-foster recreation. Many have outlived their original purpose, but dam owners often don't have the money to pay for removal costs, which can range from five to seven figures, experts say.

In the meantime, the number of drownings keeps climbing.

Since 1960, low-head dams have killed at least 315 people, according to the research of hydraulic engineer Bruce Tschantz, professor emeritus at the University of Tennessee Knoxville.

It's this time of year when "the killing season" starts, he said. "It's kind of a callous way of describing it, but that's really what it is."

Dams on the Red

Of the drownings Tschantz has documented, 40 occurred in Minnesota, and four were in North Dakota, including the death of Kvien Opatz and that of college student Dan Buehner, who drowned after going over the Little Dam in a raft last year.

While Tschantz has done his best to tally the deaths at low-head dams, he said there's no doubt the actual numbers are higher.

At Fargo's Midtown Dam alone, 19 people drowned before the low-head dam was replaced with rapids in 1998, said Luther Aadland, a river ecologist with the Minnesota Department of Natural Resources.

Aadland designed the rapids at the Midtown Dam, which, with the help of strategically-placed boulders, reduced erosion, allowed for fish migration and dissipated the river's energy, making the water safer for boaters and swimmers.

Aadland said the rapids' design became a prototype used over the years to replace other low-head dams on the Red. At those dam sites where rapids were installed, the number of drownings has essentially been cut to zero, he said.

With the exception of the Drayton Dam, all the low-head dams on the U.S. stretch of the Red River have been altered to eliminate deadly currents, said Christine Laney, executive director of River Keepers, a Fargo nonprofit group.

"People in Fargo-Moorhead had been told to stay away from the river for years, and mostly that was because of the undercurrents that were at those low-head dams," she said. But now, "you feel better going out on the river."

Who owns them?

Across the country, low-head dams are owned by a patchwork of public and private entities. In North Dakota, many are owned by cities and water resource districts, said Karen Goff, the state's dam safety engineer.

Goff keeps a list of the state's 51 low-head dams, 11 of which have been retrofitted with rocks on the downstream side to curb drowning dangers.

"Whenever the opportunity presents itself, we definitely encourage the dam owners to modify those structures," she said of low-head dams.

The Little Dam, also known as the Valley City Park Dam, was built in 1937, and it's owned by the Barnes County Water Resource District. In the wake of the recent drownings, the district has hired engineers to research options for removing the dam's undercurrents, said Jerry Hieb, chairman of the county water resource board.

"If we own it, we want to get that risk factor out of there," he said.

It's too soon to say how long that process will take. But in general, altering or removing a low-head dam can take years.

Minnesota has about 70 low-head dams, and over time, dozens of them have been made safer by placing rocks just downstream. The work is part of an ongoing effort by the DNR to remove or modify low-head dams, said Jason Boyle, the state's dam safety engineer.

"If there's not a purpose for the dam, we prefer the dam just to be removed," he said.

However, taking out a dam involves overcoming a couple of major hurdles. "First, you have to have an owner who's willing to remove the dam, and then you have to come up with funding," Boyle said.

'Endless cycle'

A low-head dam, sometimes called the perfect drowning machine, generates currents that have the power to capsize boats, not to mention pull swimmers under.

Tschantz said wearing a lifejacket is helpful but not a guaranteed lifesaver. He said his research has shown that about 45 percent of drowning victims at low-head dams were wearing a lifejacket, which becomes less effective in frothy, aerated water.

Upstream of a low-head dam, the water often looks smooth and inviting. But in fact, the current there is picking up enough speed to sweep a boater or swimmer over the dam, Tschantz said.

Once water falls over the dam, it starts moving in a circular pattern, first dropping to the bottom and then bubbling up 25 to 30 feet downstream before recirculating back to the dam. This reverse current can pull a swimmer toward the dam where the water can exert 300 pounds of downward force, Tschantz said.

"You get caught in this endless cycle, and you can't escape," he said, noting that even world-class swimmers are helpless. "You're at the mercy of the water."