VIDEO: Roller dams seen as 'drowning machines'

Called “drowning machines” by Department of Natural Resources river programs personnel, low-head dams like the one that sucked 30-year-old Christopher Clark of

Cedar Rapids into its tumbling vortex Wednesday too often live up to their nickname.

Driving a personal watercraft, Clark ventured too close to the roller dam on the Cedar River near the 2500 block of Old River Road and could not escape the deadly trap.

His is the state's second dam-related death this year and the 16th since 1999, according to Nate Hoogeveen, the DNR's river programs coordinator.

The south Cedar Rapids “drowning machine” claimed four lives in little more than a three-year span in the decade after it was built.

In April 1973, Marion brothers Donald Chapman, 18, and Danny Chapman, 24, drowned after their rubber raft capsized in the turbulent water below the dam.

They clung to the raft for an hour while firefighters and Linn County deputies tried vainly to save them, and two firefighters themselves had to be rescued when their boat capsized, according to Gazette reports.

On May 20, 1976, two Cedar Rapids firefighters, Melvin Goebel and Robert Simon, drowned when strong currents pulled their boat over the dam while they were practicing rescue procedures.

Though the dam is commonly called “the roller dam,” it is more accurately described as a low-head dam, one of about 160 on Iowa's navigable streams, according to the DNR's Hoogeveen.

“It's basically a wall of concrete straight across the river. There is nothing mechanical that could be called a roller. The term refers to the back-rolling current,” he said.

Water tumbling over the dam rebounds off the bottom and back to the surface, creating a recirculating current that is much more dangerous than it often appears, Hoogeveen said.

The danger zone at the roller dam is clearly delineated by a visible boil line that marks where the normal downstream flow changes to an upstream flow, he said.

Hoogeveen said people caught in the circulating flow rarely escape on their own. The motion is disorienting, the aerated water impairs vision, and contact with the dam and floating debris can injure the victim, he said.

“It's miraculous if anyone survives,” his colleague, John Wenck, outreach coordinator for DNR river programs, said.

As painful as it may be to watch friends or loved ones in peril, untrained and ill-equipped people are well advised not to attempt a rescue, Wenck said.

With recent appropriations from the Legislature, the DNR is working to reduce the danger of low-head dams by installing more warning signs, establishing more and better portages and modifying or removing dams whenever feasible.

Unlike most low head dams, which have long since been rendered obsolete, the roller dam in south Cedar Rapids is still used for the same purpose for which it was built in 1966, according to Ryan Stensland, a spokesman for Alliant Energy.

The dam was built to assure an adequate supply of water to cool its Prairie Creek Generating Station, he said.

Companion charged

The woman who was riding another jet ski with Clark has been charged with drunken boating.

Bobbiejo McDanniel, 36, of 4420 Bowling St. SW, who was riding a jet ski with Clark Wednesday night, was charged with operating a water vessel under the influence, according to court records. The complaint said officers responding to the scene suspected McDanniel intoxicated and took her to the Marion Police Department for a breathalyzer test. McDanniel refused to provide a sample for the test, the complaint said.