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Great Lakes Article:

Killer currents
Scientists closer to predicting danger on Lake Michigan
By Jeremy D. Bonfiglio
South Bend Tribune
Posted August 14, 2005


Most summer days, the shoreline of Lake Michigan looks inviting: warm, soft sand. A gentle breeze. Rolling waves.

But in an instant such serenity can turn deadly.

That's what happened on July 4, 2003, when seven people drowned within hours along a three-mile stretch of Berrien County beach.

It's what happens each summer on American waterways, contributing to about 100 deaths a year.

It's a called a rip current, a fast-moving and deadly force of water, once thought only to occur on ocean shorelines.

Scientists have only recently confirmed that the phenomenon occurs daily along Lake Michigan's 1,638 miles of sandy coastline. In fact, rip currents can be found on any sandy shore where waves are present. And at almost any time.

"A lot of people don't know rip currents occur on the Great Lakes. We didn't know until recently," says Ron Kinnunen, a Marquette, Mich., agent for Michigan Sea Grant, a joint program between the University of Michigan and Michigan State University that studies this natural occurrence. "Some of the rip currents on Lake Michigan can rival those of Southern California."

Rip currents form when wind and wave conditions combine to push water onto a beach, forming a sandbar close to shore.

"You get water picking up, and eventually there's too much pressure," says Jennifer Read, associate director of Michigan Sea Grant. "The sandbar rips open, and water pours out through that point. It's very swift, and it's almost literally perpendicular to the shoreline."

These minirivers of fast-moving water can cut across the surf zone, carrying sand, debris and sometimes swimmers out to sea.

Although rip currents usually run out of steam beyond the breakers, they can move faster than 5 mph and carry even Olympic swimmers hundreds of yards offshore. Many swimmers who try to fight rip currents quickly exhaust themselves and drown.

"There were about 30 drownings related to rip currents in Lake Michigan in 2002 and 2003," says Kinnunen, who has been with Sea Grant for 24 years. "People don't even have to be swimming. They can be in waist-deep water when a rip current knocks their feet out from under them."

Which may be why rip currents are often erroneously called riptides or undertow, but they are not caused by tidal action. Although waders may end up underwater, the currents themselves pull people along the surface, not down.

According to the United States Lifesaving Association, 80 percent of all rescues on U.S. beaches are related to rip currents. So far this summer, scientists suspect rip currents in five incidents on Lake Michigan, including two separate drowning deaths near Muskegon in late July.

Because such drownings and near drownings occur one by one up and down the shore, rip currents have only recently been recognized as a major hazard, although they claim more lives annually than floods, hurricanes and tornadoes.

The National Weather Service, the United States Lifesaving Association and the National Sea Grant Program have pooled resources to better understand rip currents and educate the public as meteorologists and coastal geologists continue to collect data.

"We're getting to the point where we can almost tell where they are going to occur," says Kinnunen. "If you have a long stretch of water and the wind is blowing toward shore, all that energy has to dissipate back out."

Guy Meadows, a professor from the University of Michigan, has studied rip currents for 35 years.

He says the conditions on Lake Michigan are not only conducive to rip currents, they are ideal.

Underwater erosion has created a steep drop off on the shoreline, which has allowed larger waves to break closer to shore. This creates more water piling up and more rip currents.

"The beach is changing very rapidly," says Meadows. "Our prediction is that the frequency and intensity of rip currents on Lake Michigan will increase over the next few years."

Which is why researchers are hoping to devise better ways of predicting when and where rip currents are most likely to appear.

But, Meadows says, rip currents aren't easily predicted.

"Can we say, 'There will be a rip current on this beach at this time'?" says Meadows. "We're a long ways away from that."

What scientists can do is predict when conditions are right for rip currents by using wave height, wind direction, wind speed and a few other variables.

"I think we're closer to predicting the where and when," says National Weather Service meteorologist Dave Guenther. "We are making bigger strides every year. Hopefully, within a year or two, we will be able to forecast various strength levels."

The National Weather Service now includes a basic rip current forecast on its hazardous weather outlook for Lake Michigan (www.crh.noaa.gov/grr in Michigan and www.crh.noaa.gov/iwx in Indiana).

In the future, Meadows says, scientists hope to use such forecasts to detect rip currents before they form with a portable shore-based radar unit.

"This would be a real-time tool like Doppler radar," says Meadows. "That's one of the things we're really pushing for on Lake Michigan."

In the meantime, swimmers can protect themselves by recognizing subtle signs of rip currents.

"There might be debris on the surface," says Read. "The color of water may be different. In general, it's going to look different than the water around it."

"If people are caught in a rip current they should know what to do," Kinnunen says, "and if they can't swim, they shouldn't even be in waist-high water when conditions are right."

Staff writer Jeremy D. Bonfiglio:

jbonfiglio@sbtinfo.com

(574) 235-6244

 

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