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  5. System alerts Great Lakes swimmers of dangerous currents

System alerts Great Lakes swimmers of dangerous currents

Swimmers at Park Point Beach in Duluth, one of three sites where UW-Madison researchers will test a pilot system for anticipating rip currents in the Great Lakes. Photo courtesy Brent Schleck, Minnesota Sea Grant.

The history of Great Lakes is one of people who underestimate their destructive power, often with tragic results. From two massive waves that smashed into Chicago’s harbors in 1954 to a rip current that drowned a young swimmer in Port Washington, Wisconsin, in 2012, Lake Michigan and its neighbors have a track record of catching people off-guard with dangerous currents. 

People still commonly refer to such events with terms like “sneaky waves,” as if these incidents were aberrations that couldn’t have been helped or anticipated. 

Chin Wu isn’t having it, because in fact such incidents are a long-established part of the lakes’ behavior. “I say, ‘sneaky waves?’ These sneaker waves appear without warning, often surging high up on the beach with deadly force and creating rip currents,” says Wu, a professor of civil and environmental engineering at the University of Wisconsin-Madison. 

Between 2002 and 2013, rip currents—essentially strong channels of water that flow out from the shore—were involved in 85 deaths and 256 rescues in the Great Lakes. But this still hasn’t changed the common misperception rip currents are only a threat in the ocean. Currently, however, the lakes’ only safety measures against rip currents rely on observation of factors like wave heights and water levels—a passive approach that doesn’t take into account the more complex factors that cause rip currents, leaving a dangerous gap in the region’s defenses.

Wu says it's possible to anticipate them based on possible causes in weather, the current’s interaction with structures along the shore, and formations in the sea floor and sandbars.

Wu’s research team, consisting of PhD students Yuli Liu, Adam Bechle, and Josh Anderson, is developing a real-time warning system for dangerous rip currents on Great Lakes beaches. Supported by a $200,000 grant from the National Oceanic and Atmospheric Administration Great Lakes Coastal Storms Program, Wu recently began testing and implementing pilot systems at beaches in Port Washington and Milwaukee in Wisconsin, and also in Duluth, Minnesota. 

Staying ahead of danger

His system will alert safety officials when conditions become conducive to rip currents, or when alarming wave patterns are poised to radiate along the shoreline. Dubbed the Integrated Nowcast/Forecast Operation System (INFOS), the pilot program offers a mix of data on current conditions in an area and ideally will catch the first stirrings of dangerous currents before they endanger people near the shore. 

"There are only risk level warnings for beachgoers, but that's kind of a reactionary approach, and Chin's is more of a proactive approach,” says Julia Noordyk, a coastal storms specialist with the Green Bay office of the Wisconsin Sea Grant Institute. “Right now, there's no way to do real-time observation of dangerous currents forming. Hopefully, this project will change that.”

INFOS builds on the principles of the wave imaging and modeling systems Wu’s research group has pioneered. His research team has developed automated trinocular stereo imaging system, for example, using three calibrated cameras to created 3D analyses of motions of  the water surface. The system now can be calibrated on-site, making them easy deployment and maintenance, in comparison with  weather buoys and wave gauges. Once INFOS is refined at the test sites, Wu hopes the system can be deployed throughout the region, protecting swimmers and the economies of communities that depend on beach tourism. 

"Part of the process is science, but an equally big part is outreach and education, bringing it to local communities,” Wu says. 

In addition to his project’s  partners at the Wisconsin and Minnesota Sea Grant Institutes, Wisconsin Coastal Management Program, and the National Weather Service, Wu has spent a lot of time coordinating with local officials at each pilot site. In the tradition of the Wisconsin Idea, he’s determined to spread the benefits of science and engineering to people throughout the state and the region.

A diagram shows how some rip currents form. Diagram courtesy of the National Weather Service.

Reading the lakes

The pilot sites were selected in part because each one is prone to a different kind of rip current, which creates an opportunity to flesh out some of the basic science of rip currents and to protect swimmers from a greater range of potentially dangerous conditions. Park Point Beach in Duluth sees a high occurrence of “bar gap” currents, which form in the gaps between sandbars. Bradford Beach, in Milwaukee, most often has “headland” currents, which sweep along the shoreline and then out, amplified by variations in the sea floor. Finally, North Beach in Port Washington faces “structure-induced” rip currents, which occur when currents deflect off a pier or a breakwater.

The key thing is to understand the basic mechanisms that cause rip currents, Wu says—especially as empirical factors like wave heights aren’t always an accurate predictor of whether or not rip currents will occur. As inland, relatively enclosed seas, the lakes are subject to seiches—standing waves that essentially reverberate back and forth across a body of water—and to weather-generated tsunamis, known as meteotsunamis. Wu says researchers will need to pay more attention to those factors if they ever hope to  capture  dangerous currents in the lakes.

“Currently it is known that rip currents in general are caused by surface waves,” Wu says. “One of the major science questions is to address the role of seiches and meteotsunamis in generating rip currents or modulating the formation of rip currents in the Great Lakes.”

Despite these gaps, INFOS will still draw on deep and nuanced knowledge of how the Great Lakes are different from, and in some respects actually are more dangerous than, other bodies of water. Spreading that knowledge, too, is a key aspect of improving the region’s safety culture, and fighting the assumption that the lakes are inherently safer than the oceans. "In the Great Lakes, people underestimate the waves,” Noordyk says. “In the ocean, there's a longer wave period, whereas in the Great Lakes, they just keep coming and coming.” 

"One of the big challenges is that the near-shore system in the Great Lakes is very dynamic,” says Brent Schleck, a coastal storms outreach coordinator with the Minnesota Sea Grant College Program in the Twin Cities. “It's not apparent, with much forewarning, where these currents will be occurring. Where those rip channels in the sandbar are created is something that's not necessarily known, and that leads us to the need for real-time observation on beaches.”

A community’s response to tragedy

When these threats resulted in the death of a teenage swimmer, Port Washington residents and Mayor Tom Mlada vowed that it wouldn’t be in vain. Over Labor Day weekend 2012, Tyler Buczek, 15, drowned in a rip current off one of the city’s beaches. “When you see somebody's life cut short, you're reminded again of the power of lake Michigan, and the need to respect that power,” Mlada says. “The indication of a community’s strength and character is not whether it suffers a tragedy, but how it responds.” 

Wu had previously addressed safety issues on the Great Lakes, including freak waves  that endanger kayakers in the Apostle Islands area in Lake Superior, and Buczek’s death helped motivate him to start the INFOS project, well before he received the NOAA CSP grant. 

Wu has spent the last couple of years meeting with the Port Washington beach-safety committee, hashing out an approach that factors in the unpredictability of Lake Michigan. "The lake is changing on a daily basis,” Mlada says. “Structurally, there certainly are areas that may be better to stay away from, but the reality is that to try to designate generically a place that folks should stay away from is pretty difficult to do.” 

Like many communities along the lakes, Port Washington faces logistical barriers to safer beaches, including a lack of dependable cell-phone service in some beach areas, which can make it hard to reach emergency responders. (The city may install some wi-fi networks in certain beach areas to at least aid in INFOS transmissions, Mlada says.) And unlike on the ocean coasts, it’s uncommon for Great Lakes beaches to have lifeguards.

Mlada says he has faced some criticism that the emphasis on safety will stir up fear among potential beachgoers, potentially damaging the $6 to $10 million economic impact the beaches annually draw into the local economy. But Mlada argues that INFOS will ultimately make beachgoers in Port Washington feel more confident by connecting them with a wealth of information. “This is cutting-edge, but cutting-edge in all the right ways,” he says. “It empowers people and keeps people informed."

Scott Gordon
8/4/2014