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Underwater sensor may detect deadly rip currents

Researchers lay underwater cable from the south pier of the Duluth Ship Canal to the spot where they sank an underwater sensor designed to detect rip currents. (Steve Kuchera / skuchera@duluthnews.com)1 / 4
NRRI’s Jerry Henneck (from left), UW-Madison’s Chin Wu and NRRI’s Matt Santo lower an underwater sensor into Lake Superior near the south pier of the Duluth Ship Canal on Thursday. The device may give advance warnings of deadly rip currents along Park Point. Steve Kuchera / skuchera@duluthnews.com2 / 4
Chin Wu of UW-Madison and Jerry Henneck and Matt Santo of NRRI examine the video feed from an underwater camera before deploying an underwater sensor designed to give advance warnings of rip currents. (Steve Kuchera / skuchera@duluthnews.com)3 / 4
UW-Madison graduate student Yuli “July” Liu looks up at coworkers who had just deployed an underwater sensor for detecting rip currents. Liu was using her laptop computer to make sure the sensor was transmitting data. (Steve Kuchera / skuchera@duluthnews.com)4 / 4

University of Wisconsin researchers this week installed an underwater wave pressure sensor along Duluth's Park Point beach that could help detect deadly rip currents.

The wave sensor, underwater off the South Pier of the Duluth Ship Canal, will be used in conjunction with a live video camera installed Friday on the Park Point Beach House to offer real-time data on what’s happening on and under the water.

The project is the brainchild and personal mission of Chin Wu, a UW-Madison professor of civil and environmental engineering. The University of Wisconsin Sea Grant Institute is helping coordinate the effort.

“Rip currents claim more lives on the Great Lakes annually than tornadoes, lightning and floods,” Wu said. “Our project will address these tragic statistics.”

In addition to the Park Point beach, rip current detectors are in place at beaches in Port Washington, Wis., and McKinley Beach in Milwaukee.

The data will be used by local forecasters for the National Weather Service as they try to issue rip warnings for beachgoers from mid-June to mid-October, an effort that has been underway since 2010, but until now depended on more traditional data like wind speed and direction.

The wave sensors and cameras will be used to detect rip currents and to provide input into near real-time surf zone modeling of the currents, said Dan Miller, science and operations manager at the National Weather Service office in Duluth.

“We are hoping that this will enhance our ability to detect and forecast rip currents, at least in the immediate short term’’ of one-to-three hours, he said.

Beachgoers now depend on beach forecast from the weather service that estimate conditions for when dangerous wave action is likely to occur, but is not necessarily happening. Strong onshore winds spur a beach advisory that -- in addition to electronic forecast sources like the internet and weather radio -- includes a red flag placed at two popular access points along Park Point warning people to stay out of the water.

In Duluth, those winds are generally easterly or northeast with speeds of 17 mph or more off the lake, pounding waves onto shore.

In some cases, after those waves peak on shore and head back into Lake Superior, they move rapidly through underwater breaks or “rips” in the sand. That outgoing water has been known to pull people quickly out into the lake, often prompting a panicked and sometimes deadly effort to swim back against the current.

The solution is simple but apparently not well known: don't fight the current by heading directly back to shore. Instead, turn sideways to the beach and swim along the beach until you swim out of the current, then head back to shore. Rip currents are usually 30 yards wide or less.

There are incidents nearly every year in Duluth when rip currents are blamed for near-drownings. In 2003, 21-year-old Matthew Rheaume drowned, apparently after a rip current formed off the 12th Street Beach on Park Point. That same hot August day, with a strong easterly wind, several other swimmers needed rescuing from rip currents, including then-University of Minnesota Duluth hockey player Junior Lessard.

The “Integrated Nowcast/Forecast Operation System” project is funded with $200,000 from the National Oceanic and Atmospheric Administration Coastal Storms Program, which is a regional effort to make Great Lakes coastal communities safer and more resilient to storms, weather hazards and climate change.

Data from the Duluth beach, when it comes online, can be seen at infosportwashington.cee.wisc.edu/Duluth.html.

Park Point beach conditions are updated hourly from June 15 to Oct. 15 and can be found, along with other weather and wave information, at parkpointbeach.org.

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