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Dangerous Breaking Waves

breaking wave

Although water on Lake Superior and Lake Michigan is six to eight inches higher than last summer, it is still below the long-term average level. The continued low levels increase the chances of dangerous breaking waves forming outside of harbor entrances, according to Philip Keillor, University of Wisconsin Sea Grant coastal engineering specialist.

Breaking waves are most likely to occur in approaches to harbors whose channels are too shallow for large ocean freighters and lakers, Keillor said. Some breaking waves can develop very quickly and, for a few seconds, can be nearly vertical walls of water, Keillor said.

"In just a couple hours, wave heights out on the lake can go from a couple of feet to nine feet or more," Keillor said. "When waves that high reach shallow harbor entrances, they can form breakers and present a danger of capsizing to recreational boaters."

Boaters should carry marine radios and watch the weather closely, Keillor said. They should return to shore before large waves develop. If breaking waves do form outside a harbor they wish to enter, they should go to the nearest harbor with a wave-sheltered entrance or with deeper water in the entrance and less chance of large breaking waves.

For further information, contact Keillor at (608) 263-5133.

By Sea Grant Staff
June 2002

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