What you need to know about lakeshore flood warnings

Plastic flood protection sandbags stacked into a temporary wall along lakeshore Photo by Artem Zavarzin/Shutterstock

Given last year’s historic flooding, we lakeshore residents can be forgiven for being a bit jittery as we move into flood season. Those of us on the Great Lakes particularly so, with news that levels on lakes Michigan, Superior, Huron, and Erie are already very near their all-time record high for spring.

Both Environment Canada and the National Weather Service in the United States monitor water levels and issue flood warnings and watches, though many of us of aren’t exactly sure what those mean.

Michael Fries, a Warning Coordination Meteorologist with the National Oceanic and Atmospheric Administration in Buffalo, New York, is happy to explain what we need to know as we adjust to this new normal of higher-than-average water levels.

“For the past three years, the highs that we’re seeing have exceeded any historical high that we’ve seen on the Great Lakes,” says Fries. It’s more important than ever, he says, for people to manage their shorelines in a way that mitigates erosion, primarily by ensuring it’s a natural shoreline, not a hardened one.

A Lakeshore Flood Watch is “issued farther ahead of time and with less confidence,” explains Fries. “We have to have 50 per cent confidence that lakeshore flooding will start to occur in a two- to four-day timeframe. A Lakeshore Flood Warning is issued when the National Weather Service has 80 per cent confidence that it will occur.

What both Environment Canada and the National Weather Service are watching for is a combination of water level and wave action.

“We take the combination of the lake level [how much above or below sea level it is], plus the wave forecast to determine whether we’re going to issue lakeshore flood watches or warnings. We essentially try to highlight the time when the overlay of those two things will be the worst and do the most damage,” says Fries.

Expect to see more warnings and watches, he says, because the water levels are already so high. “We don’t need waves as large as we would…to cause lakeshore flooding problems.”

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