Estimating Flood Probability in Wisconsin

Challenge

When high lake levels combine with storm surge, Suamico, Wisconsin, faces significant flooding along a main road, impacting dozens of homes and the village’s only public access to Lake Michigan. In just one year, these conditions caused at least seven flooding events. Compounding the problem, a culvert designed to drain a wetland into the lake actually works in reverse during high water, sending water overtopping the road. The village identified an operable gate culvert as the best solution. However, while seeking grant funding, they quickly realized they needed to include flood probability estimates in their application.

Solution

The village enlisted the help of the Wisconsin Sea Grant program, which used NOAA’s Lake Level Viewer to quickly and easily assess the Lake Michigan water level elevations that would produce road flooding. Once Sea Grant determined these water level elevations, they used FEMA data to determine the probability of storm-induced water levels reaching this elevation. This information was then used to complete a benefit-cost analysis to complete the village’s grant application.

Screenshot from NOAA’s Lake Level Viewer showing the Lake Michigan water level at which the road would first begin to experience flooding. The white circle shows the location of the culvert that allows water to overtop the road at high lake levels. The Lake Michigan water level of this scenario is highlighted in the red box.

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