In late August, significant rainfall pummeled Madison, causing flooding throughout the city, damaging infrastructure and private residences, and costing the city millions of dollars. According to a report by Daniel Wright, assistant professor in the department of civil and environmental engineering at UW-Madison, the amount of rain that fell on the Yahara watershed was by no means historical. Rather, Wright wrote, it fell around a 30 year recurrence interval, meaning “over the course of a 30-year mortgage, a homeowner will, on average, experience one storm similar in magnitude.”
The four inches of rain that fell across the lakes produced a 100-year flood event in Madison due to the high lake levels of Lakes Monona, Mendota, Waubesa and Kegonsa — especially Lake Mendota. The Wisconsin Department of Natural Resources set the minimum and maximum lake levels in 1979. The storm on August 20 caused the lake levels to rise well above their minimums and 100-year flood levels.