A little farther south, 810 square miles were submerged along the Baraboo River, closing Interstate 90-94-39 for days and causing millions of dollars in property damage.

What if that storm had been centered over Lake Mendota where the Tenney dam and earthen embankments separate the lake from the Isthmus?

Potter’s analysis found that enough water would have accumulated for the lake to top the dam by 3 feet. The water would have then rushed downstream at a rate of 3,400 cubic feet per second — five times the normal rate – and far more than the Yahara River could contain.

Potter didn’t examine how much property damage might have been caused, or how long it might have taken the water to drain downstream, but UW-Madison research done subsequently showed portions of the Isthmus would have been inundated.

Since the 2008 rain events, Dane County and the university have developed an advanced system for monitoring weather and water levels that helps in managing the lakes by adjusting flows through three dams.

Madison and other communities continually replace and improve stormwater systems, but Potter is concerned that it may not be enough.