The State Journal asked an unsettling question just three weeks ago, as part of the reporter Steven Verburg’s five-part series on the importance and vulnerabilities of Madison’s lakes:
“Would a massive rain flood the Isthmus?” asked a headline in the Aug. 5 edition of our newspaper.
We now know the answer.
Seven Madison streets on the Isthmus were closed on Friday because of flooding, following heavy rain that had begun Monday night. By Friday, the city was notifying some 1,700 Isthmus residents that their properties were at risk.
As much as 10 inches fell on the city’s West Side, drowning a 70-year-old man who was swept away from his car, flooding countless basements and raising lake levels to historic highs.
The one bright spot, as emergency officials and volunteers filled sandbags late last week, was that the Tenney lock and dam — which holds back water in Lake Mendota — was deemed sound and “highly unlikely” to be breached.
Yet the forecast called for 2 or 3 more inches of rain into early this week, and Lake Monona — already at its high water mark Friday — was expected to rise half a foot more by today. More than $100 million worth of damage has occurred in Dane County, much of it in the villages of Mazomanie, Black Earth and Cross Plains in western Dane County, where more than a foot of rain fell within 24 hours.
Ken Potter, a retired professor of civil and environmental engineering at UW-Madison, was featured three weeks ago in the State Journal’s five-part series, “The Yahara Lakes/Giants Among Us.” The State Journal published Potter’s startling image of what the Isthmus would look like if dozens of blocks were deluged. His work drew heavily on projections of what would happen in 14 inches of rain fell on the central city. A downpour of that size in Sauk County northwest of Madison in 2008 caused Lake Delton to breach, washing away homes and emptying the lake.
Potter’s calculations and warnings earlier this month about flooding on the Isthmus have quickly proved prophetic, even though the Isthmus missed this week’s heaviest rains.
“It could have been a lot worse,” Potter told the State Journal last week. “If you move the storm a little bit to the east — this is exactly the kind of storm I feared.”
The Isthmus is especially vulnerable to heavy rain because it is surrounded by lakes, and because its abundance of pavement and rooftops don’t absorb water. Moreover, the city and region continue to expand, which is why Potter is recommending new developments be placed under stricter stormwater regulations. Current urban-design standards essentially double the amount of water that ends up in ditches, streams and eventually the lakes, he said.
A changing climate also is producing heavier downpours, which flood our waterways with excessive phosphorus pollution from farms, lawns and construction sites. That, in turn, feeds algae and gives rise to stinky green scum in the water, harming wildlife and damaging our quality of life.
We can’t take our lakes for granted, as “The Yahara Lakes/Giants Among Us” so powerfully showed — and as the past week of flooding has only reinforced. We must protect our lakes because, ultimately, doing so protects us.