9 inches of rain flood thousands of Chicago basements

Heavy rains that flooded Chicago neighborhoods, rendered freeways impassable and wreaked havoc on NASCAR street races downtown Sunday are serving as stark reminders of urban centers’ vulnerability during extreme weather events.

Warmer air over metropolitan areas combined with many square miles of concrete add up to intensifying storms that generate billions of gallons of run-off rainfall with nowhere to go, stressing cities’ sewer systems, experts say. In major cities, extreme weather causes water and debris to flow into homes, businesses, and underground train systems.

Cities like Chicago will have to look for new ways to mitigate flooding, said Max Berkelhammer, an associate professor in earth and environmental sciences at the University of Illinois-Chicago.

“That’s really where the challenges are,” Berkelhammer said. “You can build a lot of infrastructure but in a city like Chicago, in a storm like yesterday, you have to find a place for (the run-off) to go.”

Sunday’s flooding was caused by a storm system that stalled over the northeastern corner of Illinois. Instead of moving east over Lake Michigan, the storm pinwheeled around Chicago, dumping as much as 9 inches of rain in some areas over the course of Sunday afternoon.

Ed Staudacher, assistant director of maintenance and operations for the Metropolitan Water Reclamation District of Greater Chicago, said so much run-off flowed into the city’s sewer system that it filled one of the city’s three reservoirs with almost 5 billion gallons of water.

The Chicago River rose six feet during the storm, forcing workers to close a series of locks and reverse the river’s flow from west to east into Lake Michigan to prevent more flooding, he said. The mayor issued a statement asking people to refrain from taking showers and washing dishes to prevent even more run-off from filling the sewers.

Still, three feet of water poured into thousands of basements on the city’s west side, said Rich Guidice, Mayor Brandon Johnson’s chief of staff.

Portions of some interstates crossing the city were closed due to flooding. Low-lying streets, especially under overpasses, became ponds too deep to cross with a car. NASCAR cancelled a downtown Xfinity Series race that was slated for Sunday morning — and delayed the start of a Cup Series race set to follow that afternoon.

Chicago is expanding the reservoir that caught Sunday’s rain, with completion set for 2029.