• Urban hydrology;
  • flood impacts;
  • urban-induced rainfall


A record setting 24-hour rainstorm hit Chicago in September 2008. It created an opportunity to assess its impacts and to compare the storm water management with that used in other recent rainstorms. Flooding impacted all forms of transportation and thousands of homes and businesses, 10,000 homes had to be evacuated. One lesson learned is that this storm's magnitude was enhanced by urban and lake influences on the atmosphere that extended over the large suburban areas west of the city. This helped intensify the rainfall over a large area. A second lesson learned is when 6-hour and 24-hour rainfall amounts exceed once-in-25-years recurrence values, the water management facilities cannot handle the large volume of water. Hence, major diversions of flood waters were needed to be made into Lake Michigan and the Illinois River.