Twenty-five years from now, rain events in Evansville, Indiana, will result in much less environmental damage than they cause today.

Instead of running off into an open sewer called Bee Slough, overwhelming the city’s wastewater treatment plants, and pouring millions of gallons of untreated water into Pigeon Creek and the Ohio River, rain events will be managed through a comprehensive overflow control program called Renew Evansville.

The plan — agreed upon by the...