The researchers studied how adding more impermeable surfaces like pavement affects stormwater runoff in cities. They tested different ways to manage stormwater, like using low impact development (LID) techniques. Their computer models revealed that using LID methods can help reduce stormwater issues, but even the best methods couldn't bring runoff levels back to what they were before development. This means that there's still work to be done to manage stormwater effectively in urban areas with a lot of hard surfaces.