Chicago was recently used as an example of a city that is so paved over it can't drain properly. http://www.theatlanticcities.com/neighborhoods/2013/05/way-w... I wonder if that's a valid interpretation, given its natural drainage problems?
Oddly though flooding in the city proper where there building density is high is generally not a problem. This past year when we had very heavy rains, it was the northern suburbs that had real get out your boat type flooding.