When it rains heavily in D.C., the surrounding ecosystem takes a beating.
A full 43 percent of land in the city is impervious to rainwater. As it flows down the streets, it picks up motor oil, pet waste, fertilizers, garbage, and whatever else is lying there, flushing it into the sewer. For two-thirds of the city, that all empties into the nearest river or stream, with enough force to gauge the banks of the smaller tributaries.
