Polluted runoff from the road sweeps into a stream. Photo by Jeff Rogge/CBF Staff
Map: Pavement and Other Hardened Surfaces in the Bay Watershed
This aerial image (below) shows the locations of roads, roofs, parking lots, and other developed surfaces that rain cannot penetrate.
Researchers have concluded that when two to 10 percent of a stream or river's drainage area is covered in hardened surfaces, fish and amphibians begin to disappear.
There are local streams in the Bay region whose aquatic life is at risk because their watersheds are at least four to nine percent covered. See three examples.