Researchers have concluded that when two to 10 percent of a stream or river's drainage area is covered in hardened surfaces—roads, roofs, parking lots, and other developed surfaces that rain cannot penetrate—fish and amphibians begin to disappear.
In the Mid-Atlantic region, suburban and urban runoff is responsible for thousands of miles of waterways that are so polluted they are legally "impaired" under the federal Clean Water Act. This includes 2,451 miles of rivers and streams in Pennsylvania and 2,590 miles in Maryland (numbers are not available for Virginia).
Here are just three examples of local streams in the Bay region whose aquatic life is at risk because their watersheds are at least four to nine percent covered.
HARFORD COUNTY, MD:
The Bynum Run/Bush Creek Watershed northeast of Bel Air is at least nine percent covered in pavement, roofs, and other developed surfaces.
CUMBERLAND COUNTY, PA:
The Hogestown Run and Wertz Run Watersheds west of Harrisburg are at least five percent covered.
ALBEMARLE COUNTY, VA:
The South Fork Rivanna River Watershed north of Charlottesville is at least five percent covered.
