Stormwater Runoff from Developed Lands

Moore, J. (2016) Stormwater Runoff from Developed Lands. Vermont Journal of Environmental Law, 17(4), 766-784.

Polluted runoff often occurs anywhere people use or alter the land. Much of the pollution problem in the developed—especially urban— landscape is caused when untreated runoff from hard—or impervious— surfaces such as rooftops, patios, sidewalks, driveways, parking areas, and roadways cannot seep into the ground and instead is conveyed directly to the nearest stream via ditches and storm drains. In Vermont, about ninety percent of our annual storm events result in one inch or less of rainfall. Although such individual storm totals may sound modest, a one-inch rainstorm over one acre in an urban setting with a high percentage of impervious surfaces can produce upwards of 25,000 gallons of runoff compared to only about 2,000 gallons of runoff in a forested environment. Further, a significant body of research has shown that, across a variety of climates and ecologies, once ten percent of a watershed’s area is covered with impervious surfaces, receiving waters show clear signs of declining health – including impacts to hydrology and flow regimes, channel stability, in-stream habitat, water quality, and biological diversity.