Do you ever think about what happens to a drop of rain that falls onto the ground? It may land on a tree and evaporate; it may land on a farm field and be absorbed into the soil; or it may land on a rooftop, driveway or road and travel down the street into a stream or storm drain.
Any precipitation in an urban or suburban area that does not evaporate or soak into the ground, but instead pools and travels downhill, is considered stormwater. Stormwater is also referred to as urban stormwater, runoff and polluted runoff. Increased development across the Bay watershed has made stormwater runoff the fastest growing source of pollution to the Bay and its rivers.
Stormwater picks up nutrients, sediment and chemical contaminants as it flows across roads, yards, farms, golf courses, parking lots and construction sites. This polluted runoff travels into storm drains and local waterways that eventually drain into the Bay.
Sources of pollution from urban and suburban runoff include:
When it rains, water either runs off the land or filters into the ground. In urban and suburban areas, where roads, rooftops, parking lots and other impervious surfaces are common, most stormwater runs off the hardened surfaces and into local streams and storm drains, and eventually to the Bay.
Development activities like clearing vegetation, mass grading, removing and compacting soil, and adding impervious surfaces have increased stormwater runoff in the Bay watershed.
Stormwater from urban and suburban areas contributes a significant amount of pollutants to the Bay. Every time we drive our cars, fertilize our lawns, leave pet waste on the ground or forget to fix car leaks, we contribute to pollution in our local rivers, streams and the Bay.
Impervious surfaces are paved or hardened surfaces that do not allow water to pass through. Roads, rooftops, sidewalks, pools, patios and parking lots are all impervious surfaces. Impervious surface data is used to measure the rate of development across the watershed, as well as to identify high-growth areas and potential sprawling development patterns.
Impervious surfaces that replace natural, vegetated areas do not allow precipitation to soak into the soil. Instead, water runs off the hardened surfaces and into sewers, local rivers, streams and the Bay.
As more land is covered by impervious surfaces, more polluted runoff enters our rivers, streams and the Bay. When as little as 10 to 15 percent of a small drainage area is impervious, there are measurable impacts on water quality and aquatic species. As development and urbanization have increased, stormwater has become the fastest growing segment of pollution in the Bay watershed.
Between 1990 and 2007, impervious surfaces associated with growth in single-family houses are estimated to have increased by approximately 34 percent while the Bay watershed population increased by only 18 percent. This increase in impervious cover indicates that our personal footprint on the landscape is growing.
Urban and suburban lands—developed lands that range from major cities to small, single subdivisions—are a major source of pollution to the Bay. Everything we do on the land—from driving our cars to fertilizing our lawns—has an impact on the health of the Bay and its tributaries. Because of rapid population growth and related development, nitrogen, phosphorus and sediment from urban and suburban lands is the only pollution category in the Bay watershed that is still growing.
The Green Streets, Green Jobs, Green Towns initiative supports grassroots-level green development.
Nutrient pollution and floating trash posed problems for the Harbor in 2012.
The "rain tax" funds practices that mitigate the harmful effects of impervious surfaces.
Stormwater runoff is a source of pollution for the Maryland waterway.
Potomac Conservancy calls for the reduction of runoff in river report card.
When rainfall runs across roads, lawns and golf courses, it can pick up pollutants before it enters local waterways. Mike Fritz from the Chesapeake Bay Program explains why so-called “stormwater runoff” is a major source of pollution to the Chesapeake Bay and what we can do to prevent it.
Produced by Matt Rath
Music: “A Moment of Jazz” by Ancelin
Publication date: May 27, 2009 | Type of document: Policy Memorandum | Download: Electronic Version
Letter from Chesapeake Bay Leadership to Congress to Reduce Polluted Runoff from Federal Highways
Publication date: December 03, 2001 | Type of document: Directive | Download: Electronic Version
Increased population and development within the watershed have created projections regarding urban and suburban growth and the increase of imperviousness in the watershed, managing stormwater runoff is an important activity for reducing…
Publication date: August 01, 1987 | Type of document: Report | Download: Electronic Version
This is a report on vegetative filter strips for agricultural runoff treatment