How can a rain garden help?

Increased development and impervious surfaces like roads, rooftops and parking lots are reducing the amount of water that can be absorbed by the ground and increasing the amount of contaminants that wash off these surfaces into near by stormwater collection systems and ultamately into our rivers, lakes, streams and ocean. Contrary to popular belief, stormwater does not get diverted to a water treatment facility. Pollutants like car oils, grease and fertilizers that are common products generated by households and commercial sites, get picked up by stormwater and literally dumped directly into our waters. One natural way to reduce this threat to our water and the ecosystems that rely on it is to use rain gardens.

Rain gardens are shallow, generally flat bottomed depressions, designed to collect rainwater and allow selected plants, bacteria and soils to naturally filter and remove pollutants from the water as it soaks into the ground. Rain gardens can allow an estimated 30 percent increase in water absorption into the ground, compared to conventional urban landscapes. Not only do rain gardens provide a line of defense for our waters by increasing ground water absorption and reducing stormwater pollution, but they also serve as beautiful features to the landscape.

 

The effectiveness of a rain garden in removing pollutants

Pollutant	Source of pollutant	% Removed by rain garden
Copper	Roof shingles, oil, grease, soil	43-97%
Lead	Roof shingles, oil, grease, soil	70-95%
Zinc	Roof shingles, oil, grease, soil	64-95%
Phosphorus	Detergents, fertilizers, pet waste	65-87%
Total nitrogen	Fertilizer, pet waste, organic matter	49-67%
Calcium	Fertilizer, pet waste, organic matter	27%

Source: U.S. EPA on National Pollutant Discharge Elimination System storm water program

To learn more about the potential benefits of a rain garden in your yard or place of business, please visit Clemson University’s non-point source toolbox at http://www.clemson.edu/public/carolinaclear/cc_toolbox/, where you can find information on how to construct a rain garden, what native plants work best and the rain garden manual itself.

See also “What Can I Do? Build A Rain Garden!” for more information on how to be proactive in preventing stormwater pollution and rain gardens
Resource: Rain Garden Presentations