According to a report due to appear in the journal Environmental Science & Technology on February 15, properly designed rain gardens can trap and retain almost all common pollutants from urban storm water runoff. The finding could have a huge impact on improving water quality and ensuring that potentially harmful pollutants are remediated into less harmful compounds.
Most important, however, is that rain gardens are affordable and easy to design, say the authors, Michael Dietz and John Clausen of the University of Connecticut.
The gardens mimic the natural water cycle that existed before roads and other impervious surfaces. As the water collects and soaks into the rain garden, it infiltrates the ground rather than draining directly into sewers or waterways.
More than half the rainwater falling on a typical city block leaves as runoff, according to EPA info, this runoff contains metals, oils, fertilizers and putatively harmful particulate matter. The Connecticut team reckons shallow depressions in the earth landscaped with hardy shrubs and plants such as chokeberry or winterberry surrounded by bark mulch – so-called rain gardens – offer a very simple and esthetically pleasing solution to this problem.
A PDF file explaining more about rain gardens was previously available at http://cleanwater.uwex.edu/.