DEFINITION
A rain garden is a topographic depression designed to receive surface run-off. Compost-amended soil acts like a sponge holding stormwater while microorganisms and bacteria in the soil remove pollutants. Surface vegetation enhances evapotranspiration and pollution removal. Geotechnical conditions will determine whether stormwater can infiltrate or will overflow during the peak of a rain event. Even in limited spaces, small rain gardens are very efficient in improving water quality because it is the first part of the run-off that carries the majority of pollutants during a storm. After a few hours there shouldn't be any water on the soil's surface. Run-off from non-polluting surfaces typically requires only a medium of crushed rock or gravel to allow infiltration.

AKA
infiltration garden, biofiltration garden

PERFORMANCE CRITERIA
improvement in water quality and slowing of stormwater

ILLUSTRATION


CASE STUDIES
links to separate pages documenting specific places or projects where this element is on display
Oxbow Park, Seattle
Glencoe Elementary School, Portland
Cedar River Watershed Education Center, Cedar Falls
Helen Gordon Child Development Center, Portland
High Point, Seattle
New Harbor, Malmo
FUPAM, Sao Paulo
Sidwell Friends Middle School, Washington, D.C.
Mount Tabor Middle School, Portland
St. Margaret Mary School Native Garden, Chicago
Kitsap Homebuilders LID demo project, Bremerton
Northgate Green Parking Lot, Seattle
EPA Headquarters, Washington, D.C.

ADDITIONAL RESOURCES
Raingarden Network: http://www.raingardennetwork.com/
http://www.wikihow.com/Create-a-Rain-Garden (explains how to build a residential rain garden)
Washington State University Extension Rain Garden Brochure (2 page version): http://www.pierce.wsu.edu/Water_Quality/LID/Raingarden_brochure.pdf
Washington State University Extension Rain Garden Handbook (43 page version): http://www.pierce.wsu.edu/Water_Quality/LID/Raingarden_handbook.pdf
LID Center's rain garden templates for Chesapeake Bay Watershed: http://www.lowimpactdevelopment.org/raingarden_design/
American Rivers' Rain Garden Video

Raingarden at theConnectiicut NEMO project in the winter

Toronto's Green Parking Lot Guidelines

Where to place raingardens?

How to design raingardens.