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The Effects of Rain Garden Size on Hydrologic Performance
STANDER, E., M. BORST, T. O'CONNOR, AND A. ROWE. The Effects of Rain Garden Size on Hydrologic Performance. In Proceedings, World Environmental & Water Resources Congress 2010, Challenges of Change, Providence, RI, May 16 - 20, 2010. Environmental & Water Resources Institute (EWRI) of ASCE, Reston, VA, 3018, (2010).
To inform the public.
Rain gardens are vegetated depressions designed to accept stormwater runoff. Manuals and guidance documents recommend sizing rain garden cells from 3% to 43% of the associated drainage area, based on factors including soil type, slope, amount of impervious cover in the drainage area, and distance from the runoff source. This wide range in sizing recommendations provides little guidance to designers and urban planners grappling with finding locations for rain garden installations where available land is both scarce and expensive. Few studies have specifically evaluated hydrologic performance of rain garden cells with regard to their surface area. EPA’s National Risk Management Research Laboratory constructed six rain garden cells of three sizes at the Edison Environmental Center to accept stormwater from equal drainage areas. Cells were instrumented with sensors to quantify the magnitude and timing of the wetting front and detect mounding of infiltrating water at several depths, thus allowing for a systematic analysis of hydrologic performance with rain garden size. Preliminary results indicate that the size and timing of the wetting front, as detected by time domain reflectometers, was not significantly different among rain garden size classes. There were significant differences between the engineered rain garden media and the underlying soil in responses to rain events.
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