They’re called rain gardens, bio-swales or simply swales, but they all do the same thing. These bowl-shaped landscaping wonders are designed to capture and absorb rainfall or snowmelt that is collectively referred to as “stormwater.”

just after planting in October 2010

Placing plants in future rain garden Oct. 2011

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When stormwater runs off impervious surfaces (including compacted soils), it accumulates pollutants and delivers them to existing water bodies, either directly or via a storm drain. Stormwater pollutants typically include sediment; nutrients (nitrogen and phosphorus); bacteria from animal waste; and oil, grease, and heavy metals from cars. Stormwater also causes increased flooding resulting in erosion.

However, if captured by a rain garden, the damaging effects of stormwater are mitigated.

The rain garden functions as a soil and plant-based filtration device that removes pollutants through a variety of physical, biological and chemical treatment processes.

Why are rain gardens important? As towns grow, increased stormwater run-off from impervious surfaces becomes an even greater problem. By reducing stormwater runoff, rain gardens can be a valuable part of changing these trends. While an individual rain garden may seem like a small thing, collectively they produce substantial neighborhood and community environmental benefits. They also provide a  valuable habitat for birds, butterflies and many beneficial insects.

It was a packed house when Kate Venturini, Landscape Restoration Specialist at the University of Rhode Island Landscape Restoration Program, spoke at the TWI-sponsored workshop on Bioswales also known as Rain Gardens. When on the Vineyard for the workshop, Kate gave her seal of approval for the Bioswale TWI created at the base of Owen Little Way which helps filter out polluting elements from storm water runoff from reaching the harbor. To learn more about Bioswales and other steps homeowners can take to combat the damaging effects of storm water runoff, view Kate’s comprehensive website: and watch the video where Kate shares her knowledge of coastal landscape management on PBS’s This Old House. Kate was a member of the team for TOH’s Barrington, RI project:,,20573591,00.html

Kate Venturini’s power point presentation on how to create and maintain an effective bioswale or rain garden.