Rain Gardens
A Nature-based Practice for Reducing Pollution and Flooding
Rain gardens are simple, low-cost, effective—and beautiful–ways to reduce the polluting effects of water runoff. Simply stated, a rain garden is a shallow depression on a slope that has been planted with native plants. It is designed to temporarily hold and soak up rainwater.
When rainwater flows off roads, driveways, parking lots–and even lawns–it takes with it pollutants that eventually end up in our rivers, streams, and oceans. These pollutants are typically substances such as oil, grease, pet waste, and fertilizer. But rainwater that flows into a rain garden is trapped and filtered, removing pollutants. The water in the rain garden pools and soaks into the ground in less than 48 hours, preventing the shallow depression from being a home to mosquitoes.
As a nature-based practice, rain gardens rely on natural processes. In addition to reducing and filtering runoff, rain gardens enhance habitat for native plants and animals. These gardens can help promote important pollinators and beneficial insects using attractive plants, such as Butterfly Milkweed, Scarlet Bee Balm, and Purple Coneflower. What’s more, deep rooted plants hold the soil in place and soak up more water than shallow root systems of lawn grasses.
Salem Sound Coastwatch promotes rain gardens for municipalities and individuals. We do outreach and education on how rain gardens support a healthier watershed and provide resources. We work with municipalities to identify locations where rain gardens can have the most impact, assist in finding funding, design, permitting, construction, planting, and maintenance. Salem Sound Coastwatch volunteers play a critical role in the planting and maintenance of these municipal rain gardens.
Commercial Street Rain Gardens, Salem
Salem Sound Coastwatch worked with the City to obtain funding, design, and construct a series of rain gardens along the North River. These rain gardens absorb pollutants before they reach the river. When the tidal river overflows its banks, the gardens slow the flooding of the street.
In 2024, Salem Sound Coastwatch completed a case study on the Commercial Street Rain Gardens, a project funded by the MA Office of Coastal Zone Management. This project highlighted the rain gardens along Salem’s North River with two how-to videos produced by SSCW and documentary filmmaker Perry Hallinan. The videos discuss the polluted history and recovery of the North River, as well as how the rain gardens help to capture and filter stormwater runoff before it enters the river. They also outline how the rain gardens were constructed and how they are maintained. Salem Sound Coastwatch shares lessons learned from the construction of the rain gardens to make future green stormwater infrastructure projects successful. This resource increases the capacity for municipalities to address non-point source stormwater pollution and promotes the use of green infrastructure in urban areas to improve equity and access to clean coastal waters. The Story Map below pairs with the videos and provides additional resources for municipalities considering green stormwater projects.
Building Rain Gardens to Treat Stormwater
Rain Gardens at Work
Winter Island Park Rain Garden, Salem
This video shows the construction of the the rain garden at Winter Island Park. When Salem Sound Coastwatch saw the pollution running off the parking lot after a July thunderstorm, we worked with the City of Salem to fix the problem. We helped find the funding to build a large rain garden and one smaller one. When one inch of rain falls over 30,000 gallons of water flows into the rain gardens because the buildings, pavement, and compacted soils are hard or impervious surfaces, which prevent the rain from soaking into the ground. Now it soaks in through the rain gardens. The average yearly rainfall for Salem is 47 inches. That means this rain garden will remove pollutants from over a million gallons per year that would, otherwise, go into the ocean.