Rain gardens are a phenomenon I was unfamiliar with until a recent encounter with the Bronx River Houses, a development that’s part of the New York City Housing Authority. Last fall, NYCHA and the NYC Department of Environmental Protection teamed up to help solve the problem of flooding and pollution of the Bronx River by stormwater overflow. The two public entities cooperated and spent $1 million on updates to include a blue roof, stormwater chambers, a perforated pipe system, and the rain garden. All these improvements work to divert and absorb water that might otherwise overwhelm the sewer system and flood into nearby waterways. The rain garden and other project elements are evidence of the commitment to environmental sustainability that NYCHA Chairman John B Rhea has promoted as part of Plan NYCHA, the Authority’s roadmap to preserve public housing.
So what is a rain garden, exactly? Rain gardens are designed to improve the water quality of neighboring bodies of water that are often polluted by runoff. A shallow depression is made in the ground and planted with wetland vegetation like small trees, wildflowers, sedges, rushes, ferns, and shrubs that drink up excess water flowing into the garden. Water caught in the rain garden also filters through layers of soil before reaching the groundwater system, and is “cleaned,” in a sense by the time it gets there. Rain gardens are often built near runoff sources such as downspouts or driveways. At the Bronx River Houses, the water is infiltrated and cleaned in shallow basins or swales that can store more than 18,000 gallons of rainwater from surrounding grassed and paved areas. Basins and swales contain a mix of engineered sand and stone that provide temporary storage space for stormwater before the water is naturally absorbed by the ground instead of entering the sewer system.
The Bronx River Houses rain garden not only helps as a stormwater solution, but also adds green space to the neighborhood, improving both the natural environment and the aesthetics. You can read more about the Bronx River Pilot Project on the NYCHA website, and more about NYCHA’s Green Agenda at GreenNYCHA.