Rain gardens are an attractive green solution to reduce storm water pollution and improve overall water quality. Storm water becomes polluted when it runs over pavement and comes into contact with automotive fluids, sediment, trash, pet waste, etc. Ordinarily, this storm water "runoff" flows directly to rivers, lakes and streams without treatment. By directing storm water runoff to a rain garden filled with native plants, pollutants can be absorbed by the deep plant roots instead of contaminating our rivers, lakes and streams.
There is a growing trend by municipalities and homeowners to incorporate natural processes to help relieve flooding andpollution. One way is to incorporate a rain garden.
A rain garden is a shallow depression that is planted with deep-rooted native plants and grasses.
It can be thought of as a water quality system because it filters the runoff from roofs and lawns and recharges the groundwater.
Rain gardens can make a big difference in the water quality and environment in the surrounding area. When it rains, impervious surfaces such as roads, sidewalks, and roofs not planted with gardens, trees, or turf, produce runoff that goes straight into storm sewers. The problem with this is that many North American cities have combined sewer systems, through which some storm drains carry water to treatment plants, while water from other storm drains wash directly into local waterways. The Environmental Protection Agency (EPA) estimates that pollutants in storm water runoff are responsible for about 70 percent of all water pollution in lakes, rivers and creeks. Fifty percent of that pollution is chemical pollution such as oil, salt, fertilizer, pesticides, pet waste, transportation chemicals, and sediment.
A rain garden can capture that runoff and hold not only thousands of gallons of rainwater that can be used in a garden and yard, but all of the pollutants that contaminate the waterways. The soil, plants, and mulch in a rain garden break up the pollutants and make them inert, while irrigating nearby plants and trees, breaking up hard soil and infiltrating water and nutrients deep into the soil.
Additionally, rain gardens are beautiful, creating habitat for birds and beneficial insects, reducing pest and harmful insects, and can be used to teach people about nature.
Rain Garden Necessities
Whether you’d like to plant your rain garden in a small space of land between a building and a sidewalk, or as part of a larger yard, there are fundamentals to rain garden construction.
- The garden should be positioned near a runoff source like a downspout, driveway or sump pump to capture rainwater runoff and stop the water from reaching the sewer system.
- Do not plant your rain garden in an area where water already pools. The goal of a rain garden is to encourage infiltration. Small pools of water in your garden or yard are a sign of slow infiltration.
- Rain gardens need to be constructed to drain within a few hours from an inch of rainfall. This is to protect the health of the plants while absorbing the water, and mosquito concerns.
- The soil in which the garden is planted must be lightweight and porous, so it will likely need to be amended prior to planting. Leaf compost, sand, vermiculite, and loamy soil additions are good mixtures for rain gardens.
Plants for Small Rain Gardens
It is best to use native, non-invasive species that are resistant to the stress from both brief periods of pooling as well as dry periods between rainfall events. A variety of plants with large root structures makes a rain garden more effective and less susceptible to disease. It is also better to use plants with a developed root structure instead of starting plants by seed. Seeds will have a hard time establishing in the conditions of a rain garden, and leave the soil exposed and prone to erosion.
To see a rain garden doing its thing, visit Pelion Community Garden on Best Street. With the help of the Community Foundation for Greater Buffalo and volunteers, Groundwork Buffalo and City Honors School have installed a rain garden in the rear of a four-lot garden.
Reference & Additional Sources:
- Philadelphia Water Department - http://phillywatersheds.org/what_were_doing/green_infrastructure/tools/rain_
- Rain Garden Design Templates - http://www.lowimpactdevelopment.org/raingarden_design/whatisaraingarden.htm
- Rain Garden Network - http://www.raingardennetwork.com/whyplantraingarden.htm