Last week I wrote about why it can be a good idea to disconnect your home’s downspouts and consider other ways to deal with rainwater on site. Fortunately, there are several different ways to either capture or infiltrate this water and this week's post is all about rain gardens! Rain gardens are a shallow depression (6”-12” deep) with a designed soil mix and collection of plants that mimic a native forest’s drainage system by collecting, absorbing, and filtering rainwater. Unlike standard lawns, they can safely infiltrate greater amounts of water, allowing homeowners a way to redirect runoff that would otherwise go to a municipal stormwater or sewer system (bonus: they look good too!). Furthermore, when it rains, the first inch of rainfall (also called the “first flush”) picks up pollutants from roofs, driveways and sidewalks. By directing this water to a rain garden, it not only slows down absorption (preventing overflows) but it also allows the plants to help filter out some of these pollutants.
The type of plants in a rain garden can be selected based on what you like and what does well in your area, but there are three different zones that should be accommodated. Plants at the bottom of the garden should do well in wet conditions, since there can be standing water in this area. Plants on the sides of the garden should do well on slopes and tolerate semi-wet conditions, while plants at the outer edge of the garden should be drought-tolerant. Ideally, rain gardens should be located where runoff can flow freely to them, with enough space for overflow during big rainstorms. They should also be located away from utilities, big tree roots and areas of steeper slopes. Like any garden, these systems require maintenance and irrigation to establish the plants but are relatively easy to care for after the first couple of years. If you think a rain garden would be a good solution for where you live and want to take a DIY approach, check out these great resources:
- Washington State University Rain Garden Handbook
- City of Portland Plant Choices for Stormwater Management