A rain garden is a ground depression allowing water runoff from rain events and snow melt to absorb into the soil instead of in the street to storm drains. The plants that are typically involved include native perennials and grasses designed to store runoff, absorb water, and remove sediment and pollutants.
Rain gardens can be beneficial to neighborhood landscapes by absorbing stormwater runoff and allowing the runoff to percolate through the soil media. This process helps remove the pollutants and slow down runoff. Slowing down runoff alone is a major advantage that rain gardens offer on top of improving the water quality in the process. The less runoff that makes it way to creeks and streams means less chances for flooding and stream bank erosion. Along with being a beneficial solution to retaining storm water runoff, rain gardens are also an attractive alternative to stand alone grass landscaping and can offer the opportunity to feature a variety of plantings with qualities to store water, remove pollutants, and provide beauty to your lawn.
Rain gardens can be an easier installation than other bioretention practices like bio cells or bioswales but will vary on the degree of difficulty depending on percolation rates of the current site. A typical rain garden design is meant for sites with percolation rates of 1 inch per hour or more and are able to allow water to drain within 12 to 24 hours.
The basic rain garden design for percolation rates of 1 inch or more per hour have flat bottoms with a layer of modified or engineered soil mix. But when rain gardens are located where percolation rates are below 0.5 inches per hour, taking 24 hours or more to drain, an enhanced rain garden design may be necessary with the inclusion of a sub drain system. In either case, it is recommended to consult an engineer or professional installer before beginning. Rainscaping Iowa is an excellent place to start your search with their list of Certified Rainscapers that have experience installing many different Best Management Practices. Find other helpful resources and design ideas in the links below.