As extreme rainfall events become more common, one response is to plant rain gardens. A shallow depression filled with absorbent but free-draining soil and planted with vegetation, a rain garden absorbs runoff and prevents it from immediately draining into waterways. This helps reduce the chances of flooding.
Also known less attractively as bioretention facilities, the plants and earth hold water rather than letting it flow away as hard surfaces do. Replacing concrete and paved areas with rain gardens mitigates heavy rainfall.
Rain gardens are typically planted with a wide variety of wild species. Resistance to short periods of flooding is essential so marsh plants such as flag iris flourish better than Mediterranean species. They are low maintenance and do not usually require watering except in very dry conditions.
As a secondary benefit, a rain garden filters pollutants and prevents them from running into waterways. Pollution is a particular problem with stormwater as runoff does not soak into the ground like normal rainfall. A rain garden captures and breaks down many pollutants by natural processes.
A planted area also reduces the surrounding temperature compared with a surface such as concrete.
Many projects worldwide are encouraging the creation of rain gardens in urban areas, and converting existing green spaces into rain gardens which are attractive as well as highly functional.
