Rain gardens are designed to mimic the natural water retention of undeveloped land and to reduce the volume of rainwater running off into drains from impervious areas and treat low level pollution.
Rain gardens were first developed in the United States in the 1990s, where they have become increasingly popular. In the UK, the mimicking of natural drainage in urban areas is officially encouraged and known as Sustainable Drainage Systems (SuDS). This approach is part of a new philosophy to urban water management, developed in Australia, which is known as Water Sensitive Urban Design (WSUD).
For more information please check: Rain garden GUIDE.