Bioretention facilities or rain gardens, fulfil two main functions in urban stormwater management: flood control and pollution control. Local governments in the United States have been promoting them ever since new stormwater-discharge standards were introduced in 1987.

A rain garden is a shallow depression in the earth, landscaped with permeable soil and local plants or tress, and covered by a thin layer of mulch. It collects stormwater runoff from impervious surfaces, such as roofs and driveways, and allows it to percolate into the ground instead of draining into sewers or waterways. Rain gardens can be fitted to both individual houses and buildings. Their potential to remove pollutants and nutrients from runoff was confirmed by a recent study [1].

In 2005, Kansas City, MI, is one of the latest US cities to promote rain gardens. The city’s “10,000 Rain Gardens” programme [2] is a public-private initiative aimed at both construction and public awareness about stormwater issues. The programme is supported by Kansas City mayor, Kay Barnes, who believes it fits in with the city’s plans to overhaul and improve the ageing stormwater infrastructure.

[1] Dietz, M.E. and Clausen, J.C. (2006). Saturation to improve pollutant retention in a rain garden. Environmental science and technology ; vol. 40, no. 4 ; p. 1335-1340. DOI: 10.1021/es051644f

[2] 10,000 Rain Gardens

Web sites:

• Sanicon - Stormwater Management and Urban Drainage in Developing Countries
• Rain Gardens of West Michigan
• Rain Garden Network

Source: ENS, 27 Jun 2006 ; Lizz Thrall, American Chemical Society, 28 Dec 2005

Tags: on-site sanitation, urban wash