Low impact development

Low Impact Development (LID) is a term used in the United States to describe a land planning and engineering design approach to managing stormwater runoff. LID emphasizes conservation and use of on-site natural features to protect water quality. This approach implements engineered small-scale hydrologic controls to replicate the pre-development hydrologic regime of watersheds through infiltrating, filtering, storing, evaporating, and detaining runoff close to its source. [Prince George's County, Maryand. Department of Environmental Resources. Larry Coffman et al. [http://www.epa.gov/owow/nps/lidnatl.pdf "Low-Impact Development Design Strategies, An Integrated Design Approach."] Published by U.S. Environmental Protection Agency, Washington, D.C. Document No. EPA 841-B-00-003, June 1999.]

LID is similar to Sustainable urban drainage systems (SUDS), a term used in the United Kingdom, and Water Sensitive Urban Design (WSUD) [http://wsud.melbournewater.com.au/] , a term used in Australia.

Alternative to Conventional Stormwater Management Practices

A concept that began in Prince George's County, Maryland in 1990, LID began as an alternative to traditional stormwater best management practices (BMPs) installed at construction projects. [Prince George's County, Maryland. Department of Environmental Resources. 1997. Landover, MD. "Low Impact Development Design Manual."] Officials found that the traditional practices such as detention ponds and retention basins were not cost-effective and the results did not meet water quality goals. The Low Impact Development Center, Inc., a non-profit water resources research organization, was formed in 1998 to work with government agencies and institutions to further the science, understanding,and implementation of LID and other sustainable environmental planning and design approaches, such as Green Infrastructure and the Green Highways Partnership.

The LID design approach has received support from the U.S. Environmental Protection Agency (EPA) and is being promoted as a method to help meet goals of the Clean Water Act. [U.S. Environmental Protection Agency. Washington, D.C. [http://www.epa.gov/owow/nps/lid/lid.pdf "Low Impact Development (LID): A Literature Review."] October 2000. Document No. EPA-841-B-00-005.] Various local, state, and federal agency programs have used materials supplied by the LID Center (a non-profit group dedicated to advancing the practice). LID techniques can also play an important role in Smart Growth and Green Infrastructure [http://www.todaysgreenconstruction.com/2008/07/low-impact-developments-lid-are-green.html land use planning] .

Typical LID Practices and Controls

Planning practices include several related approaches that were developed independently by various practitioners. These differently-named approaches include similar concepts and share similar goals in protecting water quality.
*Conservation design, also called Conservation Development
* [http://www.cwp.org/Resource_Library/Better_Site_Design/ Better Site Design]
*Green Infrastructure.

Planners select structural LID practices for an individual site in consideration of the site's land use, hydrology, soil type, climate and rainfall patterns. There are many variations on these LID practices, and some practices may not be suitable for a given site. Many are practical for retrofit or site renovation projects, as well as for new construction. Frequently-used practices include:
*Bioretention cells, also known as rain gardens
*Cisterns and rain barrels
*Green roofs
*Permeable paving, also called "porous pavement"
*Grassed swales, also known as bioswales. [U.S. Environmental Protection Agency. Washington, DC. [http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm?action=factsheet_results&view=specific&bmp=124 "Fact Sheet: Low Impact Development and Other Green Design Strategies."] June 1, 2006.]

Benefits of LID

*Habitat protection
*Improved management of water quantity (e.g. reduced risk of flooding)
*Reduction of impervious surfaces and runoff (peak flow volume and rate)
*Groundwater recharge through infiltration
*Water quality improvements
*Community value (i.e. increased aesthetics)
*Cost savings. Fact|date=March 2008

ee also

*Sustainable development
*Sustainable urban drainage systems
*Water pollution

References

External links

* [http://extension.ucdavis.edu/cwlu UC Davis Center for Water and Land Use] - Provides a map with approximately 40 case studies of LID on the west coast. Also provides a detailed stormwater calculator for development.
* [http://www.cwp.org/ Center for Watershed Protection] - Provides practical guidance for runoff reduction
* [http://www.lowimpactdevelopment.org/ Low Impact Development Center] - A water quality research organization; many links to green infrastructure, low impact development practices and projects and stormwater resources
* [http://www.stormwaterauthority.org StormwaterAuthority.org] - General reference on stormwater management
* [http://cfpub.epa.gov/npdes/stormwater/casestudies_specific.cfm?case_id=14 Case Study: Incorporating LID into Stormwater Management] U.S. EPA
* [http://www.lid-stormwater.net/] - Low Impact Development Urban Design Tools