|
Low Impact Development
LID has shown itself to be effective, flexible, economical, and aesthetically pleasing. LID works to include multiple site-specific stormwater controls that work with the natural landscape and are cost effective, in the design process. Most of the LID methods try to control runoff at the source in order to replicate the predevelopment hydrology. Controlling water at the source reduces the need for stormwater conveyances, lowering costs for developers and muncipalities. LID is a fantastic tool because it can save developers and municipalities money, increase lot values, add beauty to the site, and protect the environment. In addition, LID can be used in new developments, redevelopments, and even ultra urban redevelopments. LID for New Developments New developments, especially ones is suburban area, have more choices of LID methods. Many methods aim to reduce the amount of impervious surfaces that are created. Examples include: reducing the width of streets, reducing the size and number of parking spaces, creating alternative designs for cul-de-sacs, employing innovative development designs that increase the amount of open space, such as cluster developments, and having sidewalks on only one side of the street. All of these methods increase open space and decrease stormwater runoff, and many of them are more cost-effective than their alternatives. For example, a California study found that an excessively wide street (36 feet as compared to 24 feet) cost about $12,500 more per 100-foot section (HUD). A 130 acre development in Arkansas that was redesigned to save an additional 22 acres of open space and include LID practices ended up saving the developer $2.2 million and allowed for the creation of a neighborhood park with some of the savings (HUD). LID for Redevelopments and New Developments The city of Bellingham, Washington created two rain gardens instead of the traditional vault method of stormwater storage. Not only do they have two beautiful gardens to enjoy, but they saved $62,000 in construction costs. A developer in Maryland created bioretention areas that eliminated the need for a stormwater pond, allowed for the development of an extra six lots, and saved the developer over $4,000 per lot.
Sources/ More Information Center for Watershed Protection, Slideshows, Introduction to Better Site Design slideshow 2004. City of Portland, Sustainable Site Development: Stormwater Practices for New, Redevelopment, and Infill Projects, November, 2003. Green roofs for healthy
cities Metropolitan Area Planning Council Low Impact Development Toolkit Natural Resources Defense Council, The Problem of Urban Stormwater Pollution Natural Resources Defense Council, Low Impact Development Puget Sound Action Team, Reigning in the Rain, case study on rain gardens Rain Gardens of Western Michigan- Great source on rain gardens Roofscapes- Case studies and info about green roofs U.S. Department of Housing and Urban Development, The Practice of Low Impact Development, July 2003.
|
The
stormwater problem is largely due to developments and the excessive
amounts of impervious surfaces that are laid down. Low Impact Development
(LID) is a method of site planning that works to reduce the impacts
of development while still allowing development to occur. According
to the Natural Resources Defense Council, "LID is grounded in a
core set of principles based on the paradigm that stormwater management
should not be seen as stormwater disposal and that numerous opportunities
exist within the developed landscape to control stormwater runoff
close to the source. Underlying these principles is an understanding
of natural systems and a commitment to work within their limits
whenever possible. Doing so creates an opportunity for development
to occur with low environmental impact.
The
following methods can be used for both redevelopments and new developments
and are very common in LID projects: rain gardens or bioretention
areas, green roofs, vegetated swales, filter strips, tree preservation,
rain barrels and cisterns, permeable pavements, soil amendments
for increased permeability, impervious surface reduction and disconnection,
and pollution prevention. 
Green
roofs, such as the one on city hall in Chicago, have many benefits
including: extending the life of the roof (green roofs last twice
as long as conventional roofs), cleaning the air, beautifying the
area, reducing cooling and heating costs, increasing sound insulation,
adding open space, reducing urban heat islands, and reducing stormwater
runoff. The city of Portland, Oregon conducted a study that determined
that green roofs can capture and evaporate an average of 69% of
rainfall.