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Low Impact Development (LID) – a site-based design approach to going ‘green’ Posted: November 18th, 2009 Tags: bioretention, Design, Landscape Architecture, LEED, LID, Stormwater, Sustainability, Trends Robin Pelensky, Landscape Designer, LEED® Accredited Professional Low impact development (LID) strategies and techniques are green, clean and lean — three good reasons why developers, municipalities and homeowners are turning to landscape architects for a more sustainable approach to conventional stormwater management.
A bioswale cross section with an underdrain. Surface runoff from the adjacent impervious area enters the swale through a gravel strip and then flows through vegetative buffers along the edge of the bioswale. Image from UF IFAS Extension Bioswales Fact Sheet
Unlike conventional solutions, LID is a cost-effective design approach that uses a variety of creative strategies to generate less and cleaner stormwater runoff from developed land. Rather than employing the traditional stormwater management approach that uses costly pipes and acres of stormwater ponds to deal with runoff, LID uses small-scale treatment systems to treat and infiltrate stormwater runoff close to where it originates. Some of the most common LID practices include:
The benefits of Low Impact Development are many. For starters, LID is definitely green. LID systems and practices preserve and recreate natural landscape features. That translates to less impervious surfaces and more groundwater recharge. Rather than getting rid of stormwater as quickly as possible, LID practitioners find ways to harvest it on site, use it for irrigation, or call attention to its value and function through ornamental water features. In essence, LID treats stormwater as a resource rather than a waste product.
An on-site design feature, this fountain in an office plaza is also a rainwater conveyance and filtering system. Image from Landscape Architecture Magazine, 9/2006
LID design practices are recognized as vital features of sustainable site development by several green building certification programs including the Florida Green Building Coalition, the Sustainable Sites Initiative, Green Globe, Inc., NAHB National Green Building Standard, Florida Yards & Neighborhoods, and the U.S. Green Building Council. LID inspired LEED credits have been earned for stormwater management, wastewater and energy reduction, reduction of heat island effect, maximizing open space, protection and restoration of habitat, recycling and water efficiency, among others. That brings us to LID’s second attribute – it‘s all about being clean. Because the goal of LID is to mimic natural site hydrology, LID focuses not just on water quantity, but also on water quality. Stormwater planters, bio swales, rain gardens and other LID practices have been proven to improve water quality by filtering out pollutants through the use of natural processes. The Florida’s DEP and the South Florida Water Management District are currently drafting new statewide stormwater rules that will include Best Management Practices including LID technologies to achieve better water quality solutions. On a recent visit to the Florida Aquarium in Tampa, I took a few photos of the 11.5-acre parking lot, the site of a stormwater research/demonstration project since 1993. The original concrete and asphalt parking lot was modified by installing a variety of LID techniques including end-of-island bioretention cells, permeable pavers, and bioretention strips between parking stalls. After monitoring dozens of rainfall events, results showed that the LID practices achieved 60-90% reduction in runoff volume, and, at the same time, removed more than twice the amount of harmful pollutants and suspended solids compared with conventional stormwater management techniques (www.lowimpactdevelopment.org).
The experimental parking lot at Tampa’s Florida Aquarium features bioretention areas and other LID techniques. This rain garden captures stormwater, filters pollutants, and helps to educate visitors about the importance of keeping Florida’s water sources clean.
Finally, LID can be lean on the wallet because LID typically reduces the amount of impervious cover and storm structures needed leading to reduced infrastructure costs. For the developer of the 130-acre Gap Creek subdivision in Arkansas, the decision to commit to a LID design approach meant considerably less site clearing and grading, as well as less drainage infrastructure. Streets were designed to flow with the existing landscape, native vegetation was preserved and street right-of-ways were reduced to 27 feet (www.nrdc.org). Additional economic benefits were realized including lower landscaping and maintenance costs, more common open space and recreational areas, a higher lot yield, and in the end, larger profits. By reducing land use requirements for stormwater control, and by reducing the need for heavy maintenance equipment, LID practices can actually offset or even reduce the costs of conventional stormwater systems. Developers of urban sites can even benefit from utilizing LID techniques in sidewalks, parking lots, rooftops and other small outdoor spaces by reducing or avoiding paying stormwater mitigation fees. For those who need an LID primer, I recommend the Low Impact Development Center’s website: www.lowimpactdevelopmentcenter.org. You’ll find a wealth of information on LID including definitions, case studies, images as well as upcoming LID workshops and conferences. Formed just over 10 years ago by a small group of researchers, the LID Center is dedicated to sharing best design strategies and techniques for effective and common-sense stormwater management. It’s easy to see why Low Impact Development has a lot of things going for it. It’s green, clean and lean – almost sounds like an advertisement for the times we’re in. It also looks good, but that topic deserves a blog of its own. Comments Leave a Comment |
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