Introduction to Low Impact Development
Principles of Low Impact Development
“Low impact development,” or LID, is an ecologically friendly approach to site development and stormwater management that aims to reduce development impacts to land, water, and air. It seeks to accomplish three goals at every development site: to reduce the amount of impervious cover, to increase natural lands set aside for conservation, and to use pervious areas for more effective stormwater treatment. The approach emphasizes the understanding of natural systems present on a site and a commitment to work within their limits whenever possible. Doing so creates an opportunity for development to occur with low environmental impact. Specifically, LID aims to:
- Preserve open space and minimize land disturbance
- Protect natural systems and processes (drainage ways, vegetation, soils, sensitive areas)
- Reexamine the use and sizing of traditional site infrastructure (lots, streets, curbs, gutters, sidewalks) and customize site design to each site
- Incorporate natural site elements (wetlands, stream corridors, mature forests) as design elements
- Decentralize and micromanage stormwater at its source
LID, also known as “Better Site Design” and “Environmental Site Design,” uses a systems approach that emphasizes the integration of site design and planning techniques that conserve and/or mimic natural systems and hydrologic functions on a site. The practice has been successfully integrated into many municipal development codes and storm water management ordinances throughout the United States.
Economic Benefits of Low Impact Development
Low Impact Development practices can be both fiscally and environmentally beneficial to communities. Recent research has shown that LID techniques, when installed properly, can achieve sediment retention and pollutant removal goals at a lower initial cost than conventional systems, in part because they require less pipe and underground infrastructure. Additionally, in cases where LID designs have had higher initial costs than traditional approaches, their lower maintenance and operating costs frequently lead to lower total life-cycle costs than traditional approaches. In a 2007 report on the cost of stormwater management, the EPA found that infrastructure costs were lower, in general, for projects where open space was preserved and cluster development designs were employed, when compared to conventional development. In most cases, significant savings were realized due to reduced costs for site grading and preparation, stormwater infrastructure, site paving, and landscaping. Total capital cost savings ranged from 15 to 80 percent when LID methods were used, with a few exceptions in which LID project costs were higher than conventional stormwater management costs.
More economic analyses:
Economic Benefits Of Runoff Controls - US EPA report discussing two types of structural controls that have been documented as providing economic benefits: urban runoff ponds and constructed wetlands.
Synthesis of Existing Cost Information for LID vs. Conventional Practices - This memorandum developed for Chesapeake NEMO quantifies some of the economic cost information for low impact development through the examination of case studies from around the United States. The case studies selected compare the costs and benefits of LID practices against the costs of conventional stormwater treatment and control practices. Center for Watershed Protection.
Low Impact Development Documentation - Factsheets on LID practices and an evaluation of their effectiveness and cost.
Other Benefits of Low Impact Development
LID is an innovative stormwater engineering and design approach that has economic and environmental benefits that conventional techniques lack. However, LID techniques have additional benefits such as enhanced pollutant removal rates, increased open space, reduced downstream flooding, increased property values and redevelopment potential, public health protection, reduced automobile traffic and fuel consumption, habitat preservation, erosion prevention, and improved quality of life.
- Watershed Protection Benefits (pollutant removal, reduced flooding, increased aquifer recharge)
- Ecosystem Benefits (soil conservation, wildlife habitat, mitigate climate change)
- Quality of Life Benefits (open space amenities, farmland protection)