Low Impact Development

What is LID?

LID is an approach to site development and stormwater management that incorporates site level planning, design, and control techniques that are focused toward restoring and optimizing the land’s ability to absorb water, capture pollutants and process pollutants into the landscape.

What are the basic principles of LID?

  • Optimize Conservation. Conserve natural resource areas, sensitive areas, vegetation and soils and wisely use them to reduce and treat runoff to maintain the site’s ability to retain and detain runoff.
  • Mimic the Natural Water Balance. Infiltrate water at the same manner and rate as predevelopment water infiltration. This requires careful evaluation of the soils onsite, taking particular notice of the sandier soils. Evaluate where the most permeable, sandy soils are located. These areas are most often the most appropriate for LID control strategies.
  • Decentralize and Distribute Controls. The more LID techniques applied to a site, and the more uniformly those techniques are distributed throughout the landscape, the more effective LID will be.
  • Disconnect Impervious Surfaces. Impervious surfaces should be disconnected, rather then connected. The runoff characteristics of the site are completely changed when impervious surfaces are disconnected and drain to a landscape feature or LID practice. This approach prevents the adverse cumulative effects of concentrated flows.
  • Create Multifunctional and Multipurpose Landscapes. Many features of the urban landscape can be designed in a way to provide more functionality and reduce impacts. Every landscape feature should be designed with some beneficial hydrologic aspect to store, retain and detain or treat runoff.
  • Think Small Scale. Integrate multiple, small systems into numerous aspects of the site. The most efficient use of the landscape is to design smaller more numerous techniques. With several LID techniques, the stormwater system is not likely to fail. The disconnection of one or two rain gardens will only have a minor impact on the effectiveness of the entire system. Contrast this with using one large stormwater pond – if that fails, the whole system fails.
  • Instill Pollution Prevention Programs. Create an effective public education and outreach effort to ensure the proper use, handling and disposal of pollutants after the site has been developed.
  • Account for Cumulative Impacts. Combine a series of LID techniques to mimic the natural hydrologic regime of the land in its predevelopment condition.

 

What are County officials and staff currently doing to encourage LID in New Hanover County?

On October 6, 2008, the New Hanover Board of Commissioners adopted a resolution supporting a Joint City-County LID Guidance Manual and spreadsheet modeling tool and encouraging the use of LID techniques in New Hanover County. County and City planning staff worked with the N.C. Coastal Federation, N.C. DEQ, and several local developers, engineers and homebuilders over the course of 1-1/2 years to develop a comprehensive LID manual written specific for the unique conditions in our area. To complement the manual, a spreadsheet tool was also developed for engineers to use for stormwater permitting processes when attempting to incorporate LID into their projects.

 

Are training courses available to obtain certifications for LID design?

  • LID Inspection and Maintenance Certification – The NCSU Biological and Agricultural Engineering program offers certification courses for BMP installation. CLICK HERE to learn more about upcoming courses.

 

Helpful Links to Other LID Resources:

230 Government Center Drive, Suite 110 • Wilmington, NC 28403
Planning & Land Use: Phone 910-798-7165 • Fax 910-798-7053
Building Safety: Phone 910-798-7308 • Fax 910-798-7811
Engineering: Phone 910-798-7139 • Fax 910-798-7051