Let That Soak In
Breaking ground with low impact development methods.
By Brian P. Kane, ASLA
Low impact development" (LID) is a bureaucratic buzzword for Earth-friendly methods that minimize the impact of stormwater runoff downstream and encourage on-site storm-water retention, most notably through bioretention and infiltration methods that allow stormwater to be distributed evenly around a site. Reducing stormwater runoff rates, cleaning pollutants from stormwater, and recharging stormwater into the ground are key tenets of LID thinking. By reducing water pollution and increasing groundwater recharge, LID methods improve the quality of receiving waters and stabilize the flow rate into adjacent streams. LID strategies are a marked change from techniques advocated by landscape architects just a few decades ago when concrete pipe, curbs and gutters, catch basins, and detention ponds directed stormwater efficiently to central holding areas or off-site channels.
LID methods are gradually gaining recognition thanks to publications, workshops, and successful project implementation. The Department of Environmental Resources in Prince George's County, Maryland, developed its now well-known manual on LID in 1999. In its six chapters, Low Impact Development Design Strategies: An Integrated Design Approach covers everything from hydrological calculations and site planning strategies to design guidelines for infiltration trenches, filter strips, and planting of bioretention areas. This illustrative manual went national in 2000 and today may be downloaded from the Environmental Protection Agency's web site at www.epa.gov/owow/nps/lidnatl.pdf. The manual inspired many jurisdictions nationwide to consider reforming their zoning ordinances. Many colleges and universities have altered their curricula to incorporate LID methods in courses dealing with stormwater and site design, continuing the advocacy of LID with upcoming practitioners.
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