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Implement Low-Impact Development Designs
Minimizing Impacts at the Local or Site Level
In response to growing concerns for watershed protection and minimizing impacts of development several Counties in the United States came up with guidelines and manuals for development that cause least change. Several of these are available in electronic and paper format. Low-impact development (LID) design minimizes impacts by reducing imperviousness, conserving natural resources and ecosystems, maintaining natural drainage patterns, reducing road, streets and parking spaces and minimizing clearing and grading.
Detention and retention storage units for runoff generated by the development are evenly spaced throughout a site with the use of open swales, flatter slopes, depression storage, rain gardens for bioretention and other such features. As far as possible the predevelopment time of concentration is maintained by strategically routing flows to maintain travel time.
In a LID every feature is multifunctional. Green spaces, landscaped areas, grading, streetscapes, roads and parking lots are balanced to reduce stormwater impacts or provide and maintain hydrologic functions. The cumulative benefits of LID techniques allow the site designer to maintain or restore watershed’s natural relationship between rainfall, runoff, infiltration and evaporation.
The effective use of LID design techniques can significantly reduce the cost of providing stormwater management. Savings are achieved by eliminating the use of stormwater management ponds, reducing pipes, inlet structures, curbs and gutters, less road paving, less grading and clearing. Depending on the type of development and site constraints LID design construction and maintenance costs can be reduced by 25% to 30% as compared to traditional approaches. (Coffman, 1999; PGC, 1997).
