Low impact development (LID) is a sustainable stormwater management approach that is used to restore the natural ability of an urban site to absorb stormwater. By means of infiltration, evapotranspiration, and reuse of rainwater, LID techniques manage water and water pollutants at the source and thereby prevent or reduce the impact of development on rivers, streams, lakes, coastal waters, and ground water.
New and redevelopment projects have a multitude of opportunities to incorporate LID into the infrastructure, yet it is more difficult to incorporate these facilities into dense urban or retrofit projects, as a greater number of site constraints will exist which limit the possibilities. Often times, the soil in urban areas is poor, which makes infiltration more difficult. Utility conflicts and mature trees can also be an issue. Competing interests for the use of the public space in urban areas can also pose a challenge—some LID facilities require a large area in order to be effective and this may be difficult when trying to balance pedestrian, biking, transit and vehicular traffic in the same limited space. But even with these challenges, there are opportunities to introduce LID features in an urban area, has been proven in such cities as Seattle, Chicago, Portland, and Philadelphia. The most common LID Practices that work successfully for urban street rights of way are bioretention (rain gardens), grass swales, tree box filters, vegetated filter strips, and pervious pavements. These have been and will be the primary practices implemented in the District of Columbia as this action plan is carried out.
To prevent or reduce the impact of urban development on rivers, streams, lakes, coastal waters, and ground water.