Fourth Symposium on the Urban Environment


The benefits of ‘Low Impact Development’ for urban climate / hydrology


Sandra Traci Arthur, Low Impact Development Center, Inc., Beltsville, MD; and N. A. Weinstein

Low Impact Development (LID) is an innovative stormwater management approach that has significant beneficial implications for both urban climate and hydrology. LID's goal is to mimic a site's predevelopment hydrology by using uniformly distributed integrated design techniques that infiltrate, filter, store, evaporate, and detain runoff close to its source. The benefits of this approach for the urban climate are generally mentioned in the LID literature, but some of the first quantifiable results on the ability of the LID practices to mitigate the urban heat island effect, increase soil moisture, and increase the overall urban canopy will be presented here. A conventional residential development will be analyzed next to a similar scale LID development using Landsat TM and ETM imagery. Maps of various environmental indicators derived from the imagery will be presented, including soil moisture, vegetation coverage, surface temperature, impervious surfaces, evapotranspiration, and land use. These parameters will be used to quantify the climate-related benefits of such LID practices as soil renovation, limiting disturbed areas, tree conservation, reduction of impervious surfaces, bioretention, and maintaining hydrologic and hydraulic regimes. A time series of images will be presented that monitor the paired developments’ vegetation, surface temperature, and soil moisture patterns in various pre- and post-construction phases. The differences in these environmental measures for lots of similar size will be used to document this new realm of LID benefits. Graphics will be presented distinguishing between the two types of development by the evidence of local “hot,” unvegetated, and / or “dry” spots. Additional results from the Landsat analyses will be given based on several ultra-urban retrofit projects that also used LID techniques. Since almost all components of the urban environment have the potential to be used in LID design (including open space, rooftops, streetscapes, parking lots, sidewalks, medians, etc.), LID can be applied equally well to new development, urban retrofits, and redevelopment / revitalization projects.

Session 6, Mitigation of urban heat islands: scientific and regulatory aspects, implementation and cost-effectiveness issues, local perspectives, and quantification of environmental impacts.
Tuesday, 21 May 2002, 11:00 AM-2:14 PM

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