Impervious Surface Increase
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2007
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Impervious Surface Increase

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One of the more significant landscape impacts attributable to urbanization is the construction of impervious surfaceâasphalt, concrete, etc.âcreated by development. The creation of impervious surface changes the natural hydrologic cycle by impeding precipitation infiltration to groundwater while increasing the amount of surface runoff.

Developed lands can vary in the percentage of impervious coverage depending on how intensely land is urbanized. For example, single unit residential housing can have relatively low percentages of impervious cover such as 15 percent whereas commercial land uses can have impervious coverage of over 90%.

The animated Impervious Surface map provided here depicts intensities of impervious cover for pre-1986 development in four shades of grey and 1986 to 2007 development in four shades of red.impervious surface legend The shading denotes areas with less than 25%, 25 to 50%, 50 to 75% and 75 to 100% impervious surface coverage. Watershed boundaries are depicted in brown dashed lines. By navigating through the map, one can get an idea of how much impervious surface is in a given watershed and how rapidly the impervious surface increased over the study period.

New Jerseyâs total impervious footprint as of 2007 was 508,681 acres or nearly 800 square miles of concrete and asphalt. During the T3 (2002-2007) period, New Jersey generated 21,348 acres (33.4 square miles) of additional impervious surface representing an annual rate of 4,270 acres of impervious surface increase per year or 9 American football fields of new impervious surface per day (including end zones).

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While impervious surface creation is a useful indication of water quality, it is also a proxy for other land resource impacts attributable to development such as forest loss, farmland loss and wetlands loss. Comprehensive regulation of impervious surface may hold promise to reigning in sprawl. In another study, we are working on a conceptual framework for combining impervious surface regulation with Transfer of Development Rights (TDR) as a tool for steering development patterns away from sprawl and toward smart growth.