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ESTIMATING AND PROJECTING IMPERVIOUS COVER IN THE SOUTHEASTERN UNITED STATES
Citation:
EXUM, L. R., S. L. BIRD, J. HARRISON, AND C. PERKINS. ESTIMATING AND PROJECTING IMPERVIOUS COVER IN THE SOUTHEASTERN UNITED STATES. Presented at 18th Annual National Tanks Conference, Memphis, TN, March 20 - 22, 2006.
Impact/Purpose:
Develop and test small watershed scale methods to identify potential hazards to streams from urbanization processes, including methods to quantify the current amount of impervious cover and project possible impervious cover levels in the near future. Apply the best methods developed to estimate impervious cover throughout Region IV. Test the utility of landscape metrics as indicators in Piedmont watersheds.
Description:
Urban/suburban land constitutes the fastest growing land use class in the Southeastern United States. Predominant development practices increase impervious surface--areas preventing infiltration of water into the underlying soil. Uncontrolled increase of impervious areas (roads, buildings, parking) can cause detrimental hydrologic changes, stream channel erosion, habitat degradation and severe impairment of aquatic communities. Development practices that reduce impervious area and include preventative strategies to protect water quality are more effective and less costly than remedial restoration efforts. The extensive hydrological alteration of watersheds associated with increased impervious cover is very difficult to control and correct. Complete identification and eventual prevention of urban water quality problems pose significant monitoring, smart growth and water quality management challenges. Simple and reliable methods to estimate and project impervious cover can help identify areas where a watershed is at risk of changing rapidly from a system with relatively pristine streams to one with significant symptoms of degradation. We provide a multiple data source (MDS) estimation of imperviousness in the Southeastern U.S. In this study, a method for estimating and projecting impervious cover for 12/14 digit hydrologic units over a large area was developed and tested. These methods were applied throughout EPA Region 4's eight southeastern states to provide a screening tool to guide monitoring and educational efforts. These estimates demonstrate an inexpensive method to determine impervious cover with known accuracy at the watershed and sub-watershed scales, and characterize imperviousness changes over time. Additionally, this report estimates future impervious cover in the Southeastern U.S. using the MDS technique. These estimates can guide in-situ monitoring to confirm problems, aid listing of impaired waters under Section 303(d) of the Clean Water Act and total maximum daily load(TMDL) development, provide reliable information to enable sound local planning and land-use decisions, and promote protection and restoration of urban streams.