Using a Geographic Information System to Rank Urban Intensity of Small Watersheds for the Chattahoochee, Flint, Ocmulgee, and Oconee River Basins in the Piedmont Ecoregion of Georgia and Alabama

摘要

The National Water-Quality Assessment (NAWQA) program of the U.S. Geological Survey is conducting a study of the effects of urbanization on the water quality and ecology of streams throughout the Nation. Pilot studies were conducted during 1999-2001 in the Birmingham (Ala.), Boston (Mass.), and Salt Lake City (Utah) metropolitan areas. For each of the studies a multimetric urban intensity index was developed to aid in the selection of approximately 30 watersheds representing a range, or gradient, of urban intensity. To develop the index, researchers used principal component analysis to identify population density as the most important factor in explaining statistical variation among basins with similar natural features. The urban intensity index was developed based on approximately 50 socioeconomic and landscape variables with an absolute Pearson correlation of 0.5 or greater with 1997 population density. Full implementation of the urban gradient study approach in the NAWQA program began in 2002. Three metropolitan areas, including Metropolitan Atlanta, Georgia, in the Georgia/Alabama Piedmont Ecoregion, were chosen for water-quality sampling in 2003; studies are scheduled to begin in three additional metropolitan areas in 2004.