Patterns of watershed urbanization and impacts on water quality

In six urban and urbanizing watersheds in Durham, NC, the relationship between streamwater quality and the type and pattern of watershed urbanization was explored. Urbanization was defined using metrics for the type and distribution of impervious surfaces, household census data, city infrastructure, and natural features. Each of the watersheds is described briefly. A series of 14 geographic information system-derived variables was calculated for each of the nested watersheds, including two relating to urbanization density, four relating to type of urbanization, four relating to access to city services, and five relating to natural watershed features. The resulting regression models suggested that while the quantity of watershed urbanization impacted water quality, the type of urban development within a watershed was also important, as was access to city services. Indicators of urbanization density had significant, positive correlations with nonpoint-source pollution.