Factors Influencing Variations in Stormwater Runoff Quality from Single-Family Residential Land Uses

Differences in stormwater quality are often associated with impervious cover and/or land use. However, two watersheds with similar impervious cover and land use may exhibit significantly different stormwater quality. This study examined the relationship between population demographics and stormwater quality in runoff from eleven single-family residential land use watersheds in Austin, TX. Event mean concentration data for seventeen pollutants were standardized so all data could be combined resulting in one indicator value of water quality in the monitored watersheds. The data were then statistically compared demonstrating significant differences in water quality from watersheds with similar land use. A statistical relationship between population demographics (income, rental rate, education and population density) and the indicator variable was developed (r²=0.78). This relationship was then applied to single family areas in the Austin area creating a map of areas with potential water quality problems. This relationship may be useful in targeting areas for water quality programs including education and/or structural controls.