IMPERVIOUS SURFACES IN URBAN WATERSHEDS

Urbanization causes profound changes in the hydrology of the area, specifically the timing of the runoff, the water use, runoff volume and flow rates, channel complexity, and especially pollution in receiving waters. Water quality problems increase with increasing imperviousness of the watershed. Impervious areas cause increased runoff and contaminated discharges from these areas and also contribute to receiving water contamination. Although much interest has been expressed concerning impervious areas in urban areas, actual data for the patterns of use of these surfaces is generally lacking. In this study, 125 neighborhoods were surveyed to determine the critical development characteristics representing 16 major land use areas located in the Little Shades Creek Watershed, near Birmingham, AL. The details of the impervious surfaces in these areas are described in this paper. Future project activities will include detailed stormwater modeling of each of these areas so that the expected variations of important stormwater attributes can be quantified. A parallel study is investigating six drainage areas that have been extensively monitored as part of the Jefferson County, AL, stormwater permit program. The surfaces making up the drainage areas are described in detail and that information is being used to re-verify the WinSLAMM stormwater model for these local conditions. The final local version of the model will be used to measure the variation of the stormwater from the Little Shades Creek land use areas.