Land Development Characteristics in Jefferson County, Alabama
For a stormwater monitoring study to be successful, a careful examination of the study watershed is required. An inventory of watershed development conditions is needed both as part of a comprehensive stormwater quality plan for an area, and for many decision support activities. Past studies using the Source Loading and Management Model (WinSLAMM) (Pitt and Voorhees 1995) have demonstrated the importance of knowing the areas of the different land covers in each land use category and the storm drainage characteristics (grass swales, curb and gutters, and the roof drains). As this chapter describes, six to twelve homogeneous neighborhoods usually need to be surveyed for each land use category. Aerial photographs or satellite images of each site are also needed for measurements of each source area type.
Impervious cover has been increasingly used as an indicator in measuring the impact of land development on drainage systems and aquatic life (Schueler 1994). It is also one of the variables that can be quantified for different types of land development. There are many different types of impervious surfaces; how they connect to the drainage system is important. Although much interest has been expressed concerning impervious areas in urban areas, data for their patterns of use is generally lacking. The procedures described in this chapter to obtain the field data information have been used for many years in stormwater research projects, including several Nationwide Urban Runoff Program (NURP) projects that were conducted in the San Francisco Bay Area (Castro Valley, California), in Bellevue, Washington, and in Milwaukee, Wisconsin (EPA 1983). Pitt and McLean (1986) also used these procedures to determine development characteristics in test watersheds in Toronto, ON, Canada. These stormwater studies, amongst others, showed that land development characteristics, especially directly connected impervious areas, are generally similar amongst US and Ontario regions, but each land use category shows variabilities in land development characteristics. One of the objectives of this chapter is to report variabilities in these characteristics in an area in Jefferson County, Alabama.
In order to determine how land development variability affects the quantity and quality of runoff, different land surfaces (roofs, streets, landscaped areas, parking lots, etc.) for different land uses (residential, commercial, industrial, institutional, etc.) can be directly measured. In a case study described in this chapter, 125 neighborhoods located in the Little Shades Creek watershed (Jefferson County, near Birmingham, Alabama) and 40 neighborhoods located in five highly urbanized drainage areas situated in Jefferson County (in and near the city of Birmingham) were surveyed to determine the development characteristics and their variabilities.
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