No abstract

Data from about 160 neighborhoods in six Jefferson County, AL drainage areas were intensively investigated to determine the surface covers for each land use type. The data shows that the watersheds are highly impervious, with three of them having more than 50% of the watershed area composed of impervious cover. However, TR-55 guidance still shows that the impervious cover for all land uses investigated to be much greater than we observed for our area. It was also concluded that the variabilities of the surface covers within the different land uses for the investigated areas was small, especially for the impervious covers.WinSLAMM, the Source Loading and Management Model (Pitt and Voorhees 1995 and 2002) was used to determine the sources of critical pollutants, and to evaluate different combinations of stormwater controls. The program estimated that the stream quality in the receiving waters is in poor condition based on the flow distribution, as confirmed by in-stream investigations by the Jefferson County Storm Water Management Authority biologists. The residential watersheds are closer to the threshold between fair and poor biological conditions than the industrial and commercial watersheds, as expected.

No abstract

No abstract

Data from about 160 neighborhoods in six Jefferson County, AL drainage areas were intensively investigated to determine the surface covers for each land use type. The data shows that the watersheds are highly impervious, with three of them having more than 50% of the watershed area composed of impervious cover. However, TR-55 (USDA 1986) guidance still shows that the impervious cover for all land uses investigated to be much greater than we observed for our area. It was also concluded that the variabilities of the surface covers within the different land uses for the investigated areas was small, especially for the impervious covers. The percent of directly connected impervious cover (DCIA) was determined by direct field observations and was also estimated by empirical equations. Equations for determining DCIA developed as part of several different studies were use to predict DCIA for our data, but did not give good estimates especially when analyzed at land use level. There was a similarity between "highly connected basins" Sutherland equation and the fitted equation for our overall data. However, the residual analysis for the regression model failed, suggesting that the power equation is not the proper equation to be used for those six drainage areas. Consequently, equations for each existing land use were developed, concluding that a single equation cannot accurately estimate DCIA for all regions and land uses.