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<br />e <br /> <br />natural vegetation under existing conditions is 272 acres while the total 31110uol of land <br />classified as natural vegetation WIder 1990 conditions is 141 acres. <br /> <br />Locatiotll1/ A ttmctiveness AtII1/ysis <br /> <br />Attractiveness analyses for a number of potential uses within the basin were performed. <br />The output is standard overprint grey shades indicating the relative attributes of each grid <br />cell with respect to the others. The attractiveness display (Figure 4) used to illustrate <br />the capability was for neighborhood park locations. In the display the darker sbaded <br />areas are, in a relative sense, more attractive for park development than the lighter shaded <br />areas. The data variables of damage reaches (areas within the flood plain are preferred <br />over areas outside the flood plain), land surface slope (flat and mild ~opes are preferred <br />over steep slopes), existing land use (natural vegetation, agriculture and pasture are <br />favored over other categories), and distance to housing (areas near low, medium and high <br />density residential areas are preferred to areas removed and to areas near otrer land uses) <br />were used in determination. <br /> <br />e <br /> <br />Water Quality <br /> <br />The water quality analysis planned for the pilot study includes urban storm water <br />quality forecasting and in-stream dynamic water quality simulation of the response of the <br />receiving water to storm water inflows and projected domestic/industrial loading. The <br />quantity and quality of urban storm runoff will be detennined for a single synthetic event <br />and for wet weather events during a critical continuous period of historic record that will <br />be used as input to the in-stream dynamic simulation. <br />The utility computer program HYDPAR accesses the data file and formats the appro- <br />priate data (land use, etc.) for operation by the model STORM. STORM is then executed <br />for events of interest generating pollutographs for each watershed (such as Trail Creek) <br />for a single event and wet weather events pollutographs for each watershed for a short <br />continuous period. The pollutograph procedure incorporated into STORM wiil predict <br />the mass and concentration of five pollutants normally of interest in storm water runoff <br />studies (suspended solids, settleable solids. BOD, total nitrogen, and total orthophos- <br />phate). Runoff quantity is computed using the Soil Conservation Service Curve Number <br />technique. Pollutant masses are computed during each time step using an exponential <br />function which represents a "scheduled release" of pollutants from the land use. <br />In.stream water quality simulation is planned for the main stem Oconee River. The <br />stream will be modeled some distance above the study area to a specified distance beyond <br />the lower boundary of the study area. The input data for the simulation modeling wiil <br />be very general in nature consistent with the objective of providing a general assessment <br />of alternative land use patterns_ The quality simulation, however, wiil be quite specific <br />and complex and will be perfonned using the WQRRS model. Model parameters will be <br />determined primarily by transfer of coefficients developed in other studies for nearby <br />areas such as metropolitan Atlanta. Dry weather sanitary. and treated effluent loading <br />will be developed from general relationships that will relate land use as cataloged in the <br />data file to quantity and quality of loadings_ Storm water loadings wiil be computed by <br />STORM as described above. <br /> <br />: <br /> <br />e <br /> <br />15 <br />