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Lake Sidney Lanier (Figure 1) is a man-made reservoir created in 1958 when Buford Dam was built in northeast of Atlanta, Georgia. It is the primary source of fresh water for the Atlanta metropolitan area. The lake has a dendrite shape due to presence of numerous creeks and rivers that flow into it. Small dams have been constructed on a few of these small creeks to create retention ponds. One such example is Ada creek creating Lake Knickerbocker, a large retention pond. On the opposite side of Lake Knickerbocker, Longwood cove has a similar morphology but has no retention pond. The main goal of this study was to determine the impact of retention ponds for the purpose of increasing longevity of the bigger reservoir by sediment trapping. The method employed is to compare interpolated topographies of the two coves from the period before the lake was created and the present. The pre-impoundment topography of both Lake Knickerbocker and Longwood cove was created by hand digitizing elevations from digitized United States Army Corp of Engineers (USACE) topographic maps and using ArcMap topo to raster tool to create a Digital Elevation Model (DEM) for the period. Present day topography was created from the Hall county two foot contour map located on the Gainesville State College (GSC) server and bathymetry data collected for the study with a Hummingbird fish finder/GPS combo unit. The present day bathymetry and land topography were combined using the ArcMap topo to raster tool. The comparison of the DEMs from the two periods was done by using the minus tool in ArcMap, subtracting the current DEM from the historic DEM with negative numbers indicating deposition and positive numbers indicating erosion. This study found a significant difference in sedimentation in the two coves which we attribute to sediment trapping by the Lake Knickerbocker retention pond. Thus, we concluded that creation of retention ponds would enhance the longevity of large reservoirs, in this case Lake Sidney Lanier. Another study was conducted by applying the RUSLE model on the Ada creek watershed that creates Lake Knickerbocker to estimate the total amount of sediment per year coming to the retention pond (sediment trap). An automated geospatial model was developed in ArcGIS 9.3 Model Builder to obtain annual soil erosion amounts from the Ada Creek watershed. According to the model results, on average 451.5 tons of sediment was delivered to the retention pond every year with a sediment delivery ratio of 0.1. It was also calculated that the entire retention pond will be filled in with sediment in 52 years if no soil erosion control measures are taken in the watershed. The study proved the efficacy of retention ponds which helps in increasing the longevity of the main reservoir.