RECONSTRUCTION OF THE HISTORICAL GEOMORPHOLOGY OF A DYNAMIC STREAM IN MIDDLE GEORGIA

The primary goal of this study was to investigate the history of a tributary of the Oconee River, Fishing Creek, in Milledgeville, Georgia. Fishing Creek is a dynamic fluvial system that has constantly been changing over event scales, annual time scales as well as over decades. This study focused on investigating the history of an abandoned side channel and determining the fate of McMillan Island, which once existed in this area. Based on our preliminary investigation, we speculated that Fishing Creek once occupied the abandoned side channel, which flowed against the main gradient of the Oconee River. We evaluated several different hypotheses that could have caused the abandonment of the side channel. One hypothesis is that the channel was a man-made diversion created to allow water vessels to turn around, during the steamboat era of Milledgeville. A second possibility is that the abandoned channel was formed when Fishing Creek was forced to alter its course during the construction of a sewer line during the late 1960s. Our research hypothesis was that the Oconee River cut through McMillan Island and exposed Fishing Creek to a new outlet, causing the abandonment of the side channel. Evidence supporting this hypothesis included historic maps and photographs which displayed the disappearance of the island as an identifiable landform. This hypothesis was tested using Geographical Information Systems, based on aerial photographs from 1942, 1951, 1956, 1960, 1966, 1973, 1993, 1999, and 2007. The shift of the island and timeline of when the abandoned channel formed were determined. Additional data included a high resolution topographic model of the channel and its surroundings. The results from this project demonstrated that McMillan Island had been eroding for years before the construction of the sewer line, and that the likely cause of the cut through was the additional erosion of Fishing Creek. Our project allows a clear understanding of the fate of McMillan Island and the cause and creation of the abandoned side channel, which is important for the management of the Oconee River Greenway located at this site.