Lateral Migration of the Oconee River, Georgia, USA: Piedmont versus the Coastal Plain

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This paper hypothesises that geology plays a significant role in determining the rate of planform change in the Oconee River. The section of the river studied passes through two contrasting geologic provinces: one with more resistant igneous and metamorphic rocks and the other with less-resistant sedimentary rocks. The hypothesis is that the section of the river within the more resistant geology would exhibit less lateral movement than the section in the less-resistant geology because the rates of erosion would be significantly different. Using aerial photographs taken over a period of 80 years with roughly seven decadal time periods, a comparative analysis of migration rates between the two sections reveals that in the Piedmont Geologic province, there seems to be a less-direct influence of the rock type. Though rocks within this zone are more resistant to erosion, the evidence shows that the channel is still actively eroding and depositing within this zone. There is strong evidence that the material that makes up the bank and bed of the river channel is just as, or almost as easily susceptible, to erosion as the material in the Coastal Plain province. This correlates with the principle that geology plays a role in determining migration rates. However, the findings show that the degree of variability between decadal steps does not clearly show why the rate of lateral change varies from one step to another. Other factors besides geology play a significant role in the rate of planform change of the river.

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• Land Management, Land Tenure, & Agricultural Issues