EROSIONAL RESPONSE TO FLOODING AND LOGGING IN A HIGH RELIEF, FORESTED WATERSHED RECORDED IN THE SEDIMENTARY RECORD OF LITTLE KENNEBAGO LAKE, NORTHWESTERN MAINE

Natural and anthropogenic disturbances can result in both distinct episodes of catastrophic erosion and persistent changes to erosion rates. Increased erosion can pose threats to natural resources, water quality, life, and built infrastructure. An improved understanding of the origin of and response to both natural and human landscape disturbances is needed to better manage their impacts. In New England, recent climatic change trending towards wetter conditions and more frequent high magnitude rainfall/runoff events have occurred in combination with changing patterns of human land use. To better constrain the relative impacts of climatically forced erosion and human impacts related to intense logging, we collected a sediment core from Little Kennebago Lake, Maine. Little Kennebago was targeted based on its large, high relief watershed which should increase its sensitivity to the input of terrestrially derived sediment. A 1.8 m long sediment core was collected in June 2017 in order to reconstruct past changes in the magnitude of watershed erosion. Primary analyses focus on bulk composition determined through loss on ignition, magnetic susceptibility, and scanning X-ray fluorescence. Radiocarbon dates and short-lived radioisotope profiles help constrain the timing of past watershed disturbances and highlight changes in the rate of sediment delivery to the lake. Preliminary results suggest that this core spans a 1,200 yr interval of continuous sediment accumulation and inferred erosion of the surrounding landscape. The core contains discrete layers of inorganic sediment believed to be evidence of terrestrial sediment washed into the lake episodically. These events are infrequent throughout most of the sequence which contrasts with the upper most portion of the record that is characterized by more frequent discrete layering and an overall increase in the proportion of clastic sediment. We interpret the recent change in the pattern of sedimentation as an indication of increased sensitivity to erosion due to active logging in the watershed, moderated by the occurrence of major runoff events responsible for sediment mobilization. These results highlight the potential for human activity to make the landscape more susceptible to erosion.