HIGH-RESOLUTION TOPOGRAPHIC CHANGES AT THE VOTER BAR, SANDY RIVER, NORTHWESTERN MAINE, 2002-2004

The Sandy River, a tributary of the Kennebec River, traverses a narrow, sediment-filled valley through the Longfellow Mountains of northwestern Maine. Renewed controversy has arisen over the environmental impact of gravel removal from active sediment bars. In response, the Maine Geologic Survey and the University of Maine at Farmington initiated this project in 2002 with the objective of documenting the sedimentary dynamics at five sites along the river. We focus on the Voter site, which includes three point bars, the central one transected by an avulsion channel. This site extends 700 m along the river and encompasses a width of 150 m and relief of less than 10 m. High-resolution topographic data was collected with a total station during the summers of 2002, 2003, and 2004. These data were used to assess patterns of erosion and deposition and their relationship to climate variables, particularly flood vs. low-flow. Whereas discharge varied only moderately during the first year, a 20-year flood occurred during December 2003. The year of low-flow resulted in cut bank erosion, sparse deposition and a general lowering of the site on the order of 5 cm, possibly due to compaction. Net volumetric loss was significant. Cut bank erosion continued through 2004 but spatially extensive deposition, including considerable foreset progradation, countered much of the volumetric loss. Over the two-year interval, the single flood event of December 2003 seems to have dominated the pattern of deposition.