A Report of Sediment Erosion on Buck Island, U.S. Virgins Islands: Quantifying Change Through Aerial Imagery from 1954-2011

Gray, Laura; Messman, Laura

Buck Island Reef National Monument may be at risk of sediment erosion over time. Seasonal wind and current patterns contribute to annual changes in the shoreline on this island, but the National Park Service is interested in an analysis of longer-term shoreline change. This could be important as it relates to physical stability of the island and biological processes such as reef growth and sea turtle habitat. We used ArcGIS 10.2 and historic aerial orthoimagery to examine sediment redistribution on Buck Island from 1954-2011. We assessed this by means of tracing shorelines and computing island area values for each aerial image. We found that the largest amount of change occurred on the western side of the island, characterized by sediment loss in the northwest quadrant and sediment accretion in the southwest quadrant. Beach extension and contraction measured along transects shows a larger magnitude of shoreline change than has been observed due to seasonality on the island. Although constrained in our analysis by limited available imagery and knowledge of other biological and physical processes on Buck Island, our report should inform island stakeholders and future management decisions.