Changes to the coastline and to coastal features, such as spits, barrier islands, estuaries, tidal guts and lagoons were mapped for over 22,000 km of coastline along the Bering Sea and Gulf of Alaska coasts in western Alaska. Changes to rivers and lakes near the coast were also captured. The analysis was based on time-series analysis of Landsat imagery, 1972–2013. An annual imeseries of suitable Landsat imagery was compiled and analyzed for changes in near-infrared reflectance to identify areas that transitioned from land to water, or vice-versa, over the study period. The timing of changes was also identified. Thousands of coastal changes over the 42-year study period exceeded the 60-m pixel resolution of the Multispectral Scanner (MSS) data, including coastal erosion and aggradation, estuarine and delta channel dynamics, coastal lake drainage and expansion, and migrations of coastal spits. An accuracy assessment determined that change patches >5 ha were well mapped for the 1972–2013 time-series though coastal aggradation is somewhat overmapped in tidal flats. Coastal erosion was mapped for approximately 100 km² and coastal aggradation was mapped for approximately 113 km², with coastal erosion and aggradation overall close to balanced. Many local hotspots of directional change (substantial and sustained coastal erosion or aggradation) were identified. The maps of coastal change produced in this effort could be used for local and regional analyses of vulnerability and coastal processes, and for identification of vulnerable natural and cultural resources.
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