Storm impacts in western alaska documenting shoreline change and flooding through remote sensing and community-based monitoring

The frequency of storm surge impacts in western Alaska are likely to increase due to current warming trends leading to accelerated rates of erosion and further inland extent of marine inundation. This leaves the low-lying coastal communities of western Alaska vulnerable to storm surge hazards, especially because our ability to assess risk is hampered by large gaps in monitoring equipment and minimal baseline data from which to measure changes. Storm surge impact is important to consider given that it can lead to catastrophic changes to shoreline morphology, rapid habitat degradation through salinization of freshwater and terrestrial ecosystems, and the destruction of important infrastructure and cultural resources. Key storm impact indicators are the extent of shoreline erosion and flood elevation from particular storm conditions. Images taken using time-lapse photography were collected to measure the shoreline extent or water level surface at two remote Alaskan communities. Photos were processed using automated algorithms to determine either the distance of a shoreline position from a surveyed stake location or the vertical elevation of the water surface relative to a local vertical datum. The accuracy of these methods were tested against physical measurements collected by local environmental coordinators, in the case of shoreline position, and a laser-telemetered unit, in the case of the water level elevations. Results show that time-lapse photography methods for monitoring shoreline erosion and flood elevations are viable in regions with minimal monitoring equipment (positional RMSE of 0.44 m for shoreline measurements and vertical RMSE of 0.14 m for water level elevations). Time-lapse cameras are a low cost alternative to aerial remote sensing and differential global positioning system surveys to capture process-based storm impacts on a high temporal frequency (hourly) over small geospatial regions (10's to 100's of meters) throughout western Alaska.