NON-LINEAR SHORELINE CHANGE MODELING OF THE NORTHERN VIRGINIA COAST: VIRGINIA BARRIER ISLANDS AND ASSATEAGUE ISLAND

This research investigates spatial and temporal changes to long-term shoreline migration trends, short-term changes in long-term trends, the timing of those changes and migration directions using one of the most robust shoreline change datasets in the world (38 unique years of data spanning 1850-2014). The analysis used a non-linear, complexity-penalty modeling method to determine if constant, linear (monotonic), quadratic or cubic models best fit the shoreline position/time data at 50 m intervals along 125 km of Virginia’s barrier island coast (including southern Assateague Island, AI). The critical point(s) (where the slope of the first derivative = 0) of non-linear models provide an estimate of the timing of trend reversals. The second derivative provides information about the migration trend directions. Preliminary analyses of these data show that cubic model fits dominated the study area (90.9% Virginia barrier islands, VBI; 76.4% Assateague Island) and linear models only fit 6.3% of the VBIs and 19.4% of the AI coast. Of those shorelines that experienced a short-term trend reversal, the most recent change apparently occurred in the late 1880s toward landward migration. Additionally, these data also show that an “arc of (perpetual) erosion” occurs along the northern 35 km of the Virginia barrier islands (Wallops Island to Cedar Island) and has apparently extended southward to Parramore Island during the past decade.