NON-LINEAR SHORELINE CHANGE MODELING AND COASTAL STORM IMPACTS ALONG THE VIRGINIA BARRIER ISLANDS

This research sought to: (1) develop one of the most robust shoreline data sets in the world (≥ 20 shoreline positions spanning 155 years from 1851 to 2006); (2) use a complexity penalty statistical method to model long-term shoreline migration trends along the Virginia Barrier Islands (VBI) and (3) determine the causes (i.e., forcings) of the observed VBI shoreline changes. Shoreline positions along the 12 VBI were obtained at individual shore perpendicular transects (spaced 50 meters apart) using the Digital Shoreline Analysis System. At each transect, these positions were fit with a constant, linear, quadratic, or cubic model based on the tradeoff between model accuracy and complexity. The primary forcings used to correlate to shoreline migration trends included extratropical and tropical storm frequency and magnitude. Storm magnitude was quantified using a storm erosion potential index. Additionally, we developed a storm impact factor to quantify the impact of both the timing and magnitude of successive storms. Preliminary results indicate that higher order polynomials best model shoreline changes in the study area. Moreover, storm frequency has increased fourfold since 1980. Finally, the average storm magnitude has increased by 47% since 1980 and the nine most powerful storms since 1927 have occurred during this same time period. We conclude that the changing storm climate (increasing storm frequency and magnitude) most likely controls the observed shoreline changes in the study area.