The Impact of Anthropogenic Structures on the Delivery of Overwash and the Evolution of Barrier Islands

Abstract:

Climate change-induced sea level rise and the potential for more intense, more frequent storms to occur in the future, will threaten the vitality of barrier islands by lowering their relative elevation and altering the frequency of overwash thereby leading to island narrowing and/or migration. High-density development (e.g., homes, condominiums, hotels, etc.) on many barrier islands may further increase island vulnerability by restricting delivery of sand to the subaerial island via overwash. To explore the potential future response of barrier islands to these factors, we analyzed state-wide pre and post-storm LiDAR surveys of New Jersey and North Carolina conducted in response to Hurricane Sandy (2012) and Nor’Ida (2009) to assess the influence of humans on storm-driven delivery of sand. We compared natural and developed environments of various foundational properties (commercial, residential - slab and residential - piling) by extracting and analyzing shore-perpendicular profiles. We tabulated overwash extent and thickness along each profile to determine the characteristic effects of different types of development in comparison to natural areas. We then used data derived from this profile analysis to inform the overwash component of a 2D barrier island model. Using this model, we assess the long-term (decadal to centurial) impacts of the interruption of sand delivery by anthropogenic structures on barrier island evolution. Through multiple numerical experiments we address a range of scenarios for sea level rise and changes in storminess. Early results suggest that commercial zones having a large frontage area pose the greatest threat to barrier island survivability under scenarios of rapid sea level rise.