Influence of Oceanic and Estuarine Drivers on Wetland Shoreline Change: Moving Towards a Framework for Assessment of Coastal Erosion Hazards Along Sheltered Coasts

Abstract:

Barrier island and estuarine habitats act as natural buffers to wave energy and reduce erosion of mainland coasts; however, estuarine wetlands are under increasing threat from shoreline destabilization and erosion due to rising sea level and storms. Currently, the USGS National Assessment of Coastal Change Hazards estimates the vulnerability of shorelines to hurricane erosion hazards by combining physical parameters of dune, beach, and shoreline morphology with storm hydrodynamic predictions. These hazard assessments are limited to ocean-side sandy beaches. However, with the increasing availability of water-penetrating lidar and vegetation filtering algorithms, as well as estuarine wave and hydrodynamic modeling, extending physical process analyses and risk assessments to estuarine and back-barrier shorelines is possible. In this study, we investigate the relationship between shoreline type, sediment supply rate, long-term erosion rates, and shoreline geophysical features. We focus on long-term changes, such as those associated with barrier island landward migration, which is dominated by the processes of storm overwash and sea-level rise. This migration means that the long-term changes in estuarine and ocean-facing shorelines can be correlated. We focus on understanding these correlations with estuarine drivers of wetland shoreline erosion and accretion, such as waves, sediment supply, and shoreline features. Quantitatively assessing the variance of estuarine shoreline behavior relative to oceanic shorelines will improve knowledge of estuarine shoreline susceptibility to storm-induced erosion, help fine-tune estimates of future forecasts of coastal change, and provide an initial framework for estimating erosion hazards along sheltered coasts.