Morphological Response of Vegetated and Urbanized Barrier Islands to Hurricane Ian

Abstract. Barrier islands are vulnerable to extreme storm events which cause erosion and deposition of sediment. These morphological changes pose risks to both the built environment and natural habitats but are also affected by them. This study investigates the morphological impacts of Hurricane Ian (2022) on two barrier islands along Florida's Gulf Coast: the urbanized Fort Myers Beach, and Lovers Key, a naturally vegetated island and State Park. Using high-resolution pre- and post-storm topo-bathymetric datasets, we quantify patterns of erosion, sediment deposition and dune crest change. In addition, we investigated the morphological response of the developed and natural barrier islands by integrating spatially varying land cover data into the numerical model XBeach. Results show that the built environment on Fort Myers Beach significantly affects sediment transport pathways, causing localized erosion and deposition patterns distinct from those observed on the vegetated Lovers Key Island where dune crest lowering, landward migration, and storm-induced breach were prominent. Model simulations that incorporated detailed spatial variability of vegetation and built environment, replicated observed morphological changes with reasonable Brier Skill Scores, including the location of breach formation. Sensitivity analyses demonstrated that relatively small changes in roughness coefficient, wave skewness and asymmetry factor, morphological acceleration factor, and boundary water levels influence erosion intensity and sediment deposition patterns. Additionally, introducing supplemental vegetation patches in the model showed less dune erosion on vegetated barrier island, indicating that revegetation of islands may be beneficial. The findings provide insights into the complex interplay between storm forcing, land cover variability, and barrier island morphodynamics, and emphasize the importance of incorporating detailed land use and vegetation data in morphodynamic models to better assess barrier island responses to future storms under evolving climatic conditions, ultimately aiding efforts to enhance coastal resilience and adaptive management.