Coastal erosion hazards in northwest Florida due to extreme wind waves generated by tropical cyclones

Abstract

Tropical cyclones (TCs) pose significant threats to sandy coastal environments, largely due to the extreme wind-generated waves. Sandy beach-dune systems, acting as natural barriers, can significantly exacerbate coastal flood risks when eroded or breached by extreme waves. Northwest Florida's Gulf coast beaches and dunes are highly exposed to TC-generated waves, which can cause significant erosion of these natural and nature-based defenses. Using a physics-based morphodynamic model, this study quantifies TC-induced coastal erosion hazards due to extreme waves at seven sites along the northwest coast of Florida. The model is forced by wave parameters derived from synthetic TCs, which are generated based on ERA5, NCEP, and MERRA2 reanalysis datasets. The results indicate that the choice of reanalysis dataset significantly influences the estimated erosion volumes, with ERA5-based synthetic TCs consistently producing lower erosion volumes than those based on NCEP and MERRA2. However, the erosion return periods derived from the ERA5 TC dataset align well with those from the other datasets, due to the higher annual frequency of TCs in the ERA5 dataset compared to the other two datasets. We also found significant spatial variability in erosion hazards, with profiles just a few kilometers apart exhibiting different erosion responses under identical storm forcing. Our analysis highlights the important role of local morphological characteristics, such as beach slope and nearshore sandbar size, in modulating the impact of extreme waves on coastal erosion. The study findings underscore the importance of ensemble high-resolution, site-specific hazard assessments for effectively managing and protecting beach-dune systems against extreme wave events.