Hazard assessment and hydrodynamic, morphodynamic, and hydrological response to Hurricane Gamma and Hurricane Delta on the northern Yucatán Peninsula

Abstract. Barrier islands in tropical regions are prone to coastal flooding and erosion during hurricane events. The Yucatán coast, characterized by
karstic geology and the presence of barrier islands, was impacted by Hurricane Gamma and Hurricane Delta in October 2020. Inner shelf, coastal, and inland observations were acquired simultaneously near a coastal community (Sisal, Yucatán) located within 150 km of the hurricanes' tracks. In the study area, Gamma moved slowly and induced heavy rain, mixing in the shelf sea, and strong winds (>20 m s−1). Similar wind and wave conditions were observed during the passage of Hurricane Delta; however, a higher storm surge was measured due to wind setup and the drop (<1000 mbar) in atmospheric pressure. Beach morphology changes, based on GPS measurements conducted before and after the passage of the storms, show alongshore gradients ascribed to the presence of coastal structures and macrophyte wracks on the beach face. Urban flooding occurred mainly on the back barrier associated with heavy inland rain and the coastal aquifer's confinement, preventing rapid infiltration. Two different modeling systems, aimed at providing coastal flooding early warning and coastal hazard assessment, presented difficulties in forecasting the coastal hydrodynamic response during these seaward-traveling events, regardless of the grid resolution, which might be ascribed to a lack of terrestrial processes and uncertainties in the bathymetry and boundary conditions. Compound flooding plays an important role in this region and must be incorporated in future modeling efforts.
