Hazard assessment and hydrodynamic, morphodynamic, and hydrological response to Hurricanes Gamma and Delta, on the northern Yucatan peninsula

Abstract. Barrier islands in tropical regions are prone to coastal flooding and erosion during hurricane events. The Yucatan coast, characterized by karstic geology and the presence of barrier islands, was impacted by Hurricanes Gamma and Delta in October 2020. Inner shelf, coastal, and inland observations were acquired simultaneously near a coastal community (Sisal, Yucatan) located within 150 km of the hurricanes’ tracks. In the study area, Gamma moved at a slow speed and induced heavy rain, mixing in the shelf sea, and northern winds exceeding 20 m s-1. Similar wind and wave conditions were observed at this location during the passage of Hurricane Delta. However, a higher storm surge (0.5 m) 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. Moreover, net onshore sediment transport during the storm contributes to the increase in beach elevation. Urban flooding occurred mainly on the back-barrier associated with heavy rain and the confinement of the coastal aquifer which prevented rapid infiltration. Two different modeling systems, aimed at providing coastal flooding early warning and coastal hazards assessment, presented difficulties in forecasting the coastal hydrodynamic response during these seaward translating events, regardless of the grid resolution and wind forcing employed. Compound flooding plays an important role in this region and hence must be incorporated in future modeling efforts.