Modeling hurricane-induced total water level and coastal change across heterogeneous coastlines

Abstract

Abstract Elevated water levels during storms cause coastal flooding and erosion, damaging property and infrastructure. Hurricane Maria eroded about 35% of Puerto Rico's coast (Barreto et al., 2020). We developed a probabilistic assessment for coastal change in Puerto Rico under worst-case hurricane scenarios. Using the one-dimensional XBeach-Surfbeat model, we simulated 332.5 km of coastline, factoring in site-specific bathymetric profiles and bottom roughness. Synthetic hurricane data of water level and wave-forcing from the Caribbean Coastal Observing System Storm Surge Atlas (Benítez and Mercado-Irizarry, 2015) were used as initial and boundary conditions to generate worst-case hurricane conditions impacting each coastline portion. Each hurricane category was determined by the maximum sea surface elevation across all runs. We assessed the likelihood of coastal changes such as erosion, overwash, and inundation by comparing total water levels (TWL), including surge and infragravity waves contributions, and accounting for dune and cliff alongshore variability. For Category 1 hurricanes, about 95% of dunes would likely erode, 12% might overwash, and 2% could inundate. In Category 5, these percentages increased to 100%, 48%, and 23% respectively. In Category 1 hurricanes, wave-driven water levels contributed up to 90% of TWL, but in Category 5, storm surge played a more significant role, decreasing wave-driven water level contribution to as low as 5%. These results highlight the need for considering both parameters and the need for site-specific modeling. The study resulted in a web-based tool for emergency managers and planners in Puerto Rico, aiding decisions in a region vulnerable to severe storms.