Assessing Storm Impact on a Stretch of Coast of Puerto Rico using Morphodynamic Modeling

The devastating effects of the extreme storm events along the coasts of Puerto Rico between the 2017 and 2018 hurricane season have pointed to the urgent need of assessing the effects of hydro-morphodynamic phenomena at coastal areas. The coastal problems have been more drastic in the western region of Puerto Rico, particularly in the municipality of Rincon. To date, most of this coast has not recovered its pre-storm condition. Hence, this study seeks to identify the main factors controlling the storm-induced beach morphological changes (erosion & accretion processes) in Rincon during two major storms; Hurricane Maria in September 2017 and Winter Storm Riley in March 2018. The impact of each storm has been assessed through observations of waves, currents, and bathymetric change in shallow water, as well as numerical model simulations. A 3-D coupled wave-current-sediment transport numerical model (Delft3D) was used to assess the coastal response during storm conditions. A non-structured grid allowed variable spatial resolution, providing the ability to refine the grid cell size in areas of interest and/or regions where large horizontal gradients in wave height or current velocity were expected. Model-data comparisons allowed to test how storm intensity enhances sediment transport in the study area. Moreover, the validation showed that the numerical model configuration could replicate the morphodynamic processes responsible for the measured morphological changes at the beach. The numerical simulations demonstrated that west-northwesterly swells generated by Hurricane Maria cause extreme erosion while north-northwesterly swells generated by Winter Storm Riley help accrete the nearshore. Based upon findings of this study, a better understanding of the coastal dynamics of Rincon is being achieved which could provide important insights for coastal management strategies.