Connections Between Land and Sea at a Bar-Built Estuary: Morphological Modeling Carmel River Lagoon Using DELFT3D

Almost half of the world's rivers are categorized as bar-built estuaries with seasonal and climate dependency, impacting current and future Naval and Marine Corps operations near shore. These dynamic coastal systems are characterized by the interaction of sediment transport, hydrodynamics, and morphological evolution. Understanding the intricate interplay between these forces influences planning for maritime operations and coastal engineering. This study will enhance the understanding of how bar-built estuaries evolve over time and space using Delft3D numerical modeling. This research uses in-situ data from Carmel River State Beach during March 2020 and several numerical simulations. Numerical model calibration is completed by testing numerical parameters sensitivities, wave characteristics, sediment properties, bathymetry, inlet morphology, and tidal exchange. The insights gained from these simulations inform the dominant morphological processes and numerical parameters governing the geomorphologic response of the system while refining existing numerical models for predictive capability. Simulations indicate that the river bathymetry most influences the water level response more than the location of the inlet. Shallower bathymetry yields rapid widening of the channel with northward migration compared to deeper bathymetry. Offshore wave direction has minimal impact on the inlet morphology. Removing river discharge impacts inlet geometry and reduces the migration rate north.