Presenter: Yan Ding (USACE-ERDC-CHL)

Description:
Understanding long-term evolution of regional shoreline and tidal inlet morphology in barrier islands is essential for planning and management of coastal erosion protection measures (e.g. beach fills), navigation channel dredging, and offshore sand borrow sources. Prediction of regional-scale shoreline changes needs to quantify sediment exchanges between inlet morphological elements and adjacent beaches. Those morphological elements include an ebb shoal, flood shoal, bypass bars, and attachment bars. Even though some existing multi-dimensional coastal processes models can simulate the evolution of tidal inlet morphology, the capabilities of predicting long-term shoreline changes with erosion protection measures are still lacking. In this study, a shoreline evolution model with an inlet morphology model for predicting volumetric evolution of inlet morphological elements was applied to simualte long-term regional shoreline evolution around two coastal inlets (Indian River Inlet and Absecon Inlet) in the east coast of the United States. The simulations considered various coastal processes such as nearshore wave dynamics, longshore sediment transport, coastal erosion due to sea level rising. The shoreline model also simulated nature-based erosion protection measures (e.g. sand bypassing, beach nourishment, and beach fills) around inlet and coastal structures. Model validations over a decadal period were performed by evaluating statistic errors of simulated shoreline positions. Efficacy of sediment exchange between inlet and shores was quantified by the volumetric changes of shoals and bars estimated by the inlet model, in which dredging operation at sand borrow site was included. Numerical simulation of long-term evolution of shoreline and inlet morphology provides better understanding of sediment pathways through inlet shoals and adjacent shorelines, and facilitates long-term impact assessment of erosion protection measures.