Abstract A new numerical model was developed to simulate regional sediment transport and shoreline response in the vicinity of tidal inlets based on the one-line theory combined with the reservoir analogy approach for volumetric evolution of inlet shoals. Sand bypassing onshore and sheltering effects on wave action from the inlet bar and shoals were taken into account. The model was applied to unique field data from the south coast of Long Island, United States, including inlet opening and closure. The simulation area extended from Montauk Point to Fire Island Inlet, including Shinnecock and Moriches Inlets. A 20-year long time series of hindcast wave data at three stations along the coast were used as input data to the model. The capacity of the inlet shoals and bars to store sand was estimated based on measured cross-sectional areas of the inlets as well as on comprehensive bathymetric surveys of the areas around the inlet. Several types of sediment sources and sinks were represented, including beach fills, groin systems, jetty blocking, inlet bypassing, and flood shoal and ebb shoal feeding. The model simulations were validated against annual net longshore transport rates reported in the literature, measured shorelines, and recorded sediment volumes in the flood and ebb shoal complexes. Overall, the model simulations were in good agreement with the measured data.