Modeling fluvial processes in tidal inlet

Small sandy tidal inlets of coastal lagoons usually exhibit dramatic changes in morphology under the interaction of storm flow and tidal exchange. While storm flow may keep the inlet open by flushing, the oscillating tidal flow contributes to a net sediment replenishment, or recharge, of the inlet channel. A numerical model has been developed to simulate the fluvial processes during inlet recharge. It provides the time and spatial variations of flow characteristics, sediment transport, and changes in channel morphology for the inlet channel during the recharge period. The model was applied to the inlet channel for the San Dieguito Lagoon in southern California. The recharge is elucidated by the simulated flow pattern that contributes to a net transport of beach sand into the channel. Time variations of the recharge rate were obtained. The total duration of recharge before inlet closure was found to be sensitive to the recharge rate which is affected by the supply of littoral sand. The simulated changes in channel morphology were substantiated by measurements. The study provided inlet opening durations that were used in assessing the enhancement in marine resource value by keeping the inlet open permanently.