Hydrodynamic Controls on Multiple Tidal Inlet Persistence

摘要

The importance of the persistence of multiple inlets in coastal systems is fundamental for issues such as navigability, beach/barrier stability, and for more efficient flushing and water exchange between the embayment and the ocean. Previous approaches to analyze inlet stability have focused on single rather than multiple tidal inlet systems. At present, the only multiple tidal inlet stability model available combines a linear analytical model for the flow and an empirical relationship for equilibrium, suggesting that multiple inlet systems are unstable. Focusing on a shallow multiple inlet coastal lagoon in Portugal, the morphodynamic and hydrodynamic response to disturbances in the lagoon and inlets was studied through the analysis of historical data, tidal data (velocity and water surface elevation), and through the numerical modeling of the system hydrodynamics under various inlet scenarios, with emphasis on the contribution of the hydrodynamic response (changes in tidal prism, residual flow, sediment transport capacity, tidal distortion, and cross-sectional averaged maximum velocity) to maintain multiple inlets open. The results show that multiple tidal inlet systems can exhibit stable inlet configurations, and that the strong hydrodynamic interaction between inlets, as well as the non- linear distortion of the tide, play a major role in multiple inlet persistence.