Morphologic modelling of tidal inlet on a barrier-lagoon coast: Case study of the Laolonggou tidal inlet in the Bohai Bay.

• Morphodynamic hindcast of evolution of multiple-inlet system on barrier-lagoon coast was studied by a process-based model. • The evolution mechanism of two deep channels were studied respectively under a series of initial conditions. • Numerical results revealed how the shape of Barrier Islands and changes of sediment supply affect the morphologic evolution. Understanding the long-term morphodynamic evolution of tidal inlet systems and their control mechanisms has great significance in the management and sustainable development of coastal regions. This study addresses this issue by applying a process-based morphological model (Delft3D) to hindcast morphodynamic evolution of the Laolonggou tidal inlet (LTI) for a duration of 68 years and then analyze the mechanism of morphologic evolution and factors affecting it in tidal inlets. The morphodynamic model is validated against two periods, a natural stage (1938–1983), and a recent erosion stage with reservoir construction (1983–2006). Results show that the evolution pattern, sediment volume changes, and hypsometry curves simulated by the model agree well with field data. A series of scenarios were designed to analyze the mechanism of morphologic evolution and impacting factors. The model results reveal that the asymmetry of the tidal currents in the channels leads to tide residual sediment transport, which causes morphodynamic evolution. The inconsistency of tidal flow path, i.e., ebb dominance occurs in the west channel and flood dominance occurs in the east channel, is an important mechanism for the evolution of the whole system. In addition, the decrease of sediment supply caused by reservoirs in Luanhe River, and extension of the barrier island contribute to the evolution of LTI. Although this study is site-specific, the results are expected to provide valuable information for sustainable management of tidal inlet systems. [ABSTRACT FROM AUTHOR]