The Research Of Wave Currents Effects On The Topographic Evolution Of Lagoon Coast

The lagoon coast is an important part of the sedimentary coast,and its formation and evolution are inseparable from the effects of offshore hydrodynamics.As a main component of the offshore water dynamics,the wave current has an important impact on the formation and evolution of the lagoon coast.Studying the influence of wave current on the landslide coast topography has important practical significance for channel development,dredging and coastal engineering construction..In this paper,the numerical simulation method is used to explore the influence of wave current on the topography and evolution of the lagoon coast.The numerical model used in this paper is composed of three parts: hydrodynamic model,sediment transport model and terrain evolution model.The hydrodynamic model considers the effects of tidal current and wave current,and gives the corresponding difference format and Discrete method.In order to ensure the accuracy and effectiveness of the numerical model,this paper verifies the hydrodynamic model by comparing with the experimental test data,and uses the method compared with the theoretical solution to verify the sediment transport model.In this paper,the typical lagoon coast-Shuidongwan lagoon coast is used as the numerical simulation object,respectively,in the flow of individual tidal current,separate residual current,individual wave stream,wave current and tidal current coupling,wave current and residual current coupling.The field and terrain evolution process is simulated.The simulation of the flow field shows that the flow field of Shuidong Bay is dominated by tidal currents,and the residual current characteristics are more significant.The waves are broken on the outside of the lagoon and have little effect on the flow field in the lagoon.Affected by the topography,the development of deltas on the east and west sides of the tidal channel has obvious asymmetry.The single tidal current contributes a lot to the formation of the delta in the west.The waves in different directions cause different scouring and silting on both sides of the tidal channel,of which SSW direction Waves contribute a lot to the formation of the eastern delta,and the waves in the SSE direction contribute more to the western delta.When the wave flow and the tidal current formed by the SSE direction wave act together,the topographic evolution law has the characteristics of the tidal current and the wave flow alone.When the wave flow and the residual flow work together,the topographic evolution has obvious residual flow characteristics.Finally,the formation and recent evolution of the ebb-tide Delta in Shuidong Bay are simulated by using the data of wave stations,and the contribution of wave-induced current and tidal current in the formation of the ebb-tide delta is analyzed.The main contribution of tidal current is sediment deposition in the estuary.The contribution of wave-induced current is mainly reflected in sediment deposition on both sides of the tidal channel caused by sediment transport along the coast.Sousbly and suspended sediment transport weighted model are used to simulate the recent topographic evolution of Shuidong Bay.The simulation results are in good agreement with the recent delta erosion in Shuidong Bay.By analyzing the effects of wave-generated currents and tidal currents,the erosion of 1 m Isobaths in ebb-tide delta is related to the weakening of recent tidal current and the relative enhancement of wave action in Shuidong Bay.