Numerical Simulation Of The Formation And Evolution Of The Geomorphic Characteristics Of Huangmao Sea

Huangmaohai Estuary Bay is a semi-enclosed sea area with runoff inflows.It is an important area for establishing ports,stretching channels and logistics trade.Studying the topography and evolution of the Huangmaohai and analyzing the formation of topography and geomorphology is of great significance for studying the formation and evolution of the gully landform.In this paper,the numerical simulation method is used to reveal the relationship between seawater dynamics,sediment deposition,landform evolution and the relationship between the three,and to study the development mechanism of the Huangmao beach trough.The numerical calculation models applied in this paper include hydrodynamic model,sediment transport model and terrain evolution model,and introduce the differential and discrete methods of the model.In order to ensure the accuracy of the numerical model calculation,the pre-statistical tidal level and flow rate results are verified to ensure the accuracy of the hydrodynamic model;the results are compared with the previous statistical results to ensure the accuracy of the sediment transport model;the results are compared with previous simulated terrain changes to ensure the accuracy of the terrain evolution model.Taking the estuary-type bay Huangmaohai as the simulation object,under the suspended sediment transport mode,the ideal slope topography was used to simulate the topographical features of the “two-slot three beaches” of Huangmaohai before 1936,and the bedrock was considered at the entrance of the runoff.The suspended sand model corrects the results.The simulation results show that the suspended sediment transport is also the main sediment transport mode formed by the sand shoal between the island of Hebao and the Dagu Island at the offshore end of the estuary.The contribution of the sediment transport is mainly caused by the deep trough in the upper section of the eastern trough.The main reason for the formation,the formation of the downstream end of the eastern trough(the triangular mountain area)only appeared in the terrain simulation results modified by the Hansen sediment transport model.However,the formation of the west trough between Hebao Island and Dagu Island is only due to the contribution of suspended sediment transport.Discussing the effects of separate runoff,tidal current and residual current,it is concluded that the runoff promotes the extension of the Dongtan and Xitan-2m contour lines to the central river channel,but the runoff has little impact on the geomorphology of the remote delta mountain island and Dagu Island.The tidal action caused the-3m isobath to shift to the west bank,indicating that the trend promoted the formation of the east trough,the shoal and the west trough.The remaining stream participates in the formation of the West Beach,the sea ring shoal and the west trough.Taking the actual terrain of Huangmaohai in 1936 as a simulation object,the topographic evolution of Huangmaohai after 1936 was simulated under the suspended sediment transport mode.By comparing with the actual sea chart of Huangmaohai in 1977,1994 and 2003,the simulation results are more reasonable.The simulation shows the evolution law of the Huangmao beach trough: the west beach is silted up year by year,and the sedimentation degree is greater than that of Dongtan;the sand shoal of the barrier gate moves toward the sea year by year;the west trough shrinks,and the upstream part gradually disappears in the sand shoal of the gate,the east trough the bottom of the water continues to accumulate.