A Study On The Impact Of Sediment Transport Rate In Coastal Topography Evolution

Coastal sediment transport is the main cause of coastal deformation.Therefore,it is of great value to study the influence of sediment transport rate in the evolution of coastal topography for studying the characteristics of coastal landforms.In this paper,the formation of three types of coastal topography,including sandbars,sandbar trenches and coastal oblique sandbars,is studied in Yueliangwan,and the influence of sediment transport rate on the evolution of different coastal topography is discussed.For the formation of the island-connected sandbar terrain in Yueliangwan,the results show that the oblique incidence of waves will cause coastal sediment transport,and the sediment will accumulate between the inland side of the trestle and the coast to form the island-connected sandbar terrain.Incident waves from different directions will affect the formation process of the Liandao sandbar.When the wave incident angle θ=-45°,the sand body develops from the trestle to the coast.When the wave incident angle θ=-30°,the sand body formed by sedimentation between the trestle and the coast develops toward the trestle and the coast at the same time.When the wave incident angle θ=-15°,the sand mouth formed on the shore moves from the coast to development in the direction of the trestle.When the terrain of Moon Bay becomes deeper,sediment will accumulate between the trestle and the coast,which in turn promotes the formation of the island-connected sandbar.The flow term of the sediment transport rate promotes sediment deposition on the inland side of the trestle.Both the shortwave term of the sediment transport rate and the acceleration term of the water quality point can promote the formation of the sand bar in Liandao.The acceleration term of the sediment transport rate aggravates the deposition of sediment on the shore and promotes the development of the spit to the sea.For the formation of the sand bar trench topography,the results show that a small periodic disturbance is applied to the sand bar peak and before and after the dam peak.Driven by terrain instability,a stable sand bar trench topography will eventually be formed.The flow term of sediment transport rate plays a leading role in the formation of sand bar trenches.Neither the short-wave term of the sediment transport rate nor the acceleration term of the water quality point will affect the position and width of the sand bar groove.The short-wave term of the sediment transport rate causes sand transport to the shore,and the sediment is deposited in the sand bar trench and between the sand bar trench,which reduces the water depth at the sand bar trench.Since the sediment deposition between the trenches of the sand bar is larger than that at the trench of the sand bar,the depth of the trench of the sand bar is further deepened.The acceleration term of the water quality point of the sediment transport rate causes the sand transport to the shore,which intensifies the scouring of the sediment on the offshore side between the sand bar trenches,but there is no scouring at the sand bar trenches.The scoured sediment is deposited on the dam peaks between the trenches of the sand bar,which further deepens the depth of the trenches of the sand bar.For the formation of the topography of the oblique sand bar on the coast,the results show that after a slight topographic disturbance is applied to the flat sloping coast,the interaction between the coastal current and the topography will produce terrain instability,resulting in the topography of the oblique sand bar on the coast.Formation.The flow term of the sediment transport rate promotes the development of the coastal oblique sand bar and plays a leading role in the formation of the coastal oblique sand bar topography.Neither the short-wave term of the sediment transport rate nor the acceleration term of the water quality point will affect the position of the oblique sand bar on the coast.The short-wave term of the sediment transport rate promotes the development of the oblique sand bar on the coast,inhibits the development of the oblique sand bar in the seaward direction,and weakens the scour at the groove of the oblique sand bar.The water quality point acceleration term of the sediment transport rate inhibits the lateral development of the oblique sand bar,aggravates the sedimentation at the connection between the oblique sand bar and the coast,and changes the inclination angle between the oblique sand bar and the shoreline.