| Straits linking two bodies of sea water provides a channel for the transport and exchange of a variarity of materials (e.g. sediment, nutritients, contaminants, and microorganisms). In the field of marine geology, it is of particular interest to consider sediment sxchange through the starit. Because of the highly variable topological and hydrodynamic condifitions at a strait, the distribution of sediment is complex, with a large gradient in grain size parameters. This is a favorable condition for the understanding of the processeses and mechanisms of sediment transport and the associated local and regional effects. As a channel for the exchange of sediment between the Bohai and the Yellow Seas, the Bohai Strait is a good example.On the basis of considerationbs of the physical domain, the characteristics of the tides and sediment distribution patterns of the Bohai Strait, a 2-D horizontal model has been designed to study the long-term transport of sediment and accumulation over the Bohai Strait region. The model output is consistant with field observations, and can be used to explain patterns of long-tern transport and deposition of sediment in the study area.The vertically averaged current velocity is transferred into the current velosity at 1 m above the seabed using the Von Karman-Prandtl equation. Such a transformation is proved to be suitable in the study area by the verification using the ADCP data from 4 stations within the Strait. An expression is derived using basical concepts of physics (i.e. mass conservation), to define the relationship between sediment transport rate and vertical flux of sediment to the seabed. Using this method, satisfactory results about the evolution of the seabed are obtained, which is consistent with in situ observations. This method is better than the traditional method that relates the divergence of sediment transport rate to the deposition rate.The output of the tidal modelling reaches the required precision according to a comparison between the calculated tidal amplitudes/phases and the observed ones at 42 coastal tide gauge stations. Thus, the co-tidal patterns from calculations match observations, indicating .the validity of the tide model.The distributing patterns of the Eulerian residual currents of the four major tide constituents (i.e. M2, S2, Ol and Kl) imply that fine-grained sediment transport over the central mud of the northern Yellow Sea is weak. The Eulerian residual currents of Kl and S2 respectively form an anti-clockwise eddy near the coastal mud-deposit area of northern Shandong Peninsula, which may increase the deposition rate of mud. Although the patterns of residual currents are likely to reflectthe patterns of fine-grained sediment transport, it is difficult to relate such patterns to the transport of coarse-grained sediment.The result of long-term net sediment transport calculations confirms the hypothesis proposed by Cheng (2000) that in this area transport of sediment directed to northeastward occurs in addition to the main trend of transport towards the east. In the central mud of the northern Yellow Sea there lies an anti-clockwise eddy, indicating that sediments converge here, and once again confirming the conclusion reached by Cheng (2000) that sediment convergence occur in the central northern Yellow Sea. Off the south coast of Liaodong Peninsula, the net transport patterns from the model and from grain size trend analysis (Cheng, 2000) differ. The results of grain size trend analysis for this particular location is in doubt, because erosion is taking place here and the premise of the use of trend analysis is violated.Excellent correlation exists between the distribution of bottom shear stress and that of sediment types. Low shear stress occurs in the central mud area; where only fine-grained sediment can be imported by weak tidal currents. Once settled into the bed, it is difficult for set the sediment into motion. Therefore, the central mud represents an area of continuous depositon of fine-grained sediment.Good corre...
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