| The source-sink process of terrigenous sediments from the basin in the argillaceous sedimentary system is a hot topic in current research.However,the relevant research is mainly concentrated in large river basins,and the source-sink system for small and medium sized rivers are slightly weak.The Yalu River is located at the mid-high latitude and is a typical small and medium sized mountain stream river.The source to sink processes of fine-grain sediments from the Yalu River basin in the muddy area on the east coast of the Liaodong Peninsula are unique.Fine-grained sediments from the basin are an important source of argillaceous sedimentary systems and a carrier of nutrients and pollutants.The study of the sedimentation of fine-grained sediments from the basin to the argillaceous sedimentary system for the analysis of sediments in coastal areas The formation mechanism of landforms,the spread of pollutants and the ecosystem are of great significance.Water color remote sensing,sedimentary dynamics observation and numerical simulation are three common methods for studying suspended sediment transport.The cost of sedimentary dynamics field observation is high,and it is difficult to obtain synchronized survey data in a wide range of sea areas;water color remote sensing is suitable for simultaneous observation of large-scale sea areas,but instantaneous remote sensing images are difficult to explain dynamic suspended sediment concentration changes;It is lower,but many parameters are determined by empirical formulas,and the simulation results are difficult to match the real situation.Therefore,combining the three methods to study the sediment source-sink process can make up for the deficiency of the single method and improve the reliability of the research resultsTherefore,this paper takes the muddy area on the east coast of the Liaodong Peninsula as the research site,and conducted two voyages in the east coast of the Liaodong Peninsula from July 14 to 31,2016,and from February 26 to March 17,2017.Observation.These include the collection of water samples from 23 stations and the full-scale hydrological observations of four anchor stations.Based on the measured concentration of suspended sediment and the GOCI image,the concentration of suspended sediment in the surface of the sea from April 2011 to March 2017 was inferred,which revealed the temporal and spatial characteristics of surface sediment concentration in the sea area.The impact of tidal currents,windy weather and floods on the concentration of suspended sediment.Using MIKE 21,a two-dimensional wave-flow coupled numerical model for the muddy area on the east coast of the Liaodong Peninsula was established.The flow field of the tidal period,the tidal period and the flood season in 2016-2017 were simulated,and the anchor system was used.The hydrodynamic data of the station observations were verified and the results are as follows.(1)The concentration of suspended sediment in the muddy area on the east coast of the Liaodong Peninsula is generally from east to west,decreasing from land to sea,and the estuary is a high value center;the wave enhancement caused by north and northerly winds is the cause of the dry season.The distribution of sand concentration and high suspended sediment concentration is significantly larger than that of the flood season.Although the suspended sediment concentration in the flood season study area is generally low,the suspended sediment concentration during the flood period can be significantly improved,and shows the diffusion process from east to west;affected by the fluctuation tide,the concentration of suspended sediment during the ebb tide and The distribution of high suspended sediment concentration is significantly larger than the high tide.(2)The seawater flow rate in the study area has seasonal changes.The seawater flow rate during the flood season is large in the east and small in the west.The seawater flow rate during the dry season is small in the east and large in the west.The eastern sea area is affected by the estuary circulation,and the vertical velocity changes greatly,while the vertical velocity of the western sea area changes little.The concentration of suspended sediment in seawater is large in the dry season and small in the flood season,and gradually increases from the surface layer to the bottom layer,indicating that the suspended sediment concentration in this area is significantly affected by the resuspension.According to the calculation results,the sediment transport in the study area has spatial and temporal changes.In the sediment transport,the sediment transport in the western part of the study area is larger than that in the east;the sediment transport in the dry season is greater than the flood season.In the direction of suspended sediment transport,the suspended sand flood season in the western part of the study area is transported to the southwest and transported to the southeast in the dry season;the suspended sand in the eastern sea is transported to the southwest throughout the year.(3)Numerical simulation results show that there is a seasonal difference in water level and flow velocity in the study area.In the whole study area,the water level in the flood season is significantly larger than that in the dry season;in the eastern part of the study area,the seawater flow rate during the flood season is greater than that in the dry season,while in the western part of the study area,the seawater flow rate during the flood season is less than that in the dry season.The Euler residual current in the nearshore area is significantly larger than the offshore area,and the direction is mostly from west to east,parallel to the shoreline.In the vicinity of the Changshan Islands and Wangjialie Island,the island is shielded to form a residual vortex that rotates counterclockwise around the island.(4)The suspended sediment concentration and suspended sediment transport flux in the dry season of the study area were significantly greater than the flood season.In the dry season,the suspended sand transport direction in the nearshore area is transported to the southwest,while the suspended sand transport direction in the offshore area is transported to the northeast;in the flood season,the suspended transport direction of the entire study area To transport to the southwest.Due to the influence of island shielding,the suspended sand transported to the northeast in the dry season is deposited on the southeastern part of the Changshan Islands and Wangjialie Island.In the windy weather,the residual flow from the near shore to the southwest of the study area is enhanced,so that the suspended sand is mainly transported to the southwest.The suspended sediment transport pattern of the study area is similar to that of the Yangtze River and the Yellow River which characterized by "deposit in summer and transport in winter",but the location and mechanism of summer storage and winter transport may be different,which needs further study. |
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