| The sediment concentration is one of the important physical quantities which can reflect sediment movement,so it is of great importance to understand and grasp characteristics of coastal sediment concentration distribution.For coastal seas near tidal flat,as one of the most important sources of sediment supply in coastal waters,tidal flat reclamation may lead to the change of the hydrodynamic conditions and the input of marine sediment,which will have a far-reaching impact on the sediment concentration.Therefore,it is also necessary to research the response of sediment concentration to the tidal flat reclamation.Based on field measurement data in the winter of 2011,summer of 2012 and autumn of 2014,this paper analyzed the variation in suspended sediment concentration(SSC)in a tidal cycle,the seasonal differences of SSC,the spatial distribution of SSC and the forming reasons of them in Damutu seas by the methods of comparison and induction.The two-dimensional coupling model of water and sediment under current and wave was established by MIKE21.The distribution of suspended sediment field after reclamation of lm isobaric line and 3m isobaric line was simulated respectively,and the simulation results were analyzed and explained.The results suggest that clockwise rotation flow is dominant in Damutu seas,and the flow nearshore affected by the terrain presents a certain degree of reciprocation.The basic flow of the trend line is with the coastline,and ebb current prevails in coastal area.The tidal power distribution of the sea area has the characteristic of "coastal area is small,offshore area is large,northern area is small,southern area is large,winter is small and summer is large".And standing wave characteristic is significant.The process of variations in SSC in a tidal cycle mainly presents no-peak pattern in the nearshore and central seas.However,one-peak pattern mainly occurs in the external seas.Only in the southern nearshore seas,the SSC shows two-peak pattern.About the average SSC during the flood tide and e'bb tide,the former is more likely larger than the latter in the nearshore seas,while in the external seas it is totally the opposite.The vertical gradient of the sediment concentration in the non-peak and two-peak varies remarkably with the flow,while one-peak pattern seas performs as "sediment concentration is high and vertical gradient is large in ebb tide,and vice versa".In winter,the vertical distribution turns collimation line pattern,while oblique line is the main pattern of vertical distribution in autumn.However,in summer,the vertical distribution of SSC appears exponential pattern.The distribution pattern of the sediment concentration doesn't change under the large-sale reclamation according to the lm isobath and the 3m isobath,but it has a great influence on the sediment concentration in the coastal waters,followed by the middle seas and the influence on external seas is real small.The lm isobaric reclamation makes the variation of sediment concentration up to 13%,and the maximum sediment concentration change of 3m isobaric reclamation is 26%.The sediment concentration in the spring tide is generally larger than that in the low tide period.The winter sediment concentration changes obviously,and the summer effect is less than 2%. |
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