SPATIAL AND TEMPORAL VARIATION OF SUSPENDED SEDIMENT IN THE AREA SURROUNDING MIAODAO ISLANDS AND ITS RESPONSE TO SUMME TIDE

Data of suspended sediment concentration and spring and neap tidal fluctuation are collected at 6 stations in the vicinity of the Miaodao Strait. Temporal and spatial distribution and variation in suspended sediment are studied. Upon the basis, we discussed the influence of tidal current onto the concentration of suspended matter. The results show that the concentration of suspended sediment is quite high in the Strait, but lower in the deepwater area surrounding the strait in horizontal direction. The suspended concentration gradually increases from the surface to the bottom and decreases from spring to neap tide. The variation of the concentration of suspended sediment has an obvious periodic pattern with time. In spring tide, the change mainly happened on 6-8 h, while in neap tide there are two kinds of cycle happened at 4-6 h and 6-8 h respectively. The concentration of suspended matter increases with increasing flow velocity. However, the maximum concentration of suspended sediment is 1-2 hours behind the peak value of current. Owing to the resuspension, water stratification and deposition in surface layer, the response of suspended sediment concentration to the flow velocity is in a specific manner. It is obviously responding to high flow velocity in the bottom layer, but to low velocity in the surface layer.