A Study Of Suspended Sediment Dynamic Processes Based On Observations Using ADP And OBS In The Changjiang Estuary

Suspended sediment concentration (SSC) is the main carrier of the nutriment and contamination. The movement of SSC is the important mechanism of scouring and silting of the topography. Thus, study the movement of SSC is very significant for zoology, environment, engineering and management.The Changjiang Estuary is the important estuary over the world. It is the main channel of the forth transport sediment, the fifth larger river discharge, the first drainage basin of the population in the world, respectively. It is bearing heavy responsibilities for offering the ground in support of the city in Shanghai which is the world-class metropolis, and the deep navigation channel of the important harbor. The problem of SSC is much more stand out in the Changjiang Estuary recently. There two reasons for this, first, the sediment transport to the Changjiang Estuary is decreasing quickly due to lots of significant irrigation projects (such as the Three Gorges) which cause the estuary delta turns from silting to eroding. Secondly, some significant projects in the estuary delta are being built or going to be constructed, such as the deep navigation channel of North Passage, the reservoir of Qingcaosha and the enclosing tidal-flat in the near future. The demand of economic development and the question of the science itself need to deeply understand the dynamics of suspended sediment in the high turbidity estuary - Changjiang Estuary.Study the law and mechanism of the variations in SSC are the important parts of the dynamics of suspended sediment. The traditional observation method of SSC is to sample water and analyse them in lab. Although this method can obtain the values of SSC immediately, it has the long time interval (1 hour interval) and the big range in water column (the method of 3 or 6 layers) and it is natural to miss the peak value of SSC. The traditional method of dynamic process of suspended sediment is usually uses the current meter which is 1h interval and 3 or 6 layer in the water column. The method of the field observation in the inter-tidal flat is needs more improving. Observations of the SSC and the dynamic processes using the optical (such as OBS) and acoustic (such as ADP/ADCP) instruments are becoming very popular in the world. There are many questions require to research when using these instruments because of the development of the instruments and the different of the study areas.The South Passage which is little affects by the human being is the main channel of water discharge and sediment in the Changjiang Estuary. East Chongming Island is the tidal flat which is the most representative and potential utilizing in the Changjiang Estuary. The two areas were selected as the study subjects in this paper. Observations were deployed to obtain the field data of SSC and the dynamic process using the OBS and ADP. The purposes of this paper are trying to improve the cognition of the variations of suspended sediment law and the dynamic mechanisms, and at the same time, offering the theory support for the decision-making of managing department and construction of the costal engineering.The new cognitions and conclusions in the paper are including: (1) Observation on profile of SSC in the water column was deployed using OBS-5, which is setting 1 s interval. This can obtain much precise and reality vertical profiles than that of the traditional method. The "Far" parameter from OBS-5 can calculate the SSC which is making up the shortage of the NTU is no more than 500. This is means OBS-5 is also better used to observe the SSC in the Turbidity Maximum (TM) in the Changjiang estuary. (2) The semi-empirical model of SSC which is...