Distribution Of Surface Suspended Sediment And Characteristics Of Estuarine Front In The Changjiang Estuary Area After The River Closure At Three Gorge

This paper collects the inversions of the surface suspended sediment concentrations at the Changjiang estuary before and after the interception of the Three Gorges from 1988 to 2007 using twelve Landsat TM images. The spread environment of the surface suspended sediment of Changjiang estuary during flood season and dry season and the changjiang trend of the scope of high turbidity water is qualitatively described. The characteristics of the morphological change of the river sediment's moving into the sea and surface suspended sediment concentration are analyzed.The distribution characteristics of the surface suspended sediment after the interception of the Three Gorges is studied through experimental processing on sample data of the surface suspended solid collected from the offshore area of the Changjiang estuary from 2002 to 2004; Data of field observation were obtained in the Yangtze estuary, to study the characteristics of dynamics. Using data of current velocity and suspended matter concentration, the location of estuarine front is identified, which locates along the line of (122°10'E, 30°50'N) to (122°20'E, 31°00'N). Due to strong interaction of river and sea, the changes of current velocities do not correspond with typical current velocity curve of logarithm. Interaction between river water and sea is confined to 5m depth. And in the front, suspended matters are transported above sea water.Due to the storage function of the Three Gorges, the concentration of suspended solid in the Changjiang estuary is found to decline, while the spread scope of suspended solid and correspondingly the pinnate frontal zone of the offshore area move toward the estuary gate.Using two-dimensional simulation, the flow condition outside the Changjiang estuary in each season as well as the development situation of the frontal zone in the estuary is successfully simulated. It shows that estuary frontal zones tend to appear in spring, summer, and autumn and be most well-developed during neap tides. The ocean dynamic of the estuary of Changjiang is relatively strong in winter, which is likely to bring seawater intrusion, especially in the northern branch. Summer is the main construction period of the Changjiang Delta. The frontal zone leads to sedimentary around it; spring and autumn are balance periods; winter is the major period of erosion.