The Effects Of The Floods On The Typical Region Evolution In The Changjiang Estuary

The situation of the three-order bifurcations and four outlets into the sea was formed mainly by the flood in the Changjiang estuary. Flood is a basic force to the evolution of the riverbed in the Changjiang estuary. The geomorphology changes easily in flood. The sediment moves consumingly, shoals-eroded and new-channel often occur. There are many researches on the evolution of the Changjiang estuary. Many of them notice the importance of the effect of the flood. But there are few researches on the effect of the flood as a special topic. So further anglicizing the regulations of the estuary evolution affect by the flood, mastering the trend of the Changjiang Estuary not only enrich the estuary theory, but also can supply the scientific reference to the development and utilization of the Changjiang estuary.On the basis of the former research, according the data of the flood in the Changjiang, the thesis analysis the characters of the flood and the sea-map by the DEM in the GIS, Digitizes the sea-maps during 1842 to 2001, builds the DEM with the method of the Kriging, and then analysis the cross sections, the contours, the erosion and the accumulation of the riverbed, expounds the process of the estuary, analysis the reasons of them.With the research of the flood and its effect to the estuary evolution, we can learn that: the frequency and the max flood peak increase, mainly relate to the globe warming and the human activity. In the effect of the flood, the North and South channel was the main channel alternate, which is relate to the flood. The changes of the channels in the bifurcations are related to the loose boundary, the transverse slope and the axes deflexion in the process of the channels. The geomorphology changes easily with the flood enhance the ebb flow in the estuary. The North Channel changed more consumingly than the South Channel in the Changjiang Estuary, because the channel on the Biandan Shoal in the upper channel changed easily, the sediment move intensely. The cause of the changes of the South Channel is the movement of the Liuhe shoal. The South Channel became a compound channel with the formation of the Ruifeng Shoal. With the analysis of the erosion and accumulation, the North Channel accumulated all around and the South Channel was eroded in the upper section, accumulated little in the lower section from 1880 to 2001. Recently the evolution range of the Changjiang estuary decrease due to the constructions that the Three Gorge, bank revetment, the Deep-Water Channel Project et al. But the effect of...