Basin Flow & Sediment Transportation Model And Its Application In The Upper And Middle Yangtze River

Chinese people have being suffered by the flood disaster. With the development of human activity, sediment has been an important factor that affects the flood disaster. The sediment disaster and water disaster combine the water and sediment disaster. Since 1990s', the new features of the flood disaster happened such as small discharge and high water level, big area and large range and so on. With the development of economy and human activity, the risk caused by the water and sediment hazard will increase. It is of important value for the prevention and control of water and sediment disaster to study the forming process and mechanism.The study of water and sediment disaster includes different aspects of water and sediment transport, all the disasters such as soil and water loss and flood disaster and so on are reflected by them. Because of the sediment motion features of accumulation, group generation, chain generation, the disaster chain and the integrative disasters in the whole basin can be formed through the water and sediment transport, which includes water and sediment loss, reservoir deposition in the upper basin and channel deposition, lake shrinkage in the middle and downstream basins and so on. The sediment yield, transport and accumulation in the basin have become the critical factor. So the basin water and sediment transport is the premise of forming water and sediment disaster. The study on water and sediment transport process is the key problem of studying water and sediment disaster. Based on the previous conditions, according to the insufficiencies of existed studies, this paper presents a new idea and a frame of basin water and sediment simulation. The basin transport model of water and sediment is established by the approach of dividing the basin into different calculated units, applying several associated methods and combining many models. The transport mechanism of basin water and sediment in the middle and upper reaches of the Yangtze River is studied systematically by using this model. Some conclusions are obtained through analyzing the transport changes of water and sediment in the middle and upper reaches.In the first chapter the origination, background and significance of the topics are described. The recent research status and the current advances of the research methods of the forming mechanism of water and sediment disaster are summarized. With the development of water and sediment disaster, the single flood simulation is difficult to reflect the natural and true situation. The partial water and sediment model can't reflect the conjunction and response mechanism between the upper and downstream basin. The transport simulation of water and sediment in the whole basin is necessary which is studied rarely at home and abroad without the good examples using for reference. The main research contents are summarized in the end of this chapter.In the second chapter, according to the feature of the transport of water and sediment, the disadvantages of the present researches and existing problems, the transport model of basin water and sediment is established. The model shows the relation between the upper and downstream reaches based on the macro basin and provides an advantageous tool to study the water and sediment disaster in the whole basin.In the third chapter, on the basis of reviewing the present studies on the soil and water loss and water sediment yield in the middle and upper reaches of the Yangtze River, the soil and water loss in the upper reaches of the Yangtze River is researched comprehensively on the definition, types, status, influence factors and impact to the water and sediment hazard. Then, the process of sediment erosion, transport and deposition are studied preliminarily after soil and water loss. The transport law of water and sediment in the middle reaches of the Yangtze River is studied on the historical evolution process of river and lake, the transport change of water and sediment in different regions. The increasing water and sediment disaster in the middle reaches are caused by the recent change of sediment deposition in those different regions. The large sediment deposition in Chenglingji to Hankou reach is an important factor that caused the phenomenon of small discharge and high water level. The quantitative study on water level change at Luosan and the flood storage capacity in Dongting Lake caused by sediment deposition are given in this chapter.In the fourth chapter, the basin transport model of water and sediment is applied to study the mechanism of water and sediment in the middle and upper basins of the Yangtze River. According to the factual situation and varied units, the different simplified models are established such as water and sediment yield model using ANN method, the water and sediment regulation model benefiting to flood control and electricity generation in the three Gorges Reservoir, 1-d model of water and sediment in the middle reach of the Yangtze River, the empirical model of water and sediment in Dongting Lake and so on. Those models are integrated to the basin model of water and sediment. The impact of the different water and sediment sources in the upper Yangtze River to the sediment amount in Yichang station, the response of the different regions in the middle reach to the changes of water and sediment in the upper reach of Yangtze River before and after the construction of TGP are analyzed by the established model. In the end of the chapter, the prevention and control strategy of water and sediment disaster in the Yangtze River basin is presented.The conclusion and prospect is given in the fifth chapter.