DIVERSION MODEL OF FLOW AND SEDIMENT TRANSPORT WITH EROSION AND DEPOSITION IN RIVER

摘要

In Yangtze River, from Chenglingji to Jiangyin with a total length of 1,150km, there are 41 braided reaches, the typical ones of these include Tianxing Bar in Wuhan, Zhangjia Bar in Hukou, and Bagua Bar in Nanjing, etc. In addition, the levee break forms new diffluent rivers, the famous three diversions, Songzi, Taiping, and Ouchi, which connect Yangtze River witch Dongting Lake, were formed during the great floods in 1860 and 1870. Human activities, such as the construction of reservoir, river cutoff, etc, have profound impact on the river system. It follows the change of flow and sediment transport condition, which in turn change the diversion ratio of flow and sediment. As the river diversion is the of many factors, which are interact each other, the evolvement of Diversion River is the more complicated than Single River. Particularly, when scouring-silting occurs in main channel occurs, it will cause the change of water, sediment, and riverbed in river system. Therefore it will ultimately lead to the adjustment of division of flow and sediment. However, former researches basically neglect the flow structure near the entry of distributaries channel. In this paper, influence of the erosion and deposition of Riverbed on the diversion of flow and sediment is discussed. Based on the characteristics of circulation flow and vertical distribution of sediment concentration, a quantificational equation is developed, which can describe the relation between erosion& deposition in mainstream riverbed and the variation of diversion ratio of flow and sediment. Using the equation, the flow & sediment diversion ratios of three diversions in Jingjiang River are estimated after the construction of TGP.