Variation Of The Processes Of Flow And Sediment And Response Of The Evolution In The Yellow River Estuary

The variation of flow and sediment has been appeared in the Yellow River estuary sincel986. Under the new condition of flow and sediment, the law and direction of evolution are becoming a new problem needed to solve urgently in the Yellow River estuary. By studying the variation of the processes of the flow and sediment, the response of the evolution is in-depth analyzed in the Yellow River estuary. The main works of thesis are illustrated as follows:1. The processes of flow and sediment from 1950 to 2000 are divided into three phases with the boundary of 1968 and 1986 in the Yellow River estuary. By analyzing the characteristics of flow and sediment of three phases, it can be concluded that the variation of the processes of flow and sediment were complex in the Yellow River estuary, the characteristics of year-by-year, distributing in one year, arranging in pairs or groups, composing of incoming sediment and the typical characteristics of hydrology changed all, the variation of flow and sediment in the Yellow River estuary was synthetic embodiment of all changes mentioned above. A synthetic parameter named ξ is formed, ξ can express the flow and sediment condition of the Yellow River estuary. The formulas of the relationships between ξ and the incoming flow and sediment of three phases were different., it proved that the variation of the processes of flow and sediment happened in the Yellow River estuary.2. With the variation of flow and sediment, tail channels atrophied badly in the Yellow River estuary. The processes of erosion and deposition, adjusting of vertical section, modality of cross section changed all in the tail channels. Longitudinal mode curve of the atrophy of tail channels generalized is f =-0.00007x3+ 0.01x2-0.14x+7.6, transverse mode is generalized as the fig 3-10. The atrophied reason comprises reducing of dominant discharges increasing of resistance of riverbed changing of characteristic of erosion and deposition, reducing of coupling power of river and sea; after atrophy of tail channels came into being, vertical section and cross section atrophied would reduce the transporting power of flow and sediment, it would prick up atrophy of tail channels. A distinguishing target named Tn is imported, Tn=0.2, 0.3, 0.45 can be regarded as limits of seedtime of the atrophy of tail channels, it will be as reference value of controlling atrophy of tail channels.3. The relationship between the estuarine sandbar evolution and flow and sediment conditions is correlation nearly. When the incoming flow and sediment are big, the speed of longitudinal advancing of the estuarine sandbar is fast, the transverse swing of the estuarine sandbar is frequent the size of the estuarine sandbar is big, with the variation of flow and sediment, the speed of longitudinal advancing become slow, the transverse swing become puny, the size become small, when the flow and sediment reduce definite degree, the body of the estuarine sandbar become eroding. The relationship between the advancing of the estuarine sandbar and the atrophy of tail channels reflects that the atrophy of tail channels goes against the growth of estuarine sandbar. By synthetic analyzing, the solid dynamic advancing mode of the estuarinesandbar is gained in the Yellow River estuary . During period of time; the longitudinal advancing is primary; the transverse swing is secondary; during next period of time; the transverse swing is primary; the longitudinal advancing is secondary; the estuarine sandbar advance perpetual in the direction of ocean as this.4. The evolution of the Yellow River estuary bring the feedback influences to the lower reaches of the Yellow River; according as the typical developmental process of the feedback influences; the developmental process of the feedback influences comprises two phases: the first is eroding trace to the source; the second is depositing trace to the source; the characteristics of the two phases are different; eroding trace to the source is intensity; depositing trace to the source is faintness. The development of the feedback influences is related to the extending and shortening length of the reaches the flow and sediment conditions the border conditions of the channels regulated by the large hydraulic hinge etc. By choosing the farthest length of eroding trace to the source as the length of the feedback influences; a formula of the feedback influences is gained. The transferring of the feedback influences is accomplished by the concatenate regulating of reaches; the physical figure of regulating of longitudinal grade is a broken line.