Experimental Study On Natural Development Laws Of The Lower Yellow River

After the Yellow River flows through the Loess Plateau, with large amounts of sedimentand low flow velocity, it reaches to the downstream through Xiaolangdi Gorge. Because ofsediment deposition, the North China Plain gradually formed during thousands of years. Atthe same time, the Yellow River kept on developing and changing. In the history, theevolution of the Yellow River downstream followed characteristics of siltation and wandering.People had to construct cross-strait embankments to develop. So the relationship betweenriver and embankments became the most direct expression for people and water downstreamthe Yellow River. However, until now, interpretation of this relationship in many cases is stillnot harmonious. Therefore, with river spatial and temporal natural shaping model, it hascertain guiding significance for the lower Yellow River to explore the cross-sectional shapeadjustment as the river forms in the deposition area, to clarify the formation and developmentlaws of rivers and to seek the transformation conditions of different river patterns of alluvialrivers.Firstly, by analyzing the formation causes and transformation conditions of river patternsand the fluvial features of the lower Yellow River, the paper offered the following overallconception of the natural development of the Lower Yellow River. The natural river wouldquickly be broaden after it flows through the valleys with braided morphology in order toweaken the flow energy. The relatively stable curve of river reaches could not be formedunless the river flows in a certain distance. That is, rivers tend to develop into the stablemeandering rivers. So, a certain wandering space should be given to the Yellow Riverdownstream reaches.Secondly, with river spatial and temporal natural shaping model, the sediment depositionin the deposition area is considered to move forward in sector shape. Now matter how thewater-sediment condition is, as long as the river is without constraints, it does have the naturalwandering characteristics after flows through the valleys. The greater the flow and sedimentconcentration are, the greater the wandering frequency and amplitude would be. And theincoming sediment amounts determines the rate of siltation. In the natural process ofdevelopment of rivers, diffusion deposition zone sediment often forward fan and siltationelevation; With sediment deposition and gradually out of the water, the early river which was shorter formed in a mountain pass; With continued siltation of the initial formation river,water level was elevated, sediment was also mix to the river banks on both sides to a certainextent; Transverse slope began to increase and the river began to broaden, river enters thecritical state of adjustment and the river began to swing to one side; After swung to the side,the new river was gradually washed out in low-lying areas and the river tends to be bendingstability. The process developed in cycle, in this cycle, river regime are often experiencingstable, unstable, very unstable and stable state alternately development.Finally, based on the analysis of a large number of test data,J hFused as ther Bcan be discrimination index to judge the river was stable or not.