黄河下游河道萎缩过程中洪水水位变化研究

摘要

Using the methods of field data analyses and theoretical study, the variation characteristic and mechanism of floodwater stage during the atrophy process of channel is researched in the Lower Yellow River. The results show that the lower channel atrophy seriously by reason of variation of flow and sediment of Yellow River since 1986. Incipient rising floodwater stage hoisted markedly, the swelling rate of floodwater stage increase evidently, and the stage of main channel and floodplain are inconsistent. The hoisting of in- cipient rising floodwater is due to aggradation of the main channel of the Lower Yellow River. The hoisting of incipient rising floodwater influences the rising extent of flood peak stage greatly. The Lower Yellow Riv- er has a wide channel with powerful adjusting function of cross section during the travelling of floodwater, which results in the suddenly rising and fiercely declining easy. Its infection can＇t be ignored. Via by intro- ducing the parameter 0 of the swelling rate of floodwater stage, the relationship between 0 and the width of main channel, the rough rate ratio of main channel and floodplain, the expelling sediment ratio are established. The results show that during the atrophy process of the Lower Yellow River channel, transporting sediment capability of channel decrease, river breadth become narrow by a long way, resistance of floodplain increase obviously, they are all bring on the increasing of swelling rate of floodwater stage. The theoretical study is based on Chezy formula, which proves that the swelling rate of floodwater stage have non-linearity relationship to the atrophy of channel. The more serious atrophy of the Lower Yellow River is, the bigger increasing extent of swelling rate of floodwater stage becomes.%采用实测资料分析和理论探讨相结合的方法，研究了河道萎缩过程中黄河下游洪水水位的变化特征与变化机理。研究结果表明：1986年后，黄河水沙过程变异，下游河道严重萎缩，洪水起涨水位显著升高，洪水上涨过程中水位涨率明显增大，滩槽水位变化不一致性增强。洪水起涨水位的升高主要是河道萎缩过程中主槽持续淤积抬高所致，起涨水位的升高对洪峰水位抬升幅度影响大，而行洪过程中黄河下游宽河段强大的断面调整功能极易造成洪水水位的陡涨猛落，其影响也不容忽视。通过引入洪水水位涨率特征参数θ，建立了目与黄河下游河道主槽宽度、滩槽糙率比、排沙比等因素的定量关系，结果显示，黄河下游河道萎缩过程中，输沙能力降低，主槽宽度大幅度缩窄，滩地阻力明显增大，均会导致洪水水位涨率增大。以谢才公式为基础的理论分析进一步证明，黄河下游河道洪水水位涨率与河道萎缩具有非线性响应关系，河道萎缩越严重，洪水水位涨率增大的幅度越大。