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黄河下游洪水涨落迅速,河床易冲易淤,水位变化无常,历年水位～流量关系成扇形散开变化,比较同流量水位值,历年最大差近3.0米,一次洪水涨落过程差也达0.7—1.0米。(如图1)造成这种变化和差值的主要原因是断面冲淤变化大,而断面冲淤又取决于上游来水来沙条件和前期河床情况。此外,河势、断面形态的变化和河道冲淤引起的河床组成的粗化和细化等,又直接
The flood in the lower reaches of the Yellow River fluctuates swiftly, the river bed is easy to sink and silt, the water level fluctuates erotically and the relationship between water level and flow rate changes fan-shaped over the years. When compared with the same flow level value, the maximum difference in calendar year is nearly 3.0 meters, -1.0 meters. (Figure 1). The main reason for this change and difference is the large variation of erosion and deposition in the section, which in turn depends on the conditions of incoming and outgoing water and sediment in the upper reaches and the bed conditions of the previous period. In addition, the change of river regime and section morphology and the roughening and refinement of the riverbed composition caused by the erosion and deposition of the river are also directly