黄河下游河道萎缩对冲淤临界的影响

通过实测年系列水沙资料分析,运用统计分析方法,按照非萎缩期(1950~1985年)和萎缩期(1986~1999年)两个时期,分别得到黄河下游河道的冲淤临界值。对于年沙量、>0.05mm年粗沙量、年均含沙量、年均粗泥沙含沙量、年均来沙系数而言,冲淤临界值均有不同程度减小。这意味着河道萎缩后,由于输沙功能减弱,在年沙量、>0.05mm年粗沙量、年均含沙量、年均粗沙含量、年均来沙系数处于比非萎缩期更低的水平时,下游河道就有可能出现淤积,从而使得控制河道淤积抬高变得更为困难,使河道防洪面临新的问题。

Fill-scour Thresholds of Lower Huanghe River Influenced by Channel Shrinkage

Fill-scour threshold is often related with specific combination of sediment load and stream flow, and determining of this combination may provide important reference to the operation of Xiaolangdi Reservoir. Based on annual hydro-metric data and using statistical method, a study has been made to determine the fill-scour thresholds of the lower Yellow River, for two periods separately, namely, the period with channel shrinkage from 1986 to 1999 and the period from 1950 to 1985 without channel shrinkage. A number of fill-scour thresholds have been obtained, which show that the fill-scour thresholds related with annual suspended load, with annual mean sediment concentration, with annual concentration of coarse sediment and with the ratio of annual sediment concentration to water discharge (known as incoming sediment coefficient) all decreased from the non-shrinkage period to the shrinkage period. This means that in the latter period sedimentation might occur even if the annual mean sediment concentration and the incoming sediment coefficient is at a lower level than that in the former period, and thus, flood protection in the lower Yellow River would face higher pressure.