黄河下游河道萎缩的不稳定性

Discussion on channel shrinkage and its instability of the Lower Yellow River

20世纪80年代后期至90年代,黄河下游河道发生了新的河床演变现象-河道萎缩,其特点是河床持续淤积,过水断面和过流能力持续减小。本文指出河道萎缩的主要原因是具有较高含沙量的连续枯水系列造成的河床淤积,特别是主槽的淤积,而高含沙的中小洪水使嫩滩淤高,强烈压缩主槽,促进河道的萎缩。文章分析了形成河道萎缩的主要水文泥沙条件,认为枯萎的平面河势及断面形态具有不稳定性,只要来水来沙有利,萎缩河道的复是可以期待的。因此,充分发挥小浪底水库的调水调沙作用,加速河道整治,开源节流,增加黄河下游的可用水量是改善当前黄河下游河道萎缩的当务之急。

The authors discussed the hydrological and sediment conditions for the formation of channel shrinkage in the Lower Yellow River, which happened during the period from the mid 1980s to the late 1990s. This new problem of fluvial processes was characterized with continued siltation in channel bed, continued decrease of cross-sectional area of channel and continued diminution of flow conveying capacity. Deposition has continuously happened in the main channel by moderate and low incoming runoff with hyper sediment concentration in a series of dry years and resulted in channel shrinkage. The deposition also occurs in low floodplains so that the main channel is narrowed and the channel shrinks strongly. The configuration and cross-section of the withered channel are instable and would possibly be modified under favorable conditions of incoming runoff and sediment load. Therefore, the resuscitation of the shrunk channel could be anticipated. Some measures are suggested to accelerate the resuscitation. Especially, regulation of flow and sediment in the Xiaoliangdi Reservoir would play a significant role.