黄河下游河道萎缩过程初步分析

Analysis of lower Yellow River shrinkage

黄河下游河道萎缩与来水来沙条件具有复杂的响应关系.根据黄河下游汛期实测水沙过程及断面形态资料,采用河槽过水面积、来沙系数、同流量水位变化、河相系数变化描述河道萎缩过程.结果表明:20世纪90年代以来,由于来水来沙条件的变化,黄河下游来沙系数增大,同流量的水位进一步抬高,河道过水面积大大减少,河道萎缩进一步加剧,并且河道萎缩与来沙系数有一定的关系,当来沙系数大于某一值后,河道由冲刷转化为淤积,河道过流能力下降;随着河道的萎缩,河床形态会有一定的调整,二者关系密切.

The shrinkage of the lower Yellow River has a complex relationship with the incoming water and sediment. Based on the measured data of watersediment process and sectional form during the flood season of the lower Yellow River, the shrinkage of the river channel is analyzed according to the variation of the discharge area, incoming sediment coefficient, water level under the same flow rate, and coefficient of river facies. The results show that, since 1990, the variation of incoming water and sediment has resulted in increase of the incoming sediment coefficient, rise of water level under the same flow rate, and large decrease of the discharge area of the river channel, further accelerating the shrinkage of the river channel. It is also indicated that the shrinkage of the river channel has a certain relationship with the incoming sediment coefficient. When the incoming sediment coefficient is larger than a certain value, the deposition of the river channel will reduce its discharge capacity, and the further shrinkage of the river channel will also result in the adjustment of its bed form.