水沙变异条件下黄河下游河道横断面形态特征研究

Studies on the features of cross section's profile in lower Yellow River under the conditions of variable incoming water and sediment

通过对黄河下游各水文站1950～2003年实测资料的分析，探讨了过去50多年间黄河下游河道横断面形态变化过程及其与来水量的响应关系。分析得出，过去50多年间，黄河下游河道主河槽发生了明显的淤积萎缩，游荡性河段的萎缩程度大于弯曲性河段，平滩面积呈明显减小的趋势，宽深比有增大的趋势，但各河段河型没有发生转化；平滩面积随年来水量和当年最大洪峰流量的增加而增大，宽深比随来沙系数的增加而增大。由黄河下游排沙比与来水来沙的关系分析表明，黄河下游花园口-利津河段不淤积的花园口临界年均来沙系数约为0．012，临界年平均流量约为1850m^3／s。综合分析认为，在目前下游河道来水偏枯的条件下，下游河道的平滩流量不宜也不可能太大，从维持中水河槽和满足流域经济社会发展需要考虑，在花园口年米水量为200—250亿m^3时，花园口控制洪峰流量在4000m^3／s左右、年均来沙系数不大于0．012的来水来沙过程比较合适。

Having analyzed the data from 1950 to 2003 of hydrological stations in the Lower Yellow River, this article discusses the evolution of cross section＇s profile and its response relations to the incoming runoff. The author figures out the obvious deposition and shrinkage of the main channel in the Lower Yellow River. They were more severe in wandering reaches than in meandering ones, and the sections＇ bankfull area showed a decreasing trend, and the aspect ratio showed an increasing one. The reaches＇ patterns changed little; the sections＇ bankfull area increased with the annual sum of incoming water and the maximum peak discharge of the same year, while the aspect ratio increased with the incoming sediment coefficient. The analyzed relations between sediment outgoing ratio and the incoming water and sediment show that, in the reach from Huayuankou to Lijin without deposition, the Huayuankou＇s critical coefficient of annual incoming sediment is 0.012, the critical annual average discharge is 1 850m^3/s. Synthetically analyzed, under the current conditions of pool incoming water, a very large bankfull discharge is improper and impossible. Considering of maintaining a mean-runoff channel and meeting the need of economy and society＇s development in the basin, the proper incoming water and sediment process is, when annual total incoming runoff is 20 billion - 25billion m^3 at Huayuankou, to control a peak discharge of 4 000m^3/s and an annual average incoming sediment coefficient not higher than 0.012.