高含沙型曲流河床形成机理的初步研究

MEANDERS CAUSED BY HYPERCONCENTRATED WATER FLOW: AN EXAMPLE FROM THE LOESS PLATEAU, CHINA

本文描述了在我国黄土高原宽谷中发现的含沙量超过100kg/m^2的曲流河床,并运用高含沙水流的作用对其成因进行了探讨。指出当水流进入高含沙范围时,水流能耗率大幅度降低,挟沙能力大大增加,这是促使河床向弯曲发展的主要原因。由于高含沙水流的稳定输送有赖于边界条件,故边界条件在这种曲流河床的形成中起了重要的作用。文中并讨论了这一地区游荡河型与弯曲河型的判别条件。

This paper has described meandering alluvial rivers with mean annual suspended sediment concentration of more than 100kg/m3 on the Loess Plateau, China, and explained their formation cause by the effect of hyperconcentrated water flow. When the river is predominated by hyperconcentrated flow, its rate of energy expenditure needel for isediment transport will decline significantly. Accordingly the river channel will adjust itself to a lower channel gradient by increasing the river length, and then a meandering channel is achieved. Since the stable transportation of sediment by hyperconcentrated flow is' dependent on river channel boundary conditions, the latter plays an important role in formation of meanders of this kind. Also, this paper has discussed the conditions for the discrimination of meandering and braided rivers in this area.