黄河下游游荡段河床调整对于水沙组合的复杂响应

以黄河资料为基础,提示地包括非高含沙水流和高含沙水流在内的河道挟不流的复杂冲淤行为。由于这种复杂冲淤行为的作用和高含沙水流特殊能耗特征的影响,使得河床横断面形态及平面形态对于水沙组合的响应出现非线性特征,这可视为流水地貌系统复杂响应的又一表现形式。这种复杂响应不能用Ｓｃｈｕｍｍ的河床调整来解释,因而需要对这一理论作必要的修正。

Complicated Fill-scour Behaviors of the Huanghe River and the Channel-forming Processes

Based on the data from 159 flood events at the Tongguan station on the Huanghe River, we have found the rule to describe the complicated relationship between the fill scour features and the event maximum suspended concentration ( C max ). When the C max is low, the depth of scour is large. With an increased C max , the depth of scour decreases and channel fill occurs. However, when the C max further increases and enters the ranges of hyperconcentrated flows, scour occurs again. Controlled by the foregoing complicated fill scour behaviors, the channel adjustment of the Huanghe River is also complicated. When the suspended concentrations are low, channel scour occurs, and thereby the channel shape tends to be narrower and deeper, and the thalweg more sinuous. When the suspended concentration increases, channel fill occurs, leading to an increase in the channel width depth ratio and a decrease in the channel sinuosity. However, when the suspended concentration further increases and exceeds a certain threshold, channel scour occurs again, and the adjustment of channel morphology turns to the opposite direction. The rules outlined in the paper for the channel adjustment of the lower Huanghe River may provide a new thinking for the regulation of the channel morphology of the lower Huanghe River after the closure of the Xiaolangdi Dam, through the regulation of the lower Huanghe River's water and sediment by choosing some specific operation modes of the reservoir. Either by releasing clear water or by releasing man made hyperconcentrated flows, the downstream channel may tend to be narrower, deeper and more sinuous. If some proper engineering measures are taken afterwards, the channel conditions for a better flood releasing and sediment transport may be greatly improved.