Study on channel variation in mountain rivers

山区河流河道变化研究

基本信息

批准号：
01460183
负责人：
ASHIDA Kazuo
金额：
$ 3.52万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

A large amount of sediment is commonly deposited in the regions with a wide section of mountain streams where sediment yields are very active. Stream channels formed there are braided even in a high flood because the flot width is too wide to form a stable stream. The project of this study is to investigate the processes of channel variation and their associated phenomena such as variation of bed load, sediment sorting and so on. The results obtained from the research are summarized as follows :1. Several streams are commonly produced in a flume bed chosen for the present study. resulting in a braided channel system. The flow direction and width of each stream change in time and space, which brings about varieties of the number of stream as well as of the whole flow width in the braided channel system.2. Such variations of streams in the system are more active in the bed with graded material than with uniform one, because a stream bifurcation occurs more frequently due to a sediment sorting in the former case.3. The sediment discharge rate increases with the decreases of the flow width and the number of stream in the cross section under consideration. In other words, it increases in a converging process of stream and vice versa in a bifurcating phase.4. It is necessary to specify the parameters such as the flow width of each stream and the number of stream formed in the system for the prediction of bed load distribution. A formula of the flow width is developed in terms of a criterion for alternating bar formation. It is very useful for evaluating a temporally averaged sediment rate.

大量沉积物通常沉积在众多山流的地区，那里的沉积物产量非常活跃。即使在高洪水中也形成了辫子，因为车站的宽度太宽，无法形成稳定的流。这项研究的项目是研究通道变异及其相关现象的过程，例如床负荷的变化，沉积物分类等。从研究获得的结果总结如下：1。几个流通常在选择用于本研究的水槽床上产生。导致编织的通道系统。每条流的流动方向和宽度在时空会变化，这带来了编织通道系统中的流数量以及整个流量宽度的品种。2。与均匀的材料相比，系统中的这种流在床上具有比均匀材料更活跃，因为流分叉发生的频率更高，这是由于前一种情况中的沉积物分类而发生的。3。沉积物排放速率随着流量宽度的下降和所考虑的横截面中的流数量而增加。换句话说，它在分叉阶段的流中融合过程中增加，反之亦然4。有必要指定参数，例如每条流的流宽度以及系统中形成的流数以预测床负荷分布。流动宽度的公式是根据交替杆形成的标准开发的。它对于评估时间平均的沉积物速率非常有用。