Spatial Variations of Channel Patterns
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摘要: 论述了现代冲积河流系统中常见河型的自然分布及转化特征,归纳了河型从上游向下游发生空间转化的 5种主要模式。这些河型转化模式发生的相对频率是不同的,其中从辫状河流向曲流河流转化的发生频率最大。文中通过具体实例总结了这些转化模式分别发生时的主要影响因素。Abstract: The formation of channel patterns and its characteristics are important aspects in modern and ancient fluvial system studies, and thus become the main concern for hydraulic engineers, geomorphologists and sedimentologists. So far, there are still some questions not clear in this area, for example, the classification of channel patterns, formation cause of anastomosing fluvial rivers, critical conditions of evolution of some fluvial channel patterns, and further studies are still needed. Another problem related to channel pattern is the transformation of the patterns. In the present paper, four ordinary patterns are discussed, which include the braided, meandering, anabranched (in which include the anastomosing) and straight patterns. Comprehensive study to the spatial transformation of above channel patterns has significance not only for management of modern river and prevention of flood,but also for prospect and exploitation for hydrocarbon and some mineral resources in ancient fluvial depositional systems. The spatial longitudinal variations of river patterns not only show the characteristics of individual channel patterns, but also the transformation between the patterns. The different transformation will shadow different characteristics and consenguencies, but the same transformation has definite general characters and analogous controlling factors. In this paper, the spatial transformation models of fluvial channel patterns and its influences are discussed. Five conceptual models for the spatial transformation of river channel patterns are presented, which include the models of "Braided-Meandering", "Straight-Meandering", "Meandering-Braided", "Meandering-Anabranched" and "Anabranched-Straight". Although the possible spatial transformations among the braided, meandering, anabranched and straight fluvial channel patterns possibly occur in nature, the others except above five in 12 possible transformations have not been observed so far. Furthermore, each one of the five models has different occurring frequency, the model of "Braided-Meandering" occurs generally in larger frequency. The 5 types of transformations are elucidated and interpreted in terms of various examples. The driven factors that control the trend of transformation are also discussed in details. In general, the transformations determined by the integration of geotectonics, climate, vegetation, river valley slope, bank sediment composition and hydraulic factors, but their influence to each type of the models are different.
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Key words:
- channel patterns /
- model of spatial variations /
- controlling factors
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