Keywords: 
• channel patterns /
• model of spatial variations /
• controlling factors

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.