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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Form and growth of bars in a wandering gravel-bed river
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Form and growth of bars in a wandering gravel-bed river

机译：游荡的砾石河床中条的形态和生长

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摘要

The changing form of developing alluvial river bars has rarely been studied in the field, especially in the context of the fixed, compound, mainly alternate gravel bars that are the major morphological feature of the wandering style. Century scale patterns of three-dimensional growth and development, and the consequent scaling relations of such bars, are examined along the gravel-bed reach of lower Fraser River, British Columbia, Canada. A retrospective view based on maps and aerial photographs obtained through the twentieth century shows that individual bars have a life history of about 100 years, except in certain, protected positions. A newly formed gravel bar quickly assumes its ultimate thickness and relatively quickly approaches its equilibrium length. Growth continues mainly by lateral accretion of unit bars, consistent with the lateral style of instability of the river. Bar growth is therefore allometric. Mature bars approach equilibrium dimensions and volume that scale with the overall size of the channel. Accordingly, the bars conform with several published criteria for the ultimate dimensions of alternate barforms. Sand bars, observed farther downstream, have notably different morphology. Fraser River presents a typical wandering channel planform, exhibiting elements of both meandered and low-order braided channels. Hydraulic criteria to which the Fraser bars conform illustrate why this planform develops and persists. The modest rate of bed material transfer along the channel typical of the wandering type - determines a century-length time scale for bar development. This time scale is consistent with estimates that have been made for change of the macroform elements that determine the overall geometry of alluvial channels.
机译：在田间很少研究冲积河坝的变化形式，特别是在固定的，复合的，主要是交替的砾石坝的情况下，这是流浪风格的主要形态特征。沿着加拿大不列颠哥伦比亚省的弗雷泽河下游的砾石层河床，研究了三维增长和发展的世纪尺度模式，以及由此产生的比例关系。根据二十世纪获得的地图和航拍照片进行的回顾性研究表明，除在某些受保护的位置外，单个酒吧的使用寿命约为100年。新近形成的碎石棒会迅速达到其最终厚度，并很快达到其平衡长度。增长主要通过单元条的横向增加而继续，这与河流不稳定的横向样式一致。因此，条形增长是异形的。成熟的条接近平衡尺寸和体积，该尺寸和体积随通道的整体尺寸成比例。因此，这些条符合替代条形的最终尺寸的一些公开标准。在更下游观察到的沙洲形态明显不同。弗雷泽河（Fraser River）呈现出典型的游荡河道平面图，同时呈现出蜿蜒和低阶辫状河道的元素。 Fraser导杆所遵循的液压标准说明了该平面图发展并持续的原因。沿着漂移型通道典型的床料传输速率适中-确定了棒材开发所需的百年时间尺度。该时间尺度与为确定冲积河道总体几何形状的宏观形态元素变化所做的估算一致。

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