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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >The influence of lithology on channel geometry and bed sediment organization in mountainous hillslope-coupled streams
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The influence of lithology on channel geometry and bed sediment organization in mountainous hillslope-coupled streams

机译：岩岩在山地山坡耦合流中的沟道几何和床沉积物组织的影响

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摘要

Sediment transport and channel morphology in mountainous hillslope-coupled streams reflect a mixture of hillslope and channel processes. However, the influence of lithology on channel form and adjustment and sediment transport remains poorly understood. Patterns of channel form, grain size, and transport capacity were investigated in two gravel-bed streams with contrasting lithology (basalt and sandstone) in the Oregon Coast Range, USA, in a region in which widespread landslides and debris flows occurred in 1996. This information was used to evaluate threshold channel conditions and channel bed adjustment since 1996. Channel geometry, slope, and valley width were measured or extracted from LiDAR and sediment textures were measured in the surface and subsurface. Similar coarsening patterns in the first few kilometres of both streams indicated strong hillslope influences, but subsequent downstream fining was lithology-dependent. Despite these differences, surface grain size was strongly related to shear stress, such that the ratio of available to critical shear stress for motion of the median surface grain size at bankfull stage was around one over most of the surveyed lengths. This indicated hydraulic sorting of supplied sediment, independent of lithology. We infer a cycle of adjustment to sediment delivered during the 1996 flooding, from threshold conditions, to non-alluvial characteristics, to threshold conditions in both basins. The sandstone basin can also experience complete depletion of the gravel-size alluvium to sand size, leading to bedrock exposure because of high diminution rates. Although debris flows being more frequent in a basalt basin, this system will likely display threshold-like characteristics over a longer period, indicating that the lithologic control on channel adjustment is driven by differences in rock competence that control grain size and available gravel for bed load transport. (c) 2020 John Wiley & Sons, Ltd.
机译：山坡耦合物流中的沉积物传输和通道形态反映了山坡和通道过程的混合物。然而，岩性对渠道形式和调整和沉积物传输的影响仍然很差。在两条砾石床上流中调查了渠道形式，晶粒尺寸和运输能力的图案，其中俄勒冈州俄勒冈州海岸范围对比底岩石（玄武岩和砂岩），在1996年广泛的山体滑坡和碎片流动的地区。这个自1996年以来，信息用于评估阈值通道条件和频道床调整。在LIDAR和沉积物中测量或提取频道几何形状，斜率和谷宽度在表面和地下测量沉积物纹理。在两个溪流的前几公里处的类似粗化图案表明了强烈的山坡影响，但随后的下游罚曲是岩性依赖性。尽管存在这些差异，但表面粒度与剪切应力密切相关，使得可用于临界剪切应力的可用比例在基础上的中位表面粒度的运动的运动是大部分受测量的长度的一个。这表明供应沉积物的液压分类，与岩性无关。我们推断在1996年洪水洪水，从阈值条件到非冲积特性，在两种盆地的阈值条件下推断到沉积物的调整循环。砂岩盆地还可以经历完全耗尽碎片尺寸的碎片尺寸，导致基岩曝光，因为速度高。尽管在玄武岩盆地中更频繁地频繁频繁，但该系统可能会在较长时间内显示阈值状特征，表明渠道调整的岩性控制是通过控制晶粒尺寸和可用砾石的岩石能力的差异驱动运输。 （c）2020 John Wiley＆Sons，Ltd。

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