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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >UAS-based remote sensing of fluvial change following an extreme flood event
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UAS-based remote sensing of fluvial change following an extreme flood event

机译：极端洪水事件发生后基于UAS的河流变化遥感

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The effects of large floods on river morphology are variable and poorly understood. In this study, we apply multi-temporal datasets collected with small unmanned aircraft systems (UASs) to analyze three-dimensional morphodynamic changes associated with an extreme flood event that occurred from 19 to 23 June 2013 on the Elbow River, Alberta. We documented reach-scale spatial patterns of erosion and deposition using high-resolution (4-5 cm/pixel) orthoimagery and digital elevation models (DEMs) produced from photogrammetry. Significant bank erosion and channel widening occurred, with an average elevation change of -0.24 m. The channel pattern was reorganized and overall elevation variation increased as the channel adjusted to full mobilization of most of the bed surface sediments. To test the extent to which geomorphic changes can be predicted from initial conditions, we compared shear stresses from a two-dimensional hydrodynamic model of peak discharge to critical shear stresses for bed surface sediment sizes. We found no relation between modeled normalized shear stresses and patterns of scour and fill, confirming the complex nature of sediment mobilization and flux in high-magnitude events. However, comparing modeled peak flows through the pre- and post-flood topography showed that the flood resulted in an adjustment that contributes to overall stability, with lower percentages of bed area below thresholds for full mobility in the post-flood geomorphic configuration. Overall, this work highlights the potential of UAS-based remote sensing for measuring three-dimensional changes in fluvial settings and provides a detailed analysis of potential relationships between flood forces and geomorphic change. Copyright (C) 2015 John Wiley & Sons, Ltd.
机译：大洪水对河流形态的影响是多变的，人们对此知之甚少。在这项研究中，我们使用小型无人机系统（UAS）收集的多时间数据集来分析与2013年6月19日至23日在艾伯塔省肘河发生的极端洪水事件相关的三维形态动力学变化。我们使用摄影测量法生成的高分辨率（4-5厘米/像素）正射影像和数字高程模型（DEM）记录了侵蚀和沉积的达到尺度的空间格局。发生明显的河岸侵蚀和河道拓宽，平均海拔变化为-0.24 m。随着通道调整到大多数床面沉积物的完全动员，通道的模式被重新组织并且总体高度变化增加。为了测试从初始条件可以预测地貌变化的程度，我们比较了峰值排放二维水动力模型的剪切应力与床面沉积物尺寸的临界剪切应力。我们发现建模的归一化剪切应力与冲刷和充填模式之间没有关系，这证实了在高强度事件中泥沙动员和通量的复杂性。但是，比较通过洪水前和洪水后地形的模型峰值流量可以看出，洪水导致了调整，有利于总体稳定性，较低的床层百分比低于洪水后地貌构造中可完全移动的阈值。总的来说，这项工作强调了基于UAS的遥感技术在测量河流环境中三维变化方面的潜力，并详细分析了洪水与地貌变化之间的潜在关系。版权所有（C）2015 John Wiley＆Sons，Ltd.

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