Lindsay Marie Capito, Enrico Pandrin, Walter Bertoldi, Nicola Surian, Simone Bizzi
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We developed this method using flume experiments where bed topography and sediment flux were measured and then applied it to published field data with physical path length measured from tracer measurements. Our sediment transport estimates were not significantly different than the measured sediment flux at lower discharges in the lab. However, we observed an underestimation of sediment flux at the higher discharges in the flume study. We interpret this as a limit of the method in confined settings, where sediment transport becomes decoupled from morphological changes. 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引用次数: 0
摘要
摘要由于难以测量砾石床河流中的床面负荷迁移量,因此产生了一种形态学方法,即通过河床高程的变化和沉积物移动距离的估算(即路径长度)来推断沉积物的迁移量。由于目前估算路径长度的方法耗时耗力,我们提出了一种从重复数字高程模型(DEMs of difference,即 DoDs)中估算特征路径长度的方法。我们提出了一种自动方法,通过应用信号处理方法变异模态分解(VMD)来提取差异数字高程模型上侵蚀点和沉积点之间的间距,从而量化间距作为路径长度的替代值。我们利用测量床面地形和沉积通量的水槽实验开发了这一方法,然后将其应用于通过示踪测量测量物理路径长度的已公布实地数据。我们的沉积物输运估算值与实验室测量的较低排水量下的沉积物通量没有明显差异。不过,在水槽研究中,我们观察到较高排水量下的沉积物通量被低估了。我们将此解释为该方法在封闭环境中的局限性,在这种环境中,沉积物运移与形态变化脱钩。我们还探讨了勘测采集之间的时间间隔、形态活动宽度与河道宽度的相对关系以及 DoD 临界值技术对拟议方法的影响,以及它们对一般形态学方法造成的潜在问题。
Path length and sediment transport estimation from DEMs of difference: a signal processing approach
Abstract. The difficulties of measuring bedload transport in gravel-bed rivers have given rise to the morphological method wherein sediment transport can be inferred from changes in riverbed elevation and estimates of the distance traveled by sediment: its path length. Because current methods for estimating path length are time- and labor-intensive, we present a method to estimate a characteristic path length from repeat digital elevation models (DEMs of difference, i.e., DoDs). We propose an automated method to extract the spacing between erosional and depositional sites on the DoD by the application of variational mode decomposition (VMD), a signal processing method, to quantify the spacing as a proxy for path length. We developed this method using flume experiments where bed topography and sediment flux were measured and then applied it to published field data with physical path length measured from tracer measurements. Our sediment transport estimates were not significantly different than the measured sediment flux at lower discharges in the lab. However, we observed an underestimation of sediment flux at the higher discharges in the flume study. We interpret this as a limit of the method in confined settings, where sediment transport becomes decoupled from morphological changes. We also explore how the time between survey acquisitions, the morphological active width relative to the channel width, and DoD thresholding techniques affect the proposed method and the potential issues they pose for the morphological method in general.
期刊介绍:
Earth Surface Dynamics (ESurf) is an international scientific journal dedicated to the publication and discussion of high-quality research on the physical, chemical, and biological processes shaping Earth''s surface and their interactions on all scales.