The joint probability distribution of streamwise particle hop distance, lateral particle hop distance, and travel time constrains the relationships between topographic change and sediment transport at the granular scale. Previous studies have investigated the ensemble characteristics of particle motions over plane bed topography; however, it is unclear whether reported distributions remain valid when bedforms are present. Here, we present measurements of particle motion over bedform topography obtained in a laboratory flume and compare these to particle motions over plane bed topography with otherwise similar conditions. We find substantial differences in particle motion in the presence of bedforms that are relevant to macroscopic models of sediment transport. Most notably, bedforms increase the standard deviation of streamwise and lateral hop distances relative to the mean streamwise hop distance. This implies that bedforms increase the streamwise and lateral diffusion lengths and, equivalently, increase diffusive‐like fluxes.

中文翻译：

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平衡移动床形上粒子跳跃距离和传播时间的概率分布

流向粒子跳距，横向粒子跳距和行进时间的联合概率分布限制了地形变化和粒度范围内泥沙输送之间的关系。先前的研究已经研究了平面形貌上粒子运动的整体特征。然而，目前尚不清楚当存在床单时报告的分布是否仍然有效。在这里，我们介绍了在实验室水槽中获得的床形地形上的粒子运动测量结果，并将这些与在其他类似条件下在平面床形貌上的粒子运动进行了比较。我们发现在存在与沉积物运移的宏观模型有关的床形的情况下，粒子运动的实质性差异。最为显着地，床形相对于平均河道跳距增加了河道和侧向跳距的标准偏差。这意味着床形增加了流向和侧向扩散长度，并等效地增加了类似扩散的通量。