Morphological bedload transport rates

河流将泥沙负荷的一部分作为河床负荷运输——即沿着河床滚动或弹跳移动的较大颗粒。河床荷载对河流的形态和动态具有重要意义，因为河床荷载的时空变化直接导致了池塘、沙洲和岛屿等特征的形成，而这些特征是许多河流地貌的主要组成部分。同样，河床荷载过程影响河流动力学，如河道迁移和形态变化速率。这项研究旨在帮助理解控制河床负荷通量的变量，特别是当河流迁移和改变其形态时，颗粒运动与形态相互作用的方式。目标是将河流形态的发展描述为粒子转移过程的结果。这是理解河流动力学的基础，在缓解侵蚀问题、理解河流过程和水流对河内栖息地的影响以及修复被工程改变的河流方面有直接的应用。在野外很难测量河床颗粒的运动，但对于砾石河床的河流，许多过程和特征可以在实验室水槽的小尺度物理模型中重现。我们将使用物理模型来研究在各种流动条件和不同通道形态下对河床颗粒动力学的控制（侵蚀/沉积频率和运输距离），以了解形态特征如何从颗粒路径和路径长度发展，进而限制这些运动。我们将使用示踪粒子和摄像机测量粒子运动，并使用数字摄影测量和图像处理来获得河床地形，地形随时间的变化以及河床粗糙度和粒度数据。河床的搬运可能完全受河堤和河池的动力学影响，而不是像人们经常设想的那样在这些特征上自由移动。如果是这样的话，这就创造了一个全新的关于河床输运过程和河道动力学的概念和理论图景。

Rivers transport part of their sediment load as bed load - the larger particles that move by rolling or bouncing along the river bed. Bed load is important to river morphology and dynamics because its spatial and temporal variation in rate is directly responsible for the formation of the features, such as pools, bars and islands, which are major elements of the geomorphology of many rivers. Similarly, bed load processes affect river dynamics, such as channel migration and rates of morphological change. This research is intended to contribute to understanding the variables that control bed load flux and, in particular, the way in which particle movement interacts with the morphology as the river migrates and changes its morphology. The goal is to describe the development of river morphology as the outcome of the particle transfer process. This is fundamental to understanding river dynamics and has direct application in mitigating erosion problems, understanding the effects of river processes and flow on in-stream habitat and in restoring rivers altered by engineering. It is difficult to measure the bed particle movement in the field but for gravel-bedded rivers many of the processes and features can be reproduced in small-scale physical models in a laboratory flume. We will use physical models to investigate the controls on bed particle dynamics (erosion/deposition frequency and transport distances) under various flow conditions and different channel morphologies to understand how the morphological features develop from the particle pathways and path lengths and, in turn, constrain those movements. We will measure particle movement using tracer particles and video cameras and use digital photogrammetry and image processing to derive river bed topography, topographic change over time and bed roughness and particle size data. It is possible that bed load transport is completely tied up in the dynamics of the bars and pools of the river rather than moving freely over those features ( as it is often conceived). If so, this creates an entirely new conceptual and theoretical picture of bed load transport processes and river channel dynamics.