Morphological bedload transport rates

河流以推移质的形式输送部分泥沙--较大的颗粒通过在河床上滚动或反弹而移动。推移质对河流形态和动力学很重要，因为它的时空变化直接导致了诸如池塘、沙洲和岛屿等地貌特征的形成，这些地貌是许多河流地貌的主要元素。类似地，推移质过程影响河流动态，如河道迁移和地形变化率。这项研究旨在帮助理解控制推移质通量的变量，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。其目的是将河流形态的发展描述为颗粒转移过程的结果。这是理解河流动态的基础，在减轻侵蚀问题、了解河流过程和水流对河流栖息地的影响以及恢复被工程改变的河流方面具有直接应用。现场测量河床颗粒运动是很困难的，但对于砾石河床河流，许多过程和特征可以在实验室水槽的小比例物理模型中重现。我们将使用物理模型来研究不同流动条件和不同河道形态下对床面颗粒动力学(冲刷/沉积频率和输送距离)的控制，以了解颗粒路径和路径长度的形态特征是如何发展的，并反过来限制这些运动。我们将使用示踪颗粒和摄像机测量颗粒运动，并使用数字摄影测量和图像处理来得出河床地形、随时间变化的地形以及河床粗糙度和颗粒尺寸数据。推移质运输可能完全受制于河流沙洲和池塘的动态，而不是像人们通常认为的那样，在这些地物上自由移动。如果是这样的话，这就为推移质输运过程和河道动力学创造了一幅全新的概念和理论图景。

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.