Morphodynamics and sedimentology of gravel bed rivers

总体研究目标是分析河流的形态和动态，有助于对河流景观和河流对环境变化的敏感性的基本理解。这需要理解创造特定类型河流形态和动态的过程。该理论的核心思想是，河流是由自身的侵蚀、沉积物运输和沉积过程形成的，这些过程形成了沙洲、河道和河流景观的其他特征。这些过程工作方式的差异是景观中河流形态变化的主要原因。分析河流中泥沙运移的传统方法是将其视为水力驱动的传送带过程，但这一概念并不能直接解释河流形态的差异以及形成这种形态的局部过程。我正在探索一种替代但互补的方法，它认为沉积物运动和河流形态的动力学本质上是相同的过程，因此专注于河床地形的动力学，以观察河流作为动态地貌的实际工作方式。在山区和丘陵地区常见的充满活力、多通道、辫状河是测试这种方法的有用河流类型，因为它们不断地改变和重新配置它们的形态，特别是在高流量事件期间。目的是研究这些形态变化发生的过程，量化变化的速率及其随时间的差异，将这些形态变化与河床物质运输的速率联系起来，并比较不同形态和沉积特征的河流。简而言之，了解这些河流如何作为动态地貌发挥作用。同时，目的是开发新的方法来表征和预测泥沙输运率的河流形态的动力。由于河流的形态动力学相对缓慢，我们在实验水槽中使用小规模的物理模型来加速这一过程，控制条件，观察河道形态的发展，测量变化速率以及侵蚀和沉积的体积（使用摄影测量法绘制河床地形），监测沉积物的运输速率，并从河床物质颗粒运动的统计数据中观察形态的发展方式。使用现场数据验证模型数据。结果将是进一步发展这种直接将河流形态和沉积物运输联系起来的形态动力学分析，特别是对河流形态和河流动力学“风格”差异的定量理解。这为预测各种环境变化、工程或流量控制对河流施加的变化的影响提供了更完整的河流动态图景，也是评估地貌质量和恢复河流形态和动态的基础。

The overall research goal is to analyze the morphology and dynamics of rivers and contribute to fundamental understanding of river landscapes and the sensitivity of rivers to environmental change. This requires an understanding of the processes that create particular types of river form and dynamics. At the heart of this is the idea that rivers are formed by their own processes of erosion, sediment transport and deposition, and that these processes form the bars, channels, and other features of the river landscape. The differences in the way these processes work is a primary cause of the variety of river forms seen in the landscape. The conventional approach to analyzing sediment transport in rivers is as a hydraulically-driven conveyor belt process, but this conception does not directly explain differences in river form and the local processes creating this form. I am exploring an alternative but complementary approach which considers sediment movement and the dynamics of the river form as essentially the same process, and so focuses on the dynamics of the river bed topography to look at the way that rivers actually work as dynamic landforms. Energetic, multi-channel, braided rivers, common in mountain and foothills areas, are a useful river type in which to test this approach because they continuously change and reconfigure their morphology, especially during high flow events. The goal is to examine the processes by which these morphological changes happen, quantify the rates of change and their differences over time, connect these morphological changes to the rates of bed material transport, and compare rivers of differing morphology and sedimentary features. In short, to understand how these rivers function as dynamic landforms. At the same time, the intent is to develop new methods for characterizing and predicting sediment transport rate in rivers based on the dynamics of river form. Because morphological dynamics of rivers is relatively slow we use small-scale physical models in an experimental flume to speed up the processes, control the conditions, observe the development of channel morphology, measure rates of change and the volumes of erosion and deposition (using photogrammetry to map bed topography), monitor rates of sediment transport and observe the way in which morphology develops from the statistics of bed material particle movement. The model data are validated using field data. The outcome will be the further development of this morphodynamic analysis directly connecting river morphology and sediment transport, and especially a quantitative understanding of differences in river morphology and `styles' of river dynamics. This provides a more complete picture of river dynamics from which to anticipate the effects of changes imposed on rivers by various environmental changes, engineering or flow manipulation, and also a basis for assessing geomorphic quality and for restoring river morphology and dynamics.