Morphodynamics and sedimentology of gravel bed rivers

砾石床河流的形态动力学和沉积学

• 批准号: RGPIN-2019-05124
• 负责人: Ashmore, Peter
• 金额: $ 3.13万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=754767
• 关键词: Morphodynamics; sedimentology; gravel; bed; rivers

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.

总体研究目标是分析河流的形态和动态，有助于从根本上理解河流景观和河流对环境变化的敏感性。这需要了解形成特定类型河流形态和动态的过程。其核心是这样一种观点，即河流是由它们自己的侵蚀、泥沙输送和沉积过程形成的，这些过程形成了沙洲、河道和河流景观的其他特征。这些过程的不同工作方式是景观中看到的各种河流形态的主要原因。分析河流泥沙运动的传统方法是液压驱动的传送带过程，但这个概念不能直接解释河流形态和造成这种形态的局部过程的差异。我正在探索一种替代但互补的方法，它将泥沙运动和河流形态的动态视为本质上相同的过程，因此专注于河床地形的动态，以查看河流实际作为动态地貌的工作方式。山区和丘陵地区常见的充满活力的多通道辫状河是测试这一方法的有用河流类型，因为它们不断地改变和重新配置其形态，特别是在大流量事件期间。其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输送速率联系起来，并比较不同形态和沉积特征的河流。简而言之，了解这些河流是如何作为动态地貌发挥作用的。同时，目的是发展基于河流形态动力学的河流输沙率特征和预测的新方法。由于河流的形态动态相对缓慢，我们在实验水槽中使用小比例物理模型来加速过程，控制条件，观察河道形态的发展，测量变化率和侵蚀和淤积的体积(使用摄影测量来绘制河床地形图)，监测泥沙输移速率，并根据底质颗粒运动的统计数据观察形态发展的方式。使用现场数据对模型数据进行了验证。其结果将是进一步发展这种将河流形态和泥沙运动直接联系起来的地貌动力学分析，特别是对河流形态和河流动态的“风格”的差异有一个定量的了解。这提供了一幅更完整的河流动态图景，从中可以预测各种环境变化、工程或水流操纵对河流造成的变化的影响，也是评估地貌质量和恢复河流形态和动态的基础。