Morphodynamics of gravel-bed rivers

砾石床河流的形态动力学

• 批准号: 41186-2012
• 负责人: Ashmore, Peter
• 金额: $ 3.35万
• 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: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=568836
• 关键词: Morphodynamics; gravel; bed; rivers

The overall research goal is to analyze the dynamics of rivers to contribute to understanding of the response of rivers to environmental change and human modification, and to the development of methods for restoration of impacted rivers. 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 transporters of sediment and that this sediment transport also creates the river form. If we can understand these sediment transport processes we can explain why rivers with different morphology occur and how rivers change in morphology over time. The classical approach to analysis of sediment transport is to develop mathematical functions that predict transport rate from the hydraulics of the flow. But this hydraulically-based analysis does not directly explain differences in river form and the local processes creating this form, and ignores the possibility that there are elements of the transport process that are not directly related to local hydraulics but are inherent properties of morphological instability. I am exploring an alternative approach which is to measure rates and 'styles' of morphological development - morphodynamics - that are the outcome, and driver, of spatial and temporal patterns of sediment transport. By measuring the morphological change we can make a direct link between the sediment transport processes and differences in river form and dynamics. This also leads to development of new methods for predicting sediment transport rate in rivers. Because the morphological dynamics of rivers is relatively slow we use small-scale physical models in an experimental flume to observe the development of channel morphology, measure rates of change and the volumes of erosion and deposition (using photogrammetry to map bed topography), and observe the way in which morphology develops from the statistics of the collective displacement of bed material particles. The outcome of the research will be a new way of analyzing river morphology and sediment transport, and of understanding variations in river morphology and morphological change, with practical application in river management and fluvial sedimentology.

总的研究目标是分析河流的动态，以帮助了解河流对环境变化和人类修改的反应，并制定修复受影响河流的方法。这需要了解形成特定类型河流形态和动态的过程。这一观点的核心是，河流是泥沙的运输者，泥沙的运输也创造了河流的形态。如果我们能够理解这些泥沙输移过程，我们就可以解释为什么会出现不同形态的河流，以及河流形态是如何随着时间的推移而变化的。分析泥沙运动的经典方法是建立数学函数，根据水流的水力学来预测输沙率。但这种基于水力学的分析不能直接解释河流形态和形成这种形态的局部过程的差异，并忽略了输送过程中可能存在的元素，这些元素与当地水力学没有直接关系，但是形态不稳定的固有属性。我正在探索另一种方法，那就是测量形态发育的速度和‘风格’--形态动力学--这是泥沙运移的时空模式的结果和驱动因素。通过测量形态变化，我们可以将泥沙输送过程与河流形态和动态的差异直接联系起来。这也导致了预报河流输沙率的新方法的发展。由于河流的形态动态相对较慢，我们在实验水槽中使用小比例物理模型来观察河道形态的发展，测量河道的变化率和冲刷淤积量(使用摄影测量来绘制河床地形)，并通过统计床料颗粒的集体位移来观察地形的发展方式。研究成果将为分析河流形态和泥沙运动，了解河流形态和形态变化的变化提供一种新的途径，在河流管理和河流沉积学中具有实际应用价值。