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: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=633936
• 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.

总体研究目标是分析河流的动态，以帮助理解河流对环境变化和人类改造的响应，并为受影响河流的恢复方法的发展做出贡献。这需要理解创造特定类型河流形态和动态的过程。其核心思想是河流是沉积物的运输者，而沉积物的运输也创造了河流的形态。如果我们能够理解这些沉积物的运输过程，我们就可以解释为什么不同形态的河流会出现，以及河流的形态如何随着时间的推移而变化。分析泥沙输移的经典方法是建立数学函数，根据水流的水力学来预测输移速率。但是，这种基于水力的分析并不能直接解释河流形态的差异和形成这种形态的局部过程，并且忽略了这样一种可能性，即运输过程中存在与局部水力学没有直接关系的因素，但这些因素是形态不稳定的固有特性。我正在探索另一种方法，即测量形态发展的速率和“风格”——形态动力学——这是沉积物时空运输模式的结果和驱动因素。通过对形态变化的测量，我们可以将泥沙输运过程与河流形态和动力的差异直接联系起来。这也导致了预测河流中泥沙输运率的新方法的发展。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物理模型来观察河道形态的发展，测量变化速率和侵蚀和沉积的体积（使用摄影测量法绘制河床地形），并从河床物质颗粒的集体位移统计中观察形态的发展方式。研究结果将为分析河流形态和输沙、了解河流形态变化和形态变化提供新的途径，并在河流管理和河流沉积学方面具有实际应用价值。