Flow processes and river dynamics

冲积河是自然环境的复杂和基本组成部分，也是人类活动和野生动物的关键资源。尽管过去已经对河流系统进行了广泛的研究，但对其动态和对自然和人为环境变化的反应仍远未被了解。对冲积河道的形状、大小和模式造成重大和不可预见的影响的许多壮观例子都是由严重的洪水或干旱造成的，例如最近在欧洲、北美和其他地方目睹的那些时期。为了了解河流的行为，我们需要提高我们对驱动河流系统的基本机械过程的知识。本研究主要研究河流水流结构、泥沙运动及由此产生的河床(形态和床料分布)调整之间的关系、反馈和相互调节。研究的具体范围是关于流动湍流(即流体流动中较小的运动尺度)在这些关系中的作用。研究方案的目标是：建立一个更好的均匀和非均匀河流中大尺度湍流结构的性质、起源和演变的模式；量化和了解水流结构随着水流阶段的变化而发生的变化；将湍流纳入斑块变异性的表征，并评估湍流对鱼类行为的作用；量化水流结构和推移质泥沙输送之间的关系；确定河床形态对河段尺度河床颗粒运动的影响。这些目标将通过相互关联的项目来实现，这些项目将依赖于经典和创新的方法以及实验设计。这些实验将在魁北克东部选定的一些野外地点的河流中进行，其中一些现场有永久性的设备来测量水流、河床地形和颗粒位移。这项研究的结果将用于改进目前关于湍流发展和湍流对鱼类行为和泥沙输送影响的模型。

Alluvial rivers are complex and fundamental components of the natural environment and a key resource for human activities and for wildlife. Although river systems have been extensively studied in the past, their dynamics and response to environmental changes, both natural and anthropogenic, are still far from being understood. Numerous spectacular examples of major and unforeseen impacts on the shape, size and pattern of alluvial channels have been caused by severe floods or by periods of drought such as those recently witnessed in Europe, North America, and elsewhere. In order to understand the behaviour of rivers we need to advance our knowledge on the fundamental mechanical processes that drive the river system. This research program focuses on the relationships, feedbacks and mutual adjustments between flow structure, sediment mobility and the resulting adjustments of the bed (form and bed material distribution) in rivers. The particular scope of the research is on the role of flow turbulence (i.e. smaller scales of motion in fluid flow) in these relationships. The objectives of the research program are to: develop a better model of the properties, origin and evolution of large-scale turbulent flow structures in uniform and non-uniform river flows; to quantify and understand changes in flow structures as flow stage changes; to integrate turbulence in the characterisation of the variability of patches and to assess the role of turbulence on fish behaviour; quantify the relations between flow structures and bedload sediment transport; determine the effects of bed morphology on bed particle movements at the reach scale. These objectives will be met through interconnected projects that will rely on both classical and innovative methods and experimental designs. The experiments will be conducted in rivers in eastern Québec at a selection of field sites, some of which have permanent installations for the measurements of flow, bed topography and particle displacements. The results of this research will be used to improve current models on the development of turbulence and on the effects of turbulence on fish behaviour and sediment transport.