Flow processes and river dynamics

冲积河流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重要资源。尽管过去对河流系统进行了广泛的研究，但其动力学以及对自然和人为环境变化的反应仍远未得到理解。严重的洪水或干旱时期，例如最近在欧洲、北美和其他地方发生的干旱，对冲积河道的形状、大小和格局造成了许多重大和不可预见的影响。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认识。该研究计划的重点是河流水流结构，泥沙流动性和由此产生的河床调整（形式和床料分布）之间的关系，反馈和相互调节。研究的特定范围是在这些关系中流动湍流（即流体流动中较小尺度的运动）的作用。该研究方案的目标是：建立一个更好的模型，说明均匀和非均匀河流中大规模湍流结构的性质、起源和演变;量化和了解随着流动阶段变化的流动结构变化;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;量化水流结构与推移质输沙之间的关系;确定河段尺度上河床形态对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方法以及实验设计。实验将在魁北克省东部的河流中进行，在选定的实地地点，其中一些有永久性的装置，用于测量流量，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以及湍流对鱼类行为和沉积物迁移影响的模型。

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.