Fluvial 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进行了广泛的研究，但它们的动态和对自然和人为环境变化的反应仍然远未被了解。对冲积河道的形状、大小和模式产生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。该研究计划的长期目标是在河流更大范围的行为(时间和空间)内整合湍流。该研究计划的具体目标是：1)测试宏观湍流结构和水流脉动的性质、起源和演变的一般性；2)量化水流湍流与其他大尺度水流运动(如脉动、二次流)相互作用时的作用；3)将输沙事件的性质和动力学与砾石河床中的湍流/脉动水流结构联系起来；4)量化水流不稳定和不均匀对泥沙输移和形态变化的影响和反馈。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现场实验设计。实验将在魁北克南部和安大略省的一些现场进行，其中一个现场安装了高分辨率的流动、床面地形和颗粒位移测量设备。实验室实验将补充关于天然河流的工作。

Alluvial rivers are complex and fundamental components of the natural environment and a key resource for human activities and for wildlife. Although rivers 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 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 fluvial 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 long-term objective of the research program is to integrate turbulence within the larger scale behaviour (time and space) of rivers. The specific objectives of the research program are to: 1) test the generality of the properties, origin and evolution of macroturbulent flow structures and flow pulsations; 2) quantify the role of flow turbulence as it interacts with other large scale flow motions (e.g. pulsations, secondary currents); 3) link the properties and dynamics of sediment transport episodes/events to the turbulent/pulsations flow structures in gravel-bed rivers and 4) quantify the effects and feedbacks of flow unsteadiness and non-uniformity on sediment transport and morphological changes as flow stage changes. These objectives will be met through interconnected projects that will rely on both classical and innovative methods and in situ experimental designs. The experiments will be conducted at a selection of field sites in southern Québec and Ontario, one of which has permanent installations for the high resolution measurements of flow, bed topography and particle displacements. Laboratory experiments will complement the work on natural rivers.