Fluvial Processes and River Dynamics

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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.