River dynamics and resilience of fluvial systems in perturbed environments

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River systems are under considerable pressure due to human impacts and global environmental changes. It is increasingly recognized that river management approaches must move away from hard-engineering structures that maintain rivers in a fixed position. Instead, an approach based on freedom space for rivers, which integrates more natural processes such as meander dynamics and floodplain connectivity, should lead to more resilient systems, particularly in a climate change context. The long-term objective of the research program is to test how freedom space for rivers may or may not modify the long-term condition of fluvial systems under various environmental perturbations. Environmental perturbations that are specifically examined are reduced lateral mobility of streams resulting from heavy bank stabilization associated with protection of infrastructure, river straightening and dredging in agricultural streams, and climate change resulting in more frequent flash floods in tributary watersheds. The long-term objective will be reached through the combination of and interactions between numerical modelling and field experimentation. The short-term objectives are to 1) develop tools to characterize river reaches that are more vulnerable to discharge variability in order to estimate where it is most effective to provide more space for natural river processes to operate in fluvial systems; 2) examine the applicability of management approaches which incorporate hydrogeomorphological concepts for straightened and dredged streams in agricultural watersheds in the Quebec context; and 3) assess the role of increased flash floods in small tributary watersheds on the confluence zone and on the mobility of the main channel. The scientific approach of this research program is based on the collection of field data at several river reaches that are affected by human perturbations. Field measurements include detailed bed topography, surface and sub-surface grain size, bedload transport, velocity, turbidity, stage and discharge. The field component is combined with Geographical Information System (GIS) analysis and numerical modelling experiments. Hydrogeomorphological GIS tools recently developed in my research laboratory, making use of the increased availability of fine-resolution LiDAR Digital Elevation Models (DEMs), will be further developed to help characterize both main branches and tributary channels in specific watersheds in terms of stream power and vulnerability to the anticipated increase in discharge variability in future climate. This program will allow significant progress in establishing an expertise in river management based on hydrogeomorphological concepts to tackle major environmental problems in a range of rivers, and on developing GIS and modelling tools to better inform river managers about vulnerable river reaches in a climate change context.