Morphodynamic response of alluvial rivers to changes in flow

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Across Canada there is growing concern regarding the effect of changes to flow regime in rivers and the security of water resources. Rivers are very sensitive to alterations in flow. The anticipated changes in precipitation patterns associated with climate change will result in more intense and frequent flooding events in rivers and streams. The potential for more drastic changes over both the short- and long-terms pose serious threats to the integrity of rivers, compromising their ability to satisfy economic, social and ecological functions. These extreme events can significantly alter the morphodynamic (interaction between flow and sediment) processes in rivers. From a practical standpoint, it is important to be able to quantify and predict these changes as they involve substantial erosion and sedimentation which can damage hydraulic structures, erode land, and negatively impact aquatic ecosystems. The ability to predict morphodynamic response becomes increasingly important in urban environments where there are increasing demands on rivers, encroachment into the floodplain, and greater risk of economic loss resulting from extreme events. Due to their complex and dynamic nature, river morphodynamic adjustments in response to temporary increases in flow prove difficult to accurately predict and assess. Considering this, the goal of this research is to develop a greater understanding of the nature and temporal morphodynamic response of alluvial meandering streams to changes in flow associated with extreme events. To accomplish this goal, this research will apply a combination of laboratory and numerical tools to evaluate alterations to sediment and erosion processes in meandering streams resulting from increases in flow. Laboratory experiments will reveal the morphological adjustments of the stream bed and banks associated with temporary increases in flow, including the effect of gradual and rapid changes. The temporal evolution of the stream morphology, sediment transport rates and flow structure will be measured. In addition to morphological adjustments, the nature and response of non-uniform sediment beds (more representative of conditions in nature) to increases in flow will also be examined. Numerical modeling will use the acquired laboratory data to simulate the long-term stream morphological changes associated with successive extreme precipitation events and will create a predictive tool for river engineers and managers. The contributions made by this research will provide greater knowledge on the anticipated effects of climate change on stream morphodynamics. This will enable more accurate guidelines for future land-use and development around rivers and streams, and improved design of erosion and sedimentation protection measures to ensure the security of hydraulic structures and river engineering infrastructure. Results will also be of practical importance to river engineers and hydrologists, providing greater understanding of natural river behaviour for improved stream restoration, rehabilitation and re-naturalization efforts, and an increased level of detail for numerical modelers. This research will result in the training of hydro-environmental engineers, capable of working in a dynamic and multi-disciplinary field. Results and practical applications of this work will lead to more informed management of rivers and streams, thus ensuring sustainable management of Canada’s water resources.