Fluid and Sediment Dynamics in Bedrock Rivers

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The objective of this research program is to advance our understanding of fluid and sediment dynamics in river systems, with a particular focus on bedrock rivers. Understanding the linkages amongst surface processes and solid earth dynamics represents one of the greatest challenges in Earth Science. Active incision in bedrock rivers sets the pace of landscape evolution. The relief of mountain ranges is ultimately controlled by the depth of bedrock incision by rivers. Furthermore, rivers actively cut deep valleys and canyons into bedrock, and transport that material to the sea, unburdening the Earth’s surface and allowing isostatic uplift of majestic mountain peaks in tectonically active settings. Our ability to predict the behavior of alluvial river channels (rivers that flow through their own deposits) has steadily increased over the past century and, in the past few decades, models have been developed that capture many of the essential morphodynamic processes. However, our understanding of the morphodynamics of non-alluvial, bedrock-bound channels is not nearly as well developed. Improved understanding of large-scale, long-term landscape evolution requires a better understanding of fluid and sediment dynamics in bedrock rivers. Recent work by my research group has shown that bedrock canyons exhibit a complex flow structure that causes velocity inversions and radically alters the distribution of shear stress in bedrock canyons, which influences the patterns and magnitude of rock erosion. Work proposed here seeks answers to the following research questions: 1) How are channel morphology and flow dynamics linked in bedrock constrained channels? 2) What causes velocity inversions in bedrock rivers? 3) Are non-uniform flow structures important for predicting the long term incision rate in bedrock rivers? These questions will be answered using a combination of targeted field campaigns in the Fraser Canyon, British Columbia and physical modelling in the River Dynamics Lab (RDL) at Simon Fraser University (SFU) to explore flow, sediment movement and erosion patterns. The work will also involve numerical modelling of outcomes from the field and lab to integrate results over geologic time scales. Vast tracts of Canada are drained by rivers carved in bedrock and weakly consolidated sediments. A better understanding of flow dynamics in these rivers informs recreational activities, rescue and recovery operations, and pollutant spill dispersion and cleanup in Canada’s bedrock rivers. A better understand of the evolution of these channels informs questions about how to manage, conserve and preserve bedrock landscapes over annual to millennial time scales while at the same time answering questions about how landscapes develop over geologic time scales.