Linking sediment transport in gravel bed rivers to channel migration and bed stability

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Recent progress In mountainous regions, most of our major transportation routes, communication infrastructure, cities and towns are located at least in part on a deposit created by an active gravel bed stream. As a result, lateral stream migration often puts roads, houses and railways at risk, while vertical incision can expose and potentially rupture buried infrastructure such as pipelines and fiber optic communications cables. The techniques for managing these kinds of hazards are inadequate. Recent work by my group suggests that: a stochastic modelling approach may be more appropriate than the conventional deterministic ones for describing stream channel change; and, the body of work describing bed material sediment transport is not sufficient for understanding stream channel stability (as has been previously assumed). Objectives The long-term objective of my research program is to improve the theoretical basis for predicting stream channel response to environmental change, including the development of channel stability as it own, independent topic of study. There are three short-term objectives, to: (1) quantify the effect of flow and sediment supply variability on stream channel dynamics; (2) explore the relation between bed surface texture and organization (which together represent the bed state) and the processes producing channel stability; and (3) relate the spatial and temporal variations in bedload transport to the lateral activity of the stream. Methodology The first set of experiments will test whether streams subject to constant flow and sediment supply rates exhibit similar dynamics to those with variable flows and sediment supply rates; in particular, we wish to ascertain whether the processes of channel migration and avulsion that occur during variable flow experiments also occur at similar rates in the constant flow experiments. To develop a better understanding of how bed state influences channel stability, we will test a new approach for measuring the bed state using a wavelet approach. By combining these measurements with state of the art data on sediment transport using the light table approach pioneered at UBC, we will bridge the gap between sediment transport and channel stability. Finally, we will use our experimental results to develop a method to quantify river stability, and use it as a diagnostic tool for estimating river stability in the field. HQP This Discovery Grant will fund experimental research in the Biogeomorphic Experimental Laboratory at UBC. The work will be conducted by teams of graduate and undergraduate researchers, while a post-doc fellow will help develop the conceptual links between the various experiments. I will use this grant to train 1 post-doc, 4 PhDs, 4 MSc and 5 Undergraduates. Impact Ultimately, I aim to substantially improve the scientific basis for understanding how rivers behave at the spatial scales relevant to human development and infrastructure adjacent to rivers.