Fluid and sediment dynamics in sand-bedded river systems

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The objective of this research program is to advance our knowledge of the mechanics of sand-bedded river channels and, in particular, to develop physically-based tools to assist in the prediction of sediment movement between their source and ultimate sink in the ocean. The program uses the sand-bedded reach of the lower Fraser River as a natural laboratory to investigate and quantify processes. The Fraser also serves as inspiration (and in some cases the prototype) for more detailed observations in the River Dynamics Laboratory (RDL) flume channel at SFU. The mechanisms responsible for moving sediment through the 85 km river reach that passes through British Columbia's Lower Mainland are understood only conceptually, but the dynamics of the sediment control how the river responds to flood flows and the quality of aquatic habitat in the channel, delta, and tidal flat environments. Empirical methods for estimating sediment movement based on historical data collection programs are no longer reliable because of ongoing adjustment of the river to dredging required to maintain the Port of Vancouver. A physically-based modeling approach for sediment routing is required to make reliable predictions of how the sand-bedded channel and the delta environments will respond to various perturbations (e.g. a warmer climate, changes in water flux, changes in sediment flux associated with land use practices and contemporary variation in sea level). This research focuses on establishing methods to monitor suspended sediment delivery to the sand-bedded lower Fraser River, development of models for predicting suspended sediment transport based on the physical interactions between large-scale turbulent motions in the water column and examination of bedform response to variable flows (hydrographs or tides). There is a pressing need to make predictions of sediment transport in sand-bedded rivers that empty into the sea, such as the lower Fraser River, because they are often sites of intense urban development world-wide and the dynamics of these natural landscape processes significantly affect the socio-economic viability of this development.