River morphodynamics research for flood mitigation

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This research will apply better understanding of river morphodynamic processes to mitigate flood risk. Floods are the costliest natural hazard in Canada. Major river floods have occurred recently in cities across the country. The 2013 Alberta flood that inundated downtown Calgary resulted in five deaths, evacuation of 100,000 people, and $6B in damage. Flood risk is typically defined within the 1:100 year floodplain, which is the land surface predicted to be inundated during a river flow with a 1% likelihood of occurring in any given year. The 1:100 flood extent is usually estimated using a 1D or 2D hydrodynamic model with a fixed bed geometry. However, it is known that sediment transport during a flood can change the river bathymetry and thereby exacerbate flood levels. For example, sediment deposition upstream of flow obstructions such as bridges can reduce local flow conveyance capacity, causing the river to flow over its banks. Similarly, sediment transport during a flood can lead to active river migration causing catastrophic loss of infrastructure. Despite this awareneness, the influence on flood levels of morphodynamic river bed geometry change during the flood is rarely considered in practice. Furthermore, simplified one-dimensional hydraulic models, or even two-dimensional models if not properly designed and calibrated, are not capable of predicting rapidly varying non-uniform flow flood levels in complex landscapes such as urban centres where there is greatest risk. Developing solutions for these challenges is pressing, as climate change appears to be accelerating the frequency and magnitude of flood events, increasing the probability that existing flood protection works will fail. For the proposed research I will utilize field, laboratory, and numerical modelling river characterization methods to understand the interactions between morphodynamic processes, spatially distributed flow, and flood extents. The research will include spatially intensive field surveying of three dimensional unsteady flow fields and sediment transport in complex urban flood zones. These field data will complemented by detailed laboratory physical model parametric studies to examine the influence of various arrangements of shoreline infrastructure on channel morphodynamics and spatiotemporally distributed overbank flood levels. The data generated from these research activities will be utilized to develop improved 3D unsteady morphodynamic river models to predict overbank flood levels in complex urban landscapes. These models will ultimately be used to develop and evaluate optimal strategies and design standards to mitigate flood risk in Canada's rivers. This research will thus lead to better protection of Canadian communities from flooding.