Climate, erosion & sediment dynamics: Investigating controls on landscape evolution

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Landscape evolution models (LEMs) integrate our best understanding of hydro-geomorphic processes and provide the opportunity to systematically evaluate and test hypotheses related to the interactions among environmental forcing, surface processes, and solid Earth dynamics. However, a linchpin in our LEMs is our understanding of rivers, which control local topographic relief and set regional erosion rates. While decades of process-based studies have improved our understanding of the vast, non-linear and interacting processes shaping Earth's surface, there are still critical gaps in our understanding of fluvial processes that limit our ability to accurately predict landscape evolution. Thus, my research program will focus on two inter-related problems: 1) the effects of local precipitation on rock erodibility and erosion in bedrock rivers, and 2) the response behavior of river networks to changing hydro-geomorphic fluxes. First, my recent work in Hawai'i provided the first evidence that streambed erodibility can be modulated by local rainfall-dependent chemical weathering. Further, this process was shown to influence the rates and patterns of bedrock river erosion. My first objective is, therefore, to establish whether this effect is also observed in other landscapes, specifically the precipitation gradient across British Columbia (BC). Using a combination of fieldwork, laboratory rock strength testing, and river profile analysis, HQP and I will evaluate these climate-erosion trends and the influence of variable geology and tectonics. Second, increasing wildfire activity in western North America is leading to dramatic increases in flooding and erosion, which provides the opportunity to evaluate the watershed-scale controls of and responses to pulsed inputs of water and sediment. My group's recent work has focused on building state-of-the-art models of watershed-scale sediment dynamics to predict water supply risks after wildfire. These models now provide a novel opportunity for widespread geostatistical analysis of watershed controls on sediment connectivity following sediment disturbances, as well as a framework for predicting post-fire response. Thus, by running these models and conducting post-fire field monitoring studies in BC, we will advance our understanding of the controls on sediment bottlenecks in river networks and channels morphodynamics in these locations. Addressing these objectives will advance our understanding of fluvial processes and fill critical knowledge gaps that limit the ability of LEMs to predict Earth surface dynamics over geologic timescales. Further, this research will tackle key environmental issues in Canada, which is dissected by bedrock rivers and is experiencing increasing wildfire activity. Improving LEMs, particularly as they relate to climate-erosion interactions and fire disturbance, will better prepare Canadians for future risks and inform resource management under rapidly changing environmental regimes.