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

景观演化模型(LEMS)融合了我们对水文地貌过程的最好理解，并提供了系统地评估和检验与环境强迫、地表过程和固体地球动力学之间相互作用的假设的机会。然而，在我们的LEM中，一个关键是我们对河流的理解，河流控制着当地的地形起伏，并设定了区域侵蚀率。虽然几十年的基于过程的研究提高了我们对塑造地球表面的巨大、非线性和相互作用的过程的理解，但我们对河流沉积过程的理解仍然存在严重差距，限制了我们准确预测地貌演变的能力。因此，我的研究计划将集中在两个相互关联的问题上：1)局部降水对基岩河流岩石可蚀性和侵蚀的影响，以及2)河网对变化的水文地貌通量的响应行为。首先，我最近在夏威夷的工作提供了第一个证据，证明河床的可蚀性可以由当地依赖降雨的化学风化来调节。此外，这一过程被证明影响了基岩河流侵蚀的速度和模式。因此，我的第一个目标是确定这种影响是否也在其他景观中观察到，特别是不列颠哥伦比亚省(BC)的降水梯度。通过结合实地调查、实验室岩石强度测试和河流剖面分析，HQP和我将评估这些气候侵蚀趋势以及不同地质和构造的影响。其次，北美西部野火活动的增加导致洪水和侵蚀急剧增加，这为评估流域尺度对水和泥沙脉冲输入的控制和反应提供了机会。我的团队最近的工作重点是建立最先进的流域尺度沉积物动力学模型，以预测野火后的供水风险。这些模型现在为在沉积物扰动后对沉积物连通性的流域控制进行广泛的地质统计分析提供了新的机会，并为预测火灾后的反应提供了一个框架。因此，通过运行这些模型并在不列颠哥伦比亚省进行火灾后现场监测研究，我们将加深对这些地点河网和河道地貌动力学中泥沙瓶颈的控制的了解。解决这些目标将促进我们对河流沉积过程的理解，并填补限制LEM在地质时间尺度上预测地球表面动态能力的关键知识空白。此外，这项研究将解决加拿大的关键环境问题，加拿大被基岩河流解剖，正在经历越来越多的野火活动。改善生态系统，特别是与气候-侵蚀相互作用和火灾干扰有关的系统，将使加拿大人更好地为未来的风险做好准备，并为快速变化的环境制度下的资源管理提供信息。

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.