Fluid and Sediment Dynamics in Bedrock Rivers

这项研究计划的目的是促进我们对河流系统中流体和泥沙动力学的理解，特别是对基岩河流的关注。了解地表过程和固体地球动力学之间的联系是地球科学面临的最大挑战之一。基岩河流的活跃切割决定了景观演变的步伐。山脉的起伏最终受控于河流基岩切割的深度。此外，河流积极地将深谷和峡谷切割成基岩，并将这些物质输送到海洋中，减轻了地球表面的负担，并允许在构造活跃的环境中均衡地抬升雄伟的山峰。在过去的一个世纪里，我们预测冲积河道(流经自身沉积物的河流)行为的能力稳步提高，在过去的几十年里，已经开发出捕捉许多基本地貌动力学过程的模型。然而，我们对非冲积、基岩边界河道的地貌动力学的了解还不够深入。要更好地理解大规模、长期的地貌演变，就需要更好地了解基岩河流中的流体和沉积物动力学。我的研究小组最近的工作表明，基岩峡谷表现出一种复杂的流动结构，导致速度反转，并从根本上改变基岩峡谷中剪应力的分布，从而影响岩石侵蚀的模式和程度。本文提出的工作旨在回答以下研究问题：1)在基岩受限的河道中，河道形态和水流动力学是如何联系在一起的？2)是什么导致了基岩河流的流速倒置？3)非均匀水流结构对预测基岩河流的长期切削率是否重要？这些问题将结合不列颠哥伦比亚省弗雷泽峡谷有针对性的实地活动和西蒙弗雷泽大学河流动力学实验室(RDL)的物理模型来回答，以探索水流、泥沙运动和侵蚀模式。这项工作还将包括对现场和实验室的结果进行数值模拟，以整合地质时间尺度上的结果。加拿大的大片地区被刻在基岩和弱固结沉积物中的河流排干。更好地了解这些河流中的水流动力学有助于加拿大基岩河的娱乐活动、救援和恢复行动以及污染物泄漏的扩散和清理。更好地了解这些渠道的演变有助于提出如何管理、保护和保存年度至千年时间尺度上的基岩景观，同时回答有关景观如何在地质时间尺度上发展的问题。

The objective of this research program is to advance our understanding of fluid and sediment dynamics in river systems, with a particular focus on bedrock rivers. Understanding the linkages amongst surface processes and solid earth dynamics represents one of the greatest challenges in Earth Science. Active incision in bedrock rivers sets the pace of landscape evolution. The relief of mountain ranges is ultimately controlled by the depth of bedrock incision by rivers. Furthermore, rivers actively cut deep valleys and canyons into bedrock, and transport that material to the sea, unburdening the Earth's surface and allowing isostatic uplift of majestic mountain peaks in tectonically active settings. Our ability to predict the behavior of alluvial river channels (rivers that flow through their own deposits) has steadily increased over the past century and, in the past few decades, models have been developed that capture many of the essential morphodynamic processes. However, our understanding of the morphodynamics of non-alluvial, bedrock-bound channels is not nearly as well developed. Improved understanding of large-scale, long-term landscape evolution requires a better understanding of fluid and sediment dynamics in bedrock rivers. Recent work by my research group has shown that bedrock canyons exhibit a complex flow structure that causes velocity inversions and radically alters the distribution of shear stress in bedrock canyons, which influences the patterns and magnitude of rock erosion. Work proposed here seeks answers to the following research questions: 1) How are channel morphology and flow dynamics linked in bedrock constrained channels? 2) What causes velocity inversions in bedrock rivers? 3) Are non-uniform flow structures important for predicting the long term incision rate in bedrock rivers? These questions will be answered using a combination of targeted field campaigns in the Fraser Canyon, British Columbia and physical modelling in the River Dynamics Lab (RDL) at Simon Fraser University (SFU) to explore flow, sediment movement and erosion patterns. The work will also involve numerical modelling of outcomes from the field and lab to integrate results over geologic time scales. Vast tracts of Canada are drained by rivers carved in bedrock and weakly consolidated sediments. A better understanding of flow dynamics in these rivers informs recreational activities, rescue and recovery operations, and pollutant spill dispersion and cleanup in Canada's bedrock rivers. A better understand of the evolution of these channels informs questions about how to manage, conserve and preserve bedrock landscapes over annual to millennial time scales while at the same time answering questions about how landscapes develop over geologic time scales.