Investigating The Role Of Bedrock River Meandering In The Formation Of Unpaired Strath Terraces

在大多数情况下，河流切入基岩决定了景观演化的速度，是构造信号传递给景观的机制。因此，对河流切口的机械理解对于许多实际问题（例如，河流恢复，栖息地稳定性）以及解决诸如景观如何响应构造抬升率或年降水量增加等智力问题都很重要。近十年来，由于认识到基岩河流切割的重要性，对这一主题的研究激增，对河流切割过程的理解取得了实质性进展。然而，大多数的努力都是一维地处理河流。因此，河流如何在山谷中横向侵蚀在很大程度上是未知的。因此，诸如基岩（层）梯田的特征仍然是一个谜，它说明了横向和垂直切口在地质时间尺度上的交替优势。对基岩阶地如何形成的更深入的了解将阐明横向侵蚀机制，并有助于回答地貌学中一个百年的问题，即河流如何以及为什么在基岩中形成阶地？该项目结合了数值模拟、高分辨率地形数据分析以及俄勒冈州史密斯河和加利福尼亚州佩斯卡德罗河流域的实地工作，将测试有关河流如何以及为什么横向移动穿过基岩的假设，以及这对阶地形成的地点和时间的影响。更广泛的意义：通过更好地了解横向基岩侵蚀过程，我们可以检验基岩河流在形成阶地时可能记录气候或构造事件的合理性。这具有基本的科学价值，因为河流在景观中留下的记录是我们了解景观如何应对气候变化的少数直接线索之一。这项研究还将为一名博士生、一名本科生研究助理和一整个本科生地质学班提供宝贵的科学培训，他们将参与对提案中阐述的假设进行实地测试。

River incision into bedrock sets the pace of landscape evolution in most settings and is the mechanism by which tectonic signals are communicated to the landscape. Consequently, a mechanistic understanding of river incision is important for many practical problems (e.g., river restoration, habitat stability) as well as for addressing intellectual questions such as how will a landscape respond to an increase in tectonic uplift rate or annual precipitation? In the past decade, recognition of the importance of bedrock river incision has led to an explosion of research on this topic, and substantial progress has been made in understanding river incision processes. However, most efforts have treated rivers one-dimensionally. Hence, how a river erodes laterally in a valley is largely unknown. Consequently, features such as bedrock (strath) terraces, which illustrate the alternating dominance of lateral and vertical incision over geologic time-scales, remain enigmatic. A deeper understanding of how bedrock terraces form would illuminate lateral erosion mechanics and would help answer a century-old question in Geomorphology, how and why do rivers form terraces in bedrock? This project, which combines numerical modeling, analysis of high resolution topographic data, and field work focused on the Smith River in Oregon and on the Pescadero Creek watershed in California, will test hypotheses related to how and why rivers move laterally across bedrock, and the consequences of this for where and when terraces form.Broader Significance: Through better understanding of processes of lateral bedrock erosion, we can test the plausibility that bedrock rivers might record climatic or tectonic events when they create terraces. This is of fundamental scientific value because the record rivers leave in the landscape is one of the few direct clues that we have to understand how landscapes respond to shifting climates. This research will also foster invaluable scientific training for a PhD student, an undergraduate research assistant, and an entire undergraduate geology class that will be involved in field-testing the hypotheses articulated in the proposal.