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

在大多数环境中，基岩的河流切割决定了景观演变的步伐，是构造信号与景观沟通的机制。因此，从机械上理解河流切割对于许多实际问题(例如，河流恢复、栖息地稳定性)以及解决诸如景观将如何对构造抬升速率或年降雨量的增加作出反应等智力问题是重要的。在过去的十年里，人们对基岩河流切割重要性的认识导致了对这一主题的研究的爆炸性增长，对河流切割过程的理解也取得了实质性的进展。然而，大多数努力都是从一维的角度来处理河流。因此，一条河流如何在山谷中横向侵蚀在很大程度上是未知的。因此，基岩(层)阶地等特征仍然是一个谜，这些特征说明了横向和垂直切割在地质时间尺度上的交替优势。更深入地了解基岩阶地是如何形成的，将有助于阐明横向侵蚀机制，并有助于回答地貌学中一个百年来的问题，即河流如何以及为什么在基岩中形成梯田？这个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，将测试与河流如何和为什么横向穿过基岩以及这对梯田形成的地点和时间的影响相关的假设。更广泛的意义：通过更好地了解横向基岩侵蚀过程，我们可以测试基岩河流在形成梯田时可能记录气候或构造事件的可能性。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必须了解景观如何对变化的气候做出反应的为数不多的直接线索之一。这项研究还将促进对博士生、本科生研究助理和整个本科生地质学班级的宝贵科学培训，这些班级将参与对提案中阐明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.