RUI: Quantifying the effects of wildfire burning on 10Be concentrations in river sand - A study of the 2018 Woolsey Fire, Santa Monica Mountains, CA

地貌在数百至数千年间演变的速率--地质侵蚀率--提供了有关地貌稳定性、沉积物侵蚀或移动的速率、断层上的地震运动以及背景地质侵蚀之上的人为侵蚀程度的重要信息。洪水、飓风、地震、山体滑坡和野火等短暂但大规模的侵蚀事件究竟是如何影响地质侵蚀率的，人们仍然知之甚少。该项目的重点是伍尔西大火，2018年11月，这场大火烧毁了加利福尼亚州南部圣莫尼卡山脉约10万英亩的土地。伍尔西大火提供了一个独特的机会，可以了解持续时间短、规模大的火灾如何破坏和改变地质侵蚀率，这是由于2016年确定的火灾前侵蚀率的现有数据集。通过这个项目，三名本科生将接受地球科学研究的个性化培训，分析高级论文的真实数据，并了解地球表面如何应对野火。通过测量石英河沙中10-铍(10Be)的浓度，确定了世界各地数千条河流的地质侵蚀速率。测得的10Be浓度只在地球近地表产生，因此对短暂的深侵蚀事件(如沟壑侵蚀、山体滑坡和泥石流)敏感或被稀释，所有这些事件在野火后都很常见。火灾后侵蚀对测量的10Be浓度的影响在很大程度上是未知的，因为很少有来自随后受到严重燃烧影响的河流的现有10Be数据。该项目受益于2016年从圣莫尼卡山脉排水的七条河流收集的10Be数据集，也就是2018年伍尔西大火的两年前。其中四条河流被大火完全烧毁，提供了独特的机会来(1)量化因野火造成的集水区侵蚀而测得的河沙中10Be浓度的变化，以及(2)量化未烧毁集水区10Be浓度的重现性。该项目将对越来越多在工作中使用10Be数据的科学家产生明显而有益的影响，因为它将在陡峭、半干旱、易起火的地形中提供首批长期、系统收集的10Be重复样本之一。由于10Be得出的侵蚀速率被用来描述现代人类引起的泥沙径流，绘制构造活动区的地震活动图，并在具有地质意义的时间尺度上评估景观稳定性，这项工作将广泛惠及依赖地貌学家对泥沙输送和景观演变做出准确和信息解释的能力的广泛专业人员。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The rates at which landscapes evolve over hundreds to thousands of years – geological erosion rates – provide important information about landscape stability, rates of sediment erosion or movement, seismic motion on faults, and the magnitude of human-caused erosion above background geological erosion. Exactly how geological erosion rates are affected by short-lived but large-magnitude erosive events such as floods, hurricanes, earthquakes, landslides, and wildfires remain poorly understood. This project focuses on the Woolsey Fire, which burned through ~100,000 acres of the Santa Monica Mountains, southern California, in November 2018. The Woolsey fire provides a unique opportunity to understand how a short-duration, large-magnitude fire disrupts and changes geological erosion rates owing to an existing dataset of pre-fire erosion rates determined in 2016. Through this project, three undergraduate research students will receive personalized training in Earth science research, analyze real-world data for senior theses, and learn how Earth’s surface changes in response to wildfires.Geological erosion rates have been determined for thousands of rivers around the world by measuring the concentration of 10-beryllium (10Be) in quartz river sand. Measured 10Be concentrations are only produced in Earth’s near-surface and are thus sensitive to or diluted by short-lived deep-erosion events such as gully erosion, landslides, and debris flows, all of which are common following wildfires. The effect of post-fire erosion on measured 10Be concentrations is largely unknown because it is rare to have existing 10Be data from rivers that are subsequently affected by severe burning. This project benefits from a 10Be dataset collected from seven rivers draining the Santa Monica Mountains in 2016, two years prior to the 2018 Woolsey Fire. Four of these rivers were completely burned by the fire, providing the unique opportunity to (1) quantify how much measured 10Be concentrations in river sand have changed as a result of wildfire-caused erosion in burned catchments and (2) quantify the reproducibility of 10Be concentrations in unburned catchments. This project will have a clear and beneficial impact for the growing number of scientists who use 10Be data in their work because it serves to provide one of the first long-term, systematically-collected 10Be replicate sample sets in a steep, semiarid, fire-prone landscape. Because 10Be-derived erosion rates are used to contextualize modern human-induced sediment runoff, map seismic activity in tectonically-active regions, and assess landscape stability over geologically-meaningful timescales, this work will broadly benefit a wide range of professionals who rely on geomorphologists’ ability to produce accurate and informative interpretations of sediment transport and landscape evolution.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.