RAPID: Documenting the temporal variance of the isotopic signature of detrital sediments following massive stochastic events using Hurricane Maria as a case study

飓风玛丽亚直接袭击多米尼加，造成数千起山体滑坡和泥石流，沿着河床流下，并将沉积物倒入沿海沃茨。这种大规模和间歇性的沉积物侵蚀和迁移是重要的，既是影响岛上社区的地质灾害，也是因为罕见事件对从碎屑沉积物中测量的同位素示踪剂确定的侵蚀率的影响仍然是这些方法的一个主要不确定因素。该科学团队处于一个独特的位置，可以量化这场灾难性风暴对碎屑沉积物作为大规模侵蚀监测器的效用的影响，他们于2017年6月从多米尼加的31个地点收集了河流沉积物。通过尽快重新定位这些站点，他们可以比较风暴引起的地面过程状况重大变化前后沉积物中的核素活动。飞往多米尼加的航班途经波多黎各，使研究小组能够对卢基略地区进行重新采样，从而获得加勒比地区所有10 Be侵蚀率站点的风暴后数据。利用遥感图像作为指导，该团队将测量选定的风暴相关沉积物的体积，厚度和范围。该小组将与西印度群岛大学（负责英语岛屿自然灾害管理的机构）的一名研究人员和多米尼克灾害管理办公室合作，利用其网络与更广泛的社区联系。两名本科生将参与实地工作，将与当地研究人员接触，并将为他们的高级论文分析数据。这是具有挑战性的自然实验，提供明确的信息，在沉积物同位素浓度的时间变化所造成的脉冲的物质移动通过沉积物系统。研究人员建议收集沉积物进行原位和大气10 Be、210 Pb、137 Cs和7 Be分析，以推断侵蚀深度和沉积物来源，确定河流沉积物中核素浓度的时间和空间变化。收集的样本将提供宝贵的信息，说明偶发性侵蚀，特别是滑坡对用于解释时空侵蚀率的核素浓度的影响，这是一个长期存在的问题。这些方法已被广泛应用于世界各地的数千个站点，但大型随机事件对数据的影响很少得到测试。在异常强烈的风暴之后立即采样的机会可以更好地了解在不同时间整合的侵蚀测量之间经常观察到的不匹配-短时间段的数据通常无法捕获地质时间整合时驱动侵蚀速率的重大事件。飓风玛丽亚提供了一个理想的自然实验，了解侵蚀和泥沙产量的时间变化，由于一个单一的事件。

Hurricane Maria's direct hit on Dominica caused thousands of landslides and debris flows that coursed down stream beds and poured sediment into coastal waters. Such massive and episodic sediment erosion and transport is important both as a geologic hazard affecting communities on the island, and because the impact of rare events on erosion rates determined from isotopic tracers measured in detrital sediment remains a major uncertainty in these methods. The scientific team is in a unique position to quantify the effect of this catastrophic storm on the utility of detrital sediment as a landscape-scale erosion monitor, having collected fluvial sediment from 31 sites on Dominica in June 2017. By resampling these sites as soon as practical, they can compare nuclide activities in sediment before and after the major change in surface process regime occasioned by the storm. Flights to Dominica route through Puerto Rico, allowing the team to also resample the Luquillo area, thereby obtaining post-storm data for all 10Be-derived erosion rate sites in the Caribbean. Using remotely-sensed images as a guide, the team will measure volume, thickness, and extent of selected storm-related deposits. The team will work with a researcher at the University of the West Indies (the institution responsible for natural hazard management on the English-speaking islands), and with the Dominica disaster management office, using their network to reach the wider community. Two undergraduates will be involved in field work, will engage with the local researcher, and will analyze data for their senior theses. It is challenging to find natural experiments that give clear information about temporal variability in isotopic concentration of sediment caused by pulses of material moving through the sediment system. the researchers propose to collect sediment to be analyzed for in situ and meteoric 10Be, 210Pb, 137Cs, and 7Be to infer both the depth of erosion and sediment sources, defining the temporal and spatial variance of nuclide concentration in fluvial sediment. The samples collected will provide valuable information about the effects of episodic erosion, particularly landslides, on the concentration of nuclides used to interpret erosion rates over space and time, a long-standing issue. These methods have been widely applied at thousands of sites around the world but the effects of large, stochastic events on the data have rarely been tested. The opportunity to sample immediately following an unusually intense storm allows for better understanding of the frequently observed mismatch between measures of erosion that integrate over different times - short-time period data often do not capture major events that, when integrated over geologic time, drive erosion rates. Hurricane Maria provides an ideal natural experiment for understanding temporal variability in erosion and sediment yield due to a single event.