RAPID: Characterizing Sediment Mobilization and Landscape Response to the Combined Effects of Wildfire and Extreme Flooding along Fourmile Canyon, Front Range Colorado

这个RAPID项目的重点是在2013年9月的异常降雨事件之后，洪水和侵蚀对科罗拉多前山脉的Fourmile峡谷的影响。该集水区仍在对2010年一场25平方公里的野火做出反应，研究小组将测试2013年的洪水重新处理并沉积了最初由早期火灾调动的沉积物的假设。该团队将研究2013年的洪水沉积物，侵蚀的山坡，侧支流和沟壑沉积物，以及沿着峡谷的梯田下新暴露的沉积物。他们将重新考察正在进行的火灾后研究的地点，并将在这些沉积物中使用短寿命沉降放射性核素（7Be， 137Cs和210Pb）来帮助识别再活化的火灾沉积物。此外，他们将分析山谷沉积物的地球化学和地层学，并将短期野火和洪水相关的侵蚀测量与正在进行的研究进行比较，这些研究记录了过去1万至3万年的侵蚀速率和山坡过程。必须尽快对2013年9月洪水期间形成的沉积物和暴露物进行取样和研究，以免它们随着道路重建、河道治理和景观恢复的进行而退化和消失。这些新发现极大地提高了利用14C分析全新世斜坡和山谷地层的能力。这项工作将加强对野火和大规模洪水发生率增加对景观和居民的影响的理解。因此，项目成果将为减轻灾害和增强复原力提供信息。该团队将利用与美国地质勘探局科学家和博尔德溪临界区天文台的现有合作，并将直接涉及本科生和研究生。

This RAPID project focuses on the impacts of flooding and erosion on Fourmile Canyon in the Colorado Front Range following the exceptional September 2013 rainfall event. The catchment is still responding to a 25 km2 wildfire in 2010 and the team will test the hypothesis that the 2013 flood reworked and deposited sediments initially mobilized by the earlier fires. The team will study the 2013 flood deposits, eroded hillslopes, side-tributary and gully deposits, and deposits freshly exposed beneath terraces along the canyon. They will revisit locations that have been part of an ongoing post-fire study, and will use short-lived fallout radionuclides (7Be, 137Cs, and 210Pb) in these deposits to help identify remobilized fire sediments. In addition, they will analyze the geochemistry and stratigraphy of valley deposits and compare measures of short-term wildfire and flooding-related erosion with ongoing studies documenting erosion rates and hillslope processes over the past 10,000-30,000 years. Sediment deposits and exposures that formed during the September 2013 flooding must be sampled and studied soon, before they degrade and disappear as road rebuilding, channel manipulation, and landscape recovery proceeds. These new exposures greatly increase the ability to analyze and date Holocene slope and valley stratigraphy using 14C. The work will enhance understanding of consequences of increased incidence of wildfires and large-magnitude floods on the landscape and those who live there. As such, the project outcomes will inform hazard mitigation and resilience. The team will leverage existing collaborations with USGS scientists and the Boulder Creek Critical Zone Observatory, and will directly involve undergraduates and a graduate student.