Impact of Quaternary megafloods on erosion of the Tsangpo River gorge, southeastern Tibet

过去十年，关于地震、山体滑坡和洪水等极端事件在长期侵蚀和景观演变中的作用的争论再次抬头。然而，从根本上说，在人类时间尺度上观察极端事件并将其与百万年平均侵蚀率测量结果联系起来的困难，限制了这一领域的进展。这个项目通过结合实地、实验室和计算机建模方法，在地球上侵蚀最迅速的自然景观之一——西藏东南部，调查史前特大洪水遗留下来的第一个直接证据，从而弥合了这一差距。该项目将整合冰湖沉积物年代学、洪水沉积物的野外观测和定年、不同量级水流沉积沉积物的物源数据以及洪水事件的计算机模拟，以：(1)模拟洪水水力学、滑坡触发、淡水沉积物沉积和洪水灾害；(2)将洪水条件与侵蚀过程联系起来，评价特大洪水对峡谷侵蚀的集中程度；(3)开始限制特大洪水事件的时间和频率，以更好地了解它们与气候的关系以及对长期侵蚀的影响。最终，这种利用锆石U-Pb年龄对洪泛砂进行化学“指纹识别”的新方法将提高我们对河流切割与岩石隆升之间可能的反馈、青藏高原边缘演化以及冰川-间冰期时间尺度上气候与侵蚀之间的联系的理解。该模型研究将对该地区水电大坝建设相关的洪涝灾害进行评估，从而造福社会。该项目涉及华盛顿大学、美国地质调查局和印度的一个灾害管理机构之间的合作。研究生和本科生将接受实地、实验室和计算机建模方法方面的培训。为了在少数族裔高中推广K-12 STEM教育，研究人员和学生将与一名教师合作，为华盛顿大学的外展项目“摇摆”（Rocking Out）开发一门关于洪水和特大洪水侵蚀的课程和活动。此外，研究成果将通过华盛顿大学的外展和高中课程、印度灾害管理人员、大学课程、会议和出版物广泛传播。本项目由地貌学与土地利用动力学和国际科学与工程项目联合支持。

The last decade has seen a resurgence of debate over the role of extreme events such as earthquakes, landslides and floods in long-term erosion and landscape evolution. Yet progress in this area is fundamentally limited by the difficulty of observing extreme events on human timescales and linking them to million-year average erosion rate measurements. This project helps bridge the gap by combining field, laboratory and computer modeling approaches to investigate the first direct evidence of the legacy of prehistoric megafloods in one of the most rapidly eroding natural landscapes on Earth, southeastern Tibet. This project will integrate glacial lake deposit chronologies, field observations and dating of flood deposits, provenance data for sediments deposited in different magnitude flows, and computer simulations of flood events to (1) model flood hydraulics, landslide triggering, slackwater sediment deposition and flood hazard; (2) relate flood conditions to erosion processes and evaluate the extent to which megafloods focus erosion in the gorge; and (3) begin to constrain the timing and frequency of megaflood events to better understand their relationship to climate and impact on long-term erosion. Ultimately, this novel approach of chemically "fingerprinting" flood sands (using zircon U-Pb ages) to investigate erosion processes will improve our understanding of possible feedbacks between river incision and rock uplift, Tibetan plateau margin evolution, and links between climate and erosion on glacial-interglacial timescales. The modeling study will benefit society by evaluating flood hazard associated with hydropower dam development in the region. The project involves collaborations among the University of Washington, US Geological Survey, and a disaster management agency in India. Graduate and undergraduate research students will be trained in field, laboratory, and computer modeling methods. To promote K-12 STEM education in minority-serving high schools, the researchers and students will work with a teacher to develop a lesson and activity on floods and megaflood erosion for the University of Washington outreach program, Rocking Out. Additionally, research findings will be disseminated broadly through University of Washington's outreach and high school programs, Indian disaster management personnel, university courses, conferences and publications. This project is jointly supported by the Geomorphology and Land Use Dynamics and International Science and Engineering programs.