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

在过去的十年里，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辩论重新抬头。然而，这一领域的进展从根本上受到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联系起来的困难。该项目通过将野外、实验室和计算机模拟方法相结合，帮助弥合这一差距，以调查史前大洪水在西藏东南部地球上侵蚀最快的自然景观之一留下的第一个直接证据。这个项目将结合冰川湖泊沉积年表、洪水沉积的实地观测和年代测定、不同级别水流中沉积的沉积物的来源数据和洪水事件的计算机模拟，以(1)模拟洪水水力学、滑坡触发、死水沉积物沉积和洪水危害；(2)将洪水条件与侵蚀过程联系起来，并评估大洪水集中在峡谷中的程度；(3)开始限制大洪水事件的时间和频率，以更好地了解其与气候的关系和对长期侵蚀的影响。最终，这种用化学“指纹”方法(使用锆石U-Pb年龄)来研究侵蚀过程的新方法将有助于我们更好地理解河流切割和岩石抬升之间的可能反馈、青藏高原边缘演化以及气候和侵蚀在冰川-间冰期时间尺度上的联系。该模型研究将对该地区与水电站大坝开发相关的洪水灾害进行评估，从而造福于社会。该项目涉及华盛顿大学、美国地质调查局和印度一家灾害管理机构的合作。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。为了在为少数族裔服务的高中推广K-12 STEM教育，研究人员和学生将与一名教师合作，为华盛顿大学的推广项目--摇滚乐--开设一堂关于洪水和巨型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项目、印度灾害管理人员、大学课程、会议和出版物广泛传播。该项目得到了地貌学和土地利用动力学以及国际科学和工程计划的联合支持。

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.