Collaborative Research: Geomorphic legacy of megaflood deposits on river processes and form, Eastern Himalaya

地球和其他行星景观包含了过去和现在的表面过程的记录。在数千年前的寒冷气候时期，冰川和碎片偶尔堵塞河流，导致今天地球上从未见过的灾难性洪水。这样的“大洪水”在几乎每个大陆的景观上都留下了不可磨灭的印记，地质学家依靠罕见的洪水沉积物来重建大洪水如何塑造我们今天看到的景观。该项目的重点是喜马拉雅山脉东部独特的洪水沉积物，使用新的观察，测量和计算机建模来研究灾难性的洪水事件如何有助于陡峭，高起伏的山脉景观的演变。该项目还利用特大洪水的迷人故事来开发公众可访问的K-12教育材料，将科学发现与土著知识相结合，并将支持多个研究生和本科生的培训。这项工作的结果将有助于更准确地解释今天在地球和火星上看到的景观的起源-以及更好地预测类似灾难性人为类似物的危害，例如大坝故障后的洪水。先前的巨型洪水研究集中在溃坝巨型洪水流量（10^6 m3/s）对基岩河道侵蚀的影响上。本项目将进一步探索巨碎屑沉积对基岩河流长期（10^3年）演变的作用。项目组将重点关注喜马拉雅东部雅鲁藏布江-雅鲁藏布江-雅鲁藏布江水系沿着有据可查的巨碎屑沉积实例，以：1.使用先进的分析工具确定洪水沉积物的来源、沉积时代和粒度分布，2.开发基于过程的数值模型，预测突发洪水淤积后基岩河道的一阶变化; 3.通过比较有和没有大洪水历史的东喜马拉雅河流通道的形态，寻找一个独特的地形特征的大洪水过程。这些研究结果将阐明如何山间沉积物沉积的大洪水治理河谷的演变。最终，研究结果有可能改变侵蚀山地景观的数值模型中考虑沉积物沉积的方式，并将为罕见的高强度洪水事件在塑造地球和火星景观中的作用提供新的见解。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

Earth and other planetary landscapes contain a record of both past and present surface processes. During colder climate periods thousands of years ago, glacial ice and debris episodically dammed rivers, leading to catastrophic floods of a magnitude not seen on Earth today. Such “megafloods” left an indelible signature on landscapes across nearly every continent, and geologists rely on rare flood deposits to reconstruct how megafloods have shaped the landscapes we see today. This project focuses on unique flood deposits from the eastern Himalayan mountains, using new observations, measurements, and computer modeling to study how catastrophic flood events contribute to the evolution of a steep, high-relief mountain landscape. This project also uses the fascinating story of megafloods to develop publicly accessible K-12 educational materials that integrate scientific discovery with Indigenous Knowledge and will support training of multiple graduate and undergraduate students. The results of this work will help to more accurately interpret the origin of the landscapes seen on both Earth and Mars today – as well as to better predict hazards from similarly catastrophic anthropogenic analogues, such as flooding after the failure of a dam. Prior megaflood research has focused on the impact of dam-burst megaflood discharges (10^6 m3/s) on bedrock channel erosion. This project will further explore the role of megaflood deposition on the long-term (10^3 yr) evolution of bedrock rivers. The project team will focus on a well-documented example of megaflood deposition along the Yarlung-Siang-Brahmaputra river system in the eastern Himalaya to: 1. determine the source, depositional age and grain size distribution of flood deposits using cutting-edge analytical tools, 2. develop a process-based numerical model to predict first-order changes to a bedrock river channel following abrupt flood aggradation, and 3. search for a unique topographic signature of megaflood processes by comparing the morphology of eastern Himalayan river channels with and without a history of megaflooding. These findings will illuminate how intermontane sediment deposition by megafloods governs river valley evolution. Ultimately, the results have the potential to change the way sediment deposition is considered in numerical models of eroding mountainous landscapes and will provide new insight into the role of infrequent, high-magnitude flood events in shaping landscapes on both Earth and Mars.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.