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

University Of Washington, Seattle WA

Investigators

Abstract

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.