41-7 Landscape Change After a Glacial Lake Outburst Flood in the Mt. Everest Region, Nepal

Session: Philosophy of Extreme Events and Landscape Evolution on Earth and Other Planets: Thinking Geologically in the Spirit of Victor Baker

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Abstract:

Glacial lake outburst floods (GLOFs) pose a significant hazard in mountainous regions, worsened by the ongoing effects of climate change. As glaciers continue to melt, the formation and expansion of glacial lakes increase, putting additional pressure on their confining dams. GLOFs occur when the dam of a glacial lake fails, resulting in the sudden release of a large volume of water and entrained debris. Despite the complexities involved, it is important to assess the potential for GLOFs and evaluate their temporal and spatial occurrence. On August 16, 2024, two glacial lakes in the Thame Khola Valley, located in the Khumbu Himal of Nepal, catastrophically discharged from their high-alpine valleys. This caused devastating floods that destroyed buildings and farmland in the village of Thame and deposited extensive debris across the lower part of the valley. A further concern arising from the Thame GLOF is the formation of a secondary landslide hazard due to a significant incision of the stream channel below the settlement. The geological layers beneath the town are susceptible to slow-moving, deep-seated rotational landsliding when lateral support is removed during stream incision. During field investigations in the fall of 2024, drone imagery and ground photographs of the GLOF deposits around Thame and the downstream incision/landsliding zone were collected to create detailed topographic landscape models using photogrammetry. These models will help to estimate the evolution of similar paleoflood events, providing valuable insights for future evaluations. Data gathered from the sediment deposits will also provide insight into the interactions between GLOFs and subsequent geomorphological changes, offering information for assessing long-term risks. By combining field observations with photogrammetric models, this research aims to enhance our understanding of how GLOFs and their cascading effects help shape mountain landscapes.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7377

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