2025 Volume 18 Issue 1 Pages 11-26
The risk of glacial lake outburst floods (GLOFs) in high mountain regions such as the Himalayas is increasing due to the effects of global warming. In this study, we focused on Tsho Rolpa, the largest glacial lake in Nepal, and conducted on-site observations and numerical simulations based on physical processes to quantitatively assess how rising temperatures due to global warming are affecting the occurrence of GLOF. During on-site observation, moraine surface temperature was measured for 1 year from November 2018 to November 2019. In the numerical simulation, using the temperature changes obtained from on-site observations as input values, changes in the temperature distribution of the moraine from the past to the future were calculated, and the progression of the melting surface layer of the moraine was determined. Next, assuming the occurrence of GLOF due to spontaneous collapse, we estimated temporal changes in the risk of GLOF occurrence through slope stability analysis with the critical slip surface method, considering the melting surface layer of the moraine as a collapsible soil layer. The simulation results showed a significant decrease in the stability of moraines over several decades from the past to the future, which is consistent with the increasing trend of GLOF occurrence observed in recent years.
