The exacerbation of glacier mass loss due to global warming leads to the accelerating expansion of glacial lakes globally. The destabilization of lateral moraines and the following landslide into an expanding glacial lake may trigger the outburst floods greater than before, which has become an increasing threat to the communities and infrastructure downstream of the glacier lake. However, since most glacial lakes are located at high altitudes, with lack of transportation and in-site monitoring equipment, accurately assessing the risk of GLOFs remains challenging. This study aims to establish a combined approach with multi-source remote sensing and hydraulic modeling techniques for the quantitative assessment of the potential impacts of the GLOFs on the settlements and infrastructure downstream, and apply the approach to evaluate the GLOFs induced by the collapse of lateral moraines with various volumes in Qiangzongkeco in the Tibet Plateau.

The water surface areas of the Qiangzongkeco were delineated using optical remote sensing images and the lake volumes were estimated based on the empirical relationship with lake area. The cumulative deformation and deformation rate of the lateral moraines and the glacial tongue were assessed by processing a long-time series of Interferometric Synthetic Aperture Radar (InSAR) data. The volume range of the potential landslide into the lake was estimated based on the position and area of the deformative lateral moraines. The Froehlich equation was employed to predict the hydrographs of the GLOFs, each of which was input as inlet condition to the hydraulic modeling of downstream flood routing in HEC-RAS software. The distributions of flood depth and flow velocity along the channel and in the communities and infrastructure downstream were visualized to analyze the inundation risk by the floods. The results show that the deformation of lateral moraines was significant and keeps accelerating since 2010s. Variations in landslide volume and drainage volume lead to significant differences in the GLOFs peak discharge. Both Gonglema and Chentang Town’s infrastructure will be severely damaged and Gonglema will suffer more for it is closer to the lake. Our results highlight the necessity in continuous monitoring of the deformative lateral moraines around rapidly expanding glacial lakes to mitigate the hazards of GLOFs in high-altitude mountainous areas.