Glacial Lake Outburst Floods (GLOFs) Susceptibility in the Northwest Himalayas using AHP-TOPSIS and AHP-COPRAS

Abstract

Glacier retreat has become a major concern in recent decades, which is contributing to the formation and expansion of glacial lakes. These lakes are particularly susceptible to Glacial Lake Outburst Floods (GLOFs) due to adverse climatic conditions and geotectonic settings. In this paper, we utilize the multi-temporal Sentinel2 and Landsat imagery, digital elevation model (DEM), seismic and meteorological data to assess the susceptibility associated with more than thirteen hundred glacial lakes present in the Northwest Himalayan region of India. The Northwest Himalayan region witnessed ~ 8.71% growth in the total area of these lakes (area ≥ 0.01 km²) from 2018 to 2022, with elevations between 5000-6000 m exhibiting the most noticeable increase. We incorporated the analytic hierarchy process (AHP)-Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) and AHP-complex proportional assessment (COPRAS) approaches to identify potentially dangerous glacial lakes (PDGLs), using 15 key criteria. More than 6 lakes were identified as having a high susceptibility to GLOF, whereas more than 16 lakes were categorized as moderately susceptible. The Indus sub-basin has the largest glacial lakes with a higher likelihood of a potential GLOF event, followed by the Jhelum and Qura-Qush sub-basins. To validate our approach, we studied the historical GLOF events that occurred in the study area. Our analysis finds that the majority of the past GLOFs are identified as PDGLs, either in the high or moderate category. This finding is consistent with the fact that these lakes indeed led to outburst events, therefore confirming the validity of the two approaches employed to evaluate the susceptibility of the glacial lakes. Furthermore, we observed that temperature in the region shows a rising trend across seasons, while precipitation decreases in spring, followed by winter and summer, with a gradual increase in autumn.

Keywords: AHP-COPRAS; AHP-TOPSIS; Extreme Precipitation Events (EPEs); Glacial Lake Outburst Floods (GLOFs); Heatwaves (HWs).