Assessment of glacial lake prone to glacial lake outburst flood using multi-criteria decision analysis (MCDA) in Changme Khangpu basin, Sikkim Himalaya, India

Abstract Changme Khangpu (CK) basin is one of the major glaciated basins in Sikkim Himalaya with a high number of glacial lakes. A glacial lake inventory for the CK basin has been created using a semi-automated method based on Sentinel 2A images from the year 2020 and mapped 134 glacial lakes. Glacial lake outburst floods have emerged as a major concern in the Himalayan region in recent times. 20 glacial lakes were identified as being prone to GLOFs using a set of assessment parameters in the basin. We performed hazard and risk assessments for these glacial lakes using a multi-criteria decision analysis (MCDA) scheme using 13 consistent, exhaustive, and non-redundant criteria, categorized into triggering, mechanism, flood size, and impacts for assessing both the hazard as well as the risk associated with the glacial lakes for providing a comprehensive hazard and risk assessment. Based on this scheme, 14 lakes were categorized into the high-risk class and 6 lakes into the medium-risk class. MCDA scheme allows for assessing the risk scores associated with the glacial lakes by changing the threshold values of assessed criteria. Such sensitivity analysis done for the identified glacial lakes shows that even a slight change in the criteria values can significantly change the risk class of the lake. MCDA scheme can be applied at a regional scale across different lake types for the identification of potential GLOF hotspots and constant monitoring making it suitable for first order assessments.