Analytical hierarchy process based assessment of glacial lake outburst flood screening in Arunachal Pradesh, India

The Eastern Himalayas is known for its fragile mountain ecosystems and is highly sensitive towards climate change. In recent decades, rapid warming and glacial retreat caused significant changes in the number, size and distribution of lakes. These changes increased concerns over a major hazard for downstream regions called Glacial Lake Outburst Floods (GLOFs). The present study focuses on changes in the number and area of different lake classes and GLOF risks in Arunachal Pradesh, Eastern Himalaya during 1988 and 2020. Using multitemporal satellite data, results indicate a significant increase in both number and area of nonglacial lakes (NGLs) by 498 lakes and 3212.56 ha, respectively. Proglacial lakes (PGLs) decreased slightly in number but expanded in area, whereas unconnected glacial lakes (UGLs) increased in number while decreasing in area. The majority of newly formed lakes were located between 4000 and 5000 m above mean sea level (AMSL). A total of 127 lakes was selected for GLOF risk assessment using the Analytic Hierarchy Process (AHP), with lake expansion rate and proximity to glaciers as the most critical parameters. Results indicated that 2 lakes are identified as high risk, 36 as medium risk and 89 as low risk, with a consistency ratio of 0.091. The study highlights the increasing risk potential of expanding glacial and high altitude lakes under climate change. The study further emphasized the need for continuous monitoring, targeted risk mitigation strategies and early warning systems to mitigate the downstream regions in the Eastern Himalaya.