Geomorphic processes of unreported GLOF cascade and past avalanches, Jammu and Kashmir, Western Himalaya

The Warwan sub-basin in Jammu and Kashmir is a remote glaciated basin that harbors several glacial lakes and has also been showing development in terms of infrastructure and population. This sub-basin witnessed several mass movement events in the past, including avalanches and GLOF that remained unreported. This study investigates past mass movement events in the Warwan sub-basin, Jammu and Kashmir, Western Himalaya. Three major avalanche events occurred in the last two decades. The September 2005 and September 2020 avalanches occurred from glaciers GL-B and GL-A, respectively, in the same glacier complex. The March 2020 event was a rock-ice avalanche that originated from the headwall of the glacier (GL-F) located in the valley opposite the glacier complex. The avalanche terminated before reaching the ablation zone of the glacier. Mapping of the avalanche runouts revealed that the September 2020 ice avalanche initiated from the headwall of the glacier (GL-A), impacting the lake located at its terminus, causing downstream GLOF. The runout of the September 2005 rock-ice avalanche terminated before reaching the terminus, where a glacial lake started forming in 1999. Evaluation of the geomorphic processes in the glacier complex shows sediment influx through meltwater stream of GL-D and GL-E into the lake associated with GL-A. This sediment influx led to infill of the lake basin. Further retreat of GL-A led to meltwater accumulation behind the sediment infill, creating two disconnected lakes in the same lake basin. The September 2020 avalanche impacted this lake-basin, leading to complete drainage of the infill sediment and water, causing downstream debris flow. Pre and post-GLOF imagery show that the outflow channel of the lake breached, leading to channel widening. The major GLOF outwash debris formed a prominent debris fan immediately downstream of the lake. The GLOF water discharge drained into the downstream lake (GL-B), resulting in a GLOF cascade. The study highlights how GLOF events and avalanche occurrences remain unreported due to downstream cascading processes and remote locations. The study highlights how GLOF events and avalanche occurrences may remain unreported in remote locations, possibly resulting in the underestimation of a threat for downstream areas. The history of mass movement events and the growth of the glacial lakes and GLOFs in the Warwan sub-basin call for monitoring and risk assessment considering changing conditions in future.

EGUsphere preprint: https://doi.org/10.5194/egusphere-2025-6281