Glacial Lake Outburst Flood Study Using Remote Sensing and 2D Hydraulic Modeling: A Case Study of Shishper Glacier in Pakistan

Observations of glacial changes in the Hindu Kush Himalayas (HKH) region reveal significant glacier retreat, particularly in Pakistan. These glaciers melt because of climate change, and lakes form near their terminus. However, the situation worsens as the number and volume of these lakes increase, resulting in disasters. This study used satellite imageries from Landsat and Sentinel 2, and ALOS 30 m DEM, to analyze the areal and volumetric expansion of glacial lake, formed by the blockade of Mochuwar Glacier by terminus of Shishper Glacier at the point of confluence. This terminus extends further downstream and has been the cause of several GLOF events in the past. The Shishper Glacier has recently had many surges, the most recent of which occurred in 2022, 2020, 2019, and 2018. HEC-RAS 2D model was used to reproduce the Shishper Glacier lake outburst flooding (GLOF2022) and to investigate reasons behind the collapsed Hassanabad Bridge. The model results showed that a peak flow of 3,737 cubic meters per second and released 38.987 million cubic meters. At the Hassan Abad Bridge, extreme conditions included shear stress exceeding 1,000 N/m² on both sides and downstream velocity over 15 m/s. To safeguard the infrastructure, and the exposed community, it is vitally important to conduct proper monitoring and assessment of each glacier and glacial lakes. The GLOF risk associated with Shishper Glacier can be significantly reduced by implementing an early warning system and releasing the glacial lake volume steadily, which can be used for water supply and Hydel power generation. The results of the proposed study will support GLOF risk management throughout the country.