Glacial Lake Outburst Flood Hazard Assessment in the Upper Indus Basin, Ladakh Himalaya Using Remote Sensing and Hydrodynamic Modeling

Abstract. The Indian Himalayan Region (IHR), often called the “Third Pole,” contains the largest concentration of glaciers and perennial snow outside the polar regions and is highly sensitive to climate change. Rapid glacier retreat has accelerated the formation and expansion of glacial lakes, increasing the likelihood of Glacial Lake Outburst Floods (GLOFs). This study presents a multi-site GLOF hazard assessment of four glacier-fed lakes associated with the Gya, Raru, and Panikhar glaciers in the Upper Indus Basin, Ladakh. Spatio-temporal lake-area changes were mapped using Sentinel-2 imagery and geographic information system (GIS) techniques, while lake depth and volume were estimated using empirical relationships supported by digital elevation model analysis. Dam-break simulations using the Hydrologic Engineering Center’s River Analysis System (HEC-RAS) were conducted for 25 %, 50 %, 75 %, and 100 % lake-volume release scenarios for the Gya, Raru, and Panikhar lakes. Simulation outputs provided peak discharge, flow velocity, flood depth, and inundation extent. Results show that worst-case scenarios could affect downstream infrastructure such as bridges and roads, whereas the Rumbak lake poses limited hazard potential because of its low volume and natural moraine buffering. The hazard maps developed in this study support risk prioritization, early-warning planning, and climate-resilient disaster management in the Indian Himalaya.