Multi-Scenario GLOF Inundation in Nepal: Insights from Three Decades of Remote Sensing and Global Hydrodynamic Modelling

The Himalayan region, often referred to as the Third Pole, is experiencing accelerated glacier retreat due to global warming, which is rapidly triggering the formation and expansion of thousands of glacial lakes. This escalation has substantially increased the threat of catastrophic Glacial Lake Outburst Floods (GLOFs), posing a severe and growing risk to downstream communities and critical infrastructure. Despite this immense and transboundary danger, a comprehensive, national-scale, and spatially consistent hazard assessment across the Nepal Himalayas remains critically limited, hindering effective risk mitigation and adaptation planning. To address this urgent gap, our study develops an integrated framework that uniquely combines three decades (1990–2023) of remote sensing data with global hydrodynamic modeling (LISFLOOD-FP) and spatial analysis to systematically identify all vulnerable lakes, simulate multi-scenario outburst conditions, and quantify downstream flood risks across Nepal. Covering all 1,232 glacial lakes in the country, the study provides a robust, multi-temporal analysis, revealing about 26.9% increase in total lake area and the emergence of 265 new lakes primarily between 4,000 m and 6,000 m elevation. We simulate six prospective GLOF scenarios (ranging from +10% to +50% lake volume increase) to rigorously assess potential changes in flood extent and depth. The resulting National GLOF Hazard Atlas delivers the first spatially consistent and scenario-based framework for Nepal. This atlas offers critical insights into flood extent and depth that directly support targeted early-warning systems, climate-resilient infrastructure siting (e.g., hydropower assets and transport corridors), and sustainable risk reduction for high-mountain settlements.