Glacial lake expansion and GLOF hazard assessment of Kedartal, upper Ganga basin: insights from remote sensing, climatological and 2D hydro-dynamic modelling

Abstract

The Hindu Kush Himalaya (HKH) is among the world’s most vulnerable mountain regions, where accelerated glacier retreat has driven the expansion of glacial lakes and increased the potential for Glacial Lake Outburst Floods (GLOFs). This study assesses the potential GLOF hazard associated with Kedartal Lake, a lateral moraine- dammed glacial lake in the Upper Ganga Basin, by integrating climatic trend analysis with process-based hydrodynamic model ling. Multi-temporal satellite observations (2001–2025) with historical mapping, were used to quantify lake evolution. While two- dimensional hydrodynamic model (HEC-RAS) simulated down stream flood propagation under a worst-case dam breach scenario. Results revealed a seasonal expansion of lake area from 64455:86m (1990) to 105772:99m2 (2020), and 1; 33; 823:1m (2025), representing ~64.1% seasonal variation since 1990. The GLOF simulation results showed a high magnitude flood wave with the peak dis charge ~2;800m3 3=s within 15 minutes after initiation at the outlet. The flood wave attenuates as it travels down the Kedar-Ganga valley, reaching Gangotri town with a peak discharge of ~1;450m =s almost 45 minutes after the breach. Flood routing models indicate flow depths up to 2 metres in narrow gorge sec tions, and inundation depths ranging from 0 to 15 metres in the built-up areas near the confluence. Regional climatic analysis reveals a statistically significant warming trend (~0.013 °C yr; p < 0.001) and increasing extreme precipitation events, reinforcing climatic forcing as a primary driver of glacier mass loss and lake expansion. The projected hazard, consistent with SSP-based climate forecast, indicates a risk to Gangotri town. These findings demonstrate the utility of the proposed framework for identifying essential datasets, analytical methods, and monitoring requirements to support preliminary GLOF hazard assessment and future risk management in the basin.