Analysis of Glacial Lake Outburst Flood Susceptibility in the Saraswati River Basin, Uttarakhand, India, Using GIS and HEC-HMS Modeling

Abstract

Glacial lake outburst floods (GLOFs) are among the most destructive natural hazards in mountain environments. Rising temperatures have accelerated glacier retreat, leading to the growth of unstable glacial lakes, particularly in the Himalayan region. Sudden failure of these lakes can generate intense downstream flooding, severe erosion, and damage to settlements and infrastructure. The present study evaluates flood susceptibility in the Saraswati River Basin, Chamoli District, Uttarakhand, India, through the combined use of geographic information systems (GIS) and HEC-HMS hydrological modeling. Digital elevation model data were applied to delineate the watershed, generate drainage characteristics, and assess terrain influence on runoff behavior. A storm event dated 16 June 2013 was selected for rainfall-runoff simulation. The model employed the Initial and Constant Loss method, Clark Unit Hydrograph transform, and the recession baseflow approach. The computed watershed area was 590.59 km². Results showed total rainfall of 246 mm, excess rainfall of 215.10 mm, and a peak discharge of 3692.2 m³/s at 13:00 h. The study indicates that steep slopes, limited infiltration, and rapid flow concentration make the basin highly prone to flash flooding. If a GLOF event coincides with extreme rainfall, hazard intensity may significantly increase. The methodology demonstrates the usefulness of GIS-based hydrological tools for preliminary risk evaluation in remote mountainous catchments.