Basin-scale inventory and exposure assessment of hanging glaciers, Central Himalaya

Abstract Himalayan glaciers increasingly exhibit geometric and dynamic instability under rapid warming and climate variability. This instability has led to the development of hanging glaciers on steep slopes, which pose significant risk of ice break-offs with severe downstream impacts. While these glaciers have been extensively studied in the Alps, basin-scale assessments in the Himalaya remain limited. This study presents a comprehensive inventory of hanging glaciers in the Alaknanda basin, Garhwal Himalaya, and proposes a classification framework for their characterisation. A total of 219 hanging glaciers covering 71.7 ± 3.5 km² are identified, with an estimated ice volume of 2.39 ± 0.42 km³, including 0.74 ± 0.14 km³ of hanging ice mass, derived using the GlabTop2 model. These glaciers occupy steep slopes (mean ~33°) and predominantly face SE-W and N-NE, with the Upper Alaknanda basin containing ~30% of the total hanging mass volume. Avalanche simulations using r.avaflow indicate that potential runouts could impact major settlements and infrastructure, with flow heights exceeding 50 m in the Badrinath-Mana sector. Exposure is projected to increase sharply, with built-up surfaces rising from ~8000 m² in 2000 to ~152,000 m² by 2030, and the exposed population increasing from ~380 to ~8500. These findings highlight the need for targeted monitoring and risk-informed planning.