Small event, big impact: insights from Vallunaraju cascade event on April 28, 2025

A small-scale glacial lake outburst flood (GLOF) in the Cordillera Blanca, Peru, demonstrated significant downstream impacts despite its modest initial volume. The 28 April 2025 Vallunaraju cascade event, triggered by a rockfall into two small lakes, released approximately 42 million cubic meters of water but caused severe damage due to sediment entrainment, increasing the total moving mixture volume six to seven times to 296 million cubic meters. This sediment-amplified cascade resulted in two fatalities and substantial infrastructure damage, including bridges, houses, and water systems, highlighting the underassessed risks posed by small and medium-sized lakes in hazard prioritization frameworks. The study underscores the need for integrated assessments that account for trigger susceptibility, sediment availability, and exposure controls to better predict and mitigate GLOF impacts in such regions.

Cusicanqui, D., Loarte, E., Gómez, W., Villafane, H., Cook, K. L., Piton, G., Lehmann, B., Magnin, F., Racoviteanu, A. E., Zerathe, S., Filhol, S., Medina, K., Cruz, R., Concha, R., Torres-Lázaro, J. C., & Lacroix, P. (2026). Small event, big impact: insights from Vallunaraju cascade event on April 28, 2025. Npj Natural Hazards, 3(1). https://doi.org/10.1038/s44304-026-00229-0