How will Melamchi Disaster 2021 look like in warmer temperature?

Abstract

Global warming reshapes geohazard dynamics by influencing both precipitation and temperature. While precipitation remains the primary landslide trigger, temperature-driven changes in soil strength are often overlooked. This study integrates temperature-controlled shear testing with a physically based multi-hazard model to quantify thermal impacts on slope processes in Nepal’s Melamchi catchment, affected by the 2021 debris flood. Laboratory ring-shear experiments on landslide soils revealed a linear reduction in friction angle with a 4.9 °C temperature increase, indicating thermal weakening. Incorporating this relationship into a calibrated multihazard model intensified hazard metrics without altering rainfall input. The warmer scenario increased peak discharge by 7%, sediment discharge by 36%, while producing longer runouts and higher impact pressures. These findings demonstrate that rising temperatures alone can amplify disaster severity, underscoring the importance of integrating thermally dependent soil properties into future multi-hazard assessments under climate change.