[12/25] Researchers of the Institute of Hazard, Risk and Resilience, and the Geography Department of Durham University assessed the climate change impact on flood hazards for the Karnali River (Nepal, China) using large ensemble simulations.
How might climate change affect flood hazards experienced by the communities on the plains downstream of the Central Himalayan River catchments?
The Durham University researchers focused on the Karnali River, which spans Nepal and China, and has the potential to impact people in both Nepal and India.
The study coupled a set of climate projections from different research centres across the world with hydrological simulations and statistical analysis. The simulations show that extreme floods (those with a 1% chance of occurring within a year) are expected to increase significantly over time, in line with greenhouse gas (GHG) emissions. The size of these extreme floods is projected to increase by 40% for medium GHG emissions and 79% for high GHG emissions during 2060-2099 compared to 1975-2014. The additional floodwaters mainly come from rainfall rather than snowmelt or glacier melt. This study shows the urgent need to cut global greenhouse gas emissions as soon as possible, because flood hazards will continue to increase for decades after the emission peak.
These research findings will inform local flood hazard management and serve as a practical case study of the scale of the increase in flood hazards that these communities in Nepal and India are expected to experience.
The research was funded by a Charles Wilson Doctoral Studentship through the Institute of Hazard, Risk and Resilience. The simulations were carried out on high-performance computers provided by the Advanced Research Computing Unit at Durham University.
https://doi.org/10.1038/s41598-025-26815-2
Photo credit
Image 1:Gunjan Silwal. A side valley of the Karnali River. The steep slopes in the Karnali catchment cause a fast flood generation and high-magnitude floods in the downstream plains.
Image 2: Elizabeth Dingle. The downstream plains are flood-prone, and embankments have been constructed along sections of the Karnali River. These flood defences are challenged by the projected increase in flood magnitudes.
Image 3: Elizabeth Dingle. Bridges are critical for the emergency response during floods. Thousands of people live in areas which are surrounded by different branches of the Karnali and are only accessible by bridges.
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