Extreme Central Himalayan floods may rise up to 80% by century’s end.
Rainfall-runoff, not glacier melt, contributes over 90% of additional floodwater.
Urgent emission cuts and resilient infrastructure needed to reduce flood risks.
High emission of greenhouse gases may exacerbate extreme floods in the Central Himalayas, growing by up to 80% in magnitude by 2100, according to a simulation study of Nepal's Karnali river.
These extensive floods, "with a one per cent chance of happening within a year, could occur once every five to ten years at the end of the century", potentially impacting densely populated areas in Nepal and India, researchers said.
1 December 2025
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Runoff from rainfall, rather than melting snow or glacier, is likely to contribute to over 90% of the additional flood water, findings published in the journal Scientific Reports show.
"The densely populated Central Himalayan foreland is prone to flooding, and our findings show that the intensity of extreme floods is only going to get worse across the coming century as greenhouse gas emissions increase," author Ivo Pink, a geospatial data scientist at the Department of Geography, Durham University, United Kingdom, stated in a news release.
Climate change, primarily driven by greenhouse gas emissions, has been shown to increase the likelihood of extreme weather events, including floods.
The researchers coupled climate projections from research centres worldwide with hydrological modelling and statistical analysis.
Extreme floods were projected to increase by 22-26% in magnitude between 2020 and 2059, in comparison to floods in the region between 1975 and 2014.
Under a scenario, where emissions are in the medium range, the increase is expected to be within 37-43% between 2060 and 2099, the researchers said.
High greenhouse gas emissions could see the intensity of extreme floods increase by 73-84% over the same period, they noted.
"Our simulations project increases in in the 1% annual exceedance probability flood magnitude of 40% (medium-emissions) and 79% (high-emissions) for 2060-2099, with rainfall-runoff contributing 90% of the additional flood water," the authors wrote in the journal.
Pink said, the study emphasises the urgent need to cut global greenhouse gas emissions in the earliest, as flood hazards will continue to increase for decades after the emission peak.
The findings indicate the scale of flooding that communities in the Central Himalayas could experience, and could help inform local flood hazard management, the researchers stated in the journal.
Himalayan Flood Threats
The Intergovernmental Panel on Climate Change (IPCC) noted in its recent report that extreme rainfall, and resultant flood risk, is increasing on many parts of South and East Asia, with urban and rural areas both vulnerable to intensifying precipitation.
A review on urban flooding in South Asia published in the journal Land in 2023 found that rapid urbanisation, increasing of impervious surfaces and shrinking floodplains are making cities more vulnerable to floods, especially under changing climate conditions.
According to a report published by World Bank Group in 2024, the need for enhanced early‑warning systems and climate‑resilient infrastructure to manage floods is necessary for improved policy and adaptation-planning.
(With inputs from PTI.)
