Extreme floods in Central Himalayas could intensify by 80% before 2100: Study

High emission of greenhouse gases may exacerbate extreme floods in the Central Himalayas, growing by up to 80 per cent in magnitude before the turn of the century, 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.
Runoff from rainfall, rather than melting snow or glacier, is likely to contribute to over 90 per cent of the additional flood water, findings published in the ‘Scientific Reports’ journal 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, said.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 per cent 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 per cent between 2060 and 2099, the researchers said.High greenhouse gas emissions could see the intensity of extreme floods increase by 73-84 per cent over the same period, they noted.
“Our simulations project increases in… flood magnitude of 40 per cent (medium-emissions) and 79 per cent (high-emissions) for 2060-2099, with rainfall-runoff contributing 90 per cent of the additional flood water,” the authors wrote.
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.
Author Sim Reaney, professor at Durham University’s department of geography, said the study addresses uncertainties in potential future flood hazards in Nepal by combining uncertainties from both climate and river flow simulations.The findings highlight the scale of flooding that communities in the Central Himalayas could experience, and could help inform local flood hazard management, the researchers said. (PTI)