Wayanad tragedy set off by heavier rainfall, says study
While the scientists highlighted the limited nature of studies in the region, analysis found the role of climate crisis and change in land-use patterns over the years was undeniable
Bursts of rain made 10% heavier due to the climate crisis and a 62% reduction in forest cover that has increased the susceptibility of slopes which is likely to have triggered the landslides in Wayanad, that have so far killed hundreds of people, a rapid analysis of the disaster said on Wednesday.
While the scientists highlighted the limited nature of studies in the region, analysis found the role of climate crisis and change in land-use patterns over the years was undeniable.
“The landslides that killed hundreds of people in Wayanad, northern Kerala were triggered by a burst of rainfall that was made about 10% heavier by human-caused climate change,” the analysis by World Weather Attribution, an international collaboration of scientists who analyse the influence of climate change on extreme weather events, said.
The experts said that the meteorological cause of the landslides was the heavy rainfall on the day preceding the event.
The landslide followed an exceptional spell of monsoon rain that lashed Kerala on July 30. More than 140mm of rain fell in a single day in the district — equivalent to nearly a quarter of London’s annual rainfall. Since June 22, the area has been subjected to nearly continuous rainfall, with only short breaks. Kalladi, about 5km from Mundakkai, has recorded around 1,830 mm of rainfall over the past 30 days, making it one of the wettest areas in Wayanad
“The event is the third heaviest single day rainfall event on record, with heavier spells in 2019 and in 1924, and surpasses the very heavy rainfall in 2018 that affected large regions of Kerala,” the analysis noted.
Brittle earth
The rain landed on soils that were already highly saturated, the analysis underlined.
“In today’s climate, which is 1.3°C warmer than it would have been at the beginning of the industrial period, an event of this magnitude is expected to occur about once every 50 years,” the rapid analysis, conducted by 24 universities and meteorological agencies in India, Malaysia, the United States, Sweden, the Netherlands, and the United Kingdom, said.
Scientists also said that a 62% reduction in forest cover in Wayanad may have contributed to the increased susceptibility of the slopes in heavy rain events.
“Deforestation is the most pronounced land-use change in the district. Between 1950 and 2018, Wayanad lost 62% of its green cover, with tea plantation areas increasing by approximately 1800%, resulting in reduced forest cover to stabilise the hills,” the analysis said, referring to paper published in International Journal of Environmental Research and Public Health.
“While the linkage between land cover and land use changes and landslide risk in Wayanad is mixed in the limited existing studies, factors such as quarrying for building materials, and a 62% reduction in forest cover, may have contributed to the increased susceptibility of the slopes to landslides when the heavy rain fell,” the analysis added.
The district, the scientists said, “has been determined to be the most susceptible to landslides in Kerala”.
The Wayanad disaster is an example of how the climate crisis is playing out in real-time, said Mariam Zachariah, Researcher at the Grantham Institute - Climate Change and the Environment, Imperial College London in a statement.
“The extreme burst of rain that dislodged an entire hillside and buried hundreds of people was intensified by human-caused warming. Until the world replaces fossil fuels with renewable energy, monsoon downpours will continue to intensify, bringing landslides, floods and misery to India,” said Zachariah.
Rainfall patterns disrupted
To quantify the role of human-induced climate crisis, the team used both observational data and climate models with high enough resolution to capture precipitation over the relatively small study region. Overall, the available climate models indicate a 10% increase in intensity and in a future warming scenario where the global temperature is 2°C higher than pre-industrial levels, climate models predict even heavier single day rainfall events, with a further increase of about 4% in rainfall intensity.
“Given the small mountainous region with complex rainfall-climate dynamics, there is a high level of uncertainty in the model results. However, the increase in heavy one-day rainfall events is in line with a large and growing body of scientific evidence on extreme rainfall in a warming world, including in India, and the physical understanding that a warmer atmosphere can hold more moisture, leading to heavier downpours,” the analysis said.
Scientists have warned that the increase in climate change-driven rainfall is likely to increase the potential number of landslides that could be triggered in the future. India should, thus, prioritise reinforcement of susceptible slopes, landslide early warning systems, and construction of retaining structures to protect vulnerable localities.
The rapid analysis is in agreement to what climate experts had indicated immediately after the disaster.
“There has been heavy rain over two or three days in central and northern parts of Kerala. This was not sudden but continuous heavy rainfall that caused soil to become soft and runny. When the soil moisture is very high, it is saturated and can give way,” former earth sciences ministry secretary and climate scientist M Rajeevan said on July 30.
“It is also true that human intervention may have played a role in accentuating the impact. These [Western] Ghat regions that had thick forest cover mostly have plantations now which are commercially more viable.”
“I can say that the disaster location is in what is classified as ecologically sensitive zone 1 or of highest ecological sensitivity. There are many construction activities that are continuing in the area. Many tourist resorts have been constructed with some constructing lakes in them. A tunnel is planned to be constructed to connect the area to Mysore. There are several plantations, most which are old and have been there since the British period. Those are also growing. Such activities are not recommended in ESA 1. All I can say is that more such landslides and disasters can be expected in these regions classified as ESA 1, in association with climate change and extreme weather,” ecologist Madhav Gadgil had said in an interview to HT on July 30.