Extreme monsoon rains have come to India for the second year in a row, causing millions to flee their homes and leading to more than a thousand deaths since May.
Several Indian states experienced extreme precipitation in early August, causing rivers to flood their banks and hillsides to give way. In the state of Kerala, on India’s southwest coast, 121 people have died, and more than 83,000 have taken refuge in relief camps, according to the Times of India. The most casualties have occurred in the state of Maharashtra, where 245 people have died, reported AccuWeather.
The flooding comes on the heels of disastrous flooding last year that left nearly 500 dead in Kerala and over 1,200 causalities across India. Both 2018 and 2019 brought flooding that would be expected only once every hundred years.
A Warming Atmosphere
Very little rain fell in India during the first 2 months of the monsoon season this year, and scientists worried about a water deficit. Yet starting 7 August, 453.4 millimeters of rain fell on Kerala in just 6 days, according to the Times of India. The amount is nearly 5 times above the average of 92.6 millimeters. The heavy rain swept through towns, stranded fisherman, and crumbled buildings.
The onset of heavy rain came from an atmospheric disturbance called a monsoon depression that formed over the Bay of Bengal in early August. Monsoon depressions are common during monsoon season, but what was unusual was the intensity of the rain that fell in such a short time.
Arathy Menon, a postdoctoral researcher at the University of Reading in the United Kingdom, suggests two distinct changes to the Indian monsoon due to a global warming.
In a 2013 paper, Menon and her colleagues found that climate change may make India’s monsoon rains more variable day to day. Deluges one day and blue skies the next can lead to flooding and complicate agricultural processes as well as access and availability to water supplies, according to the paper.
Second, Menon said that her current research shows that the Western Ghats, a mountain range that spans six Indian states, will have higher-intensity rainfall because of climate change. Warming air temperatures from global warming are causing the atmosphere to hold more moisture because warmer air can carry more water vapor. When monsoon winds carry more moisture, they bring more intense rainstorms. This phenomenon is particularly true in the mountains, where the steep slopes push water-logged air upward, causing it to condense and rain out.
The Western Ghats run through Kerala and Maharashtra, both states hard-hit by this year’s monsoon rains. Menon cautions against attributing the recent floods to climate change, however.
“Based on only a few years of data, it is really difficult to directly, scientifically attribute the whole responsibility of these two flood events to global warming,” Menon said. “But global warming has the potential to increase the extreme precipitation events in the future.”
The rain also triggered destructive landslides in mountainous regions. A landslide on 8 August killed 46 at Kavalappara in Kerala’s Malappuram district, and officials are still searching for 13 missing more than a week later.
Thomas Oommen, an associate professor at Michigan Technological University who studies landslide hazards in Kerala, told Eos that over 3,000 landslides have occurred in the Western Ghats in the past 2 years from the excess rain.
When asked about the deadly landslide in Kavalappara, Oommen said that he had not toured the site, but he’d heard the news reports of a dozen or more quarries near the slide. “That’s quite a lot of quarries to be in one area,” he said.
Oommen traveled to Kerala after the 2018 floods to survey recent landslides, as reported in Eos. His research team found that most of the landslides surveyed occurred at sites with recent construction. New construction can lead to water pooling under the surface, becoming heavier and heavier until the hillside gives way. Constructing quarries for mining, clearing native vegetation for cash crops, and building new infrastructure change the path of water running over the landscape.
Despite the magnitude of last year’s disaster, which wiped out villages, roads, and power lines in the hilly districts of Kerala, Oommen said that the local government has yet to change their land use strategy. “There has not been much done. That’s the sad part,” Oommen said. He said that political will, both of the public and of the elected officials, is needed to prevent future risk.
“People in Kerala have been shaken by this repeat event from last year,” Oommen said. “I hope this second event has even been a second wake up call.”
In addition to his scientific work, Oommen said he is working to bridge science with policy making. Recently, he flew to Mumbai to consult on disaster management education and research.
“We have done some research, we have identified some of the vulnerable areas,” he said of his past scientific surveys. “We need to actually lead this to action.”
—Jenessa Duncombe (@jrdscience), News Writing and Production Fellow