Fifteen hours before the massive landslide, that washed away whole villages and left more than 100 people dead, struck Mundakkai in Wayanad's Meppadi, the Hume Centre for Ecology and Wildlife Biology in Kalpetta had shared a landslide warning for the region.
The warning was based on the analysis of the rainfall data they meticulously collect everyday using rain gauges spread across Wayanad. The Hume Centre, an initiative led by ecologists, environmentalists, and climate educators, had been sharing such warnings and rainfall data with the state-level disaster management agency for the past many years.
The amount of rainfall recorded by their Puthumala gauge was alarming —572 mm in 48 hours. It was more than the amount of rainfall that triggered landslides in Puthumala and Kavalappara in August 2019. Both the spots are on the western side of Vellarimala. The July 30 event happened on the eastern slope.
The Hume Centre shared the landslide warning with the district and state-level disaster management agencies at 9.30 am on July 29 morning. "But we don't know if the alert was conveyed to the local bodies or the people," said CK Vishnudas, Director, Hume Centre.
Elected representatives in the affected areas TNM spoke to said that alerts had been given for high rainfall and likely rise in water level in the river. However, it is unclear if there was a specific warning on landslides, though some residents were wary about the possibility of landslides and had moved.
"Any rainfall close to 600 mm is bound to trigger landslides in the region. The slopes had become saturated because of extreme rainfall," said Vishnudas. The Vellarimala, where the crown of the devastating landslide is located, has a steep slope and has witnessed multiple landslides before.
A Google search for Puthumala now throws up Puthumala Disaster Point. The search engine describes it as a 'scenic spot' in Vellarimala, which lies at an altitude of 2200 m. Located in the southwestern corner of Wayanad, Vellarimala, along with Chembra Peak and Vavul Mala, is part of the isolated Western Ghats high ridges known as Camel Hump Mountains.
Together, these ridges form the gateway for monsoon clouds from the southeast Arabian Sea. They hit the slopes and rise up resulting in heavy rainfall.
"The first landslide in Vellarimala happened 40 years ago in 1984. The second one in 2020 did not cause much damage. It is heavily prone to landslides and I have been telling people for years that Mundakkai is not fit for human habitation," said Vishnudas.
Not just the Hume Centre, a committee constituted by the Kerala State Disaster Management Authority (KSDMA) had also said a few years ago that all families residing in the eastern slope of the Western Ghats in Wayanad district should be shifted out.
There are more areas facing risk of immediate landslides because of extreme rainfall. "Sugandhagiri, Kappikkalam, Manikkunnu mala, Vythiri, and Thondernad are susceptible to landslides," he said. Thondernad received 419 mm of rain.
As part of their joint micro-level weather monitoring initiative with the Advanced Centre for Atmospheric Radar Research at the Cochin University of Science and Technology, Humes Centre was able to map Wayanad district (2132 sq km) into five square km grids. Hume Centre now has one or two rain gauges in every grid, which gives them access to micro-level data.
A study by a team of scientists at the National Remote Sensing Centre (NRSC), which analysed six major landslides in 2018-2020 period found that they were triggered by antecedent rainfall in the range of 200 to 600 mm. The study led by Nirmala Jain found that the Puthumala landslide on August 8, 2019 was triggered by one-day rainfall (244 mm) and Kavalappara by three-day rainfall (236 mm).
A study by the Advanced Centre for Atmospheric Centre (CUSAT) in 2022 had proposed that disastrous cloudbursts over the west coast of India in 2019 were fuelled by anomalously warm local sea temperatures. The catastrophic events including landslides in Wayanad could be due to a mesoscale cloudburst (MsCB), the study said. Such events were more common in the north but rare and never reported in Kerala. Mesoscale convective systems are thunderstorm regions, which may be round or linear in shape, spread across 100 km or more.
“The landslide that hit Mundakkai and Chooralmala too could have been triggered by such cloud systems shaped like towers,” Vishnudas said.
The Kerala State Disaster Management Authority (KSDMA) website states that the Kerala State Emergency Operations Centre (KSEOC) has joined hands in developing a customised landslide early warning system for Kerala. The agency has partnered with the Kerala University, Kerala Development and Innovation Strategic Council (K-DISC) and the Geological Survey of India for pilot projects.