Interview/ V. Ambili, deputy director general, Geological Survey of India, Kerala unit
IN THE EARLY hours of July 30, Kerala experienced its most devastating landslide in history. At the time of writing, 167 bodies had been recovered, and the search was on for hundreds of missing people. The worst-hit villages of Mundakkai, Chooralmala, Attamala and Noolpuzha in Wayanad district are part of Meppadi. This area was identified as one of the 18 ecologically sensitive areas in Kerala by a committee led by ecologist Madhav Gadgil in 2011. The report specifically warned against indiscriminate quarrying and construction in Meppadi. However, owing to political reasons, both the state and Central governments were reluctant to implement the report’s recommendations and instead pursued measures to dilute them. That, however, has not stopped either to blame the other. In response to Union Home Minister Amit Shah’s statement that Kerala did not respond appropriately to the Centre’s warning, Chief Minister Pinarayi Vijayan said that the Central meteorological department had issued a red alert for Wayanad only after the landslide had taken place and that the Geological Survey of India, on July 29, had issued a green alert for July 30 and 31, indicating a possibility of minor landslides or rock bursts.
In an interview with THE WEEK, V. Ambili, deputy director general at the GSI’s Kerala unit, said that the triggering factors during previous landslides should have been observed. Excerpts:
Q/ Could you give a brief description of the factors that led to the Wayanad landslide?
A/ This landslide primarily occurred owing to torrential rain in the region, but the area is already prone to landslides. According to the national landslide susceptibility map developed by the GSI, the crown of the landslide falls within a high susceptibility zone. Thus, the area has always been prone to landslides. However, the calamity struck five to six kilometres below that point. When a landslide is triggered from the source, if there is a stream or a similar feature, the whole mass can travel down, making the entire pathway hazardous.
There were landslides in the surrounding areas within this valley in 2018, 2019, 2020 and 2021. These should have been observed as triggering factors, but often such warnings are taken for granted until a disaster occurs.
All these areas in the Chaliyar river basin are tectonically active zones. My PhD research focused on this area, which has been classified as zone 2 in the active tectonic segment. This means that the streamlets in the area are following weaker geological zones. A river naturally tends to flow downhill owing to gravity. However, in this area, the river follows a curved path, indicating the presence of weaker zones in the upper reaches. Despite these risks, the fertility and flatness of the land attract people to settle there.
Q/ Without realising that they are living on a bomb?
A/ Yes. The river’s course has triggered a landslide because of the presence of a fracture zone―a weakened area where water can seep through. This fracture zone extends deeper into the earth, with possibly small gaps on the surface but deeper fractures below. When it rains, water percolates into these fractures, travelling deeper into the ground and potentially forming underground water flows or springs.
If the rainfall is moderate, water slowly seeps into these fractures and flows out naturally, possibly reaching wells or rivers. However, during continuous heavy rainfall, the ground becomes saturated. The fracture zone can no longer absorb the water, leading to a critical point where the pressure builds up, similar to a balloon filling with water. Once this threshold is reached, the pressure causes a sudden release or ‘blast’, resulting in a landslide. This event in Wayanad caused large rubbles and rocky pieces to be displaced, as if by a bomb blast.
Q/ Shouldn’t the Kerala government have implemented the Madhav Gadgil report?
A/ We completely agree with that view. Nature has its own processes, and events like landslides are natural phenomena that shape the earth’s morphology. While we cannot stop landslides, we can reduce their intensity and avoid actions that might accelerate them.
For example, rivers naturally have floodplains…. These floodplains provide space for the river to expand and accommodate excess water. However, when these areas are encroached upon or restricted, the river has no space to spread out during events like flash floods. As a result, the river’s energy can cause significant damage, eroding the land and impacting surrounding areas.
Q/ But is it possible to evacuate people and relocate them to another place?
A/ In a place like Kerala, the challenge is the limited space. The state has a narrow stretch of land with high mountains in the highlands, a small midland area and then the coast. We can’t expand into the sea, and we need to preserve space in the hills as well. This means people have to live in the lower reaches of the highlands, the midlands and the lowlands, leaving us with very little space.
We need to act with a long-term vision. Currently, the administration is focused on immediate concerns, but once the crisis subsides, there is a risk that people will forget and the same issues will arise again.
Q/ You were doing a trial run of the automated landslide warning system.
A/ The GSI has initiated an early warning system for rainfall-induced landslides in northeast India. We have also initiated the same in Wayanad. But the inauguration happened only on July 19. We are still doing a trial run. We were planning to make it public on August 1. The predicted rainfall data that we get from the meteorological department is fed into the system and the system then [makes a prediction].
Q/ There were previous warnings about the possibility of a landslide in the Wayanad region. So, would you call this a human-made disaster?
A/ No, the landslide was a natural event. However, raising public awareness is very important. In the northeastern regions, where earthquakes are a regular phenomenon, people are very aware and prepared. Even with a small tremor, they know they have to move to open areas. In Kerala, people often take these warnings lightly, but nature doesn’t wait for us to act.