Kerala's Monsoon Landslides: A Recurring Crisis Explained

Landslides during the monsoon have become a recurring and deadly phenomenon in Kerala, a state along India's west coast nestled in the foothills of the Western Ghats. Every year, these events claim lives, with the state's high population density and widespread habitation in vulnerable terrain amplifying the impact.

This year, the first major incident occurred in Wayanad in July, where a debris slide triggered by extreme rainfall near the entrance of an under-construction twin tunnel at Kalladi claimed eight lives. This was followed by relatively minor landslips in Idukki and Kottayam on July 31, resulting in four deaths so far.

Kerala's landscape is inherently susceptible to landslides. The state receives around 3,000 mm of annual rainfall, often in intense, uneven spells that are becoming more frequent and extreme due to global warming and climate change. Its steep terrain, weathered soils, and complex geology further heighten the risk.

The record of past events underscores the severity. In 2018, an anomalous monsoon brought about 36% excess rainfall over the seasonal normal, triggering as many as 4,728 landslides across the state and killing 48 people, most associated with a single extreme rainfall event on August 16. In 2019, the Puthumala landslide in Wayanad killed 17, while the Kavalappara landslide in Malappuram claimed 59 lives, both on August 8. In 2021, catastrophic landslides struck Idukki and Kottayam, with the worst at Kokkayar, Palappally, and Kavali. The most disastrous event in Kerala's history occurred in 2024 when a landslide devastated Mundakkai and Chooralmala in Wayanad on July 30, claiming 231 lives, with 41 people still missing.

Although extreme rainfall is the immediate trigger for most of these disasters since 2018, the geographical distribution and human interventions also contribute to the susceptibility of the Western Ghats. The Landslide Atlas of India, prepared by ISRO's National Remote Sensing Centre and released in 2023, shows that while the Western Ghats experience fewer landslides than the Himalayan region, Kerala records a disproportionately high number of fatalities due to its dense population and extensive settlement in vulnerable areas.

According to the Kerala State Disaster Management Authority, around 4.75% of the state's total area is classified as a high landslide hazard zone. The recent landslide susceptibility map identifies approximately 3,300 sq km as highly susceptible and another 2,886 sq km as moderately susceptible.

Addressing this challenge is difficult. Implementing stringent measures such as habitation-free and construction-free zones in vulnerable areas is particularly hard due to Kerala's dense settlement and limited land availability. Moreover, many catastrophic events have occurred in the midlands, where plantations dominate land use. Landslides are influenced by a combination of anthropogenic, agricultural, geomorphic, and tectonic factors. A common trigger is high-intensity rainfall exceeding 204 mm within 24 hours. When such rainfall occurs over already saturated and unstable slopes, the likelihood of slope failure increases sharply, according to experts.

As Kerala continues to grapple with these recurring disasters, the need for a comprehensive approach that balances land-use planning, early warning systems, and community preparedness becomes ever more critical.