Geomorphological Evolution of the Multi-Chain Cascading Disaster of Wayanad (30 July 2024), Kerala, India

This is the authors' abstract. We don't add key points for this paper.

The Western Ghats are increasingly vulnerable to landslides due to extreme rainfall, complex geological structures, and anthropogenic activities. This study examines the catastrophic multi-chain disaster that occurred in the Vellarimala Hills of the Western Ghats, Wayanad District, Kerala, on July 30, 2024. Triggered by unprecedented rainfall of 572 mm over two days, the event involved a large-scale landslide in the early hours (2 AM), transforming into a debris flow along the Punnapuzha channel. The debris flood at 4 AM caused widespread devastation, including the destruction of villages and infrastructure, with significant casualties and displacement. This paper aims to reconstruct the catastrophic event through detailed field observations, analysis of rainfall and channel topography, and comparisons of pre- and postevent imagery, engaged with local administrative authorities and survivor interviews. Our findings reveal that the landslide was triggered by prolonged and intense rainfall, infiltrating deeply weathered charnockite bedrock. The affected region transversed by the lineaments and fractures acted as conduits for water infiltration, increasing pore-water pressure and reducing slope stability. The landslide transformed into a high-mobility debris flow, depositing significant material in downstream floodplains. Extreme rainfall, steep topography and high channel stream power caused extensive erosion (~ 30 m) and channel widening. Pre- and post-event analyses indicate substantial channel widening and erosion, reshaping the river morphology. This catastrophic landslide has drastically affected the land use/ land cover features in the Punjirimattom, Mundakkai, and Chooralmala villages, and it is estimated that 219 built-ups were thoroughly washed out, and more than 400 built-ups were severely damaged; moreover, the channel flow widened from 20.98 ha to 84.43 ha after the landslide event. This study highlights the Western Ghats’ increasing landslide susceptibility, linking slope failures to geological structures and extreme rainfall, and emphasises the need for hazard assessment, early warnings, and sustainable land-use planning.