The disaster struck on the night of July 30, 2024, when exceptionally heavy rainfall of nearly 573 mm within 48 hours triggered a massive slope failure in the upper catchment of the Punnapuzha river. File
| Photo Credit: Thulasi Kakkat
The devastating 2024 Wayanad landslides cannot be attributed to extreme rainfall alone but was also likely influenced by a combination of geological, geomorphological and structural factors, according to a new study published in the international peer-reviewed journal Landslides.
The study, published online on the journal’s website, notes that while intense monsoon rain triggered the collapse, underlying geological conditions played a critical role in determining where the landslide began, how it travelled, and why it became one of the most destructive landslides recorded in the Western Ghats. The study was conducted by researchers from the University of Kerala, the Indian Institute of Science Education and Research (IISER) Mohali, and Savitribai Phule Pune University.
The disaster struck on the night of July 30, 2024, when exceptionally heavy rainfall of nearly 573 mm within 48 hours triggered a massive slope failure in the upper catchment of the Punnapuzha river. The disaster rapidly evolved into a high-speed debris flow that travelled nearly 8 km, descending about 768 metres while sweeping through Punchirimattam, Mundakkai and Chooralmala. It carried enormous quantities of rock, soil and vegetation, causing widespread destruction.
To understand why the landslides became so destructive, the researchers conducted extensive field investigations across the affected valley in April 2025. Geological mapping was carried out from Chooralmala to Punchirimattam, while rock samples were analysed in the laboratory. As the landslide crown remained unsafe to access, drone-mounted LiDAR and high-resolution aerial imagery were used to investigate the upper part of the failure zone.
According to the study, the hills in the affected area are underlain by ancient crystalline rocks that have undergone repeated deformation over hundreds of millions of years. These processes created natural planes of weakness, including shear zones, fractures and foliations. Over time, rainwater penetrated these fractures, causing extensive chemical weathering and transforming large volumes of hard rock into soft, deeply weathered material beneath the surface.
The study suggests that the landslide originated within a highly weathered shear zone near the crown, where a first-order stream crossed the weakened rock. During the extreme rainfall, water rapidly infiltrated the interconnected fractures, increasing water pressure within the slope. Once the strength of the rock mass was exceeded, a large block detached, initiating the landslide.
As the debris rushed downhill, narrow sections of the valley underlain by stronger rocks such as metagabbro and granite acted as natural barriers. Debris temporarily accumulated behind these constrictions, forming short-lived natural dams. Their subsequent collapse released powerful surges of water, mud and boulders, greatly intensifying downstream destruction.
“The study reveals the interplay of climate and geology. Extreme rainfall acted as the immediate trigger, but the pre-existing geological framework determined where the slope failed, how the debris moved and why the event became exceptionally destructive,” said Y. Anilkumar and K.S. Sajinkumar, assistant professors at the Department of Geology, University of Kerala, who led the study.
Published – August 09, 2026 01:35 pm IST
