The remnants of catastrophic debris flow that flattened Mundakkai and Chooralmala in Wayanad still pose serious danger, researchers who were part of the study commissioned by the Kerala State Disaster Management Authority (KSDMA) have warned.
A note prepared by the research team warns of lingering danger posed by the debris flow in Mundakkai. The team comprises experts from IISER (Indian Institute of Science Education and Research) Mohali, the University of Kerala and the KUFOS (Kerala University of Fisheries and Ocean Studies).
The team employed cutting-edge LiDAR technology and photogrammetric methods to assess the stability of the debris deposits left in the wake of the disaster. The researchers mapped the area which showed large boulders and loose debris remaining precariously positioned beneath the crown area of the landslide. It poses a significant risk of further movement during heavy rainfall, particularly with the impending North-East monsoon, the note says.
The study warns that these unstable deposits could easily cascade down, potentially blocking narrow channels and creating dangerous damming effects that could lead to sudden and catastrophic flooding. "During heavy rainfall, the water of Punnapuzha appears turbid, indicating presence of huge boulders upstream whereas the tributary shows clear water.
It is a serious threat," said assistant professor in Geology department of Kerala University Sajin Kumar K S, who is part of the research team. According to the researchers, if the large boulders move down during heavy rainfall, it could again cause the damming effect which was responsible for the devastating landslide in Wayanad.
The finding assumes significance in the wake of a meeting being scheduled this week to finalise the safe and unsafe zones demarcated by the expert committee in the area. The research team will submit a detailed report on its findings to the state government.
The team said that the scale of this event is nothing short of monumental. According to the mapping estimates, the volume of material generated by this disaster ranges from 35 times (Kerala University study) to a staggering 300 times (GSI study) larger than the devastating 2020 Pettimudi landslide in Munnar, making it one of the most significant landslide events in India's history.
In addition to the debris survey, IISER Mohali MS student Adin Ishan conducted a critical analysis of sediment levels in the Chaliyar River during the event. His findings revealed a staggering 185 per cent increase in suspended sediment, underscoring the sheer magnitude of the disaster.
The research team, led by Sajinkumar KS, Yunus Ali Pulpadan, and Prof. Gireesh, along with students Sahil Kaushal, Jiyadh Thanveer, and Achu, emphasized the urgent need for ongoing monitoring and the swift implementation of mitigation strategies. They warned that the risk of reactivated debris flows and subsequent flooding remains high, particularly with the intense rainfall expected during the North-East monsoon.
Government authorities said that the expert committee has submitted a report on the suitability of land parcels from the hazard susceptibility angle.