Multiple Agencies Warned of Landslide Risk at Wayanad Tunnel Site Before Disaster
Multiple agencies had flagged the Anakkampoyil-Kalladi-Meppadi twin-tube road tunnel project site in Wayanad as prone to landslides, weeks before the debris slip at Kalladi occurred. A joint site inspection and geological assessment of the tunnel project last month warned of potential 'localised or large-scale slope failure.'
The State Level Expert Appraisal Committee (SEAC), Kerala, which reviewed the project proposal, had also highlighted landslide and related risks in the region. The joint inspection team, comprising representatives from the Geological Survey of India, TUMAS India Private Limited, and Dilip Buildcon Limited, noted that 'continuous and intense rainfall has resulted in progressive saturation of the overburden mass, leading to the development of multiple instability signatures.' These included widening tension cracks, localised earth slumps, rill erosion, cavity formation, and discharge of muddy seepage water.
The report observed that the soil mass appeared to have poor drainage characteristics, resulting in slow dissipation of pore-water pressure under prolonged rainfall. It also noted that very fewer drain holes were functioning effectively on the treated left-wall slope, indicating inadequate drainage performance. Field observations showed progressive widening of tension cracks on berms one, two, and three, multiple earth slumps along the benches, and sudden discharge of muddy water through self-developed openings adjacent to the Berm-4 drainage system.
These conditions suggested that the tension cracks may extend to considerable depths and act as preferential pathways for infiltration, seepage, and internal erosion. The report warned that such conditions could lead to 'rapid internal erosion and piping' within the overburden mass, progressively weakening the slope and potentially triggering localised or large-scale slope failure.
The preliminary evaluation of the left-wall slope indicated significant instability problems primarily due to ongoing heavy rainfall. The report, prepared during the first week of June, recommended regular maintenance and cleaning of drainage systems, continuous monitoring during monsoon conditions, and restriction of activities beneath the vulnerable slope during periods of intense or prolonged rainfall until the slope is stabilised.
The SEAC had earlier suggested precautionary measures during the construction stage to avert vibration-induced landslides, as the tunnel alignment passes through highly fragile terrain prone to landslides. The area has recorded landslides in the past with high fatalities and experienced an extremely severe landslide disaster with a very high death toll in 2019 and 2024. The committee emphasised that all anticipated impacts from various activities during construction and operation phases should be evaluated with adequate scientific inputs and up-to-date scientific literature.
The committee also noted that the impact of extracting a huge quantity of material for tunnel construction and effective management of muck generated during tunnelling should be addressed specifically.
