A rockslide-induced debris flow caused the catastrophic 2024 Wayanad disaster in Kerala, India
摘要
On 30 July 2024, a rockslide-induced debris flow descended into the Iruvanipuzha River’s valley near Chooralmala and Mundakkai villages of Wayanad, Kerala, India. The disaster claimed at least 224 lives, with 150 missing, marking it one of the deadliest singular landslide events in India’s history. Our analysis of precursory slope movement, damage assessment from satellite imagery and numerical model reveals that a rock mass (~ 25,565 m2) collapsed, scouring the valley and producing a debris of 0.83 (± 0.09) million m3. Intense rainfall transformed this into a mega debris flow, carrying large boulders and uprooted trees, reaching 6.9 km downstream. The flow attained a maximum simulated velocity of ~ 43 m/s, height of ~ 30 m and pressure of ~ 2.4 MPa. Transient accumulation of debris in the narrow valley has caused a secondary event at 3:30 pm IST following the main debris flow at 1:15 pm IST. Geomorphic evidences around the crown show the existence of an old landslide scarp as the origin of current slope failure. We carried out Enhanced Small Baseline Subset (ESBAS) MTInSAR analysis using Sentinel-1 data spanning 2 years leading to the landslide event to find out signs of precursory slope movement around the failed zone. The results show a zone of slope deformation around the crown area with ground deformation velocities up to ~ 11 mm/y. Damage assessment done using satellite data reveals that ~214 buildings, ~5 km of road, ~ 39 ha of forest land and ~ 36 ha of agricultural land were affected by this disaster. The event and consequent devastation underscore the need for monitoring and sustainable development in the Western Ghats of India.