The high reaches and hilly areas around the areas of recent Mundakkai-Chooralmala landslides in Wayanad, which claimed over 200 lives, remain highly susceptible to landslides, cautioned the experts of Geological Survey of India (GSI).
The GSI sounded caution about the lingering trouble following their preliminary assessment of the Wayanad mishap.
Also read: Wayanad landslides LIVE
The areas where the landslides occurred were marked as vulnerable areas in the National Landslide Susceptibility Mapping (NLSM) carried out during 2015-16. The susceptibility map of NLSM had marked all four affected areas, Chooralmala, Mundakkai, Vellaramala and Attamala, as coming under the Moderate Susceptibility Zone, said V. Ambili, the Deputy Director General, GSI, Kerala unit, said.
The preliminary assessment of the geologists, who reached the accident sites shortly after the mishap, was that the Mundakkai debris flow, which took with it the villages and lives that thrived there, began from the source area of Punapuzha, a tributary of the Chaliyar.
The huge quantities of debris flowed towards Chooralmala town in the east. The debris flow from the source area may have begun as a slide and followed the path of the stream carrying tons of overburden mixed with water with it.
The probable source of the Mundakkai debris flow was from an elevation of 1,544 metres. It rolled down at an approximate distance of 3 km from Mundakkai and 5 km from Chooralmala villages, according to the assessment.
The heavy downpour and the enormous volume of landslide material culminated in the Punapuzha changing its course.
The incessant rain resulted in rising excess pore pressure (the pressure of fluids in the pore spaces of rocks or soil) within the region triggering the flow of loose and unconsolidated overburden (material that lies above an area).
An assessment of the Google Earth images indicated that landslides began in the source area during the 2018 monsoon. The area had also witnessed an increasing number of landslides since then minor slides were found occurring along both the flanks of the stream since 2018, according Ms. Ambili.
Geologically, the landslide area belongs to the Southern Granulite Terrain comprising rocks of Wayanad, charnockite and migmatite groups, she said.
Published - August 01, 2024 07:49 pm IST
