BENGALURU: The worst-ever landslides so far in Kerala on July 30, which killed more than 221 people with more than 200 still missing, after flattening at least three villages, are a “result of multiple factors including geological, anthropogenic, change in land pattern and negligence on the part of local authorities and people”, said former director, Geological Survey of India (GSI) and National Institute of Rock Mechanics (NIRM) Dr Pramod Chandra Nawani.
“This region is extremely ecologically sensitive and has experienced calamities earlier also, but not of this scale. It should be cleared of human habitation to prevent future disasters, which are bound to happen because of the nature, age of the rock mass, geological activity and heavy rainfall due to the changed weather conditions,” cautioned the noted geologist and rock mechanics expert.
“There are mainly two kinds of rocks in Wayanad -- gneiss and schist. They are of Precambrian origin and ecologically very sensitive. Because of the intensive weathering of these older rocks on the gentle slopes, the bedrock is overlain by a thick layer of 20-25 metres of lateritic soil. Unlike the Himalayas, here the slopes are not steep, because of which they are perceived to be safe and there is a lot of human activity. The main problem of gentle slopes is that the overlying soil and highly weathered rocks lose their shear strength and become cohesion less and the water-charged interface between lateritic soil and bedrock begins to move slowly. This is creep movement, which is not visible to the naked eye. It plays havoc when the area gets incessant heavy rain,” said Nawani.
‘Satellite images illustrate regional sensitivities’
The geologist added that anthropogenic activities make the region more susceptible, and lead to man-made calamities. “There is no dearth of hydro meteorological data from the IMD and it must be available with the local authorities. There are satellite images to illustrate the regional sensitivities. The creep movement is not visible to naked eyes but detected by hard resolution satellite imagery done by the NRSC of the Indian Space Research Organisation. These reports should be carefully studied and followed by the authorities. Sensitive areas should be left as green belt and no habitation should be permitted there. Land pattern use should also be reviewed, and considered for planning developmental activities in the region. There are a lot of GSI reports but they are either not read or not taken seriously,” claimed the eminent geologist.