Two reports paint a clearer picture of the human interferences that aggravated the devastation in Kodagu district in August.
While the Geological Survey of India (GSI) has tabulated 105 landslips in human-habited areas, a team from the World Resources Institute (WRI) used satellite imagery to enumerate at least 254 various landslip instances affecting 1,060 hectares (nearly 10.6 sq km) of land.
Imagery used
Using imagery from the Copernicus Sentinel satellites (deployed by the European Commission), Raj Bhagat Palanichamy, a Senior Project Associate at WRI India, and Samrat Basak, Director (Hydrology), WRI, counted the changes in landscapes and the crowns (the area from where soil has slipped) to determine the number and pattern in landslips.
Not surprising, nearly four in five landslips are in areas with human habitation.
These are concentrated around the twists and turns of the Harangi river as well as major roads that criss-cross the district (as seen in the cluster of land slips close to Madikeri and particularly on the Mandalpatti road).
“The heavy rainfall caused landslips in forest areas too. But, these landslips are smaller in size than those in anthropogenic areas. Most probably, human-induced land changes have aggravated the situation,” said Mr. Palanichamy. The course of the Harangi is flanked by high slopes, leading to more landslips, unlike the slopes around the Cauvery or the Lakshmanthirtha in the district, their analysis has found.
Recommendations not followed
Independently, GSI recently compiled a 150-page report of 105 landslips. Of this, researchers had visited 85 spots and found that a majority of these are along the lineament (a geological feature which is an expression of faults and fold-aligned hills).
While heavy rainfall was the trigger, lack of proper drainage, unscientific slope cutting for agriculture or road works, construction of houses close to slopes or natural streams, as well as geological causes, have been identified as having aggravated the situation.
These landslips were also found to be entirely within areas that were marked in GSI’s landslip susceptibility maps in 2014-15.
The maps and reports had a list of recommendations involving slope stabilisation along roads and construction measures to ensure high slopes are protected. Most of these had not been followed.
Restrictions needed
“We have strongly recommended to the State government to have some legal restrictions and regulations in these landslip-prone areas. This is needed to ensure land use is not changed or new constructions are regulated,” said K.V. Maruthi, geologist with the GSI.
Their investigation has found that in many human-inhabited areas, the landslips had led to a cascading effect.
In the rains of August 14, smaller landslips had blocked streams creating a temporary dam. As the rains continued and water accumulated, the dam breached, letting out a torrent of water that flooded houses downstream as well as triggered further landslips.
