Thiruvananthapuram

Kerala land has lost immunity, landslips here to stay, says hydro-geologist

Troubled state: The site of a landslip that occurred in an estate workers’ residential area at Nayamakkad in Pettimudy, 30 km from Munnar, in Idukki district on Friday. It had occurred in a zone that is not considered geologically vulnerable to landslips.  

Kerala land has lost its "immunity" and landslips and related phenomena are here to stay. The State must prepare to deal with it for a long time to come, said Dr. V. R. Haridas, hydro-geologist, who had extensively studied the August 2019 Kavalappara and Puthumala landslips as advisor, Climate Adaptive Project for the National Bank for Agriculture and Rural Development (NABARD) last year.

The soil structure has changed drastically. It is no longer "immune" to events like intense rain, as witnessed over the last two years and this year. Land will continue to slip and slide and destroy lives unless pre-emptive measures are adopted, he said.

 

Soil is sensitive like the human body. Any interference with its nature and structure will have consequences. One of the most common human activities has been massive deforestation, mostly for plantations. Monocropping and quarrying is another serious interference with the structure and lay of the land, he added.

When trees are cut and their roots are left to rot, they decay over decades to form pipes through which the soil substrata is directly injected with rain water. This results in the formation of a sludge-like slippery layer that oozes to the hard rock resulting in the layer above the hardest rock layer losing grip and stability.

The conditions this week have been ideal for this type of phenomenon. Kerala's rain is traditionally spread over a period of two to two-and-a-half months. But now about half the 3,000 mm of annual rain is received in about one or two weeks. It is like pelting the earth with stones, he said, pointing out that the 'nool mazha' or yarn rain, which irrigated the land at a pace so suited to farming activities, was a thing of the past for Kerala.

 

Dr. S. Abhilash of the Advanced Centre for Atmospheric Radar Research, CUSAT, said that Munnar and neighbouring areas received about 30 cms of rain over 24 hours in the last couple of days. Any volume of rain above 24 cms is classified as extremely heavy, he said.

Dr. Haridas said that the phenomenon of piping from large-scale root decay after deforestation takes about three decades. This was quite obvious in places where landslips had occurred in the past, including at Kavalappara, where 59 people lost their lives.

He also pointed out that though landslips are unpredictable, warning signs, mostly in the form of smaller land dislocation, should be heeded to if we are to avoid massive destruction of life and property.


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Printable version | Nov 29, 2021 6:39:37 PM | https://www.thehindu.com/news/cities/Thiruvananthapuram/kerala-land-has-lost-immunity-landslides-here-to-stay-says-hydro-geologist/article32304386.ece

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