An expert committee which studied the July 30 Mundakkai-Chooralmala landslides in Wayanad district has recommended that the areas marked as unsafe be kept free of habitation.
The panel led by John Mathai, former scientist, National Centre for Earth Science Studies (NCESS), has also recommended curbs on construction and other forms of human intervention in the susceptible areas.
The panel’s September 25-dated report, “Mundakkai - Chooralmala Landslide, Wayanad district: A Comprehensive Study,” pegged the total area deemed as unsafe at 107.5 hectares, including 104 hectares affected by the landslide proper.
The total mass removed from the crown (the starting point of the landslide) till the Mundakkai Lower Primary School is about 25 lakh m3 while the mass removed from the crown region alone is about 3 lakh m3, according to the report.
The expert committee has suggested micro-zonation studies around identified landslide-susceptible zones. Probable locations of failure and their run-out should be documented in cadastral scale, and disseminated among local communities.
“Anthropogenic activities which allow saturation of the soil are to be strictly regulated in other critical/prone areas in the vicinity,” it noted.
Activities to be avoided
Activities that should be avoided include blasting and quarrying close to susceptible areas, levelling of toes regions of slopes for construction, road construction on unstable slopes and impounding water on slopes and building swimming pools and theme parks for tourism in high hazard zones.
Certain agricultural and soil conservation practices also need to be discouraged, according to the committee. These include contour bunding and terracing on slopes greater than 25%, seasonal cultivation with tilling or pitting activity in high, sloping areas, encroachment upon stream banks for agriculture or settlement.
Other recommendations
Other recommendations include bioengineering along the landslide-hit area as a solution for stabilising it. Suggested methods include planting of wild reeds, planting vetiver grass and indigenous tree varieties, wattling, and a combination of coir geotextiles and vetiver grass.
The report suggests methods to prevent the further degradation of the Punnapuzha river. Large boulders deposited by the landslides on the riverbed can be moved to the banks to prevent scouring, it said.
“The area under the river has now increased after the landslide event. This area belongs to the river to accommodate the debris and flood water. The boundary should be surveyed and records maintained. The stream banks should be free of any form of human interference,” it said.
Excess rainfall
On the causes of the catastrophe, the report blamed high-intensity rainfall while ruling out quarries as a “triggering agent.”
“Rainfall in excess of 50 mm/hr in a continuous heavy spell along with all the storm water falling on the steep slopes brought into the hollow part by converging first order streams was the triggering factor or the driving force for the initiation of this landslide,” it said. It goes on to add that “the absence of active quarries within a radius of one kilometre from the crown region rules out the role of quarries as a triggering agent.”
The committee headed by Mr. Mathai was constituted in August this year. Pradeep G.S, Hazard and Risk Analyst, Kerala State Disaster Management Authority was its convener. The other members were experts from the Department of Civil Engineering, National Institute Technology, Surathkal, and the Centre of Excellence in Water-related Disaster Management, CWRDM, in addition to the District Soil Conservation Officer, Wayanad.
Mr. Mathai said that the present report, submitted to the KSDMA, constitutes Part A of the study. Parts B and C were submitted earlier, he said.
Published - September 27, 2024 07:36 pm IST
