A report from the expert panel constituted by the state government in connection with the Mundakkai-Chooralmala landslides has recommended habitat-free zones in landslide-prone areas, restrictions on constructions, reducing inhabitation in fragile zones in a phased manner and applying bio-engineering techniques for strengthening mountain slopes and river banks.
The panel identified 107.5 hectares in the landslide-hit areas as unsafe. The July 30 landslides washed away 104 hectares; the report has marked as unsafe 3.5 hectares of adjacent land. As per the report, 60 lakh cubic meters of debris, including 3 lakh tons of surface soil, washed off from the crown of the landslide. With the debris deposits, the riverbed is now 2 metres higher.
The report prepared by a team headed by John Mathai, former scientist at the National Centre for Earth Science Studies (NCESS), Thiruvananthapuram, has also made a few recommendations. The panel said the banks of the streams should be free of any form of human interference. Large boulders spread over the river bed can be moved to the banks for arrest, scouring of the sides and their protection.
Bio-engineering for slopes and river banks
The report has suggested increased bio-engineering protection for banks of a stream in the region by planting suitable and locally available species such as bamboo, reed and vetiver to reduce the impact of landslides. The participation of the community members in field studies is also recommended to provide them with first-hand information on vulnerable spots. The master plan on 'calamity risk factors' is to be revised, the panel noted.
“There is a state-level advisory committee for landslides that will go through the report in detail, fine-tune it, and vet it before finalising an action plan,” Mathai told Onmanorama. On the bio-engineering techniques to be applied for soil conservation, he said, geo-textiles such as coir mats could be used for planting indigenous species for strengthening river banks and slopes. “The coir mats would keep the soil together, helping the plants to spread roots on the slopes up to three years.”
Landslide prevention
The report suggested avoiding harmful land utilisation practices on slopes with more than 25 per cent inclination, which includes cutting and levelling land for construction purposes, diversion or blocking of stream channels in the upper slopes, storage of water in the slopes, avoiding contour bunds and terracing farming on slopes, seasonal cultivation with tilling or pitting activity in the high slopes. The report also says construction on land with either ground cracks or piping should be avoided. Encroachment of stream banks in the highland region for cultivation or settlement, construction of roads without adequate engineering design in unstable slopes, construction of houses in the hollow portions which have been filled up with debris and blasting or quarrying close to the susceptible areas are also to be avoided.
While constructing buildings and houses on hills, the slope geometry is to be maintained. Artificial impounding of water on slopes should be discouraged. In areas identified as high-hazard zones, the construction of swimming pools and theme parks in the name of tourism should also be discouraged, the report noted.
Permanent shelters for rehabilitation
Multipurpose shelters should be in place for temporary rehabilitation of affected people living in landslide-prone zones. These shelters should be constructed at locations safe from floods and landslides.
Two parts of the report were submitted earlier. It talked about identifying unsafe spots with proper mapping and selection of the right land for rehabilitation. The committee shortlisted five from more than 20 proposals on areas suitable for rehabilitation. The government zeroed in on two - the lands of Harrisons Malayalam Plantation at Nedumpala near Meppadi and Elstone Estate, Kalpetta. If the government finalises the land near Kalpetta for the proposed township, the rehabilitation cost would be lower as additional expenditure for the construction of schools, hospitals, and religious centres can be spared.
The members of the panel were Dr T K Drissia, principal scientist at Centre for Water Resources Development and Management (CWRDM), Kozhikode; Dr Sreevalsa Kolathayar, Surathkal, NIT; Thara Manoharan, Wayanad District Soil Conservation officer and P Pradeep, hazard and risk analyst, Kerala State Disaster Management Authority.
