THIRUVANANTHAPURAM: A comprehensive study, conducted by experts in high ranges of Idukki and Malappuram districts, has found at least 21 localities “high-risk landslide areas” thanks to the improper and unscientific land use practices.
The research project, ‘Hazard and Risk Evaluation of landslide-prone areas of Malappuram and Idukki districts,’ was carried out by a team of experts headed by S Sreekumar of the Department of Geology and Environmental Science, Christ College, Irinjalakuda, with the financial assistance of the Kerala Science, Technology and Environment Council.
The report, which has already been submitted to the Council, identified certain localities, including Kumban Para, Neryamangalam, Machiplav, Munnar, Adimali, Karadipara, Katapara, Kalyanathandu, Naakakkanam, Lokhart and Ambalachal in Idukki district as “potentially dangerous”.
Specific areas in Koduleri Mala, Chekkunnu Mala, Odakkayam, Alappara, Karuvarakundu, Mukkilkadu, Aarthala Estate, Ommachan kadu, Manchola and Valankolli in Malappuram district are categorised under “high risk zones”.
The landslide hazard map, prepared at the panchayat level, shows Devikulam, Munnar, Elappara, Peruvanthanam, Kumily and Kokkayar panchayats of Idukki district and Kumili and Chungathara panchayat of Malappuram district have critical areas with an aerial extend of over 10 square kilometres.
The aspects such as drainage density, slope, relative relief, road network, land use and geo-technical properties were considered for the delineation of landslide-prone areas.
Incessant rain, a major concern
Technically, the paleo-slides in the areas fall under debris flow, rock fall and slump. However, debris flow ( Urul pottal ) is the most common type of slope failure and caused maximum destruction. According to Sreekumar, It is not only the rainfall on a particular day but also the amount of rainfall during few days before that is highly influential in triggering slope failure.
In general, landslides have occurred in locations which experience a rainfall over three or four days’ period with a minimum cumulative value of 218 mm. This amount of rainfall could be considered as the threshold value and it can be used as an indicator for taking necessary pre-disaster steps including evacuation of people from high hazardous zones.
The project was started three years ago. Deljo Davis, Sasi TS, Arish Aslam, Arun Prabhakar and Aaron Wilson are the other members of the project. Sreekumar has been doing research related to landslide for the last 15 years. Earlier, Sreekumar has prepared a project on the environmental impact of mining in the kole wetlands.