Talking Point
Climate change-induced excessively heavy rainfall with subsequent “damming effect” is not the sole or prime trigger of the landslides that wreaked havoc in Wayanad on July 30. Experts equally blame the loss of green cover, excessive mining, and quarrying, rampant building/construction activity and development projects that spare no thought for ecology…
TreeTake Network
The recent landslides that occurred near Punjirimattom, Mundakkai, Chooralmala, and Vellarimala villages in Wayanad district in Kerala in the wee hours on July 30 can be called one of the deadliest catastrophes in recent times. A torrential rain caused the hillsides to collapse, sending a deluge of mud, water, and boulders crashing down and sweeping away villages, taking a heavy toll on lives with reports of over 420 feared dead. Needless to say, the incident once again underscored the need for slope-specific early landslide warning systems, which though extremely expensive, are crucial in saving lives. |
In fact, landslides occur almost every year during the monsoon in hilly areas, particularly in states like Uttarakhand, but hardly any lesson is learnt. While little can be done about a downpour save issue an alert or evacuate people to safety, things like illegal construction, violation of building norms, deforestation, and rampant development activities that adversely impact the environment can certainly be checked. A hill or a mountain does not crack under rain, but things like wrong building construction and water management practices may certainly cause it to crumble, as per scientists.
In fact, the entire western Kerala, a hilly terrain with sharp slopes, is susceptible to landslides. The Indian Space Research Organisation (ISRO) National Remote Sensing Centre's landslide atlas released in 2023, revealed that 10 out of the 30 most landslide-prone districts in India were located in Kerala, with Wayanad ranking 13th. Here the terrain has two distinctive layers, a layer of soil sitting atop hard rocks. When there is torrential rain, the soil becomes saturated with moisture. Then water reaches the rocks and flows between the soil and the rock layers, weakening the force that binds the soil to the rocks and triggers movement, resulting in landslides. In this particular incident, as per geologists, excessive rain caused a damming effect, with a rapid flow of water downstream, carrying along boulders, mud, trees, and rocks from the hilltop.
In the Wayanad tragedy, the Kerala government may have been swift in rescue and relief but has certainly come under fire for not doing enough about climate mitigation and adaptation measures and for shelving the Gadgil report that was submitted in 2011 by a committee panel headed by Madhav Gadgil, a renowned ecologist.
According to the report, 64 percent of the Western Ghats should be declared an Ecologically Sensitive Area with varying degrees of protection. It also recommended a ban on mining, quarrying, and sand mining in sensitive areas and to regulate development activities in these areas more strictly, including curbs on building and infrastructure development. However, not only Kerala but many other states too opposed the report, saying such measures would hinder development and impact livelihoods. Consequently, another committee was formed under K Kasturirangan to examine the report and suggest a way forward. It is another matter that post the Wayanad tragedy, Madhav Gadgil told the media that had his recommendations been implemented, the catastrophe could have been avoided.
According to Dr CP Rajendran, a geoscientist and adjunct professor at the National Institute of Advanced Studies, Bengaluru, it was a human intervention, including deforestation, unplanned construction activities, and climate vagaries that caused the tragedy in Wayanad. He said studies conducted by a group of researchers from Central Coastal Agricultural Research Institute, Goa, published in 2020 indicated that the Puthumala landslide started as one of those smaller landslides that occurred deep inside the forest, and the landslide gained momentum as it reached the lower reaches of the hill as the soil structure in the lower parts was fragile and saturated with rain. It turned into a massive slide filled with rocks and mud bringing down a part of the hill. The high-intensity rainfall was the major trigger that acted as a tipping point.
As for the causative factors, Rajendran said factors like deforestation which started in the 1980s to clear the land for tree plantations must have gradually changed the soil conditions in the region. The root systems of the forest trees left out within the soil must have decayed, leaving huge cavities. Similar soil conditions with cavities under the soil cover must exist in the Mundakkai/Chooralmala area. It is possible that the water seeped into the cavities and interconnected underground channels formed by soil piping phenomena.
The area must have received on average close to 1830 mm (about 6 ft) of rain in the last 30 days (about 4 and a half weeks), according to rain gauge data reported from Kalladi, a site located about 5 km from Mundakkai. Along with these factors, unscientific construction practices and quarrying may have also contributed to the evolution of this hazard. A similar soil piping mechanism must have worked in Mundakkai/ Chooralmala as these sites share similar geology and soil structure. It is also reported that about 102 sqkm and 196 sqkm areas in Wayanad are extremely landslide prone and moderately landslide prone respectively with some locations also vulnerable to soil piping effect.
As to what should be done, Rajendran says climatic conditions are expected to worsen in the future because of the emerging global warming scenario. The frequency of landslides is likely to go up in hilly regions like Wayanad. The agencies involved in landslide susceptibility maps like the State Disaster Management should be involved in updating the existing maps. It is not clear if the Mundakkai area is part of the high-risk area in the available map. Satellite observations and digital elevation models are now widely used for landslide risk mapping. The government must frame clear policies on land management based on such zoning maps by taking the people into confidence. It should also evolve long-term strategies to address annual floods and landslides that affect poor people, who are forced to live in ecologically fragile lands. Kerala with a high-density population should initiate imaginative but humane initiatives on environmental management and new guidelines for land utilisation.
Wake up call
Landslides have taken place earlier and may continue in the future too. One cannot control nature but can certainly be better prepared and use available resources to prevent loss of life and property. According to scientists, climate change will spur more extreme weather events like landslides which may be more frequent and severe. So, it is of vital importance to mitigate the impact of these disasters, by improving local weather monitoring and risk assessment. Development projects should be planned and executed with utmost caution, considering the rainfall pattern, so environmental impact is minimal. Haphazard and unchecked development in vulnerable regions can have dangerous consequences. Disaster preparedness must also improve. More than just disaster management, a disaster mitigation strategy is needed, say experts. Also, though expensive, an early warning system for landslides is needed. As per experts, more research and remedial measures, such as afforestation in identified regions, should be undertaken.
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