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Explained: Why Landslides Keep Devastating India’s Most Vulnerable Regions, Wayanad landslide, himalayas
New Delhi:
Kerala’s Wayanad is witnessing another tragedy. Heightened by heavy rains, a major landslide struck the construction site of the Kozhikode-Wayanad twin-tunnel road project at Kalladi, near Meppady. The fresh landslide has triggered several questions in the discourse surrounding recurring landslides and the causes behind them.
The National Disaster Management Authority defines a landslide under its official guidelines as: “The downward and outward movement of slope-forming materials including rock, soil, artificial fill, or a combination of these under the influence of gravity.” The Geological Survey of India, which is the nodal national agency for landslide studies in India, further classifies them into types like falls, topples, slides, spreads, and flows based on how the material moves.
As per data compiled under the Geological Survey of India’s National Landslide Susceptibility Mapping program, about 13.17% to 15% of India’s total geographical area, roughly 4.2 lakh square kilometers, is officially marked as prone to landslides. Across regions, the reasons for the occurrence of these phenomena differ. The government of India has separated the natural causes of landslides into distinct geographical zones or hotspots.
Vulnerable Sections
The Himalayas: The youngest, highest, and most tectonically active mountain range in the world. Landslides occur here due to a fragile geology in which the rocks remain fractured, crushed, and unstable. Constant earthquakes and tremors also weaken the structure, making the mountains more prone to landslides. At such high altitudes, warm temperatures can cause glacial lakes to burst, thereby triggering massive volumes of water and debris to crash down the valleys.
The Northeastern Hill Ranges: Almost all of the Northeast region remains prone to frequent and severe landslides. Mizoram and Arunachal Pradesh historically record the highest volume of these events. The area is home to steep; rugged terrain made of sedimentary rocks that are easily eroded. Owing to high levels of precipitation, the steep slopes quickly saturate, causing the weak rock layers to give way and collapse.
The Western Ghats and Nilgiris: Running through Kerala, Karnataka, Goa, and Maharashtra, the Western Ghats face a very different kind of landslide danger. Instead of solid rock breaking apart, the problem here is the thick layer of heavy soil covering the mountains. When heavy monsoon rains pour down, this deep soil acts like a giant sponge, soaking up massive amounts of water until it turns into a heavy, muddy soup. Eventually, the mud becomes too heavy for the solid bedrock underneath to hold up and rushes down the mountain.
Dr Vipin Kumar, Assistant Professor and Head, Department of Geology, Doon University, Dehradun, outlined the primary hotspots. “There are three primary landslide hotspots in our country: the Northwest Himalaya (Kashmir, Himachal Pradesh, and Uttarakhand); the Northeast Himalaya (primarily Arunachal Pradesh, alongside the Arakan range in Nagaland and Manipur); and the Western Ghats (primarily involving Kerala). Whenever the monsoon arrives in June and July, we witness a rise in landslides, leading to severe casualties and infrastructure loss,” he said.
The Monsoon Effect
Regardless, the biggest catalyst for landslides in India is considered to be the Southwest Monsoon, which mostly spans the period from June to September. It is during these months that hilly regions receive large amounts of water in shorter spans. Climate change has exacerbated these conditions, leading to intense active rains in short timeframes. It is due to climate change that we see rainfall scattered across erratic, violent cloudbursts, wherein even a week’s worth of rainfall sometimes disperses in just a couple of hours. This heavy flow of water saturates the soil below, creates pressure that pushes soil particles apart, and destroys a slope’s stability in the hills.
Describing the prevalent environmental and rainfall patterns, Kumar said, “When relatively high rainfall saturates the soil, the slope simply comes down. These are natural geomorphic processes that occur globally, even in developed nations like the US, Switzerland, France, and Italy. While the underlying cause of the process is always natural, the scale of the disaster is driven by human presence.”
Environmentalist Veena Murathoor, based in Kerala, stresses that regional differences require custom solutions. “The main issue regarding modern development schemes is that you can’t do things in Kerala that you do in North India, even if they have proven successful there. The rains in Kerala are extremely heavy, and the summers are also intense. In the places where the landslides occur, the rainfall is often around 600 to 700 mm per day. It has even recorded about 221 mm in just a 24-hour span. Every development pattern must be tweaked based on the landscape and ecology of the place,” she said.
The Human Factor
While nature creates the vulnerability to a landslide, human action often exacerbates the damage from such a disaster. The National Disaster Management Authority mentions several issues as the root cause. Among these triggers lie concepts such as unscientific “toe cutting”, which means building and widening roads by cutting into the base of the hill, thereby making it unstable. Often, farming practices and the types of crops grown can also impact the ability of the soil to keep itself together in adverse conditions. Improper drainage systems adopted by urban areas, especially hill towns, lead to conditions where water turns the ground from a solid, stable foundation into a slippery, heavy mess that gravity pulls right down the slope.
Kumar highlighted how rapid land-use shifts increase these human risks. “Landslides have been a normal phenomenon throughout geological history, but fatalities have risen over the last decade because we are altering land use and land cover. We are cutting across mountains to build highways, creating steep slopes of 40 to 50 degrees. When these exposed rock masses face extreme rainfall, their shear strength decreases, causing them to collapse,” he said.
Disaster Preparedness
The government has launched targeted, district-level early warning systems that map landslides in the area. The Geological Survey of India has taken its mapping to the next level by launching the National Landslide Forecasting Centre, which issues active, regional landslide forecasts for specific high-risk districts when heavy rains are predicted. In fact, the government has set up portals for citizens and experts called the Bhooskhalan mobile app and the Bhusanket portal, which provide real-time landslide bulletins, hazard zoning maps, and incident reports.
However, experts warn that this may not be adequate. Professor Kumar argued that while these portals indicate where a landslide might occur, they miss out on determining when. “Existing frameworks like the Bhukosh portal provide susceptibility maps that indicate spatial probability; they tell us where a landslide might occur, but not when. To save lives and safeguard infrastructure, we must understand exactly when these risks materialise,” he said.
Citing the example of other countries, he added, “Several countries across the world, like Japan and Switzerland, have early warning signs to apprise citizens of an occurring landslide. This helps in minimizing the scale of human and economic loss.”
From hazard maps that lay out the time and details of a landslide to a reliance on local land use/land cover change studies in development projects, experts recommend using predictive research to understand disasters and subsequent cascading events.
Reflecting on the need for localised studies, environmentalist Veena Murathoor noted, “It is absolutely vital that we understand the ecology, hydrology, and geology of a place before initiating any sort of construction. Right now, we are not considering these factors at all. We are simply repeating the same destructive practices.”
While humans may never be able to halt development fully, experts maintain that the solution lies in conducting thorough studies, understanding local ecology, and acting appropriately. Installing early warning sensors may also be highly beneficial for prediction and disaster preparedness, allowing infrastructure and natural ecosystems to safely coexist.
