Why severe landslides are on the rise

The Tsergo Ri landslide occurred in the Himalayas region in the modern-day Nepal area about 51,000 years ago during the last glacial period when it displaced 10-15 cubic km of rock and made it one of the largest known landslides on earth. The debris, though largely eroded, remains unstable even today and the Nepal earthquake of 2015, which killed 350 people, occurred in that area.

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The Tsergo Ri landslide is not the only prehistoric landslide to have shaped our modern world.  The Marsyangdi Valley in the Annapurna Region may have been formed by the Manang-Braga rock avalanche at about the same time.

Landslides within recorded history in India have included mudslides and flash floods in another Himalayan region: Uttarakhand where 5,700 died in 2013. Since rivers were blocked by debris from dams and other construction, the flood waters overflowed and inundated the surrounding villages and towns in their way.

"In June 2022, the first vegetation begins to cover the spot where Matthew Oomen's house on the slopes of Keralan Idukki District was flattened by a landslide a year ago." Image: Awaaz Foundation

On June 30, in Manipur, 56 people died when a landslide within a railway construction site destroyed their homes and swept them into a river. In June, two children were among those who died in a landslide in Assam that injured and displaced several others.

While landslides in the Himalayas have been historically common, they have escalated in intensity and in the damage they cause due to human intervention including construction, blocking of rivers by large and small dams and by sand mining. Landslides have also become increasingly common in other mountainous regions which were previously stable.

Throughout the Western Ghats of India “the processes leading to landslides were accelerated by anthropogenic disturbances such as deforestation since the early 18th century, terracing and obstruction of ephemeral streams and cultivation of crops lacking capability to add root cohesion in steep slopes”, says a paper by Shekhar Kuriakose, Sankar G and Muraleedharan C published on the website of the Center for Astrophysics of the Harvard University, Smithsonian Institute and NASA in 2009.

In the thirteen years since this paper was published, deforestation, escalating sand and stone quarrying, changing cropping patterns and blockage of rivers have all contributed to worsening and more frequent landslides and consequent loss of lives and property.

According to the website of the United Nations Development Fund, “In a landmark move, on 28 July the United Nations General Assembly recognized that a clean, healthy and sustainable environment is a universal human right.”

The UNDP website reassures us: “Well, now governments have an obligation to promote, protect and fulfil this right. A clean, healthy and sustainable environment is a matter of justice, with expanded opportunities for advocacy, legal claims, strategic litigation, and ultimately, greater accountability of states and other actors.”

The Indian government reassures us too. On May 4, while addressing the inaugural session of the fourth edition of the International Conference on Disaster Resilient Infrastructure, Prime Minister Narendra Modi said: “People must be at the heart of any infrastructure growth story. And, that is exactly what we in India are doing.”

Nevertheless, infrastructure construction in eco-fragile areas entails deforestation to build more roads, railways, housing and others. Recent changes to the Forest Conservation Act have made the process of development in forest areas easier and allowed cutting of forests without consulting the tribal people who inhabit them.  

The Western Ghats are one of the most biodiverse forests of the world, recognised by Unesco as a World Biodiversity hotspot. When mountain slopes are deforested, rain water, previously held in place by trees, washes away the topsoil holding the rocks which form the mountain together. On July 27, the FAO warned that “a full 90 per cent of the earth’s precious topsoil is likely to be at risk by 2050”. They list deforestation and improper land use changes as a leading cause.

“Landslides are an increasingly dangerous reality in the Western Ghats, which were stable in the past. Activities that worsen them continue though residents who have lived here for generations express their own fear and helplessness to stop them,” says Jay Samant, who has studied the Ghats since 1971 and took part in the historic Save Western Ghats March, a relay march throughout the length of the Western Ghats from northernmost Gujarat to southernmost Kerala, forty years ago.

The destructive activities Samant refers to include sugarcane, oil palm and rubber replacing natural vegetation; terracing for crops; and construction. Numerous small and large dams have also changed the course of rivers. As a result, rocks have developed cracks and fissures on the crests of the mountains, destabilising them.

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The Western Ghats, which have never been landslide-prone in the past, are facing increasing danger as landslides, including sinking soil events, escalate. In Maharashtra, within the Western Ghats, the Malin Landslide in 2014 killed 151 people; 430 landslides and fissures were recorded in a single year of 2021; in July 2022, 41 villages, where people continue to live in high-risk zones, were placed on high alert for landslides.

“Other states where the Western Ghats are situated also face increased danger and destruction from landslides. The geographical formation of the Ghats in Kerala is different from Maharashtra,” says Samant.

The Ghats face the full onslaught of the monsoon rains and Kerala has the highest rainfall. Because of this, the rocks which make up the Western Ghats of Kerala, Goa and Maharashtra have eroded variably. “In Goa, high rainfall has washed away the silica content of rocks and left behind concentrated deposits of metal ores over millions of years,” says Dalal.

He goes on to explain: “Forts, rock caves and archaeological sites of importance contribute to landslides when they become tourist attractions and encourage activities like road building, parking and tourist facilities in their vicinity.” The sites themselves become more vulnerable and are threatened by activities which escalate deforestation.

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Like the landslide which devastated Oomen’s house, landslides are often triggered by excessive or unusual rainfall patterns. However, rainfall patterns are changing permanently in the Western Ghats and all over India. Short, intense rainfall is replacing the steady monsoon patterns which provided stability to these landscapes. Deforestation is leading to the water entering into the rock on mountain peaks instead of running off the slope into the valleys below, which is causing deep fissures in the rock, aggravating landslides.

Deforestation is a major contributor to climate change. However, India, one of the 10 countries with richest forests, did not sign the declaration to save forests that was signed by over 100 countries at CoP26 in November 2021.

Climate change has also led to changes in rainfall patterns where intense bursts of rainfall amid changing monsoon patterns, landslides and floods are manifestations, projected to become much worse in the coming decades. The IPCC Reports of 2021 and 2022 have issued increasingly dire warnings.

Based on the IPCC, Greenpeace India has projected three scenarios of global warming:

• Net Zero after 2050 when the “temperatures stabilise at 1.8°C higher by the end of the century”
• Business as Usual: Extreme with doubling CO2 in 2050: Net-Zero after 2050 when “temperatures rise 2.7°C by the end of the century”
• Business as Usual and Extreme with doubling CO2 in 2050 when “the average global temperature will be a scorching 4.4°C higher”

In the most extreme situation, the annual mean temperature of Delhi would increase by nearly 10 degrees.

2022 has already been the hottest on record. Changes in monsoon patterns, including more short, intense bursts of extreme rainfall, have intensified landslides and floods. The felt effects of climate events are worsened by local activities on the ground and cause millions of people to suffer.

On July 1, the second day of heavy rains in Mumbai this year,  the first landslide occurred next to an under-construction building on Peddar Road in South Mumbai. Less than a week later, on July 6, two houses collapsed in a landslide at Narayan Hadke Chawl in Chunabhatti, Chembur and three people were injured.  The rains continued in record-breaking torrents and brought about a landslide at Pali Hill, Bandra, and several others.

However, none of the Mumbai landslides of July 2022 were considered to be major because no one died and because previous landslides in the last decade have been so much worse: In July 2020, the Army had to be called in when 78 people died in a landslide in Ghatkopar.  In July 2021, at least 30 people were killed in three landslides in Chembur and Vikhroli.

In April 2022, the BMC identified 249 landslide-prone areas within Mumbai city. The Mumbai Climate Action Plan (MCAP) identified that most landslides occur in informal settlements and categorised landslides as one of five serious climate-related threats to Mumbai. Landslides in Mumbai endanger the lives and property of all its residents in the most densely populated city of the world ahead of Tokyo, New York and Shanghai.  

The first few rains brought the fluorescent green beauty of the Western Ghats to life, intense and beautiful, beginning to cover the broken debris, crushed suitcases and CDs, the last remnants of the Oomens’ house in ruins on the mountainside.

Increasingly devastating events signal the future of a world which faces climate change. Mr. Oomen was Headmaster of a school nearby, and his house was newly finished last year. His parents had lived here with him, next door to other extended family members, and had been on a video chat with Oomen when the landslide stuck. They had watched as several of their neighbours were crushed to death including two children.

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In May 2022, Modi told the audience at the ICDRI that “if we make infrastructure resilient, we prevent disasters not only for ourselves but for many future generations”.

However, in early June, we received news that India ranked last in the Environmental Performance Index (EPI) among the 180 countries who were judged. Almost immediately, the first reports of landslides followed when the monsoon began.

Climate events in 2022 have included heatwaves and landslides and resulted in severe hardship, including loss of property and lives across many parts of India. Even as our own actions escalate the climate crisis, we leave its rapidly worsening effects to our children.