Landslides are a very common natural hazard that kills thousands of people and destroys billions of dollars worth of property every year. Many countries are regularly affected by landslides, but only a few have managed to find innovative solutions.
Shruti grew up in the foothills of the green Western Ghats mountains in the southern Indian state of Kerala and has seen landslides her entire life.
Landslides are a part of every monsoon season.
"I didn't believe it would become so destructive," she told the BBC.
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But on the night of July 30, a mudslide buried her village.
Choralmala was the worst-hit place in Wayanad district.
The number of dead, according to reports, varied from 250 to 400.
Nine members of her immediate family were killed that day, including her parents, sister, uncle, aunt, cousins, and her uncle's children.
“When I returned to the village, I saw a large rock over the place where my house used to be. I became very emotional and broke down.”
This 24-year-old woman went to work at the time of the disaster and thus avoided certain death.
Landslides kill thousands of people every year and destroy billions of dollars worth of property around the world.
Scientists understand the causes of landslides and are experimenting with early warning systems with some success.
They argue that even if we can accurately predict the time when a landslide will occur, it will be difficult to predict the movements of all that debris, which is the main cause of death and destruction.
What causes landslides?
Landslides occur when slopes can no longer resist gravity or through external triggers such as heavy rainfall, erosion of the slopes that occurs in coastal areas, and changes in the strength of materials under exposure to weathering.
"A landslide is the movement of a mass of material, such as rock, soil or debris, down a slope. They can occur suddenly or more slowly over a longer period of time," according to the British Geological Society.
The World Bank estimates that heavy rainfall triggers about 400.000 landslides each year, and that 130.000 of them are caused by earthquakes.
The World Health Organization says that in the three decades between 1988 and 2017, landslides caused 18.000 deaths and affected 4,8 million people worldwide.
Some scholars argue that the destruction caused by landslides is underestimated in official estimates.
"I typically record around 450 landslides causing loss of life worldwide each year, with South Asia being the hardest hit area. They claim around 4.500 lives in an average year, but that figure is sometimes much higher," explains Professor Dave Pitley, an earth scientist and vice-chancellor at the University of Hull, UK.
Climate change and the human factor
The World Health Organization warns that climate change and rising temperatures will trigger more landslides in mountainous areas with snow and ice.
Professor Petli says that the construction of roads and dams contributes most to them.
"Poor quality road construction is the biggest problem," explains Professor Pitley.
“We are also losing forests in a significant way.”
Deforestation and construction activities have contributed to landslides in the state of Kerala.
Shruti and her community knew the area was vulnerable after a deadly landslide that killed 17 people in 2019.
Like most families in her village, they had lived there for generations and did not want to move.
“We didn’t take the warning seriously,” Shruti admits.
"If we had received a specific warning, saying when and where the landslide would happen, we wouldn't have stayed," she says.
Landslide prediction
home in the Western Ghats and Himalayan region was one of the areas subject to risks.
Kala Venkat Uday teaches at the Indian Institute of Technology (IIT), Himachal Pradesh.
Its campus in the city of Mandi is located in a valley and surrounded by the majestic Himalayas.
"I see landslides from the window," he says.
In 2017, a major landslide occurred near the IIT campus, killing 48 people.
This incident left a lasting mark on the 39-year-old scientist.
He designed an early warning system device that can monitor key weather indicators such as temperature, light intensity, and humidity.
It also contains a rain gauge.
There is also a speedometer that can predict the movement of the ground below.
The instrument costs $3.500 and must be buried at a shallow depth.
"We have predicted 100 localized landslides in six years. We are using artificial intelligence and machine learning. We are getting more data and we are confident that this device will be able to predict 99,8 percent of landslides at least an hour in advance."
The early warning system is activated at more than 60 locations along the roadsides.
A challenge for science
Data is processed in real time and if there is any sign of danger, traffic is stopped on endangered sections of the road.
This device can predict movement on a specific slope.
The British Geological Society says that making a risk assessment over a large area with multiple slopes is very difficult.
"While significant progress has been made in our ability to predict landslides, research still needs to improve our understanding and develop better understanding of prediction models."
Society says that, due to the changing nature of our landscape, a degree of unpredictability will always exist.
Satellites can now predict slope movements of just three millimeters.
However, that is still not good enough to project when a slope will collapse.
Professor Dave Pitley says that sometimes the movement of rocks will speed up and then just stop.
In Norway, people living at the foot of Mount Manen were evacuated 18 times before the landslide finally occurred.
The amount of rock and debris a landslide carries is also difficult to calculate because it depends on the distance traveled from the trigger point to the impact point, and the nature of the hill itself.
"In Wayanad, the slopes themselves were known to be potentially unstable, but the disaster was caused by the landslide coming eight or more kilometres down the slope. That's very difficult to predict," says Professor Pitley.
Landslide prevention
Hong Kong has shown that it is possible to reduce the number of deaths and destruction.
This territory introduced a landslide warning system in 1977.
Landslide deaths have declined significantly since the mid-2008s, and Hong Kong has not reported a single new death since XNUMX.
“Hong Kong has a network of about a hundred gauges plus rain radar to make accurate and reliable predictions,” says Petley.
He adds that we can also intervene to stop or mitigate the consequences of landslides.
This often involves draining water from the slope.
"An important technique is to reinforce the slope, which could sometimes mean putting anchors or nails into it."
Erecting barriers such as protective dams to stop landslides is also part of the prevention plan.
Japan already uses these methods, says Petli.
“There are well-developed, very effective techniques for dealing with slopes. But they are very expensive.”
Saving lives
Many developing countries do not have the resources to erect barriers or are not in a position to evacuate people.
In Wayanad, Shruti had to endure more personal pain.
While returning from a memorial service for her parents and relatives, she was involved in a car accident in which her fiancé was tragically killed.
Her village, once home to 1.000 people, is now buried in rubble.
Šrutin's former school and old neighborhood have completely disappeared.
The picturesque village has turned into wasteland.
Because the landslide happened in the middle of the night without any warning, Shruti says, her family had no chance to escape.
She hopes that scientists will one day find a solution to prevent these types of disasters.
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