Landslides, Types, Causes, Impacts, Mitigation, Prone Areas

A landslide is the movement of rock, soil, or other debris down a slope due to gravity. Heavy rainfall can saturate the soil and make it more unstable, increasing the likelihood of landslides. As per the Geological Survey of India (GSI), nearly 12.6% of the land area of our country is prone to landslides. The northward movement of the Indian plate coupled with the heavy rains and climate change make the Himalayan regions susceptible to landslides. Western Ghat is another region of the landslides due to its steep western slopes and the erosion of the Laterite cap. With adequate planning, landslides can be minimised or even avoided and suitable preventive measures should be taken to preserve the hill-slope stability.

India’s Vulnerability to Landslides

Landslides and avalanches are among the principal hydro-geological hazards that affect vast areas of India, in addition to the Himalayas, Northeastern hill ranges, Western Ghats, Nilgiris, Eastern Ghats, and Vindhyans, in that order, accounting for approximately 15% of the landmass. 

• Out of a total of 3,782 landslides between 2015 and 2022 in India, the highest 2,239 were reported in Kerala followed by West Bengal (376), Tamil Nadu (196), Karnataka (194), and Jammu & Kashmir (184).
• Himalayan region: The Himalayan region, particularly in areas like Jammu and Kashmir, Himachal Pradesh, Uttarakhand, and parts of Northeast India, is highly prone to landslides.
  • The region is characterised by steep slopes, fragile rock formations, and high seismic activity, making it susceptible to landslides triggered by earthquakes, heavy rainfall, and snowmelt.
  • Sudden heavy rains due to climate change are also increasing landslides, according to experts. Around 73 percent of landslides in the Himalayan region are attributed to heavy rains and reduced water-absorbing capacity of the soil.
  • Rudraprayag and Tehri Garhwal in Uttarakhand are the most landslide-prone districts in the country, according to satellite data by ISRO.
  • Recent events: Over 5,300 people have been killed in landslides since 2000 when the mountain state was formed. 
    • The flash flood of 2021 in the Chamoli district of Uttarakhand which claimed at least 72 lives was due to an avalanche.
• Western Ghats: The Western Ghats, a mountain range along the Western Coast of India, is another landslide-prone area.
  • A different variety of landslides poses a constant threat to the Western Ghats in the South. 
  • This is due to the presence of a lateritic cap and its extensive erosion, along the steep slopes in the Konkan coast and Nilgiris. 
  • The region receives heavy rainfall during the monsoon season, which saturates the soil and weakens the slopes. 
  • Deforestation, mining activities, and improper land use practices further increase this region's landslide risk.

Landslides Causes

The landslides are caused by the combined effect of several factors including both natural and anthropogenic. These causes can be discussed broadly in two categories.

Natural Causes

• Gravity: Gravity is the primary reason for the landslides. Steeper slopes coupled with gravitational force can trigger a massive landslide.
• Climate: A general increase in precipitation or ground saturation drastically raises groundwater levels.
  • When slopes become entirely saturated with water, landslides can occur. If mechanical root support is absent, the soils start to run off.
• Earthquakes: When earthquakes strike regions with steep slopes, the soil often slips, resulting in landslides.
  • Ashen debris flows produced by earthquakes can also cause significant soil movement.
• Weathering: Weathering causes inundation and makes rocks weak. Landslides are then caused when the rocks become too weak and begin to slide away.
• Erosion: It is caused by periodic running water, such as streams, rivers, wind, currents, ice, and waves, which remove latent and lateral slope support, allowing landslides to develop more easily.
• Volcanoes: Volcanic eruptions can trigger landslides. If an eruption happens in moist conditions, the soil will begin to flow downhill, resulting in a landslip.

Man-made Causes

• Mining: Mining activities that utilise blasting techniques contribute to landslides. Vibrations from the blasts can degrade soils in the locations prone to landslides, such as in the Himalayas.
  • A landslip can occur at any time due to soil deterioration.
• Clear-cutting: It is a timber harvesting practice that involves removing all old trees from the area. This practice is risky since it destroys the area's current mechanical root structure, allowing landslides to occur. 
• Unsustainable Tourism: The unregulated tourism in Uttarakhand and other Himalayan States exceeds the region’s carrying capacity, causing disastrous impacts including landslides. Religious tourism sites, such as Char Dham, have been hugely commercialised and exploited to the point of becoming unsustainable.
  • For Example: In 2013, around 5000 people were killed in a massive flood and landslide in Kedarnath. In 2011, around 25 million tourists visited the region, despite its vulnerability to natural disasters such as earthquakes, landslides, and flash floods.
• Unplanned infrastructure: The Himalayas are the world's most densely populated and rapidly urbanising mountain ecosystem.
  • Urban encroachment into forests, disturbance of natural drainage, and cutting and deep excavations on hill slopes to develop buildings and infrastructure have contributed to a huge increase in landslides in Uttarakhand.
  • Example: The land subsidence incident of Joshimath in 2023 was mainly due to a lack of infrastructure for drainage, an increase in human population, and rapid expansion of infrastructure to cater for the tourism potential. 
• Climate change: The intense and sudden rainfall due to climate change as well as the melting of the glaciers in the Himalayas have aggravated the problems of landslides in India.

Landslides Impacts

Landslides can have significant consequences, both in terms of human impact and environmental damage.

• Loss of life: Communities living at the foot of hills and mountains are at a greater risk of death by landslides. A substantial landslide carries huge rocks, heavy debris, and soil with it. This kind of landslide can kill lots of people on impact.
  • For instance, the Kedarnath landslide in 2013, triggered by heavy rainfall, resulted in massive devastation and claimed the lives of thousands of people in Uttarakhand.
• Lead to economic decline: The landslide destroys properties and infrastructure, requiring substantial financial resources to rehabilitate the affected areas.
  • For example, the economic decline caused by landslides and subsequent rehabilitation efforts is the 2018 Kavalappara landslide in Kerala, India. 
• Decimation of infrastructure: The force flow of mud, debris, and rocks due to a landslide can cause severe property damage. A single landslide can decimate infrastructure such as roads, railways, leisure destinations, buildings, and communication systems.
• Affects beauty of landscapes: The erosion left behind by landslides leaves behind rugged landscapes that are unsightly. The pile of soil, rock, and debris downhill can cover land erstwhile utilised by the community for agricultural or social purposes.
  • Thus, it affects tourism as well as agriculture.

Landslides Mitigation Measures and Approaches

The problem of landslides must be addressed by mitigation and preventive measures. The measures to control landslides are as follows.

• Investigation of Site: The implementation of risk reduction measures must be preceded by locating areas, which are prone to slope failures. To identify landslide-prone areas before the construction work is taken up. 
  • Such investigation is required to suggest preventive measures or alternative routes that are less susceptible to landslide hazards. 
• Surface drainage: Surface drainage can be installed to reroute surface water away from a slope, thus reducing the likelihood of a landslide. In high rainfall areas, erosion protection via surface drainage – both at the toe and on the surface – can be very effective, positively impacting the maintenance of the angle of the slope.
• Land-Use Planning: For maximum effectiveness, the Landslide Risk and Hazard assessments should be incorporated into the comprehensive plan of infrastructure. 
• Landslide-specific regulations: By establishing landslide-specific regulations in the form of an overlay zone or a development code. These types of regulations are a low-cost strategy to restrict construction and infrastructure away from hazardous slopes, avoiding costly slope failures.
• Other measures include: 
  • Afforestation: Trees and brushes help in binding the soil particles. 
  • New technology in road construction: Roads should be constructed in such a way that a lesser amount of debris is generated. 
  • Ban on quarrying of stones and mining of minerals. 
  • Permanent crops like orchards of fruits should replace the seasonal or annual Drops. 
  • Retaining walls can be built on mountain slopes to stop land from slipping.

Landslides Steps taken by the Government

The government of India is taking several steps to prevent and minimise landslides through various policies, plans, and regulations.

• Guidelines from NDMA: NDMA released the Guidelines on Management of Landslides and Snow Avalanches, laying down national policy for the management of landslides and related activities in the country.
• Landslide Risk Mitigation Scheme: The Scheme envisages financial support for site-specific Landslide Mitigation Projects recommended by landslide-prone States, covering “disaster prevention strategy, disaster mitigation, and R&D in the monitoring of critical Landslides”.
• Landslide Monitoring and Early Warning System: The project (by NDMA) aims to develop low-cost sensors and other instruments for landslide monitoring, using micro-electro-mechanical systems (MEMS)-based sensor technology and artificial intelligence.
  • The system has been able to generate predictive messages about impending soil movements one day ahead of time as well as issue severe weather advisories two hours ahead of severe weather events.
• Landslide Strategy and Public Awareness Generation: The strategy was released by NDMA, the document addresses all the components of landslide disaster risk reduction and management, such as hazard mapping, monitoring and early warning systems, awareness programmes, capacity building and training, regulations and policies, stabilization and mitigation of landslides, etc.
• Risk Mapping of Hilly Areas: The Geological Survey of India and the Ministry of Mines have completed landslide susceptibility mapping of 4.3 lakh sq. km of landslide-prone areas under the National Landslide Susceptibility Mapping (NLSM) Programme, focusing on site-specific investigations for remedial measures.
• Indian Landslide Susceptibility Map: The map has a spatial resolution of 100 metres and is above 95% accurate. The chart shows that 13.17% of India's geographical region is prone to landslides, with 4.75% being "very highly susceptible.". 
  • According to the findings, 50% of Sikkim and Uttarakhand's lands are in the "very high susceptibility" zone.
  • The map discovered additional landslide-prone zones in the eastern ghats that had not been recorded by any previous model or official data.

Landslides UPSC PYQs

Question 1: Describe the various causes and effects of landslides. Mention the important components of the National Landslide Risk Management Strategy. (UPSC Mains 2021)

Landslides FAQs

Q1. What are landslides and their causes?

Ans. Landslides are the downslope movement of earth materials under the force of gravity. They can occur without any obvious trigger. Widespread or severe landslide events are often driven by such hazards as hurricanes, earthquakes, and volcanoes.

Q2. What are the effects of landslides?

Ans. The impact of a landslide can be extensive, including loss of life, destruction of infrastructure, damage to land and loss of natural resources. Landslide material can also block rivers and increase the risk of floods.

Q3. What are the human-induced causes of landslides?

Ans. They are frequently caused by the construction of roads and structures without appropriate slope grading, the unplanned changing of drainage patterns, and the disturbance of existing landslides. 

Q4. How can we prevent landslides?

Ans. There are several direct methods for preventing landslides, such as changing slope geometry, using chemical agents to reinforce slope material, erecting structures like piles and retaining walls, grouting rock joints and fissures, diverting debris pathways, and redirecting surface and underwater drainage.