Landslides: Types, Factors Responsible & Impacts

• The Himalayan region has witnessed frequent landslides driven by extreme rainfall, fragile geology, and unregulated development.

What are Landslides?

• A landslide is the sudden and rapid movement of a mass of rock, soil, or debris down a slope under the influence of gravity, often triggered by rainfall, earthquakes, snowmelt, or human activities.

Types of Landslides

Based on Materials Involved

• Rock slide: Movement of bedrock down a slope, typically involving detached rock masses.
• Debris slide: Rapid downslope movement of loose, unconsolidated material like soil, rock fragments, organic matter, etc.
• Soil slide: Movement of saturated, loose soil that may involve a mix of soil and vegetation.
• Loose mudslide: Flow of loosely bound mud that becomes mobilised and moves downslope.

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Based on Movement of Material

• Fall: Sudden free fall of rock or debris from a steep slope or cliff.
• Topple: Rotation of rock/soil blocks over a pivot point, causing them to fall forward.
• Slide: Downslope movement of a coherent mass along a defined slip surface.
• Rotational slide: Curved sliding motion of material along a concave slip surface, often involving a rotational component.
• Translational slide: Downslope movement of material along a planar or nearly planar slip surface.

Based on Flow of Material

• Debris flow: Fast-moving mixture of water, soil, and rock that flows like a fluid down a slope.
• Earth flow: Slow, steady movement of saturated, fine-grained soil/sediment resembling a viscous fluid.
• Mudflow: Rapid, fluid movement of a water-saturated mixture of mud, silt, and clay.
• Creep: Slow, gradual downslope movement of soil and rock due to gravity, often imperceptible over short periods.

Factors Responsible for Landslides

Natural Factors

• Heavy Rainfall: Heavy rain saturates the soil, reducing stability and triggering landslides. E.g., the 2018 Kerala floods caused numerous landslides in the Western Ghats due to intense rainfall.
• Earthquakes: Seismic activity shakes the ground, destabilising slopes and causing landslides, such as the 2009 Kinnaur landslide.
• Snow Melting: Rapid snowmelt increases water flow, weakening soil stability.
• Undercutting of Slopes Due to Flooding: Flooding erodes the base of slopes, making them unstable. E.g., landslides in the Western Ghats, exacerbated by flooding.

Anthropogenic Factors

• Excavation: This removes soil and rock, destabilising slopes. For example, construction and excavation activities worsened the 2019 Munnar landslide in Kerala.
• Deforestation: Deforestation removes vegetation that stabilises soil, increasing landslide risk. For example, hill cutting and deforestation aggravated the 2018 Kodagu landslides in Karnataka.
• Overgrazing by Cattle: Overgrazing destroys vegetation, leading to soil erosion and landslides. For example, overgrazing in the Western Ghats increases soil erosion, contributing to landslide risk.

Landslides in the Western Ghats & Himalayas: A Comparison

Impacts of Landslides

• Loss of life and property: For instance, around 300 people lost their lives in Wayanad landslides.
• Infrastructure damage: Critical infrastructure like roads, bridges, power lines, etc. are destroyed.
• Economic losses: Disrupt livelihoods, trade, and tourism. The landslides in Darjeeling, West Bengal, have impacted the region’s tea industry.
• Environmental degradation: Causes soil erosion, deforestation, and pollution of water bodies, leading to long-term environmental consequences.
• Disaster relief and rehabilitation: Government resources are diverted for rescue, relief, and rehabilitation efforts after landslides, impacting other development priorities.
• Psychological impact: Landslides can cause severe trauma and psychological distress among survivors and affected communities.

The Worst Landslides in India

• Guwahati, Assam (1948): Over 500 people lost their lives when an entire village was buried under a landslide triggered by heavy rains.
• Darjeeling, West Bengal (1968): A massive landslide caused by floods killed over 1000 people and divided a 60 km long highway into 91 parts.
• Malin, Maharashtra (2014): Heavy rainfall triggered a landslide that claimed the lives of around 151 people, with 100 others missing.
• Mapla, Uttarakhand (1998): A series of landslides over seven days wiped out an entire village, resulting in the death of over 380 people.
• Kedarnath, Uttarakhand (2013): Unprecedented rain and floods triggered massive landslides, leading to the death of over 5700 people and the destruction of thousands of villages.
• Wayanad, Kerala (2024): Recent landslides in the Wayanad district caused significant loss of life and property damage, highlighting the ongoing threat of landslides in India.

NDMA Guidelines on Landslides

• Data Inventory: Regularly updating the inventory of landslide incidents in the country.
• Hazard Zonation: Landslide hazard zonation mapping in macro and meso scales after consultation with Border Roads Organization, state governments and local communities.
• Pilot Projects: Regional studies and monitoring of select landslides for risk assessment.
• Early Warning: Setting up early warning systems, depending on the risk evaluation and cost-benefit ratio.
• Capacity Building: Training and capacity-building measures for professionals and organizations working in the field of landslide management.
• Code Revision: New codes and guidelines to be developed for landslide studies, and existing ones have to be revised.
• Research Center: Establishing an autonomous National Center for Landslide Research, Studies and Management.

Way Forward

• Strengthening Early Warning Systems: Expand ISRO’s Landslide Atlas of India with real-time monitoring through satellites, drones, and IoT-based rainfall/soil sensors.
• Comprehensive land-use planning: Restrict tourism and real estate in ecologically sensitive zones of Himalayas and Western Ghats. Promote slope-friendly urban planning in rapidly urbanizing hill towns.
• Infrastructure resilience: Ensure slope stabilization measures like retaining walls, drainage channels, gabion structures in vulnerable stretches of highways and railways.
• Community Based Disaster Risk Reduction: Involve local communities, Panchayats, and SHGs in slope monitoring, afforestation, and emergency drills.

Landslides in India highlight the fragile balance between nature and human activity; as Ban Ki-moon said, “We are the first generation to feel the impact of climate change and the last that can do something about it.” Strengthening early warning, planning, and community resilience is essential to reduce vulnerability and safeguard lives.

Reference: The Hindu

UPSC Mains PYQs – Theme – Landslides

1. [2021] Differentiate the causes of landslides in the Himalayan region and Western Ghats.
2. [2021] Describe the various causes and the effects of landslides. Mention components of the important components of National Landslide Risk Management strategy.
3. [2016] The Himalayas are highly prone to landslides. “Discuss the causes and suggest suitable measures of mitigation.
4. [2013] Bringout the causes for more frequent landslides in the Himalayas than in Western Ghats.

PMF IAS Pathfinder for Mains – Question 349

Q. Landslides are no longer a localised hazard but a recurring national disaster. Analyse the causes of landslides in India and discuss the preparedness in line with NDMA guidelines. (250 Words) (15 Marks)

Approach

• Introduction: Write a definition-based introduction and mention a recent example.
• Body: Analyse the causes of landslides in India, preparedness in line with NDMA guidelines and way forward.
• Conclusion: Emphasis on Effective mitigation and future course of action.