Landslides in India: Monsoon-Induced Slope Failures, Risk Management and Disaster Resilience

Recent Developments:

• Torrential monsoon rainfall triggered widespread landslides across Maharashtra, resulting in the temporary closure of the Mumbai–Pune Expressway and the Mumbai–Goa Highway, disrupting transport and emergency services.
• Intense rainfall saturated hill slopes, causing boulder falls, debris flows and repeated slope failures along several vulnerable transport corridors.
• The incident has renewed focus on the need for scientific slope management, early warning systems and land-use regulation in India's landslide-prone regions.

Landslides:

Definition:

• A landslide is the rapid downward and outward movement of rock, soil, debris, weathered material or artificial fill under the influence of gravity.
• Landslides occur when the shear stress acting on a slope exceeds the shear strength of soil or rock, causing slope failure.
• Landslides are a form of mass wasting and may occur as rock falls, debris flows, mudflows, rotational slides, translational slides or complex slope failures.

Landslide Scenario in India:

Key Facts:

• Nearly 15% of India's geographical area, approximately 0.42 million sq km, is susceptible to landslides.
• Major landslide-prone regions include the Himalayas, Northeast India, Western Ghats and Eastern Ghats due to fragile geology, steep slopes and intense rainfall.
• A large proportion of vulnerable areas also lie within Seismic Zones IV and V, where earthquakes further destabilize mountain slopes.
• The Geological Survey of India is the nodal agency for landslide studies and operates the National Landslide Forecasting Centre through the BhuSanket platform for forecasting and impact assessment.
• The Landslide Atlas of India, prepared by Indian Space Research Organisation, contains an inventory of nearly 80,000 mapped landslides covering 17 States and 2 Union Territories using satellite-based geospatial data.

Major Causes of Landslides in India:

Natural Factors:

• Intense and prolonged rainfall increases groundwater pore-water pressure, reduces soil cohesion and substantially increases the weight of unstable slopes.
• Earthquakes generate ground shaking that destabilizes already fractured rock masses, particularly in tectonically active mountain belts.
• Young fold mountains, weathered rocks, geological faults and highly fractured strata create natural planes of weakness that promote slope failure.
• River erosion, glacial activity and natural weathering continuously undercut hill slopes, increasing instability.
• Climate change is increasing the frequency of extreme rainfall events, thereby elevating landslide risks in mountainous regions.

Anthropogenic Factors:

• Unscientific hill cutting for highways, railways and urban expansion disturbs natural slope equilibrium and weakens hill stability.
• Deforestation removes root systems that bind soil, accelerating erosion and slope instability.
• Mining, quarrying and blasting create artificial fractures and weaken rock formations.
• Unplanned urbanisation, encroachment on steep slopes and poor drainage systems increase landslide vulnerability.
• Improper disposal of construction debris and overloading of hill slopes further aggravate slope failures.

Impacts of Landslides:

Socio-Economic and Environmental Impacts:

• Landslides cause loss of human lives, livestock and widespread destruction of houses and public infrastructure.
• Roads, railways, tunnels, bridges, transmission lines and communication networks often remain disrupted for extended periods.
• Landslides block rivers, creating temporary lakes that may subsequently trigger catastrophic flooding.
• Productive agricultural land is buried under debris, reducing agricultural productivity and affecting livelihoods.
• Mountain ecosystems experience severe habitat degradation, biodiversity loss and accelerated soil erosion.
• Tourism, local economies and supply chains suffer significant disruptions in hill regions.

Challenges in Landslide Risk Management:

Major Constraints:

• Remote mountainous terrain delays rescue, evacuation and relief operations.
• Continuous rainfall, cloud cover and recurring slope failures hamper both aerial and ground-based disaster response.
• Weak enforcement of land-use zoning regulations permits construction in highly vulnerable locations.
• Many regions lack meso-scale, real-time monitoring networks capable of detecting initial ground movement before failure.
• Hazard maps are often inadequately integrated into infrastructure planning and local development decisions.
• Coordination among multiple agencies involved in forecasting, planning and emergency response remains uneven.

National Disaster Management Authority Guidelines:

Recommended Measures:

• Geological Survey of India should continuously update comprehensive national landslide inventories and hazard databases.
• Landslide Hazard Zonation mapping should be prepared at 1:50,000 and 1:10,000 scales to guide infrastructure planning and land-use decisions.
• Engineering measures such as retaining walls, rock bolting, wire mesh netting, soil nailing, anchoring systems and slope reinforcement should be adopted in vulnerable locations.
• Efficient surface and sub-surface drainage systems should be developed to reduce pore-water pressure and improve slope stability.
• Community awareness, capacity building, preparedness planning and multi-agency coordination should be strengthened at all administrative levels.
• The National Disaster Management Authority also recommends institutional coordination, hazard mapping, capacity building and scientific land-use planning under its Landslide Risk Management Strategy, 2018 and Guidelines on Management of Landslides and Snow Avalanches.

Institutional Framework:

Major Institutions:

• Geological Survey of India serves as the national nodal agency for landslide investigation, hazard mapping, forecasting and technical support.
• National Disaster Management Authority formulates national policies, guidelines and disaster risk reduction strategies.
• National Disaster Response Force undertakes specialised search, rescue and emergency response during landslide disasters.
• India Meteorological Department provides rainfall forecasts and weather advisories supporting landslide preparedness.
• Indian Space Research Organisation supports landslide mapping through satellite observations, remote sensing and geospatial databases.
• State Disaster Management Authorities and District Disaster Management Authorities coordinate preparedness, evacuation and rehabilitation at State and district levels.

Way Forward:

Priority Measures:

• Deploy Artificial Intelligence-enabled early warning systems integrating rainfall data, ground sensors, extensometers and automated monitoring stations.
• Install rockfall barriers, steel catch fences, protective galleries and engineered shelters along vulnerable highways and railway corridors.
• Use Light Detection and Ranging, drones and high-resolution satellite imagery for periodic monitoring of unstable slopes before every monsoon.
• Make scientific geotechnical investigation mandatory before approving hill infrastructure, mining or large construction projects.
• Strictly prohibit unscientific hill cutting and adopt terraced benching, bio-engineering techniques, geo-textiles and proper drainage systems.
• Strengthen community-based disaster preparedness through trained local volunteers, mock drills, first-aid training and emergency communication systems.
• Integrate landslide risk assessment into Environmental Impact Assessment, district disaster management plans and climate adaptation strategies.
• Align national landslide risk reduction initiatives with the Sendai Framework for Disaster Risk Reduction 2015–2030 and Sustainable Development Goal 11 to enhance resilience and sustainable mountain development.

Conclusion:

Building Resilient Mountain Ecosystems:

• Recurring landslide disasters demonstrate that disaster resilience requires scientific planning, strict land-use regulation, resilient infrastructure and continuous monitoring rather than post-disaster response alone.
• A combination of risk-informed development, advanced forecasting, community participation and ecosystem-based slope management will be essential for protecting lives, infrastructure and fragile mountain environments