Landslides
Kartavya Desk Staff
Syllabus: Disaster Management
Source: IE
Context: Heavy rainfall triggered multiple landslides in Darjeeling and Kalimpong, killing at least 14 people and destroying vital infrastructure including the Dudhia bridge and Teesta Bazaar link road.
About Landslides:
What it is?
• A landslide is the downward movement of rock, debris, or soil along a slope under gravity.
• It occurs when the shear stress exceeds the shear strength of slope materials, often due to heavy rainfall, earthquakes, deforestation, or human activity.
• These events disrupt slope stability and can destroy roads, settlements, and infrastructure, especially in hilly terrains.
India’s Vulnerability:
• Nearly 13% of India’s land area (0.42 million sq. km) is landslide-prone, as per the Geological Survey of India (GSI).
• High-risk zones include the Himalayas, Northeastern hills, Western Ghats, Nilgiris, and Eastern Ghats.
• The Northeast alone accounts for 42% of the total hazard zone due to fragile geology, steep gradients, heavy monsoons, and unregulated construction.
• India’s tectonic activity and population pressure amplify the frequency and intensity of slope failures.
About Darjeeling Landslide:
• Geographical Reasons:
• Darjeeling, in the Eastern Himalayas, sits on young, unconsolidated rock strata prone to erosion and slope failure. The region receives intense monsoon rainfall, causing water saturation and loss of soil cohesion. Unscientific construction, deforestation, road cutting, and hydropower tunneling have degraded natural drainage and slope stability. The district’s seismic vulnerability adds to the cumulative risk of recurrent landslides.
• Darjeeling, in the Eastern Himalayas, sits on young, unconsolidated rock strata prone to erosion and slope failure.
• The region receives intense monsoon rainfall, causing water saturation and loss of soil cohesion.
• Unscientific construction, deforestation, road cutting, and hydropower tunneling have degraded natural drainage and slope stability.
• The district’s seismic vulnerability adds to the cumulative risk of recurrent landslides.
• Historical Record:
• Darjeeling has a century-long record of catastrophic landslides — major events occurred in 1899, 1934, 1950, 1968, 1975, 1980, 1991, 2011, and 2015. The 1968 floods were among the worst, killing over 1,000 people and reshaping the region’s terrain. The 2023 Sikkim GLOF disaster caused ₹25,000 crore in damage, illustrating how hydro-climatic hazards are now linked across Himalayan states. These recurring events show a pattern of high exposure and weak mitigation in the region.
• Darjeeling has a century-long record of catastrophic landslides — major events occurred in 1899, 1934, 1950, 1968, 1975, 1980, 1991, 2011, and 2015.
• The 1968 floods were among the worst, killing over 1,000 people and reshaping the region’s terrain.
• The 2023 Sikkim GLOF disaster caused ₹25,000 crore in damage, illustrating how hydro-climatic hazards are now linked across Himalayan states.
• These recurring events show a pattern of high exposure and weak mitigation in the region.
Current Concern:
• Rapid urbanization and expansion of roads, hotels, and hydropower projects have far exceeded the area’s carrying capacity.
• Encroachments along rivers and jhoras (mountain streams) have blocked natural drainage, increasing waterlogging and slope pressure.
• Frequent slope collapses now threaten key infrastructure like bridges, highways, and rail lines that connect the Siliguri Corridor (“Chicken’s Neck”), a strategic link to the Northeast and Bhutan.
• Hence, Darjeeling’s ecological fragility has evolved into a national security concern, demanding integrated Himalayan policy and sustainable planning.
NDMA Guidelines on Landslides:
• National Landslide Risk Management Strategy (2019): Focuses on vulnerability mapping, hazard zonation, and early warning systems using IMD rainfall forecasts and ISRO terrain data.
• Zonation Maps: Landslide Hazard Zonation (LHZ) maps at 1:50,000 scale identify risk-prone zones for planning and regulation.
• Mitigation Measures: Recommend slope stabilization through vegetation, bio-engineering, drainage improvement, retaining walls, and relocation from chronic slide zones.
• Institutional Coordination: NDMA collaborates with GSI, NRSC, DST, and CSIR to develop real-time data-sharing and GIS-based monitoring.
Way Ahead:
• Scientific planning: Enforce hill zone building codes and prohibit construction in high-risk slopes and drainage corridors.
• Early warning expansion: Extend rainfall-linked landslide forecasting systems (trialed in Kerala, Sikkim, Uttarakhand) across all Himalayan states.
• Eco-restoration: Promote afforestation, jhora rejuvenation, and slope bio-engineering to stabilize fragile hills.
• Institutional reform: Establish a Himalayan Disaster Research and Management Centre in Darjeeling for coordinated response and capacity building.
• Strategic integration: Treat the Darjeeling–Sikkim belt as a national security-sensitive eco-zone under the Act East Policy framework.
Conclusion:
The Darjeeling disaster is a reminder that the Himalayas are ecologically fragile yet geopolitically crucial. Sustainable planning, scientific monitoring, and community-based preparedness must replace ad-hoc development. India’s mountain policy must blend ecological prudence with strategic foresight to safeguard both lives and national interests.