Subject: GS Paper 3: Disaster Management
Context: Two years after the 2024 Wayanad tragedy, extremely heavy monsoon rainfall (August 1–2, 2026) triggered fresh landslides, mudslides, and floods across Kerala.
Background
- ISRO Landslide Atlas (2023): Released by the National Remote Sensing Centre (NRSC), ISRO, based on landslide events recorded during 1998–2022 across the Himalayas and the Western Ghats.
- Key Finding: Although the Western Ghats recorded fewer landslide events than the Himalayas, Kerala accounted for a disproportionately high share of landslide fatalities.
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About Landslide
- A landslide is the downward movement of rock, soil, earth or debris along a slope under the influence of gravity.
Classification of Landslides
- Falls: Sudden detachment and free fall of rock or debris from steep slopes or cliffs.
- Slides: Downslope movement of rock, soil, or debris along a well-defined failure surface.
- They are broadly classified into rotational slides (curved slip surface) and translational slides (planar slip surface).
- Flows: Rapid movement of water-saturated soil, mud, and debris behaving like a fluid (e.g., debris flows, mudflows).
- Topples: Forward rotation and overturning of rock blocks or columns around a pivot point due to gravity, weathering, or erosion at the base of the slope.
- Creep: Extremely slow, continuous downslope movement of soil or weathered rock under the influence of gravity.
- Though gradual, it can damage roads, buildings, and other infrastructure over time.
Causes of Landslides
- Conditioning Factors: Steep slopes, geology, geomorphology, soil characteristics and topography determine inherent slope susceptibility.
- Natural Triggers: Most landslides in India are rain-induced, triggered by intense or prolonged rainfall.
- Earthquakes, snowmelt and flood-induced undercutting of slopes.
- Anthropogenic Triggers: Hill cutting, excavation, quarrying, unscientific construction, deforestation, haphazard land use and overgrazing.
Meteorological Trigger of the 2026 Landslide in Kerala
- Offshore Trough: Extended from the south Gujarat coast to Kerala, intensifying the monsoon flow.
Landmark Committee Recommendations:
- Madhav Gadgil Committee (2011): Recommended strict regulation of mining, quarrying, polluting industries and large construction projects in Ecologically Sensitive Areas (ESA).
- Recommended bringing 75% of the 129,037 sq km Western Ghats under ecological sensitivity due to dense forests, endemic species, and unique geology.
- Recommended banning mining, quarrying, new thermal power plants, hydropower projects, and large-scale wind energy projects in Ecologically Sensitive Zone-1 (ESZ-1).
- Kasturirangan Committee: Recommended declaring only 37% of the Western Ghats (around 60,000 sq km) as Ecologically Sensitive Area (ESA), compared to the much larger area proposed by the Gadgil Committee.
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- Southwesterly Winds: Strong winds over the Arabian Sea enhanced moisture transport.
- Pressure Gradient: A strong north-south pressure gradient along the west coast strengthened rainfall.
- Widespread Rainfall: Heavy to extremely heavy rainfall occurred across Kerala, with several stations recording over 20.4 cm in 24 hours.
- Cumulative Rainfall: Antecedent rainfall saturated slopes, while intense rainfall acted as the immediate trigger for landslides.
Reasons for Kerala Being Highly Vulnerable to Landslides
- Fragile Western Ghats Terrain: Landslide-prone districts include Idukki, Wayanad, Kozhikode, Malappuram, Kottayam, and Pathanamthitta.
- The region has steep slopes, deeply weathered soil, and hard rock beneath, making slopes inherently unstable.
- Soil–Rock Interface Mechanism: Rainwater infiltrates the loose soil and reaches the soil-bedrock interface.
- Water flows between the soil and underlying hard rock, weakening the bond between them.
- As the soil becomes saturated, shear strength decreases, leading to slope failure.
- Human-Induced Drivers: Quarrying, road construction, and hill cutting destabilise slopes.
- Expansion of plantations alters natural drainage patterns.
- Monocropping replaces native deep-rooted forests with tea and coffee plantations, whose shallow roots provide weaker slope reinforcement.
Institutional Framework for Landslide Management:
- National Disaster Management Authority (NDMA): Frames national guidelines and policies for landslide risk reduction and preparedness.
- Geological Survey of India (GSI): Nodal agency for Landslide Hazard Zonation (LHZ) mapping, landslide investigations, and the National Landslide Susceptibility Mapping (NLSM) programme.
- National Landslide Susceptibility Mapping (NLSM) Programme: A Geological Survey of India (GSI) initiative that prepares GIS-based maps identifying landslide-prone areas to support scientific land-use planning and disaster risk reduction
- National Disaster Management Act, 2005 provides the legal framework for disaster risk reduction.
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Way Forward
- Early Warning: Strengthen rainfall-based landslide forecasting and early warning systems.
- Promote nature-based slope stabilisation: Restore natural drainage pathways and plant deep-rooted native vegetation on vulnerable slopes to reduce erosion, improve soil binding, and minimise landslide risk.
- Land-use Planning: Enforce scientific land-use planning in vulnerable hill regions.
- Ecological Conservation: Regulate quarrying and hill cutting while restoring native forests.
- Disaster Preparedness: Promote risk-informed planning and community-based disaster management.
- Scientific Hazard Mapping: Classify areas into very low, low, moderate, high, and very high landslide hazard zones (LHZ).
- Base zonation on slope, geology, rainfall, land use, drainage, and past landslide history.
- Integrate LHZ maps into land-use planning, infrastructure development, road construction, and disaster risk reduction.
3 Aug 2026
