06 · GS-III: Disaster Management, Geo-Hazards & Early Warning
Landslide Early Warning Systems (LEWS): Rainfall Threshold Telemetry in Western Ghats and Geological Survey of India
NEWS PEG
- The Geological Survey of India (GSI) operationalized dynamic regional Landslide Early Warning Systems (LEWS) across landslide-prone districts of the Western Ghats (Wayanad, Idukki, Nilgiris, Kodagu) and Eastern Himalayas.
- The system integrates satellite precipitation data from IMD, real-time soil moisture probes, and slope stability geotechnical models to issue color-coded landslide hazard bulletins 24 to 48 hours in advance of torrential monsoon downpours.
- National disaster experts highlighted that anthropogenic disturbances—unregulated quarrying, monoculture rubber/tea plantations replacing deep-rooted natural rainforests, and toe-cutting for resort roads—have heightened catastrophic debris flow vulnerabilities.
STATIC FOUNDATION
- National Landslide Susceptibility Mapping (NLSM) Programme (GSI): Mapped 4.3 lakh sq km of landslide-prone areas across India on a 1:50,000 scale, classifying zones into High, Moderate, and Low susceptibility.
- Rainfall Threshold Concept in Landslides: Empirical relationship between rainfall intensity, duration, and antecedent soil moisture saturation that triggers slope failure and debris flow.
- Western Ghats Ecology Expert Panel (Gadgil Report) & Kasturirangan Committee: Recommended notifying 64% (Gadgil) or 37% (Kasturirangan) of the Western Ghats as Ecologically Sensitive Areas (ESA) prohibiting mining and red-category industries.
- Types of Mass Wasting: Debris flow (fast-moving slurry of water, rock, mud), Slump (rotational slip), Rockfall, and Soil creep (slow downward progression).
PRELIMS TRAP & PYQ BRIDGE
MAINS ENHANCEMENT
- Scientific Disaster Forewarning: Last-Mile Dissemination of LEWS Bulletins — Translating geotechnical rainfall thresholds into actionable village-level evacuation alerts.
- Land-Use Regulation in Fragile Slopes: Enforcing Eco-Sensitive Area Guidelines — Prohibiting hill-cutting, quarrying, and commercial resort construction on slopes exceeding 30 degrees.
- Bio-Engineering Slope Stabilization: Vetiver Grass & Native Broadleaf Afforestation — Deep-rooting vegetative stabilization to anchor fragile overburden on hill slopes.