BharatNotes What is Landslide Hazard Zonation?
Landslide Hazard Zonation (LHZ) is the practice of classifying a region into zones of differing landslide susceptibility — typically from very low to very high — by analysing the factors that control slope failure. It converts complex geological and terrain data into an actionable map that planners, engineers and district administrations can use to avoid high-risk areas, regulate construction and prioritise mitigation.
In India the methodology is standardised by the Bureau of Indian Standards (BIS) code IS 14496. Part 2 (1998) provides guidelines for macro-zonation, and Part 1 (2020) for meso-zonation. Both rely on the Landslide Hazard Evaluation Factor (LHEF) rating scheme, which assigns weights to causative parameters and triggers.
Key Factors and Mapping Scales
The LHEF scheme combines several thematic layers. Causative factors include lithology, geological structure, slope morphometry, relative relief, land use/land cover and hydrogeological conditions, while triggering factors include seismicity and rainfall. Remote sensing and GIS are now central to preparing these layers.
| Type of zonation | Typical scale | Use |
|---|---|---|
| Macro-zonation (IS 14496 Part 2, 1998) | 1:50,000 | Regional planning, identifying broad hazard belts |
| Meso-zonation (IS 14496 Part 1, 2020) | 1:10,000 / 1:5,000 | Site-specific, critical sectors, road corridors |
Current Status in India
The Geological Survey of India (GSI), under the Ministry of Mines, is the nodal agency for landslide studies. Through the National Landslide Susceptibility Mapping (NLSM) programme, carried out on a 1:50,000 scale, GSI has mapped about 4.3 lakh sq km of landslide-prone terrain across parts of 19 states/UTs, covering the Himalayas, the Tertiary belt of the North-east and the Western Ghats (as per PIB/GSI, 2025).
GSI has compiled information on roughly 91,000 historical landslides, with tens of thousands field-validated. The maps and inventory are freely accessible via GSI's National Geoscience Data Repository (NGDR), the Bhukosh portal, the Bhusanket portal and the Bhooskhalan mobile application. GSI has since upscaled to meso-scale (1:10,000) mapping of critical sectors — completing 160 sectors by the end of field season 2024-25, with a target of 200 critical sectors by 2028.
On early warning, GSI — in partnership with the British Geological Survey under the LANDSLIP project — developed a rainfall-threshold-based regional Landslide Early Warning System (LEWS), first piloted in Darjeeling (West Bengal) and the Nilgiris (Tamil Nadu). Since the 2025 monsoon, experimental and operational landslide forecast bulletins have been issued for 21 districts across 8 states.
UPSC Angle
For Prelims, remember the nodal agency (GSI), the BIS code (IS 14496), the macro versus meso scales, and the key portals (Bhukosh, Bhusanket, Bhooskhalan). For Mains GS3, LHZ is a strong example of proactive disaster risk reduction — link it to the Sendai Framework's emphasis on understanding risk, to NDMA guidelines, and to the rising landslide frequency in the Himalayas and Western Ghats driven by high-intensity rainfall and unregulated hill construction. It is a foundational concept supporting the wider landslides and disaster-mitigation theme.
