INDIAN LANDSLIDE SUSCEPTIBILITY MAP

Why in the News?

IIT Delhi created the first hi-resolution Indian Landslide Susceptibility Map (ILSM).

About Indian Landslide Susceptibility Map (ILSM)

• A landslide susceptibility map divides the terrain into zones based on the likelihood of landslide occurrence.

Key Feature of ILSM

• Innovative Framework for High-Resolution Landslide Mapping: Embracing big data and use of multiple machine learning models with different underlying principles.
  • The map model incorporates 16 landslide conditioning factors such as height, slope, soil composition, road distance, river proximity, vegetation cover, precipitation, etc.
• High Spatial Resolution Mapping: Map has a spatial resolution of 100 metres with over 95% accuracy.
• Multi-Class Vulnerability Classification: Divides India into Five Vulnerability Classes (refer to map).

Key Findings of ILSM

• Overall Landscape Susceptibility to Landslides in India: Map classifies 13.17% of India's geographical area as susceptible to landslides.
  • 4.75% of the area is categorized as "very highly susceptible."
  • Geological Survey of India estimates a slightly lower figure at 12.6%.
• Regional Variation in Susceptibility:
  • Sikkim has the highest percentage of land area (57.6 %) susceptible to landslides.
  • Arunachal Pradesh has the highest absolute area susceptible to landslides.
  • Kerala, among the non-Himalayan regions, exhibits the highest area susceptible to landslides.
• Identification of New Landslide-Prone Zones: Eastern Ghats show landslide-prone zones identified by the map.
  • These zones were not reported by previous models or government records.

Significance of ILSM

• Policy Formulation and Implementation: It serves as a foundation for the formulation and implementation of policies related to disaster risk reduction, providing a data-driven approach for governments and agencies.
• Scientific Understanding of Landslide Dynamics: Helping researchers and scientists study factors contributing to landslides and refine prediction models.
• Early Warning and Preparedness: The map provides crucial information for identifying areas with high susceptibility to landslides, enabling early warning systems and preparedness measures.

About Landslide

• Phenomena: Landslides occur when gravity forces pushing on hill slope material exceed the frictional forces holding the material in place, causing slope failure.
  • Landslide susceptibility represents this potential for slope failure. 
  • Due to steep slopes and heavy rainfall most of the landslides occur in the northwest Himalayas followed by the northeast Himalayas and the Western Ghats. 
• Causes: Landslides are caused by complex interactions of geological, geomorphological, hydrological, and meteorological characteristics.
  • Geological Factors Influencing Landslides in the Himalayas: The Himalayas are composed of sedimentary rocks which are prone to denudation and erosion. 
    • Steep slopes and rapid rivers contribute to toe erosion making the slope unstable.
    • Most of the landslides in the Himalayas are rockfalls.
  • Geological Dynamics of Landslides in the Western Ghats: The presence of basalt rocks and gentle-sloped rivers in the Western Ghats resulted in fewer rockfalls. However, weathering due to heavy rainfall has led to the development of a thick layer of regolith, thereby leading to mudslides.
  • Role of Rainfall in Landslide Triggering: Rainfall intensity and duration as critical factors for landslide initiation.
    • Western Ghats require less rainfall to trigger landslides when compared to the Himalayas due to the high soil depth in Western Ghats.
    • High soil depth allows more water retention and an increased porewater pressure ultimately leading to landslides.
  • Anthropogenic Contributions to Landslide Risk: Road development and construction contribute to slope instability.

Initiatives Taken by India

• National Landslide Risk Management Strategy released by National Disaster Management Authority (NDMA): The strategy document brings out the message of the need to strengthen and mainstream landslide disaster preparedness, mitigation, response and relief mechanisms through
  • Landslide Hazard Zonation: It covers aspects of reliability and validation of landslide zoning maps in the Indian scenario and proposes a plan of activities for landslide zoning. 
  • Landslide Monitoring and Early Warning System 
  • Awareness generation and capacity building 
  • Preparation of Mountain Zone Regulations and Policies 
  • Stabilization and Mitigation of Landslide and Creation of Special Purpose Vehicle (SPV) for Landslide Management 
• National Landslide Susceptibility Mapping (NLSM) Programme: Launched in 2014-15, under it Geological Survey of India has completed landslide susceptibility mapping of 4.3 lakh sq. km. of landslide-prone areas in the country.
• Landslide Atlas of India: The database covers landslide-vulnerable regions in 17 states and 2 UTs of India in the Himalayas and Western Ghats.
  • Prepared by National Remote Sensing Centre (NRSC) of ISRO.

Conclusion

Adopting area-specific measures is crucial for landslide prevention. Enforce restrictions on construction, roads, and dams in vulnerable areas. Complement with positive actions like large-scale afforestation, bund construction for water flow control, and encourage terrace farming in northeastern hill states where Jhumming (Slash and Burn/Shifting Cultivation) is practised.