Landslides

Introduction to Landslides

Landslides are one of the most common and destructive geo-environmental hazards in India, particularly in hilly and mountainous regions. They involve the downward movement of rock, debris, or soil under the influence of gravity, often exacerbated by environmental or human-induced factors.

Definition of Landslides

A landslide is defined as the mass movement of rock, earth, or debris down a slope due to gravitational pull. These movements can be rapid or slow and are typically triggered by natural phenomena like rainfall, earthquakes, and floods, or human interventions like deforestation and construction.

Examples of Landslide Incidents

• Srinagar-Jammu Highway: Frequently blocked due to heavy landslides, especially during monsoons.
• Konkan Railway Track (Western Ghats): Disruptions due to rockfalls and landslides are common during intense rainfall.
• Varunavat Hills (Uttarkashi): A major landslide in 2003 buried buildings and disrupted life significantly.

Comparison with Other Natural Disasters

• Landslides are localized but equally destructive as earthquakes, tsunamis, or cyclones.
• Unlike other disasters, landslides are mostly influenced by local factors, making forecasting and monitoring more complex and cost-intensive.

Challenges in Monitoring Landslides

• Highly localized triggers make real-time prediction difficult.
• Requires continuous surveillance, advanced equipment, and geological mapping, which is cost-intensive and region-specific.
• Complex terrain and varied geologies make generalization difficult.

Factors Influencing Landslides

Landslide Vulnerability Zones in India

a. Very High Vulnerability Zone

• Characteristics: Steep slopes, high rainfall, active tectonics, and intense human interference.
• Regions Included:
  • Himalayan belt (J&K, Himachal Pradesh, Uttarakhand, Sikkim)
  • Andaman & Nicobar Islands
  • Western Ghats (Kerala, Karnataka, Tamil Nadu)
  • Nilgiris
  • North-Eastern states (e.g., Arunachal Pradesh, Mizoram)
• Factors:
  • High-intensity rainfall
  • Seismic activity
  • Road, dam, and hydropower construction

b. High Vulnerability Zone

• Characteristics: Similar terrain and triggers as the very high zone but with lesser intensity or frequency.
• Regions Included:
  • Remaining Himalayan States
  • Entire North-Eastern region except Assam plains

c. Moderate to Low Vulnerability Zone

• Characteristics: Gentle relief, reduced precipitation, and more stable geological structure.
• Regions Included:
  • Trans-Himalayas: Ladakh, Spiti (HP)
  • Aravali ranges
  • Rain-shadow regions: Eastern & Western Ghats
  • Deccan Plateau

Landslides due to Mining/Subsidence

• States Affected:
  • Jharkhand, Odisha, Chhattisgarh, Madhya Pradesh, Maharashtra
  • Andhra Pradesh, Karnataka, Tamil Nadu, Goa, Kerala

d. Other Areas (Least Vulnerable / Safe Zones)

• States with Minimal Risk:
  • Rajasthan, Haryana, Uttar Pradesh, Bihar
  • West Bengal (except Darjeeling)
  • Assam (except Karbi Anglong hills)
  • Coastal Andhra Pradesh, Tamil Nadu, Karnataka

Consequences of Landslides

• Loss of human lives and livestock
• Destruction of property: Homes, hotels, and religious structures
• Disruption of infrastructure: Roads, railways, dams, electricity lines
• Environmental degradation: Soil erosion, river blockades, deforestation
• Economic losses: Impact on tourism, transport, and local livelihoods

Mitigation of Landslides

a. Area-Specific Measures

• Landslide Hazard Zonation (LHZ) mapping
• Avoiding construction in high-risk zones
• Evacuation plans and community drills
• Installation of early warning systems
• Slope stabilization techniques

b. Positive Mitigation Strategies