Landslides

Why in News?

Recently there has been a heavy landslide affecting significant parts of Keralam.

What is a Landslide?

• Definition – The National Disaster Management Authority (NDMA) defines a landslide as a wide variety of processes resulting in the downward and outward movement of slope-forming materials—including natural rock, soils, artificial fills, or combinations of these—under the direct influence of gravity.
• Main Types
  • Falls – Rocks and debris break off a steep cliff or slope and drop straight down, bouncing or rolling as they hit the ground.
  • Topples – Large blocks of rock or soil tilt forward over a pivot point near the bottom and fall away from the slope.
  • Slides – A coherent mass of material moves down a slope along a clear breaking or slip surface.
  • This includes rotational slides (moving along a curved surface) and translational slides (moving along a flat plane).
  • Spreads – Fractured parts of a hard top layer stretch or move apart horizontally, usually because a weak layer underneath gives way.
  • Flows – Mixed soil, rock, air, and water rush down like a liquid or thick fluid, often called mudflows or debris flows.
• Landslides Zones of India – India currently has 87,474 active landslide zones, spread across 179 districts in 19 states and union territories, a recent report released by the Geological Survey of India (GSI) has revealed.
• These danger-prone zones collectively cover about 4.2 lakh square kilometres, underscoring the scale of the challenge.
• Arunachal Pradesh ranks first with 26,213 landslide zones, followed by Himachal Pradesh with 17,102 zones across the nation.
• Uttarakhand stands third with 14,780 zones.
• Major Recent Landslides in India
  • 2026(pathanamthitta, kerala)        
  • 2024 (Wayanad, Kerala)
  • 2023 (Irshalwadi, Maharashtra)
  • 2023 (Himachal Pradesh)
  • 2022 (Noney, Manipur)
  • 2021 (Kinnaur, Himachal Pradesh)

What are the causes of Landslides?

• Heavy Rain – Water makes soil heavy and slippery, which lowers the friction holding the dirt on the slope.
• Earthquakes – Shaking from the earth breaks rocks and shifts loose dirt on mountains.
• Volcanoes – Hot ash, melting snow, and lava flows from eruptions can start fast mudslides.
• Erosion – Rivers or ocean waves wash away the bottom part of a hill, leaving the top unsupported.
• Cutting Trees (Deforestation) – Tree roots hold the soil tightly together, removing trees makes the slope weak.
• Building and Mining – Digging into the sides of hills or using loud blasts shakes and weakens the ground structure

What are the impacts of Landslides?

• Human and Social Impacts
  • Loss of life and injuries from falling rocks and moving mud.
  • Displacement of local communities and families.
  • Psychological trauma and stress for survivors.
  • Disrupted access to schools, hospitals, and emergency services.
• Economic and Infrastructure Damage
  • Blocked roads and railways that halt trade and travel.
  • Destroyed utilities including power, gas, and water lines.
  • Costly repairs for damaged buildings and public works.
  • Loss of agricultural land and livestock for local farmers.
• Environmental Effects
  • Soil erosion and permanent land degradation.
  • Pollution of nearby streams and water bodies from heavy debris.
  • Destruction of vegetation and local wildlife habitats

What could be done to reduce the impacts of Landslides?

• Land Use and Planning – Avoid constructing homes near steep hillsides, mountain ridges, or natural drainage channels.
• Review historical hazard information and local guidelines before purchasing land or starting new developments.
• Limit residential and commercial construction in areas identified as highly susceptible to landslides.
• Drainage and Water Management – Install effective surface and underground drainage systems, such as channels, pipes, and French drains, to reduce water accumulation in the soil.
• Ensure that roof gutters and runoff are directed away from unstable slopes.
• Regularly inspect and clear storm drains and weep holes to prevent water blockages.
• Vegetation and Bioengineering – Restore vegetation on bare or damaged slopes by planting native trees, shrubs, and deep-rooted grasses.
• Preserve existing tree roots, stumps, and ground cover, as they help stabilize the soil naturally.
• Use bioengineering methods, such as live crib walls and brush layering, to combine vegetation with structural support.
• Engineering and Structural Measures – Construct retaining or deflection walls to stabilize unstable slopes and prevent soil movement.
• Reshape steep slopes into stepped terraces to reduce their incline and improve stability.
• Strengthen loose soil and rock using geotechnical reinforcement techniques, including soil nails, rock bolts, geogrids, or grouting.

Reference

The Hindu| Landslides in Kerala