Landslides in Wayanad villages
Context:
At least 122 persons were killed and 197 injured after multiple landslides flattened three villages in Vythiri taluk of Wayanad district, Kerala.
Relevance:
GS-03 (Disaster management)
Key highlights:
- Rescue and Relief Efforts:
- An intense rescue effort involving State and Central forces is underway in Mundakkai, Chooralmala, and Attamala localities.
- Prime Minister Narendra Modi announced an ex gratia payment of ₹2 lakh for the next of kin of the deceased and ₹50,000 for the injured.
- Origin and Impact of Landslides:
- The landslides originated from a waterlogged hillock 6 km from the affected villages.
- The first landslide occurred at 2 a.m. and the second at 4:10 a.m., causing massive destruction and altering the course of the Iruvanipuzha river.
- Evacuation and Survivors:
- Hundreds of landslide survivors are sheltered in nearby hill resorts and schools, awaiting evacuation to safer ground.
- Revenue officials had evacuated several settlements around the hill, including a tribal settlement at Chembra, reducing the scale of the disaster.
- State Response and Future Risks:
- The Kerala government declared a state of mourning on Tuesday and Wednesday.
- The state’s official machinery is on active footing, bracing for heavy rain in eight districts in the next 24 hours.
What is a Landslide?
A landslide is the downward movement of rock, soil, and debris on a slope, ranging from small shifts to massive, destructive events. They can occur on natural and man-made slopes and are triggered by factors like heavy rainfall, earthquakes, volcanic activity, construction, mining, and changes in groundwater levels.
Landslides are classified into several types based on their movement:
- Slides: Movements along a rupture surface, which can be:
- Rotational Slides: Curved rupture surface.
- Translational Slides: Planar rupture surface.
- Flows: Movements involving water, making the mass flow like a fluid, including:
- Earth flows
- Debris flows
- Mudflows
- Creep
- Spreads: Lateral extension and cracking of soil or rock, usually due to liquefaction or plastic deformation.
- Topples: Forward rotation and free-fall of material from a vertical or near-vertical slope.
- Falls: Detachment from a steep slope or cliff, descending by free-fall, bouncing, or rolling.
What causes landslides?
Landslides can be caused by a variety of factors, often involving a combination of natural processes and human activities. Here are some common reasons for landslides:
- Heavy Rainfall:
- Intense and prolonged rainfall saturates the soil, increasing its weight and reducing its cohesion, leading to slope failure.
- Geological Factors:
- The presence of weak or fractured rock layers, loose soil, and clay-rich materials can make slopes more prone to landslides.
- Topography:
- Steep slopes and hilly terrains are more susceptible to landslides due to the gravitational pull on the soil and rocks.
- Deforestation:
- The removal of vegetation reduces the stability of slopes as roots that bind the soil are removed, making the area more prone to erosion and landslides.
- Earthquakes:
- Seismic activity can trigger landslides by shaking loose materials on slopes, especially in already unstable areas.
- Construction and Human Activities:
- Construction activities, mining, and road building can destabilize slopes by altering the natural state of the terrain and drainage patterns.
- Water Management Issues:
- Poor drainage systems, leakage from reservoirs, and improper management of water resources can lead to increased water pressure in soil, contributing to landslides.
- Weathering and Erosion:
- Natural weathering processes and erosion can weaken rock and soil structures over time, making them more vulnerable to landslides.
- In the case of the landslides in Wayanad, Kerala, it is likely that heavy rainfall, topographical conditions, and possibly deforestation or other human activities contributed to the disaster. The specific factors would require a detailed investigation by geological and environmental experts.
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