Frequent occurrence of landslides in the Himalayas than in Western Ghats

Q. What are landslides? Why do they occur?
Answer:

  1. Landslides are simply defined as the mass movement of rock, debris or earth down a slope and have come to include a broad range of motions whereby falling, sliding and flowing under the influence of gravity dislodges earth material.
  2. They often take place in conjunction with earthquakes, floods and volcanoes. At times, prolonged rainfall causing heavy block the flow or river for quite some time.
  3. The formation of river blocks can cause havoc to the settlements downstream on its bursting.
  4. In the hilly terrain of India including the Himalayas, landslides have been a major and widely spread natural disaster the often strike life and property and occupy a position of major concern.

Q. Why there are more landslides in the Himalayas than in the Western Ghats?
Answer: Reasons can be divided as

A) Man-Made: –
• Excavation (particularly at the toe of slope)
• Loading of slope crest
• Draw -down (of reservoir)
• Deforestation
• Irrigation
• Mining
• Artificial vibrations
• Water impoundment and leakage from utilities
• Unplanned growth of houses in the hill areas. e.g. heavy load of residential and hotel structures in Nainital, Uttarakhand, this activity is less in Western Ghats.
• Population Density and Human activity is more.

B) Physical:-

  1.  The Himalayas mountain belt comprise of tectonically unstable younger geological formations subjected to severe seismic activity. The Western Ghats and nilgiris are geologically stable but have uplifted plateau margins influenced by neo- tectonic activity.
  2.  In winter there is high snow fall and this snow melts in summer hence large flow of debris.
  3.  Indian plate is moving northwards and subsiding under Eurasian plate, 5-10 cm a year, This leads to rising of Himalayas every year. Hence, it creates instability and it leads to more landslides.
  4. Great height, steep slopes, numerous streams and rivers hence it can carry high amount of debris which leads to more landslides in Himalayan region whereas in Western Ghats, Eroded and denuded, steep slope on western side, but gentle on eastern side. Western side, small swift flowing of stream.
  5. Eastern side – big rivers originated like, Godavari, Kaveri and Krishna in saline stage of erosion which cannot carry large amount of debris.

Q. Methods of protection – what can be done to avoid lanslides?

Answer: In general the chief mitigatory measures to be adopted for such areas are :
• Drainage correction,
• Proper land use measures – promotion of terrace farming.
• Reforestation for the areas occupied by degraded vegetation.
• Creation of awareness among local population.
• Control on new dam building.

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