Landslides
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. 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. The formation of river blocks can cause havoc to the settlements downstream on it's bursting. 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.
The two regions most vulnerable to landslides are the Himalayas and the Western Ghats. 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. Compared to Western Ghats region, the slides in the Himalayas region are huge and massive and in most cases the overburden along with the underlying lithology is displaced during sliding particularly due to the seismic factor.
Incidences of landslides in India
Himalayas - High to very high
North-eastern Hills - High
Western Ghats and the Nilgiris - Moderate to high
Vindhayachal - Low
Landslides Zonation Mapping is a modern method to identify landslides prone areas and has been in use in India since 1980s
The major parameters that call for evaluation are as follows:
-Slope-Magnitude, length and Direction
-Soil thickness
-Relative relief
-Land use
-Drainage-pattern and density
-Landslide affected population
Causes of Landslides
Landslides can be caused by
1. Poor ground conditions
2. Geomorphic phenomena
3. Natural physical forces
4. Quite often due to heavy spells of rainfall coupled with impeded drainage.
Ground causes of landslides:
1.Weak, sensitivity, or weathered materials
2.Adverse ground structure (joints, fissures etc.)
3.Physical property variation (permeability, plasticity etc)
Morphological Causes
-Ground uplift (volcanic, tectonic etc)
-Erosion (wind, water)
-Scour
-Deposition loading in the slope crest.
-Vegetation removal (by forest fire, drought etc)
Physical Causes
-Prolonged precipitation
-Rapid draw-down
-Earthquake
-Volcanic eruption
-Thawing
-Shrink and swell
-Artesian pressure
Man- made Causes
-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
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. 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. The formation of river blocks can cause havoc to the settlements downstream on it's bursting. 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.
The two regions most vulnerable to landslides are the Himalayas and the Western Ghats. 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. Compared to Western Ghats region, the slides in the Himalayas region are huge and massive and in most cases the overburden along with the underlying lithology is displaced during sliding particularly due to the seismic factor.
Incidences of landslides in India
Himalayas - High to very high
North-eastern Hills - High
Western Ghats and the Nilgiris - Moderate to high
Vindhayachal - Low
Landslides Zonation Mapping is a modern method to identify landslides prone areas and has been in use in India since 1980s
The major parameters that call for evaluation are as follows:
-Slope-Magnitude, length and Direction
-Soil thickness
-Relative relief
-Land use
-Drainage-pattern and density
-Landslide affected population
Causes of Landslides
Landslides can be caused by
1. Poor ground conditions
2. Geomorphic phenomena
3. Natural physical forces
4. Quite often due to heavy spells of rainfall coupled with impeded drainage.
Ground causes of landslides:
1.Weak, sensitivity, or weathered materials
2.Adverse ground structure (joints, fissures etc.)
3.Physical property variation (permeability, plasticity etc)
Morphological Causes
-Ground uplift (volcanic, tectonic etc)
-Erosion (wind, water)
-Scour
-Deposition loading in the slope crest.
-Vegetation removal (by forest fire, drought etc)
Physical Causes
-Prolonged precipitation
-Rapid draw-down
-Earthquake
-Volcanic eruption
-Thawing
-Shrink and swell
-Artesian pressure
Man- made Causes
-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
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