Landslides
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Landslides
Subject – Disaster Management
Context – Frequent landslides in the Himalayas
Concept –
- Reckless construction of hydropower projects has made earthquake-prone Himachal Pradesh more vulnerable to landslides.
What is Landslide?
- A landslide is defined as the movement of a mass of rock, debris, or earth, down a slope due to the action of gravity.
- Areas with steep slopes, for example, mountainous regions, are particularly susceptible to landslide hazards.
- Earth flow, mass movement, mudflow, rotational slip, and avalanches are all examples of landslides.
Landslide Causes
- Geological causes
- Weak or sensitive materials
- Weathered materials
- Sheared, jointed, or fissured materials
- Adversely oriented discontinuity (bedding, schistosity, fault, unconformity, contact, and so forth)
- Contrast in permeability and/or stiffness of materials
- Morphological causes
- Tectonic or volcanic uplift
- Glacial rebound
- Fluvial, wave, or glacial erosion of slope toe or lateral margins
- Subterranean erosion (solution, piping)
- Deposition loading slope or its crest
- Vegetation removal (by fire, drought)
- Thawing
- Freeze-and-thaw weathering
- Shrink-and-swell weathering
- Human causes
- Excavation of slope or its toe
- Loading of slope or its crest
- Drawdown (of reservoirs)
- Deforestation
- Irrigation
- Mining
- Artificial vibration
- Water leakage from utilities
Types of Landslides
- Falls: It happens due to the abrupt movements of the mass of geologic materials, such as rocks and boulders, that become detached from steep slopes or cliffs.
- Topples: It happens due to the forward rotation of a unit or units about some pivotal point, under the actions of gravity and forces exerted by adjacent units or by fluids in cracks.
- Slides: In this type, rocks, debris, or soil slide through slope forming material.
- Spread: It usually occurs on very gentle slopes or flat terrain.
Landslides and India
- Landslides and avalanches are among the major hydro-geological hazards that affect large parts of India.
- Around 15% of the country’s region is prone to landslides. The Himalayas of Northwest and Northeast India and the Western Ghats are two regions of high vulnerability.
- Some major recent incidents are Kerala (2018), Himachal Pradesh (2018), Uttarakhand (2018), Tamenglong-Manipur (2018), and Kalikhola, Manipur (June 2017).
