Landslides: Types, Causes,Consequences, Prone Areas,Mitigation Strategies & More

Landslides, a geological phenomenon with the potential to cause widespread
devastation, are one of the most prominent disasters of concern for India. As
societies expand into hilly and mountainous regions, the understanding of
landslides becomes crucial for sustainable development and disaster preparedness.
This article of digitalshikshaa aims to explain various aspects of Landslides,
including their types, causes, consequences, and mitigation strategies.

1. What is Landslide?
2. Characteristics of Landslide Prone Areas
3. Causes of Landslides
a. Natural Causes
b. Anthropogenic Causes
4. Types of Landslides
5. Impacts of Landslides
6. Landslide Prone Areas in India
7. Measures Taken in India
8. Suggested Measures

What is Landslide?

Landslides are a geological phenomenon that involves the sudden and rapid
movement of a mass of rock, soil, or debris down a slope under the influence of
gravity

Characteristics of Landslide Prone Areas

Landslides, usually, occur in areas having one or more of the following
characteristics:
• Steep terrain such as hilly or mountainous areas.
• Presence of joints and fissures.
• Presence of loosely-packed or weathered material
• Any area that has been burned by wildfires
• Any area that has been modified due to human activities, such as
deforestation or construction
• Channels along a river-stream
• Any area where surface runoff is directed or land is heavily saturated
with water.

Causes of Landslides

A variety of causes act as a trigger for a landslide. Some of the major causes of
landslide can be seen under the following two heads:

Natural Causes
A myriad number of natural processes can trigger a landslide. Some
prominent of them are:
• Heavy Rainfall – Heavy rainfall is one of the most common triggers of
landslides. It increases pore water pressure as well as the weight of soil
by making it saturated.
• Erosion – Clay and vegetation present within the soil or rock act as
cohesive elements and help bind particles together. By removing these
cohesive elements, erosion makes an area more prone to landslides.
• Earthquakes – intense ground shaking due to earthquakes causes
instability in rocks and soils, thus triggering landslides.
• Volcanic Eruptions – Ash and debris deposited by volcanic eruptions
overload slopes while the accompanied seismic activity causes
instability. All these, together, trigger landslides.

Anthropogenic Causes

Several human activities can directly or indirectly influence the occurrence
and magnitude of landslides. Some prominent such activities include:

• Deforestation – By holding soils as well as obstructing the flow of
falling debris, vegetation cover plays an important role in preventing
landslides in any area. Deforestation takes away this preventive cover
and increases vulnerability to landslides.
• Encroachment in Vulnerable Terrains – Of late, humans have been
encroaching in landslide-prone areas such as hilly terrains. This has led
to increased construction activities in these areas and increased
chances of landslides.
• Uncontrolled Excavation – Unauthorized or poorly planned
excavation activities, such as mining, quarrying, etc destabilize slopes
and increase the chances of landslides.
• Climate Change – Climate change caused by various anthropogenic
activities has led to abrupt alterations in precipitation patterns and
increased frequency of extreme weather events. All these, in turn, have
increased the frequency as well as the severity of landslides.

Types of Landslides

Based on the type of movement involved, there are mainly 4 types of
landslides:
• Falls – They refer to the type of landslide that involves the collapse of
material from a cliff or steep slope, which then falls down the slope and
collects near the base.
• Topples – Under this type of landslide, the falling mass undergoes
forward rotation and movement around an axis or point at or near the
base.
• Slides – Under this type of landslide, there is a distinct zone of
weakness that separates the moving material from a more stable
underlying material.

There are two major types of slides:

1. Rotational Slide – In this type of slide, the surface of rupture is curved
concavely upward and the slide movement of the falling mass is
rotational about an axis that is parallel to the ground surface and
transverse across the slide.
2. Translational Slide – In this type of slide, the landslide mass moves
along a roughly planar surface with little rotation or backward tilting.
• Flows – This type of landslide involves the movement of material
down a slope in the form of a fluid.

There are different types of flows:

1. Mud Flow – It involves the movement of wet material of which a
majority portion is comprised of sand, silt, and clay-sized particles.
2. Debris Flow – Masses such as loose soils, rocks, and organic matter
combine with water to form a slurry. It, then, flows down a slope.
3. Rock Flow or Rock Avalanches – a specific type of landslide or mass
movement involving the flow of rock material downslope.

Impacts of Landslides

Some of the key impacts of landslides can be seen as follows:
• Loss of human and animal lives.
• Damage to infrastructure and properties such as homes, roads, etc.
• They can bury or wash away agricultural land, thus affecting
agriculture.
• The aftermath of landslides may mean the displacement of local
communities.
• Landslides, often, block transportation routes such as roads. This, then,
has its own repercussions.
• The movement of huge mass during landslides can alter the natural
landscape of a region. This, in turn, affects the ecosystem, water
courses, etc.

Landslide Prone Areas in India

ISRO has recently released the Landslide Atlas of India. As per this atlas, some
of the prominent statistics regarding landslides in India are as follows:

• India is among the top five landslide-prone countries in the world.
• Excluding snow-covered areas, around 12.6 percent of India’s
geographical land area is prone to landslides.
• A rough break-up of reported landslides in India is as follows:
o About 66.5 percent from the North-Western Himalayas
o About 18.8 percent from the North-Eastern Himalayas
o About 14.7 percent from the Western Ghats.
As per the Landslide Atlas of India, major landslide prone areas in India are as
follows:
• The Northeastern Region (comprises about 50 percent of the total
landslide prone areas in India)
• Areas of Uttarakhand, Himachal Pradesh, and Jammu &
Kashmir lying along the Himalayas.
• Areas of Maharashtra, Goa, Karnataka, Kerala, and Tamil Nadu lying
along the Western Ghats.
• The Araku region in Andhra Pradesh along the Eastern Ghats.

Measures Taken in India

Some of the prominent measures taken for proper management of landslides in
India are as follows:
• The Disaster Management Act, of 2005 provides a comprehensive
legal and institutional framework for the management of various
disasters including landslides.
• The National Landslide Risk Management Strategy (2019) covers all
aspects of landslide disaster risk reduction and management, such as
hazard mapping, monitoring, and early warning systems.
• The National Disaster Management Authority (NDMA) has
issued Guidelines on Landslide Hazard Management (2009) that
outline the steps that should be taken to reduce the risk of landslides.
• The National Institute of Disaster Management (NIDM) has been
providing capacity building and other support to various national and
state-level disaster management authorities.
• Efforts have been made towards better prediction of weather. E.g.
Ensemble Prediction System. This will help predict disasters like
landslides.

Suggested Measures
• Promotion of terrace farming can help reduce landslide risks.
• Afforestation and construction of bunds to reduce the flow of falling
materials.
• Retaining walls can be built on mountain slopes to stop the falling
materials coming down.
• As suggested by the 10th FYP, mitigation measures should be built into
the development process itself.
• A more granular Hazard Mapping to have accurate knowledge of prone
areas.
• Traditional knowledge of the local community should be used to tackle
such kinds of disasters.
• Education and training can help ensure the preparedness of the disaster
management authorities as well as the local community.
Landslides as one of the prominent disasters concerning India have far-reaching
consequences. As societies continue to expand into vulnerable regions, a
proactive approach to landslide prevention and mitigation becomes imperative.
The measures suggested as above can help in this direction