landslides, disaster, landslide hazard zones in India, landslide mitigation, landslide classification

1. LANDSLIDE

2. 2
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Akhila S and Arunnya A R
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3. “The term landslide or, less
frequently, landslip, refers to
several forms of mass
wasting that include a wide
range of ground movements,
such as rock falls, deep-
seated slope failures,
mudflows and debris flows. 3

4. Causing
Tsunamis
▫ Landslides that occur undersea, or have
impact into water e.g. significant rockfall or
volcanic collapse into the sea, can
generate tsunamis.
▫ Massive landslides can also
generate megatsunamis, which are usually
hundreds of meters high.
▫ In 1958, one such tsunami occurred in Lituya
Bay in Alaska. 4

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6. CAUSES
Occur when the slope (or a portion
of it) undergoes some processes
that change its condition from
stable to unstable

7. Natural causes
A change in the stability of a slope can be caused by a
number of factors, acting together or alone.
Landslides are
aggravated by
human
activities
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Natural causes of landslides include:
▫ Saturation by rain water infiltration, snow melting, or glaciers melting;
▫ Rising of groundwater or increase of pore water pressure (e.G. Due to aquifer
recharge in rainy seasons, or by rain water infiltration)
▫ Increase of hydrostatic pressure in cracks and fractures;
▫ Loss or absence of vertical vegetative structure, soil nutrients, and soil structure (e.G.
After a wildfire – a fire in forests lasting for 3–4 days);
▫ Erosion of the toe of a slope by rivers or ocean waves;
▫ Physical and chemical weathering (e.G. By repeated freezing and thawing, heating
and cooling, salt leaking in the groundwater or mineral dissolution);
▫ Ground shaking caused by earthquakes, which can destabilize the slope directly (e.G.
By inducing soil liquefaction), or weaken the material and cause cracks that will
eventually produce a landslide;
▫ Volcanic eruptions;

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Landslides are aggravated by human
activities, such as:
▫ Deforestation, cultivation and construction;
▫ Vibrations from machinery or traffic;
▫ Blasting and mining;
▫ Earthwork (e.g. By altering the shape of a slope, or imposing new loads);
▫ In shallow soils, the removal of deep-rooted vegetation that binds colluvium to
bedrock;
▫ Agricultural or forestry activities (logging), and urbanization, which change the
amount of water infiltrating the soil.

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Morphology
of
landslides

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Morphology Of Landslides
MINOR SCARP
▫ Is a steep surface on undisturbed ground around the periphery of the landslide &
caused by movement of slide material away from undisturbed ground.
CROWN
▫ Highest point on main scarp
MINOR SCARP
▫ Steep surface on undisturbed material produced by movements with in the sliding
mass.
HEAD
▫ Upper portion of the slide material in contact with main scarp
TOE
▫ Line of intersection between lowest part of surface of rupture & original ground
surface .
FOOT
▫ Portion of land slide that has moved beyond toe & lies over the original ground
surface,

12. Classification
12
In the following
table shows a
schematic
landslide
classification
adopting the
classification of
Varnes 1978 and
taking into
account the
modifications
made by Cruden
and Varnes, in
1996. Some
integration has
been made by
using the
definitions of
Hutchinson (1988)
and Hungr et al.
2001.

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14. Place your screenshot here
14
FALLS
A fall starts with the
detachment of soil or rock
from a steep slope along a
surface on which little or no
shear displacement takes
place. The material then
descends mainly through the
air by falling, bouncing, or
rolling

15. Place your screenshot here
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TOPPLES
Toppling is the forward
rotation out of the slope of a
mass of soil or rock about a
point or axis below the
centre of gravity of the
displaced mass. Toppling is
sometimes driven by
gravity exerted by material
upslope of the displaced
mass and sometimes by
water or ice in cracks in the
mass

16. Place your screenshot here
16
SLIDE
A slide is a downslope
movement of soil or rock
mass occurring dominantly
on the surface of rupture or
on relatively thin zones of
intense shear strain

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SPREADS
Spread is defined as an
extension of a cohesive soil
or rock mass combined
with a general subsidence
of the fractured mass of
cohesive material into
softer underlying material

18. Place your screenshot here
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FLOWS
A flow is a spatially continuous
movement in which surfaces of
shear are short-lived, closely
spaced, and usually not
preserved. The distribution of
velocities in the displacing mass
resembles that in a viscous
liquid. The lower boundary of
displaced mass may be a surface
along which appreciable
differential movement has taken
place or a thick zone of
distributed shear .

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Landslide
mitigation
In order to prevent & mitigate the landslide
risk,national initiatives are required or strengthen &
the following aspects may have to be addressed.
1. LANDSLIDE HAZARD ZONATION.
2. MAPPING & MONITORING OF ACTIVE LAND
SLIDES & VULNERABLE SLOPES.

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Landslide Hazard
Zonation
▫ In case of india, it may be starting from state level(which are prone to
landslides) on a regional scale to site-specific scale will serve purpose.
▫ Recent advances in data acquisition techniques based on remote sensing
as well as ground based instruments provide sample data that can be
processed, modelled and analysed using statistical as well as deterministic
modelling techniques in GIS and prepare the quantitative landslide hazard
zonation maps.

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Landslide Prediction Mapping
▫ Landslide hazard analysis and mapping can provide useful information for catastrophic loss
reduction, and assist in the development of guidelines for sustainable land-use planning.
▫ The analysis is used to identify the factors that are related to landslides, estimate the relative
contribution of factors causing slope failures, establish a relation between the factors and
landslides, and to predict the landslide hazard in the future based on such a relationship.
▫ The factors that have been used for landslide hazard analysis can usually be grouped into
geomorphology, geology, land use/land cover, and hydrogeology.
▫ Since many factors are considered for landslide hazard mapping, GIS is an appropriate tool
because it has functions of collection, storage, manipulation, display, and analysis of large
amounts of spatially referenced data which can be handled fast and effectively.
▫ Remote sensing techniques are also highly employed for landslide hazard assessment and
analysis.
▫ Using satellite imagery in combination with GIS and on-the-ground studies, it is possible to
generate maps of likely occurrences of future landslides
▫ Early predictions and warnings are essential for the reduction of property damage and loss of life.

22. Early warning systems
▫ Landslides are generally localised
incidents except during a major
event triggering landslides
▫ The local NGO’s in hilly terrains
of Nepal and India involve the
community for monitoring(so
that evacuation is possible)
▫ Warning people not to construct
permanent structures in these
hazard prone areas
Preparedness
Awareness generation
▫ Especially in hazard prone areas to
apprise local population and all stake
holders about the landslide risk in the
region, possible cause and preventive
measures
▫ From school to college levels(media,
campaigns, seminars, meetings,
workshops)
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Thanks!
Any questions?
Reference:
▫ Disaster management, engineering
and environmental aspects – H.
Sarvothaman, K.J. Anandha Kumar
▫ Wikipedia – landslides, landslide
mitigation, Landslide classification

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Credits
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