Landslides occur when masses of rock, earth, or debris move down a slope. They are caused by geological, physical, morphological, and anthropogenic factors that contribute to slope instability. Common types of landslides include debris flows, earth flows, debris avalanches, falls, and slumps. Landslides can be triggered by heavy rainfall, earthquakes, erosion, deforestation, and more. They often damage property and infrastructure and can threaten human life. Mitigation approaches include restricting development in high-risk areas, engineering structures to stabilize slopes, monitoring systems, and managing drainage.

1. Land Slides
18EEACZ02, Disaster Management
Prepared by
Selvi Vignia R,71772271213,
M.E Environmental Engineering,
I Yr., GCT.

2. Landslides
• A landslide is the movement of a mass of rock, debris or earth
down a slope (Cruden, 1991). More specifically, it is a catastrophic
event where a block of earthen mass slides downhill which includes a
wide range of ground movement, such as
rockfalls,
deep failure of slopes and
shallow debris flows,
which can occur in offshore, coastal and
onshore environments.

3. Causes of landslides
• are usually related to instabilities in slopes.
• It is usually possible to identify one or more landslide causes and one
landslide trigger.
Causes
Geologic
al
Physical Morphological
Anthropogenic

4. Geological causes
• Weathered materials
• Jointed or fissured materials
• Adversely orientated
discontinuities
• Material contrasts
• Rainfall and snow fall
• Earthquakes
• Working of machinery
Physical causes
• Intense rainfall
• Rapid snow melt
• Rapid drawdown
• Freeze-thaw
• Ground water changes
• Soil pore water pressure
• Surface runoff

5. Morphological causes
• Slope angle
• Uplift
• Rebound
• Wave erosion
• Glacial erosion
• Erosion of lateral margins
• Slope loading
Anthropogenic causes
• Loading &Drawdown
• Land use change
• Water management
• Mining
• Vibration
• Water leakage
• Deforestation

6. Well known is Sharpe's classification (1938), made on type of movement
and transporting agent.
According to Hansen (1984):
➢ Rate of movement: This ranges from very slow creep (millimeters/year)
to extremely rapid (meters/second).
➢ Type of material: Landslides are composed of bedrock, unconsolidated
sediment and/or organic debris.
It can be mudslides, debris flows, rock falls, debris avalanches, debris slides,
and earth flows.
➢ Nature of movement: The moving debris can slide, slump, flow or fall.

8. Debris flow: Slope material that becomes saturated with water may
develop into a debris flow or mud flow. The resulting slurry of rock
and mud may pick up trees, houses and cars, thus blocking bridges
and tributaries causing flooding along its path. Debris flow is often
mistaken for flash flood, but they are entirely different processes.
Earth Flow: Earthflows are downslope, viscous flows of saturated,
fine-grained materials, which move at any speed from slow to fast.
Typically, they can move at speeds from 0.17 to 20 km/h. Though
these are a lot like mudflows, overall they are slower moving and are
covered with solid material carried along by flow from within. The
velocity of the earthflow is all dependent on how much water content
is in the flow itself: if there is more water content in the flow, the
higher the velocity will be.

9. Debris Avalanche: A debris avalanche is a type of slide characterized by
the chaotic movement of rocks soil and debris mixed with water or ice
(or both). They are usually triggered by the saturation of thickly
vegetated slopes which results in an incoherent mixture of broken
timber, smaller vegetation and other debris. Debris avalanches differ
from debris slides because their movement is much more rapid.
This is usually a result of lower cohesion or higher water content and
commonly steeper slopes.
Falls: Falls are movements in which masses of rock or other material fall
freely from cliff or steep slope through the air, and may bounce and roll.
Earthquakes commonly trigger this final type of movement.

10. • Debris torrent: is a rapidly moving slurry of soil, alluvium and large organic
debris that occur in response to intense storms and are commonly triggered
by debris avalanches entering a channel from adjacent hill slopes.
As the debris avalanche moves down the channel, it becomes a debris
torrent as it scours the stream bank and bed.
Creep: This is the gradual movement of slope materials down the
slope.
Rockslides: most common on steep slopes (roadcuts, valleys) velocities
of 100+ miles per hour
Topple: Topple is the end-over-end motion of rock down a slope. In
this, mass rotates forward about some pivot point. If a toppling mass
pivots far enough, a fall may result

12. • Slumps: sliding of material along curved surface common in
unconsolidated sediments, weaker rock units.
➢ Deep-Seated Landslide: Landslides in which the sliding surface is
mostly deeply located below the maximum rooting depth of trees
(typically to depths greater than ten meters). These typically move
slowly, only several meters per year, but occasionally move faster.
➢ Shallow Landslide: Landslide in which the sliding surface is located
within the soil mantle or weathered bedrock (typically to a depth from
few decimetres to some metres). They usually include debris slides,
debris flow, and failures of road cut-slopes. Landslides occurring as
single large blocks of rock moving slowly down slope are sometimes
called block glides

19. Short term effect
•Property Damage.
•Human loss,
•Affects all resources,
such as power supply,
water supply, hospital,
school , and many other
things
Long term effect
•Loss of property value
•disruption of
transportation route
•Loss of forest
•Water availability, and
quality also affected

20. Minimizing the effects of Landslides:
• By geological mapping, detecting slope hazards and determining the
likelihood of landslide occurrence, geoscientists can assist engineers,
developers, planners and building inspectors in avoiding high-risk
areas.
• Structures such as homes, schools, hospitals, power-lines, fire
stations and roads can be safely located away from potential
landslide risk areas.
• Mapping of landslide vulnerability that can help with the
development of emergency response scenarios.
• Engineering and geotechnical investigation that define the landslide
hazard and risk at site specific levels of investigation.

21. Covering the landslide with an impermeable
membrane
Directing surface water away from the landslide
Draining ground water away from the landslide
Minimizing surface irrigation.
Slope stability is also increased when a retaining structure and/or the weight of a soil/rock are
placed at the toe of the landslide or when mass is removed from the top of the slope
STABILITY OF LANDSLIDE

22. Approaches for mitigation:
Restricting development in
Landslide prone area
Codes for excavation,
construction
Protecting existing developments
Monitoring and warning
system
Landslide insurance and
compensation for losses

23. MITIGATION MEASURES-
Prepare a landslide inventory
map of the area which help to
develop emergency scenario
Implementation of regional
hazard and risk assessment
into land planning policies.
Engineering and Geotechnical
investigations that define the
landslide hazard and risk at sites
specific levels.
Proper Drainage &
Drainage correction

24. Additional advancement to prevent landslides
Application of following materials in landslide prone areas
• Retaining walls
• Steel nets Or Wire mesh
• Soil nails
• Geosynthetic materials

25. Our roles to prevent landslides:-
Learn more about
potential geologic
hazards in your area.
Consult an engineer or
geoscientist for
potentially hazardous
locations.
Avoid activities that result in the
undercutting of steep banks, and
avoid the construction of buildings
near the top or base of steep
slopes.
Do not undercut steep banks,
develop near the top or base of
steep slopes, or place fill on
steep slope, without expert
geotechnical advice.
Do not stand or seek
cover below or near
coastal cliffs or
overhangs.
Do not dig into sand
cliffs or dig deep hole in
sand that may bury you
if a cave-in happens

26. THINGS TO DO IF A HOME IS SUSPECTED AS BEING AT RISK FOR
LANDSLIDE DANGER:
Develop an emergency communication plan in case family member get
Make evacuation plans
Learn to recognize the landslide warning signs
In mudflow areas, build channels or deflection walls to direct the flow
around buildings.
Plant ground cover on slope and build retaining walls.
Minimize home hazards
Get a ground assessment of your property.

27. ACTION TO BE CONSIDERED AFTER A LANDSLIDE:
Avoid the landslide
area as much as
possible. There may be
a danger of additional
slides
Check for injured or
trapped persons near
the slide area.
Survival is more likely
to occur near the slide
periphery.
Provide first aid to
injured persons and
activate emergency
medical services if
necessary.
Report the event to
your local fire, police,
or public works
department.
Inform and assist affected
neighbors, especially those
who may require special
assistance such as infants,
the elderly, or person with
disabilities.
Listen to a radio or
television for the latest
emergency
information.
Watch for flooding,
which may occur after
a landslide or debris
flow.
Support the local
government

28. Landslide and India
• Out of a total 3,782 landslides between 2015 and 2022 in India ,the
highest 2239 were reported in Kerala
Tamil Nadu- 196
Karnataka -194
Jammu & Kashmir- 184
West Bengal -376

29. Major Landslides in India
1. Guwahati landslide Assam. Sep 18, 1948 – heavy rains.
2. Darjeeling Landslide, West Bengal .- Oct 4 1968- landslide triggered
by flood, a 60km highway was cut into 91 parts.
3. Malpa landslide Uttarakhand – August 11,1998 –Consecutive
Landslide –over 380 people died and worst landslide in india.
4. Mumbai Landslide Maharashtra, July 2000- Heavy rains followed by
Lan erosion -67 people died .
5. Amboori Landslide Kerala –Nov 9,2001, - heavy rains-40 people
died
6. Kedarnath Landslide Uttarakhand-June 162013-Floods-5700 Dead

31. References:
● Landslide (Mudslide) Safety. Washington D.C.: Centres for Disease
Control and Prevention, 2003.
● Matthews, William H. “Landslides.” Encyclopedia Americana. Deluxe
Library ed. 1990.
● Spilsby, Louise & Richard. Landslides and Avalanches in Action. New
York, NY: Rosen Central,
2009.
● http://www.ussartf.org/landslides.htm
● http://landslides.usgs.gov/research/other/centralamerica.ph