Landslides refer to the downward sliding of large quantities of land mass along steep slopes. They occur when the internal resistance or holding capacity of rocks is reduced, making the slope unstable. Common causes are earthquakes, construction activities that remove part of a slope, heavy rain, and increased pore water pressure within the slope. Landslides can be debris slides of unconsolidated material or rock slides involving large rock blocks. Human activities like deforestation, cultivation, construction, blasting and earthworks can also trigger landslides by destabilizing slopes. Landslides impact topography, waterways, forests and wildlife habitats.

2. DEFINITION:
 Landslides refers to the downward sliding of
huge quantities of land mass which occur
along steep slopes of hills or mountains. It can
be sudden or slow.

3. CHARACTERISTI
CS
 Large block of soil moves down
during the landslide.
 The scar above a landslide is
easily visible.
 They can occur along a slope
where the internal resistance of
the rocks are reduced or they
loose their holding capacity.
 Common after earthquakes or
after removal of part of the
slope due to construction,
particularly for construction of
roads.

4.  During the movement, landslide can
result into the Debris slides which are
failure of unconsolidated material on
a surface;
 Rock slide or Rock Fall – where
movement of large rock block rolls.
 They are also common along the
steep banks of rivers, lakes etc.
 Pore Water Pressure is the key to
monitoring landslides. Shear strength
(a resisting force) decreases and the
weight (a driving force) increases.
Cont…

5. CAUS
ESNatural causes of landslides include:
 Groundwater (pore water) pressure acting to
destabilize the slope.
 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.
 weakening of a slope through saturation by snow
melt or heavy rains.
 earthquakes adding vibrational loads to slopes.
 earthquake-caused liquefaction destabilizing slopes.

6. Cont…
Landslides are aggravated by human activities, such
as:
 Deforestation, cultivation and construction, which
destabilize the already fragile slopes.
 vibrations from machinery or traffic.
 Blasting.
 earthwork which alters the shape of a slope, or
which imposes new loads on an existing slope.
 in shallow soils, the removal of deep-
rooted vegetation (that binds colluvium to bedrock).

7. Impacts of landslides
Landslides affect the following elements of the
environment:
 the topography of the earth’s surface.
 the character and quality of rivers, streams and
groundwater flow.
 the forests that cover much of the earth’s surface;
and
 the habitats of natural wildlife that exist on the
earth’s surface, including its rivers, lakes, and
oceans.

8. Commuting disturbance due to land slide between
villages/towns