Environmental Science
The Malin Landslide
Assignment No .: 2
Name :Jayesh Anil Shimpi 438
SCHOOL OF MECHANICAL ENGINEERING AND CIVIL ENGINEERING
What is a Landslide?
Landslides are among the many natural disasters causing massive destructions and
loss of lives across the globe. According to a survey study by the International
Landslide Centre at Durham University, UK, 2,620 fatal landslides occurred between
2004 and 2010. These landslides resulted in the death of over 32,322 people. The
figure does not include landslides caused by earthquakes. This research result is
astonishing considering the number of people killed by landslides. It is, thus,
paramount to know the causes and warning signs of a potential landslide to minimize
losses.
A landslide, sometimes known as landslip, slope failure or slump, is an uncontrollable
downhill flow of rock, earth, debris or the combination of the three. Landslides stem
from the failure of materials making up the hill slopes and are beefed up by the force
of gravity. When the ground becomes saturated, it can become unstable, losing its
equilibrium in the long run. That’s when a landslide breaks loose. When people are
living down these hills or mountains, it’s usually just a matter of time before disaster
happens.
Malin landslide
On 30 July 2014, a landslide occurred in the village of Malin in the Ambegaon taluka of the Pune
district in Maharashtra, India. The landslide, which hit early in the morning while residents were
asleep, was believed to have been caused by a burst of heavy rainfall, and killed at least 151
people. Rains continued after the landslide making rescue efforts difficult.
Local official Saurav Rao told the Press Trust of India that heavy machinery and
ambulances had been sent to the village.
"The exact number of casualties is not known as we are moving slowly to ensure that
those trapped are removed safely," Mr Rao said.
More than 500 people died and several thousand people were listed as missing after
floods and landslides hit the northern state of Uttarakhand in June last year.
CULPRITS OF LANDSLIDE:
Inevitably there is huge speculation in the Indian media about the causes and triggers of
the Malin landslide. Basedupon detailed study following are found to be the culprits of
Landslide. Malin is one of the 37 villages in Ambegaontaluk that was identified
ecologically sensitive area by the Kasturirangan committee in its report on Western
Ghats.
It was only in December 2013, that orders were issued to implement Union Environment
Ministry's notification that banned mining, quarrying, construction of thermal plants and
big building complexes in such areas. Recently Ambegaon had become realty hot spot.
Several real estate developers have been advertising these farm houses or boutique
residencies as "Lake Villa" or "Hill Villa". The taluka also has several tribal villages and
one of them is Malin. Based upon the study following are found to be culprits of the
landslide.
Very Heavy Rainfall:
The region was receiving particularly very heavy rainfall in the week between 25th to
31st July. The data suggests that as much as 600 mm of precipitation may have affected
this area prior to the landslide occurring. Cumulative rainfall in the last week of July as
recorded by NASA’s (The National Aeronautics and Space Administration of US)
TRMM (Tropical Rainfall Measuring Mission, was more than 600 mm. In fact on the
29th July, the region including Malin was shown purple in 24 hr rainfall map, which
signifies the highest range of rainfall, exceeding 175 mm.
Causes of Landslides:
While landslides are considered naturally occurring disasters, human-induced changes in
the environment have recently caused their upsurge. Although the causes of landslides are
wide ranging, they have 2 aspects in common; they are driven by forces of gravity and
result from failure of soil and rock materials that constitute the hill slope:
Natural Causes of Landslides
1. Climate : Long-term climatic changes can significantly impact soil
stability. A general reduction inprecipitation leads to lowering of water
table and reduction in overall weight of soil mass, reduced solution of
materials and less powerful freeze-thaw activity. A significant upsurge in
precipitation or ground saturation would dramatically increase the level of
ground water. When sloped areas are completely saturated with water,
landslides can occur. If there is absence of mechanical root support, the
soils start to run off.
2. Earthquakes : Seismic activities have, for a long time, contributed to
landslides across the globe. Any moment tectonic plates move, the soil
covering them also moves along. Whenearthquakes strike areas with steep
slopes, on numerous occasion, the soil slips leading to landslides. In
addition, ashen debris flows instigated by earthquakes could also cause
mass soil movement.
3. Weathering : Weathering is the natural procedure of rock deterioration
that leads to weak, landslide-susceptive materials. Weathering is brought
about by the chemical action of water, air, plants and bacteria. When the
rocks are weak enough, they slip away causing landslides.
4. Erosion : Erosion caused by sporadic running water such as streams,
rivers, wind, currents, ice and waves wipes out latent and lateral slope
support enabling landslides to occur easily.
5. Volcanoes : Volcanic eruptions can trigger landslides. If an eruption
occurs in a wet condition, the soil will start to move downhill instigating a
landslide. Stratovolcano is a typical example of volcano responsible for
most landslides across the globe.
6. Forest fires : Forest fires instigate soil erosion and bring about floods,
which might lead to landslides
7. Gravity : Steeper slopes coupled with gravitational force can trigger a
massive landslide.
Human causes of landslides
1. Mining : Mining activities that utilize blasting techniques contribute
mightily to landslides.Vibrations emanating from the blasts can weaken
soils in other areas susceptible to landslides. The weakening of soil means
a landslide can occur anytime.
2. Clear cutting : Clear cutting is a technique of timber harvesting that
eliminates all old trees from the area. This technique is dangerous since it
decimates the existing mechanical root structure of the area.
Morphological causes:
Slope angle
Uplift
Rebound
Fluvial erosion
Wave erosion
Glacial erosion
Erosion of lateral margins
Subterranean erosion
Slope loading
Vegetation change
Erosion
Physical causes:
Topography
Slope Aspect and Gradient
Geological Factors
Discontinuity Factors (Dip Spacing, Asparity, Dip and length)
Physical Characteristics of the Rock (Rock Strength etc.)
Tectonic Activity
Seismic activity (Earthquakes)
Volcanic eruption
Physical Weathering
Thawing
Freeze-thaw
Soil erosion
Hydrogeological Factors
Intense rainfall
Rapid snow melt
Prolonged precipitation
Ground water changes (Rapid drawdown)
Soil pore water pressure
Surface runoff
Human causes:
Deforestation
Excavation
Loading
Water management (Groundwater Draw-down and Water leakage)
Land use (e.g. construction of roads, houses etc.)
Mining and Quarrying
Vibration
Effects of Landslides:
1)Lead to economic decline : Landslides have been verified to result in destruction
of property. If the landslide is significant, it could drain the economy of the region
or country. After a landslide, the area affected normally undergoes
rehabilitation. This rehabilitation involves massive capital outlay.
2)Decimation of infrastructure : The force flow of mud, debris, and rocks as a
result of a landslide can cause serious damage to property. Infrastructure such as
roads, railways, leisure destinations, buildings and communication systems can be
decimated by a single landslide.
3)Loss of life : Communities living at the foot of hills and mountains are at a greater
risk of death by landslides. A substantial landslide carries along huge rocks, heavy
debris and heavy soil with it. This kind of landslide has the capacity to kills lots of
people on impact. For instance, Landslides in the UK that happened a few years ago
caused rotation of debris that destroyed a school and killed over 144 people including
116 school children aged between 7 and 10 years. In a separate event, NBC News
reported a death toll of 21 people in the March 22, 2014, landslide in Oso,
Washington.
4. Affects beauty of landscapes : The erosion left behind by landslides
leaves behind rugged landscapes that are unsightly. The pile of soil, rock
and debris downhill can cover land utilized by the community for
agricultural or social purposes.
5. Impacts river ecosystems : The soil, debris, and rock sliding downhill can
find way into rivers and block their natural flow. Many river habitats like
fish can die due to interference of natural flow of water. Communities
depending on the river water for household activities and irrigation will
suffer if flow of water is blocked.
PRECAUTIONARY MEASURES:
The best option to prevent the occurrences of such landslides would be to create
awareness among the people by organizing programs that explain the basics of good hill
slope development and management practices in the simplest and generalized way. Some
of the very important practices to be followed are enumerated below:
The natural drainage shouldn’t be disturbed or blocked on the slope. Water
shouldn’t be allowed to accumulate or percolate on the slope.
For support wall, wider base and slightly incline (towards hill) are to be provided.
Weep holes are must and they should weep. This can be achieved with proper
backfilling i.e. coarser material at the bottom and successive finer layer.
Care should be taken for anything that may move/fall downward.
Exposing a very high vertical face should be avoided.
Avoid adding load very close to the edge of the slope
