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30/7 MALIN LANDSLIDE: A CASE STUDY

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A massive landslide wiped out the village of Malin located at 110 km from Pune city, in the Western Ghats on July 30. Mound of mud and debris that came down from a nearby hillock, swallowed up almost the entire tribal village of around 50 families. Due to the remoteness of the village, the tragedy came to light only when the driver of the first state transport bus reached the village a little after 7.30 am to find it uprooted. Final death toll was 153 when the rescue operation was stopped and around 100 people were missing. This tragedy has brought the focus back on the management –or mismanagement – of the vulnerable hills of India especially Western Ghats, Himalayas and North Eastern states There are many speculations about what caused such massive landslide. In this paper we are analyzing geotechnical aspects of the catastrophe. Some of the key facts to note are, heavy rainfall before the landslide (10.8 cm on July 29) and heavy downpour throughout the following day. This calamite is a lesson for sustainable geotechnical planning in future to avoid massive loss of human life and property. Detailed analysis of geotechnical facts is carried out and an attempt is made to pinpoint the cause and preventive measures are suggested.
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Proceedings of National Conference”GEPSID” held on October 11-12, 2014, Ludhiana
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30/7 MALIN LANDSLIDE: A CASE STUDY
S. M. Sarvade1, M. M. Sarvade2, P. S. Khadatare3 and M. R .Kolekar4
1
Assistant. Prof., Fabtech Technical Campus, College of Engineering & Research, Sangola, Dist. Solapur, MH
2
Assistant. Prof., Fabtech Technical Campus, College of Engineering & Research, Sangola, Dist. Solapur, MH
3
U.G. Student Fabtech Technical Campus, College of Engineering & Research, Sangola, Dist. Solapur, MH
4
U.G. Student Fabtech Technical Campus, College of Engineering & Research, Sangola, Dist. Solapur, MH
INTRODUCTION
A massive landslide wiped out the village of Malin located at 110 km from Pune city, in the Western Ghats on July
30. Mound of mud and debris that came down from a nearby hillock, swallowed up almost the entire tribal village of
around 50 families. Due to the remoteness of the village, the tragedy came to light only when the driver of the first
state transport bus reached the village a little after 7.30 am to find it uprooted. Final death toll was 153 when the
rescue operation was stopped and around 100 people were missing. This tragedy has brought the focus back on the
management –or mismanagement – of the vulnerable hills of India especially Western Ghats, Himalayas and North
Eastern states
There are many speculations about what caused such massive landslide. In this paper we are analyzing geotechnical
aspects of the catastrophe. Some of the key facts to note are, heavy rainfall before the landslide (10.8 cm on July 29)
and heavy downpour throughout the following day. This calamite is a lesson for sustainable geotechnical planning in
future to avoid massive loss of human life and property.
Detailed analysis of geotechnical facts is carried out and an attempt is made to pinpoint the cause and preventive
measures are suggested.
GEOGRAPHICAL BACKGROUND BEFORE LANDSLIDE
Malin village is a part of western ghat which is a UNESCO World Heritage Site and is one of the eight "hottest
hotspots" of biological diversity in the world. Basalt is the predominant rock found in the hills reaching a thickness
of 3 km. Other rock types found are charnockites, granite gneiss, khondalites, leptynites, metamorphic gneisses with
detached occurrences of crystalline limestone, iron ore, dolerites and anorthosites. Residual laterite and bauxite ores
are also found in the southern hills. Malin is southern part of Ambegaon taluka which falls to the foothill of Sahyadri
Mountain range and is towards the west side of Pune city. The region has heavy rainfall during south-west Manson.
In Malin region soil type is brown in color and western region have an average rainfall of 1171 mm. Common crop
in the region is rice and fingemelet.
CULPRITS OF LANDSLIDE.
Inevitably there is huge speculation in the Indian media about the causes and triggers of the Malin landslide. Based
upon detailed study following are found to be the culprits of Landslide. Malin is one of the 37 villages in Ambegaon
taluk that was identified ecologically sensitive area by the Kasturirangan committee in its report on Western Ghats.
Proceedings of National Conference”GEPSID” held on October 11-12, 2014, Ludhiana
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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.
Figure 1 Malin receives very heavy rainfall
on the 29th July, 9 pm by NASA TRMM
Figure 2 TRMM time series precipitation
graph for the Malin landslide
There was continuous heavy rainfall since the last three to four days in the area, rainwater saturated the soil along
the slope of the village. This developed as loose mud and eventually flowed down after gaining momentum,
sweeping terraces, walls and ultimately the houses in the village
Deforestation and Levelling Of Land on the Hill for Cultivation.
Environmentalists say that the area around Malin has been deforested extensively. According to the Hindustan
Times, official data indicates that close to 28,000 trees were cut, but unofficial figures put the count at 300,000. The
main purpose of deforestation was to make way for farming, construction and mining. Government in its tribal
employment project Padkai scheme implemented under Mahatma Gandhi National Rural Employment Guarantee
Act (MNREGA), initiated flattening of hill slopes and trees were also cut down to develop cultivable plots. More
recently JCB machines were employed on the hillside to developing adivasi land. Land was levelled by uprooting
trees, which in turn loosened the soil, stone bunds were not built to contain erosion and nullahs were not cut into the
soil to allow drainage. The slope of the hill was flattened almost halfway for agricultural purpose to such an extent
that the hilltop had become unstable. The experts have also reported excessive deforestation disrupting the ecology
of the hill. Such criminal errors caused the landslide, it alleged. On the other hand, massive deforestation for a
windmill project along the hillside was equally responsible, said acclaimed ecologist Dr Madhav Gadgil.
Environmental activist Sumaira Abdulali said some areas are landslide-prone because of their structure. Parts of the
some hill ranges are rocky and have nothing to hold the soil. These areas are most prone to landslides. Here in
western ghat we are creating the same condition by cutting trees & flattening of slopes. Lack of specified plan and
its implementation regarding conservation of forest is main reason for the landslides in the high rainfall intensity
region of western ghat.
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Change in Agriculture Practice
Villagers had recently shifted from cultivation of rice and finger millet to wheat, which required flattening of steep
areas, which contributed to instability of the hills. Many Landslide experts says that the root cause of the landslide at
Malin appears to be levelling of land on the hill for cultivation. From preliminary observations it appears that at
various places, land has been made plain and trees uprooted. There seems to be a direct correlation between intensity
of rainfall and slope failures. Moreover, improper land use practices such as heavy tilling, improper agricultural
practices and crowded settlement patterns have also contributed to toehold erosion in many places. There are
preliminary reports of ground cracks in the upper side of the hill, but we have not seen it yet. The size of the
individual paddy fields on this hill is very small, but the point is that they have been retaining water. Due to this, the
clay soil and stones are moving down and this created this massive landslide.
Backwater of Dimbhe Dam
Construction of Dimbhe Dam ten years ago may be one of the reasons of landslide. The Malin village falls in a
backwater zone of Dimbhe Dam. Geology experts warned of the same kind of more landslides after disaster at
Malin village. They said landslides could occur in villages located along the backwaters of Dimbhe dam. The
Geological Survey of India (GSI), Nagpur region, has sent a team to survey the areas to observe the warnings of
such upcoming catastrophe. The survey must identify cracks in hills, tilting of trees and electric poles. Wherever
such signs are seen, villagers must be relocated to safer places.
Figure 3 Backwater of Dimbhe Dam
Human Interference in Nature
Stone quarrying results in formations that are unstable and could cause sudden landslides. This reason should be mainly
considered in high rainfall region like Malin where rainwater may loosen the rocks and helps them to slide. Landslides caused by
the human activity are common in the inhabited areas of the hilly terrain. In spite of knowing the possibility of landslide after
slope cutting for construction, many a time slopes are cut without any slope stability analysis and adopting necessary preventive
measures. Similarly, slope cutting, construction of support wall etc is carried out by untrained workforce with very little
knowledge about good methods of hill slope development which results in the destabilization of slope.
Construction of
hydroelectric dams, deforestation and the spread of unregulated buildings along riverbanks magnify the impact of the monsoons.
Development works carried out in pursuit of greater economic growth – such as the construction activities and deforestation – are
putting people and the environment at greater risk when disasters strike. India is one of the most disaster-prone countries in the
world, and many of its 1.2 billion people live in areas vulnerable to natural hazards such as floods, landslides, cyclones, droughts
and earthquakes.
PROSPECTIVE MUDSLIDES
The preliminary study of the Malin site attracts attention of geologist due to some of the reasons of the landslide. Though the
human interfere is not the only reason behind the landslide but is one of the major reason. Hence we should give a special
attention towards it. As like malin there are so many sites in western ghat region where human activities caused considerable
damage to environment. This damage may cause the same condition as like Malin in future. Following shows some of the
landslide prone regions which requires special attention.
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Table 1 Recent Landslides In Western Ghat.
July 2005 Mumbai,Maharashtra Caused death and loss of property in mumbai. 4 dead on the Belapurkharghar road.
14 deaths at Nerul, and 100
deaths at sakinaka.
August 2005
Ratnagiri, Maharashtra Places affected were Mandangad,
Chiplun, and Sangameshwar talukas. Destabilization of slopes affecting manmade
features.
MITIGATION OF LANDSLIDE.
Mitigation or prevention of landslide is not so good for environment. Landslide is a one of natural process and we
should try to prevent it in an ecofriendly manner
.
Land Assessment.
To determine what areas are prone to landslides,
take Ariel photographs to look for areas of little vegetation. This is indicative of
mass wasting because after being destroyed by a landslide, the growth of vegetation is slow to resume. The growth of blackberry
bushes is, in fact, indicative of disturbed soil, so it is likely that a landslide, even a small one, occurred in that area in the past.
Next, an investigation in the field: - Is it a steep slope? Does the slope consist loose sediments such as sand or gravel? Is
development making the slope more bearable to erosion? Is it a wet climate? etc.
Slope Stabilization and Development.
Slope failures, or landslides, typically occur where a slope is over-steep, where fill material is not compacted, or where cuts in
natural soils encounter groundwater or zones of weak material. In most excavation and embankment work, relatively flat slopes,
good compaction, and adding needed drainage will typically eliminate routine instability problems.
Install slope drainage such as
deep cutoff trenches or dewater with horizontal drains.
Drainage control is fairly effective in reducing landslide risk. But in the
case of intense amount of rainfall, a drainage system can prevent storm water from infiltrating and saturating the ground. This can
be achieved above the surface, by installing drains to perform the same functions as gutters that remove water from the roofs of
houses, or by covering slopes with an impermeable layer such as soul-cement or plastic. Drains that divert water away from
unstable slopes, drain control improvement can be one of the most cost efficient means of reducing the probability of landslide.
If
there is a lot of rainfall in a short span of time, then the soil is not able to absorb the moisture, which makes it vulnerable to
erosion and slope instability, eventually leading to landslides.
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Figure 4 Balanced cut and fill Figure 5 Stabilization using vegitation
Prepare Slope Stability Maps.
Slope stability maps shall be prepared which will help in identifying the zones prone to landslides. These maps shall be regularly
updated based upon development activities in the surrounding. Regularity authority shall monitor sensitive zones to landslide
very carefully. No development activity shall be carried out without the permission from the authorities. Local authorities shall
prepare development plan in consistent with the stability maps.
Prepare Landslide Inventory Database.
An authority must prepare a database of all the past landslides in the surroundings. This inventory data will serve as an important
reference for understanding behavior of the zone over a period of time. Landslides Zonation Mopping is a modern method to
identify landslides prone areas and has been in use in India since 1980s. The major parameters that call for evaluation are as
follows:
Slope-Magnitude, length and Direction
Soil thickness
Relative relief
Land use
Drainage- pattern and density
Landslide affected population
Redirect Debris Channel.
Debris channel shall be safely redirected away from habitation zone. Local residents shall be made aware about the evacuation
plan and not to block the redirected channels.
Vegetation
Vegetation helps in stabilizing the slopes in numerous ways. The mass of vegetation is only likely to have an
influence on slope stability when larger trees are growing on the slope. A tree of 30 -50m height is likely to have a
Proceedings of National Conference”GEPSID” held on October 11-12, 2014, Ludhiana
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loading of approximately 100 -150kN/m2. The larger trees should be planted at the toe of the slope with a potential
rotational failure as this could increase the factor of safety by 10%. However if the tree is planted at the top of the
slope this could reduce the factor of safety by 10%. A design vegetation envelope shall be suggested which shows
the type of plant to be grown at each level of the slope. Erosion occurs when rainfall dislodges soil particles and
carries them off a slope, forming rills and gullies that can trigger landslides. Raindrops hitting the soil surface can
also seal the soil particles and make a crust that prevents infiltration and creates runoff.
Dewatering
Soil saturation can trigger erosion and landslides. Plants improve slope stability by removing water from the soil.
Plants use water, absorbed through their roots, to perform basic metabolic processes such as photosynthesis. Plants
release absorbed water to the atmosphere, by transpiring through pores on the leaves, much as a person sweats. The
rate of transpiration varies greatly, depending on the plant species, weather, and other factors. A single tree can
transpire hundreds of liters on a hot, dry day.
Soil Reinforcement
Roots physically reinforce soils which in turn resists erosion. Ground covers and grasses have relatively shallow
roots and low biomass, so they prevent surface erosion only, and do not stabilize deep soil. Trees possess deeper
roots than shrubs and are essential for slope plantings. Puget Sound bluff soils often feature porous sandy, gravelly
soil overtopping dense, clayey glacial till. Rainfall saturates the upper soils and then seeps laterally over the glacial
till, causing landslides. Deep tree roots penetrate into the compacted layer and help in tying the layers together,
preventing slides. Tree roots occurring at the crest and toe of a slope help to prevent wasting in these susceptible
areas where larger slides often start. When roots grow across the plane of potential failure there is an increase in
shear strength by binding particles. The roots anchor the unstable surficial soil into the deeper stable layers or
bedrock.
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:
1. The natural drainage shouldn’t be disturbed or blocked on the slope. Water shouldn’t be allowed to accumulate or
percolate on the slope.
2. 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.
3. Care should be taken for anything that may move/fall downward.
4. Exposing a very high vertical face should be avoided.
5. Avoid adding load very close to the edge of the slope.
ALERT SYSTEMS
Rainfall data across the country gets recorded at many centers, efforts shall be taken to devise a program which can
generate alerts for prospective landslides. This program shall be integrated with the local authorities of potential
zones for landslide. Separate agency shall be formed to predict, investigate and mitigate such natural calamities. One
such system is TRMM (Tropical Rainfall Measuring Mission). The NASA TRMM landslide warning tool
highlighted Malin area as a zone that was very susceptible to landslides in light of heavy rainfall. Such alert systems
shall be devised and implemented across the country, specially across sensitive zones.
Proceedings of National Conference”GEPSID” held on October 11-12, 2014, Ludhiana
697
Figure 6 TRMM data for the Malin landslide, sourced 30th July. Left image is the landslide warning area,
right is the measured precipitation.
CONCLUDING REMARKS ON THE CATASTROPHE
Bhimashankar and the surrounding region are not known to be landslide-prone. For several years, though,
people have reported that the hill slopes are unstable. They reported cracks in hillsides and houses in the
villages and tilting of trees when a study was conducted in 2003. Such occurrences were also observed in
villages in the five-kilometre radius of the Dimbhe dam's catchment area."
Villagers who mostly belong to the Scheduled Tribe community called Mahdeo Koli were encouraged by
the agriculture department to flatten large tracts of hills in the village and also uproot the trees on the hill to
promote paddy cultivation among these tribals, so that they have a permanent source of livelihood under
the government scheme called Padkai.”
Landslides are common in the area during the monsoon season, which runs from June through September.
The area around the village has been deforested extensively, increasing its vulnerability to landslides.
Similar deforestation and environmental damage have caused floods and landslides in other parts of India.
Last year, more than 6,000 people were killed as floods and landslides swept through Uttarakhand state
during the monsoon season.
According to the information obtained under RTI, In Mumbai city over 22,483 hutment in 327 hilly areas
across 25 Assembly constituencies in the city, including Western and Eastern suburbs, are dangerous and
the people living there need to be shifted as soon as possible. In the main city, 49 spots are dangerous in
which total hutments are 3986, while in Mumbai Suburb 278 spots are most dangerous.
A common factor noticed in most of these vulnerable slopes deforestation in the recent past, cultivation of
seasonal crops and increase in settlements.
Because of accelerated deforestation, rampant urbanization, high frequency of earthquakes, fragile
geological structures, steep topography and intense rainfall in the mountainous regions of the South Asia,
the number of fatal landslides, casualties and economic loss is increasing year by year.
The Himalayan and North-Eastern regions are potential sites where landslides dams have formed at many
places in the past and the potential of such occurrences in the future is high.
Improper land use practices such as heavy tilling, agricultural practices and settlement patterns have
contributed to creep and withdrawal of toe support in many cases.
Almost all mass movements occur during monsoons (SW and NE monsoon) in the western flank of western
Ghats and during occasional cyclonic events in the eastern flank indicating that main triggering mechanism
is the over- saturation of overburden caused by heavy rains
REFERENCES
Greenwood, J.; Norris, J. & Wint, J. (2004), Assessing the contribution of vegetation to slope stability,
Proceedings of the Institution of Civil Engineers, vol. 157, no. 4, pp. 199-207
Maharashtra at a Glance (2005) Directorate General of Information and Public Relation, Government
Central Press, Mumbai.
Proceedings of National Conference”GEPSID” held on October 11-12, 2014, Ludhiana
698
Report Of Western Ghat Ecology Expert Panel (2011), Ecologically sensitive zones, pp16-36, Government
Of India,
Singh C. D., Singh Joginder, (2013), Landslides Caused due to Ignorance - Case Studies from Northeast
India, Journal Geological Society Of India, Vol.82, pp.91-94.
Tikke B. B , Patil Amrut K., Chavan R. R., Ms. Desai S.S, (2014) Review Of Landslide: A Special
Attention Western Ghat Of Maharashtra, International Journal of Research in Advent Technology, Vol.2,
No.3
... As a benchmark, IMD4 gridded rainfall data sets of IMD are used in the present study. These gridded data sets (Sarvade et al., 2014)). ...
Article
Full-text available
In the present study, rainfall estimates from TRMM (Tropical Rainfall Measuring Mission) and GPM (Global Precipitation Mission) constellation of satellites are analyzed in the context of rainfall induced landslide occurrences over Western Ghats (WG) of India along with the daily gridded rainfall data developed by the India Meteorological Department (IMD) and ARW- Weather Research and Forecasting (WRF) numerical model simulations. This study aims to analyze the pattern of changes in rain rate and total rainfall triggering the large landslides over WG in TMPA (product of TRMM) and IMERG (GPM product) rainfall data sets. As a case study, performance of IMERG V5 is assessed during Malin landslide which occurred on 30 July 2014 (initial GPM era). Results indicate that IMERG shows significant increase in rain rate (> 60mm/h in half-hourly data) during Malin landslide. Near real-time IMERG V5, underestimates the rain rate but increasing pattern of rain-rate are observed which is similar to that of final version. Spatial pattern of ARW-WRF rainfall output is also close to the satellite and IMD rainfall patterns. We propose that IMERG V5 can be used as an indicator to reliably depict the higher rainfall scenario over the sites that are vulnerable to rainfall induced landslide occurrence over the WG region.
Directorate General of Information and Public Relation
@BULLET Maharashtra at a Glance (2005) Directorate General of Information and Public Relation, Government Central Press, Mumbai.
Directorate General of Information and Public Relation
  • Glance
• Maharashtra at a Glance (2005) Directorate General of Information and Public Relation, Government Central Press, Mumbai.
Ecologically sensitive zones
• Report Of Western Ghat Ecology Expert Panel (2011), Ecologically sensitive zones, pp16-36, Government Of India,
Article
Landslides may be caused either by natural process or human activity or combination of both. In many cases, modifications in hill slopes are carried out with or without proper slope stability analysis, even though the consequences are well known. In other cases, stable slopes are converted into unstable slopes by the people residing in the area by artificial modification/alterations of the hill slope without basic knowledge of hill slope management. Such cases are very common in the hilly terrain including northeast India and they have caused loss of many lives even though the size of such landslide are very small. The present paper describes four examples from different parts of the northeast India where the terraced hill slopes that remained stable for an appreciable length of time have been converted to unstable slopes.
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Many embankments and cuttings associated with the transportation infrastructure in the UK are only marginally stable. Engineering techniques such as soil nailing, geosynthetic reinforcement, improved drainage and ground improvement by stabilisation are available to improve stability, but the cost can be high. A lower-cost solution may be to utilise vegetation, either self-seeded or planted. The benefits and drawbacks associated with vegetation have been the subject of some debate. The problems caused by vegetation in relation to building foundations are well documented, and confirm that vegetation can have very significant influences on geotechnical parameters. Appropriate properly maintained vegetation can have the same significant influence to help provide additional stability to soil slopes. This paper considers the potential engineering influences of vegetation and how it can be characterised on site within a geotechnical framework for stability assessments. The direct reinforcement available from the roots of trees and shrubs is identified as providing one of the most significant contributions to slope stability. Case studies in the UK, Greece and Italy demonstrate how results from in-situ root pull-out tests may be used to estimate the potential reinforcement forces available from the roots. A scheme is presented to designate zones of influence within the soil according to the size and nature of the vegetation.