Prognosis and mitigation strategy for major landslide-prone areas Varunavat Parvat landslide in Uttarkashi

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Disaster Prevention and Management
Vol. 17 No. 5, 2008
pp. 622-644
q Emerald Group Publishing Limited
0965-3562
DOI 10.1108/09653560810918649
The current issue and full text archive of this journal is available at
www.emeraldinsight.com/0965-3562.htm
Prognosis and mitigation strategy
for major landslide-prone areas
A case study of Varunavat Parvat landslide in
Uttarkashi township of Uttarakhand (India)
Aniruddh Uniyal
Remote Sensing Applications Centre-UP, Jankipuram, Lucknow, India
Abstract
Purpose – The aim of this paper is to present a discussion on prognosis and mitigation of major
landslide zones in an attempt to minimize the impact of such disasters in future. A case study on the
sequence of sliding events of Varunavat Parvat, Uttarkashi (India), response of masses and
administration and causative factors of sliding events has been presented in detail for prognosis and
mitigation of large slide zones.
Design/methodology/approach – The prognosis and mitigation strategy discussed is based on the
monitoring of mass wasting zones through field investigations and satellite image analysis (of pre- and
post-landslide period images) and experiential learning and interaction with village elders in landslide
hazard-prone Himalayan terrain.
Findings – The paper finds that Himalayan habitations such as Uttarkashi (which is situated in an
area of fragile rocks, complex tectonics, seismic activity and cloud burst-prone unstable hill slopes
with colluvium and old slide zones) should have minimum anthropogenic activity in the form of slope
cutting for road or building construction.
Research limitations/implications – The paper reflects the author’s individual understanding of
causative factors and indications of landslides in Varunavat Parvat area in Uttarkashi township of
Uttarakhand (India).
Originality/value – The paper calls for amalgamation of experience-based local knowledge of
villagers of landslide-prone areas and modern scientific and technical know-how and above all the
coordinated efforts of community and authorities for prognosis and mitigation of large-scale
landslides in the inhabited areas. It has been further emphasized that sensitization and awareness
programs and strict implementation of land-use regulations are vital components of effective
mitigation strategy.
Keywords Landslides, India
Paper type Research paper
The author dedicates this article to his mother-in-law, the late Mrs Meena Dobhal.
The author is thankful to Dr A.N. Singh Director RSAC-UP and Mr P.N. Shah, Head ERD,
RSAC-UP for allowing the use of facilities at RSAC-UP, Lucknow to carry out the Image
Interpretation and GIS work. He is also thankful to Dr A.K. Tangri, P.I. Himalayan Glaciology
Programme, RSAC-UP; Professor C. Prasad, Head (Retd.) HNBG, Srinagar, Garhwal and Mr
Meghraj of RSAC-UP, Lucknow for valuable suggestions. He acknowledges the support and
cooperation from Department of Disaster Management, Govt of Uttaranchal (now Uttarakhand)
and district administration Uttarkashi during the course of field study. Thanks are also extended
to Professor R.C. Lakhera and Dr Vinod Kumar of N.R.S.A, Department of Space, Government of
India and Mr Ramchandra of RSAC-UP for their cooperation. He also thanks Nidhi, Prabuddha
and Pranayak for encouragement and support.

Introduction
Himalaya isolates the Indian subcontinent from the rest of Asia. This highest and
youngest mountain of the world was formed as a result of the coming together and
eventual collision of India and mainland Asia. The people of Himalaya have borne the
consequences of the quickened paces of the earth’s processes including the
ever-threatening natural hazards (Valdiya, 2001). Major part of the state of
Uttaranchal (now called as Uttarakhand) lies in the fragile mountain belt of
Himalaya and has experienced tectonic turmoil several times in the distant past.
During the last quarter of twentieth century there has been an increase in the frequency
of natural disasters in this region. Major disasters in the last few years include
Uttarkashi Earthquake of 1991, Chamoli Earthquake of 1999, infamous landslides of
Okhimath and Malpa in the year 1998 and cloudbursts and flash floods in Khetgaon
and Budakedar area during the monsoons of the year 2002. Sudden increase in
anthropogenic activities like unplanned cutting of slope, blasting of highly jointed rock
mass for road construction and unplanned disposal of the slope cut debris have further
added to the fragility of Himalayan mountains and consequently there has been an
increase in the vulnerability of this region to natural disasters (Uniyal and Prasad,
2006).
In the first decade of the twenty-first century no other landslide in Himalayan region
got more media attention than the landslide events from the hill called Varunavat
Parvat in Uttarkashi township of Uttarakhand. Uttarkashi township in situated on the
banks of Bhagirathi river (which is called Ganga in the downstream of Devprayag) at
an elevation of 1,152 mts and is the district headquarters for the northern hill district of
Uttarkashi named after this township (Figure 1). The township of Uttarkashi has a
population of about 16,218 (Census of India, 2001, 2004) and is located on
Rishikesh-Gangotri National Highway (NH-108) at a distance of about 200 km (approx.)
from Dehradun, the capital of Uttarakhand state of India. This township lies in the
fragile mountains of Himalaya and has a long history of natural disasters. Flash floods
of Bhagirathi river in the late 1970s, Gyansu landslide more than two decades back in
1980, earthquake of the year 1991 have caused wide spread damage to life and property
in Uttarkashi township and elsewhere in the district. The most recent disaster in this
township has been large-scale landsliding from the hill called Varunavat Parvat, since
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Figure 1.
Location map of study
area

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Plate 1.
View of Varunavat Parvat
on 1 October, 2003 with
large active zone of
Ramlila Ground slide and
active zone of Horticulture
Colony and Masjid
Mohalla slide is also seen
in the immediate east of
the scarp of Ramlila
Ground slide
Plate 2.
View of Varunavat Parvat
in mid-October, 2003
September 23rd, 2003, which badly affected the commercial cum residential complexes,
infrastructure facilities (a part of Rishikesh – Gangotri National Highway) in the
upslope of Ramlila Ground in the heart of the township (Plates 1-4). Since 1 October,
2003 another slide was activated from Varunavat Parvat in the vicinity of Ramlila
Ground slide and badly affected Masjid Mohalla and Horticulture colony localities
(Plates 1, 2 and 5) of the township of Uttarkashi (Uniyal et al., 2004). NRSA (2001), in its
Landslide Hazard Zonation Atlas has shown a part of Varunavat Parvat as high
hazard zone.

Sequence of sliding events of Varunavat Parvat
One month prior to this large scale sliding small slide scarps were observed by the
author on Varunavat Parvat above Bus stand, Indra Colony, Masjid Mohalla and
Horticulture colony areas and these small slide scarps were witnessing headward shift.
This phenomenon was also observed by the geologists of Geological Survey of India
and local authorities. DMMC (2003), has predicted the gradual merging of these small
slide scarps with active scarp of nearby Tambakhani slide and possible emergence of
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Plate 3.
Close view of Ramlila
Ground slide in late
September, 2003. Huge
volume of slide debris is
accumulated in the back
portion of multistoreyed
hotels located in the heart
of Uttarkashi township
Plate 4.
Close view of Ramlila
Ground slide in October,
2003 with most of the
multi-storeyed hotels are
completely buried under
slide debris along with a
part of Rishikesh-Gangotri
National Highway. The
slide debris and boulders
have even spread to the
immediate down slope
area of Ramlila Ground

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Plate 5.
Close view of Horticulture
Colony – Masjid Mohalla
slide
large slide zones in Bus stand, Masjid Mohalla and Horticulture colony areas. Present
study has revealed that during the series of cloud burst events of July/August, 2003 the
Ramlila Ground slide was triggered as a small slide zone of 40m length and 30m width
in the close vicinity of large active slide of Tambakhani on Varunavat Parvat. The
active slide zones of Ramlila Ground slide witnessed rapid headward shift during the
months of August and September, 2003 and completely merged with the active scarp of
large Tambakhani slide on 23 September, 2003, consequently, the slide debris and
rolling boulders started hitting multi-storied hotels in the Bus Stand area. It was with
in the short span of 24 hours that this slide zone transformed into a large complex slide
and multi-storied hotels, commercial and residential complexes at Bus Stand along
with 100 m stretch of National Highway were buried under the huge volume of slide
debris that gradually extended to Ramlila Ground. On 1 October 2003 the head-ward
shifting of another active slide scarp (developed in the upslope of Masjid Mohalla and
Horticulture Colony localities of Uttarkashi township) completely merged with the
active slide scarp of Ramlila Ground and Tambahkani slide (Plate 1), consequently, yet
another large slide zone emerged and slide debris and boulders damaged major part of
Masjid Mohalla and Horticulture colony.
Causative factors for these sliding events have been analyzed on the basis of
satellite image study and detailed field investigations. Interpretation of pre and post
disaster satellite images from Indian Remote Sensing Satellites (IRS 1D LISS-III False
Colour Composites of 13 April 2003 and IRS-P6 LISS-III False Colour Composites of 16
April 2004; 7 September 2004; 11 April 2005 and 9 August 2005) has been carried out to
precisely mark the extent of various landforms, extension of major discontinuities and
changes in the landscape after landslide activity of September/October, 2003. ARC GIS
9.0 software was used to create the morphotectonic map through integration of GIS
layers of geo-environmental parameters viz. geomorphology, structure and landslide in
order to assess the influence of tectonics on the landforms and landslide activity.
Response
Late in the evening on 23 September, 2003 some locals and officials of Irrigation
Department noticed major sliding activity in the form of large heap of debris material

accumulated in the backyards of multi-storied Mandakni and Relax hotels at
Uttarkashi Bus Stand area. District authorities promptly responded as they were aware
of the uphill events and probable consequences in the form of large-scale landslides.
Realizing the fact that emergency evacuation from the area was first and foremost task,
the authorities launched a coordinated effort by involving different line departments
(Police, Fire Brigade, Revenue, Irrigation Department etc.) and public representatives
of local bodies for emergency evacuation from the bus stand and surrounding area of
the township.
In sharp contrast to the devastating landslide events of Okhimath and Malpa
(Uttranchal) in the monsoon season of 1998, where hundreds of people lost their lives,
the landslide events of Varunavat Parvat in Uttarkashi recorded zero casualty figures.
This can be attributed to the slow and gradual movement of sliding mass from the hill
(Varunavat Parvat) and awareness among masses about the onslaught of disaster and
furthermore, preparedness and timely intervention by local people and administration.
Damage assessment
Devastating landslides in the Uttarkashi township during the months of September
and October, 2003 have badly affected Bus Stand and surrounding area, part of
Ramlila Ground, Masjid Mohalla and Horticulture Colony localities of the township.
Consequently, about 81 buildings including 23 government buildings and 58 private
buildings (multi-storied commercial complexes, residential cum commercial buildings)
were damaged. According to initial estimates by district authorities a population of
2,911 from 362 families was affected. A segment of Rishikesh-Gangotri National
Highway was also buried under the slide debris.
The Central Technical Team has demarcated a buffer zone around landslide
affected area of Uttarkashi and advised evacuation of the population of this zone in
order to minimize the risk to the inhabitants in near future and to ensure the detailed
investigations and treatment of hill slope (Central Technical Team, 2003). About 69
government buildings and 143 private buildings located in the buffer zone are to be
reconstructed/relocated.
According to local authorities the estimated cost of rehabilitation of affected
population, relocation of government and commercial buildings and bridges,
construction of alternate routes and hill slope stabilization is 2,552.1 million Indian
Rupees (1US$ 47 Indian Rupees).
Geology
The rocks constituting Varunavat Parvat are mainly jointed and fractured phyllites
and quartzites of Uttarkashi Formation of Garhwal Group of Lesser Himalayan
sequence, dipping into the hill at an angle of about 35 o (Plate 6e). Agarwal and Kumar
(1973) carried out detailed geological mapping of the area and recognized the lower
part of Uttarkashi Formation as Netala Quartzite and upper part as Sartali Slates.
Netala Quartizite is interbedded sequence of quartzite and slates exposed in the
northern limb of NW-SE trending Baragadi Anticline (Jain, 1971), conformably
underlying the slates. The quartzite of this sequence is white to buff coloured, fine
grained and current bedded. Sartali Slates occur as banded grey, green, purple slate
and interbedded quartzite and are conformably underlying limestone and dolomite of
Syalna Formation. In Badethi-Boga section west of Uttarkashi township the Syalna
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Plate 6.
Various natural and
anthropogenic factors
causing large scale slides
on Varunavat Parvat
Limestone occur as linear narrow and impersistent band but in the northeast of
Uttarkashi township, immediate north of Mandwa and east of Kot they attain
considerable thickness. Syalna Formation includes massive bluish grey to black light
grey limestone and dolomite at places cherty and pelletal stromatolitic with
subordinate slate and quartzite. Syalna Formation is overlain by Nagni Thank
Formation. Kot Metavolcanics member consisting of green amygdaloidal schist with
thin bands of ripple marked quartzite and arenaceous slates constitute the basal
horizon of Nagni Tank Formation (Figure 2).
Kot Volcanics are exposed around Sangrali area north of the active slide zones of
Varunavat Parvat. The younger member of Gameri Quartzite is white to purple

coloured, medium to course grained locally pebbly to conglomeratic. Pujargaon
Metavolcanics is the youngest basic flow in the area and occupies southwestern corner
of the study area (Figure 2). This member comprises green amygdaloidal schist which
amygdules of quartz and zeolite (Agarwal and Kumar, 1973).
Structure
Examination of satellite images and field investigations have revealed the existence of
some major structural discontinuities (anticlinal and synclinal axes, faults and
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Figure 2.
Geological map of
Uttarkashi and
surrounding area

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Figure 3.
Structural map of
Varunavat Parvat and
surrounding area of
Uttarkashi township
lineaments) in the area. Most conspicuous structural discontinuity observed in the area
is anticlinal axis and fault along Bhagirathi river referred to as Baragadi anticline and
fault by Agarwal and Kumar (1973) and Indravati Bhagirathi fault by NRSA (2004). In
the area under investigation the NW-SE trend of this discontinuity is traced along
Indravati river from Ladari village upto further SE of Boga village. It is at Uttarkashi
that the trend of this anticlinal axis and fault changes from NW-SE to E-W and this
E-W trend is noticed along Badethi, Chamkot and Matli area and thereafter it extends
in northwest direction. Bhagirathi river between Uttarkashi and Matli and in the
further west follows this discontinuity and the broad river valley of Bhagirathi and its
meandering channel at Uttarkashi and downstream and severe bank erosion by
Indravati River and its broad valley indicate strong tectonic control that Baragadi
anticline and fault exhibits over the river courses of Bhagirathi and Indravati at
Uttarkashi and surrounding area (Figure 3). Another geomorphic expression of this
discontinuity is the sudden change in the upstream NE-SW trend of Bhagirathi river at
Uttarkashi, as it flows NE-SW in the upstream of its confluence with Indravati river
and in the immediate downstream of the confluence Bhagirathi river follows an E-W
trend. Another E-W trending structural feature in the area is synclinal axis of Sangrali
- Khand syncline (Figure 3) also referred to as Kot syncline by Agarwal and Kumar
(1973). NE-SW trending Pata-Sangrali fault intersects the axis of Kot syncline in the
west of Sangrali. The slow flowage around Sangrali and Pata villages and escarpment
in that area can be attributed to this discontinuity. NW-SE trending Kharuwan-Badethi
anticlinal axis and fault is another major structural discontinuity in the area and can be
traced from NW of Kharuwan to the SE of Wasunga village and extends further SE of
Badethi. The NW-SE disposition of Wasunga-Badethi Fan in this area and

entrenchment of its proximal part near Kharuwan village can be attributed to
Kharuwan-Badethi anticlinal axis and fault (Figure 4). At Matli village a NE-SW
trending fault is observed and another N-S trending fault has been traced in the further
west of Matli.
Study of satellite images from Indian Remote Sensing satellites (IRS-1D & IRS P6)
has revealed the existence of three prominent lineaments trending NE-SW NW-SE and
N-S direction. Prominent among these are NE-SW trending Mandwa-Ujeli lineament,
Gyansu lineament and NW-SE trending Chamkot lineament. NE-SW trending
Mandwa – Ujeli lineament controls the Bhagirathi river course in the south of Khand
village upto Uttarkashi township, where it terminates against Baragadi anticlinal axis
and fault, whereas, in the east of Khand village this lineament intersects the axis of Kot
syncline. Gyansu lineament is traced in the western part of Uttarkashi township along
Gyansu Nala (seasonal stream) and is characterised by narrow valley of Gyansu Nala.
The excessive mass wastage on the valley walls of Gyansu Nala, in the form of small
active slides developed within the larger old slide zones and entrenchment of the
proximal part of Gyansu Fan and its NE-SW disposition are strong evidences of the
existence of Gyansu lineament (Figures 3 and 4).
Geomorphology
Geomorphic set up of the area is defined by moderate to highly dissected hills,
structurally controlled ridges and river terraces of Bhagirathi and Indravati rivers with
colluvial deposits and a number of alluvial fans developed at the junction of hills and
river terraces. However, large active and old slide zones are conspicuous in the area
and many alluvial fans deposited by small tributary streams (of Bhagirathi) are
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Figure 4.
Morphotectonic map of
Varunavat Parvat and
surrounding area of
Uttarkashi township

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Figure 5.
Landslide map of Varunat
Parvat area
Plate 7.
View of Varunavat Parvat
about one and a half
decade back
superposed over the vast terraces of Bhagirathi river. Varunavat Parvat has witnessed
extensive development of colluvial deposits due to gravity transport on its moderate to
steep slopes (Figures 4 and 5; Plates 1, 7 and 8). Salra village in the NW of Uttarkashi
township is located over colluvium and the southern slope aspects of Varunavat Parvat
(towards Bhagirathi river) also have large colluvial deposits. The northeastern part of
Uttarkashi township in the north of National Highway is located over the distal part of
colluvial fan deposits (Figure 5). Furthermore, on the southern bank of Bhagirathi river
the villages of Jaspur and Silyana are located over colluvium. On the northern bank of
the river the alluvial fans of Gyansu and Padull are conspicuous and distal part of both
these fans have habitations (Figure 4). On the southern bank of Bhagirathi river the
alluvial fans are developed around Pokhri, Dang and Kotyalgaon. In the east of
Uttarkashi township the villages of Ujeli and Tiloth are located over terrace deposits.
Major part of Uttarkashi township is also located over the terrace deposits. Joshiyara,

Ladari and Kansen villages are again located over terrace deposits, further west of
Uttarkashi town the villages of Badethi, Delesaur, Chamkot and Matli are again
occupying the terrace deposits (Figure 4). Indravati river the another major stream in
the area and left bank tributary of Bhagirathi river also has terraces and active flood
plain which are often subjected to flash floods and severe bank erosion during rainy
season.
Land use
Varunavat Parvat has dense pine forest on the ridges whereas the middle slopes of this
hill are having open pine forest with few pockets of sparse scrub. During the past
decades landuse changes have been conspicuous over the lower slopes of Varunvat
Parvat due to urban sprawl of Uttarkashi township (Plates 1 and 8) and this area of
natural vegetation mainly pine trees has gradually transformed into concrete jungle.
Landsliding activity in 2003 has completely buried Bus Stand and nearby hotels and
major part of Horticulture Colony, Masjid Mohalla and stretch of Rishikesh-Gangotri
National Highway at Uttarkashi (Figure 6). The crop fields of Gyansu, Padull and
Wasunga in the west of Uttarkashi township are developed over alluvial fan deposits.
Crop fields of Dang village in the south of Bhagirathi river are developed over alluvial
fan whereas the agriculture fields of Joshiyara, Mandwa, Kansen and Tiloth villages
are developed over the terraces of Bhagirathi river (Figure 4).
Landslide scenario in the area
Pre and post landslide field investigations during August, 2003 and October, 2003 have
revealed that the head-ward shifting and gradual enlargement of small slide zones and
their merging with the nearby large active slide zone (Tambakhani slide) has
transformed the former into large complex slide zone (Figure 5; Plates 1, 2 and 8).
Three major active slide zones observed on the Varunavat Parvat are Tambakhani
slide, Ramlila Ground slide and Masjid Mohalla – Horticulture Colony slide. Further
west of the slide zones an active debris flow slide zone is also developed in Gyansu
area. Some characteristic features of these slides are given below.
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Plate 8.
View of Varunavat Parvat
in August, 2003 with only
single prominent active
slide zone of Tambakhani
slide is seen

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Figure 6.
Handsketch of Uttarkashi
township showing active
slide zones and damage to
government buildings and
commercial cum
residential areas
Tambakhani slide
This translational debris rock fall zone has developed on the southern slope aspect of
Varunavat Parvat in mid 1990s. According to locals some cracks and a small slide zone
were developed in the upper reaches of Varunavat Parvat in the aftermath of 1991
Uttarkashi earthquake. This small slide zone gradually transformed into a large rock
fall zone during the monsoon seasons of successive years. Presently this active rock fall
zone has a total length of about 680 meters and a width of about 40 meters in the scarp
area and 5-7 meters in the root of the slide (at the intersection of the slide zone with
Rishikesh-Gangotri National Highway). Prior to the monsoon season of 2003 this was
the only active slide zone (developed over Varunavat Parvat) which was affecting
Uttarkashi township as rolling boulders and debris from this slide zone often caused
road blockage on National Highway at Uttarkashi (Figures 5 and 6 and Plate 8).
Ramlila ground slide
During the cloud burst events of July/August, 2003 the Ramlila ground slide developed
as a small slide zone of 30 meter width and about 40 meter length in the upper reaches
of Varunavat Parvat in the close vicinity (about 50 meters east) of large active slide
zone of Tambakhani (Plate 6d). This small slide zone witnessed rapid head-ward
expansion during August and September 2003 and completely merged with the active
slide scarp of large slide zone of Tambakhani on 23 September, 2003 and it was on this
day that the boulders and debris material from Varunavat Parvat were first observed
accumulating in the backyard of multi-storeyed hotels in the Bus Stand area of
Uttarkashi township. Within a short span of 24 hours the Ramlila Ground slide
transformed into a large complex slide and multi-storied hotels and commercial cum
residential complexes around Bus Stand along with the 100 meter stretch of
Rishikesh-Gangotri National Highway were buried under the huge volume of slide
debris, which gradually extended to Ramlila Ground in the down slope of National
Highway and large scale sliding activity continued till mid October, 2003. This large
complex slide named after Ramlila Ground has a length of 720 meters (approx.) and the
scarp and body portions of the slide are active furthermore, the foot of this slide is well

developed having huge accumulation of debris and the toe of the slide is steep.
Occasional falling of boulders and debris material has also been reported during the
successive monsoon of the year 2004 and 2005 (Figures 4-6; Plates 1-4 and Plate 6a).
Horticulture Colony-Masjid Mohalla-Jal Sansthan Colony slide
During the cloud burst events of July/August, 2003 another small slide zone (with
dimensions more or less similar to that of Ramlila ground slide zone) developed on
Varunavat Parvat in the upslope of Horticulture Colony and Masjid Mohalla localities
of Uttarkashi township. In mid-August, 2003 this active slide zone was disposed about
80 meters east of Tambakhani slide and merely 30 meters east of Ramlila Ground slide
zone and was experiencing continuous head-ward expansion. It was on 1 October 2003
(i.e. eight days after the initiation of large scale sliding event of Ramlila Ground slide)
that the active slide zone of Horticulture Colony-Masjid Mohalla slide merged with the
head scarp of Tambakhani and Ramlila ground slide zones, consequently another
major slide was triggered from Varunavat Parvat and sliding continued throughout
the month of October, 2003. The approximate length of this slide zone is 580 meters
and it bifurcates in the immediate upslope of Horticulture Colony and Masjid Mohalla
slide localities (Figures 4-6; Plate 5).
Gyansu slide
Gyansu slide is a debris flow slide and is developed towards the western extremity of
Uttarkashi township along a seasonal stream called Gyansu Nala. This slide zone has a
long historyof devastation. About two and ahalf decades back on the nights of 24/25 June,
1980, 24 lives were lost and a number of houses, huts and cattle yards were destroyed by
large scale debris flow along Gyansu Nala. Incessant rains in Uttarkashi township in July
and August, 2003 have once again activated this debris flow slide zone and
Rishikesh-Gangotri National Highway (NH-108) was blocked a number of times in July
and August, 2003. This debris flow slide has a total length of about 1.3 km and its width
varies from 10 to 20 meters and the slide material comprises boulders of phyllite and
quartzite along with debris material. The scarp of this flow slide is active and lies on the
west bank valley wall of Gyansu Nala and has few seepage zones, furthermore a number
oftrees are uprooted inthis portion ofthe slide. The body ofGyansu flow slide is elongated
and flow lobe is well developed with a width of about 16 meters at its intersection with
Rishikesh-Gangotri National Highway. It is in this area that the habitation of Gyansu is
developed and a number of shops and houses along both the flanks of this flow slide are at
very high risk during the rainy season (Figure 4, Plates 9 and 10).
Discussion
Cumulative effects of natural factors and anthropogenic activities have been cited as
the causative factors for some of the potential slide zones of Uttaranchal (Jayan, 2004;
Uniyal, 2004; Uniyal and Rautela, 2005).
The phenomenon of landslides in Uttarkashi township has been explained by
weaving together the different threads of evidences adduced from seismicity, geology,
morphotectonics, landuse pattern, landslide history, hydrology, rainfall pattern and
anthropogenic activities (Figures 2, 4, 5, 7 and 8; and Plate 6).
Triggering of Tambankhani landslide in early 1990s (according to locals) can be
attributed to frequent ground accelerations and heavy precipitation in an area of
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Plate 9.
View of the Gyansu flow
slide
Plate 10.
Close view of the flow lobe
of Gyansu flow slide at
Rishikesh – Gangotri
National Highway
complex tectonics and long history of mass wasting. According to Valdiya (2004) the
Uttarkashi earthquake (Mb 6.6) in October 1991 was preceded by pronounced
microseismicity for about eight years (Figure 7). Ground accelerations and movements
may have most severe effects in the areas previously affected by landslides along or
near significant faults (Northmore et al., 1988). According to Valdiya (1987) seismic
shocks are the biggest triggering factor. The ground vibrations of the intensity VIII or
more on Modified Mercalli (mm) Scale have caused landslides on instable hill slopes
(Shah and Nagarajan, 2004).
Complex tectonics has significantly contributed to the slope instability in the area.
The township of Uttarkashi is in the close vicinity of a number of major structural
discontinuities. Main Central Thrust (MCT) is merely 9 km NE of Uttarkashi township.
The zone of MCT is highly unstable domain nearly 5-20 km. wide and has highly
sheared and pulverized rocks (Valdiya, 1985) and whole MCT zone lies in high seismic

hazard zone (Valdiya, 1991). Bhagirathi river at Uttarkashi follows an anticlinal axis
and fault. NE-SW trending Sangrali-Pata fault and the synclinal axis of E-W trending
Kot syncline are only a few kilometers north of the presently active slide zones of
Varunavat Parvat. Furthermore, Ujeli-Khand lineament is also in the close vicinity of
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Figure 7.
Occurrence of small
earthquakes (of M3 or less
during 1980-1988 period)
before the main impending
event (on 10 October 1991)
of Uttarkashi earthquake
of M b6.6 (after Valdiya,
2004)
Figure 8.
Graph showing rainfall in
the study area

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Varunavat Parvat and towards the western extremity of Uttarkashi township another
lineament referred to as Gyansu lineament is disposed from NE to SW.
In the area under investigation four major sets of joints are observed. The joint set
trending NW-SE (N30 o W to S30 o E) is dipping at an angle of 80 0 towards NE and has
varying joint spacing of 30 cm to 60 cm with joint aperture of the order of 1-3 cm. Other
near vertical joint set is trending NE-SW (N45 o E-S45 o W) and has joint spacing of about
30 cm with joint aperture varying between 2 to 8 cm. Another set of joints is trending
NNE-SSW and dipping due east at an angle of 80 0 with joint spacing varying between
30 to 60 cm and aperture of the order of 3 cm. Yet another set of joints is dipping at an
angle of 20 o due NE and has joint spacing of the order of 2 to 5 cm with joint aperture or
opening of 1 to 5 mm.
Unconsolidated colluvial deposits developed extensively over Varunavat Parvat are
the major source of debris material of present day active slides of Ramlila Ground,
Horticulture Colony and Masjid Mohalla localities. Large old slide zones on Varunavat
Parvat were reported by DMMC (2003); Uniyal et al. (2004) and NRSA (2001, 2004).
During the course of present investigations an attempt has been made to delineate the
extent of old slide zones on Varunavat Parvat. It has been observed that two prominent
old slide zones exist on Varunavat Parvat. One such old slide zone is developed in the
crown portion of presently active slide zones of Tambakhani, Ramlila Ground, Masjid
Mohalla and Horticulture Colony (Figures 5 and 6). This old slide zones is observed on
the basis of concavo-convex slope morphology between 1,690 and 1,660 meter contour
lines. It is between 1,675 and 1,690 meter contour lines that the scarp of this old slide is
disposed. However, its body portion is heaping out valley ward and has angular
fragments and boulders with thin soil cover. Distinct change in the shape of tree trunks
with downward and outward bending of lower trunks about one to two feet above the
sloping and undulating ground is also observed in this area (Plate 6c). This bending of
the chirpine tree trunks is in a symmetrical pattern that might have developed due to
ground movement in the early stage of their growth. Contrary to this, the chirpine trees
of the surrounding area are not having this kind of symmetrical bending of their trunks.
On the basis of the convergence of above discussed evidences viz. concavo-convex
slope, step like morphology, transported rock fragments (by gravity transport) and
unique resemblance in curvatures of the tree trunks the existence of a large old slide
zone (Old Slide Zone-I) can well be established within and in the immediate upslope
area of the presently active slide zones (of Varunavat Parvat). It is from within this Old
Slide Zone-I that the active slide scarp of Tambakhani slide might have emerged more
than a decade back and it is this very old slide zone-I which has again witnessed the
triggering of large scale slides (Ramlila Ground and Horticulture Colony- Masjid
Mohalla slides) in September/October, 2003 (Figure 5; Plates 6b and 6c).
Another major old slide zone identified in Varunavat Parvat area is developed in
Horticulture Colony locality and immediate upslope area. The scarp of this slide zone can
be observed in the middle reaches of of Varunavat Parvat in the immediate upslope of
Horticulture Colony area. During the course of present investigations this slide zone has
been termed as Old Slide Zone-II (Figure 5). The existence of this Old Slide Zone-II is
evident by the presence of large boulders with lichen growth and weathered surfaces,
concavo-convex slope morphology, step like topography and vegetation anomaly (in the
form of dense trees as compared to surroundings) in this area. The recent sliding activity
of (September/October, 2003) has however obliterated many evidences of this old slide

zone as most of the vegetation has been destroyed and well developed drainage
(important indication of old slide zone) has been replaced by haphazard drainage lines.
Furthermore, the large boulders of earlier sliding activity have mostly been buried under
the huge amount of debris and boulders of presently active Horticulture Colony – Masjid
Mohalla slide zones. Cutting and digging of slope at the toe portion of this Old Slide
Zone-II for the construction of new houses and shops in Horticulture colony and Masjid
Mohalla localities has also added to slope instability (Plate 5).
According to locals the forest fire is an annual unfailing event in the Varunavat
Parvat and surrounding area. During the present course of field investigations in
August, 2003 many burnt out tree trunks and shrubs were observed in the area of old
slide zone-I of Varunavat Parvat (Plate 6f). According to locals this destruction of
vegetation was due to forest fire in this area during the summers of 2003. It is also
observed that many a times forest fire over Varunavat Parvat is ignited by dangerous
anthropogenic interference. In the area of pine forest very little grasses and shrubs can
grow and most of this sparse vegetation is destroyed by forest fires during summers as
the dry leaves of pine trees easily catch fire during this season. Repeated destruction of
grasses, shrubs and trees in Varunavat Parvat area has resulted in an increase in the
impact of rain splashes during the incessant rains and cloud burst events of rainy
season. This in turn has increased the soil erosion.
Another example of anthropogenic intervention in Varunavat Parvat area is
blasting of hill slope for time to time widening and clearing (removal of boulders and
debris) of Rishikesh-Gangotri National Highway, particularly in the area where
Tambakhani slide intersects the National Highway. Furthermore the road link to
Sangrali and Pata villages via Tekhala in the east of Varunavat Parvat has also been
established after blasting the hill slope at a number of places. What adds, further to
this dangerous anthropogenic interference in the fragile terrain is heavy vehicular
traffic (during the pilgrimage season of May to October) on Rishikesh-Gangotri
National Highway, that passes through the lower slope of Varunavat Parvat. Valdiya
(1987) explained that the vibrations generated by the passage of heavy vehicles create
oscillations of different frequency in the rocks and thus change the stress pattern
reducing shear strength and inducing mass movement. Uttarkashi township is an
important halt on the way to famous Hindu shrines of Gangotri and Gaumukh (the
place of origin of river Ganga). Vibrations of hundreds of vehicles (buses, trucks and
jeeps) which get their daily passage through Rishikesh-Gangotri National Highway in
the lower reaches of Varunavat Parvat and blasting of hill slope for time to time
widening and clearing of National Highway may also be considered as contributing
factors for slope instability.
It appears that major contributing factor for triggering large scale landslides from
Varunavat Parvat was excessive pore water pressure caused due to high monsoon
rainfall. Uttarkashi town experienced rainfall of the order of 652.02 mm and 602.20 mm
in the months of July and August, 2003 respectively. This was followed by 200.40 mm
precipitation in the month of September, 2003. Analysis of the available rainfall data
has illustrated that the actual monthly rainfall of 652.02 mm during July, 2003 was
second highest for this rainy month in particular (after 655 mm in July, 2000) during the
nine years period of 1995-2003. Furthermore, the actual monthly rainfall of (602.20 mm)
during August, 2003 was maximum for this rainy month during 1996-2003 period.
Interestingly the months of July and August, 2003 have together experienced the
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rainfall of the order of 1,254.22 mm which is maximum for these rainy months during
last nine years i.e. during 1995 to 2003 period (Figure 8).
Slope instability in Varunavat Parvat area was further enhanced by various natural
and man made pathways for infiltration of rainwater. Detailed field investigations
prior to large scale sliding activity of September, 2003 have revealed few major cracks
in the crown portion of the present day active slides (in the vicinity of Tambakhani
slide) on Varunawat Parvat. One such major crack trending E-W with width varying
from few centimeter to about a meter was observed in the body portion of the Old Slide
Zone-I of Varunawat Parvat. In the mid August, 2003 this crack was extending from
the large and active slide scarp of Tambakhani slide to the small slide zones of Ramlila
Ground and Masjid Mohalla. Few major cracks in the Old Slide Zone-I in the close
vicinity of the active scarp of Tambakhani slide were trending NW-SE with varying
width 10 to 20 cm. Another set of cracks observed in this area was more or less
trending ENE to WSW with a width of the order of 15 to 20 cm and these cracks were
developed immediately below the main scarp of presently active slide zones. In
addition to the E-W, NW-SE and ENE-WSW trending cracks the other major avenues
for infiltration of water were three to four sets of joints trending NW-SE, NE-SW and
E-W with varying joint aperture from 1 to 8 cm (Plate 6e).
Ill conceived unlined drains immediately above the active scarp of Tambakhani
slide within the scarp and crown portion of the Old Slide Zone-I have further enhanced
the slope instability (Plate 6g). Though these drains were constructed to flash out the
rainwater away from the slide area, yet they served as easy pathways for infiltration of
rain water because they were unlined and abruptly terminating (on the flanks of active
scarp of Tambakhani slide) with no connecting vertical drain. Infiltration of rain water
from these horizontal drains into the active scarp of Tambakhani slide and small
scarps of Ramlila Ground and Masjid Mohalla slides has further increased pore water
pressure and hence enhanced the slope instability.
It can be deduced from the foregoing discussion that prolonged sessions of
incessant rains in the months of July and August, 2003 and excessive infiltration from
a number of surface cracks, joints and unlined drains have altogether altered the
hydrology and increased the pore water pressure, this in turn has caused rapid
head-ward extension of small zones of Ramlila Ground and Masjid Mohalla slides
during July to September, 2003 and by September 23rd, 2003 the small slide zone of
present day Ramlila Ground slide completely merged with the scarp of large active
zone of Tambakhani slide. Interestingly, all these active slide zones were developed
within the large Old Slide Zone-1 of Varunavat Parvat wherein, the soil was not so
competent, number of openings were developed for infiltration of rain water and rocks
of the area were highly sheared and weak. Furthermore, the major discontinuities
(faults, anticlinal and synclinal axis) in the vicinity of Varunavat Parvat, active
tectonics, pronounced seismic activity (Uttarkashi earthquake of 1991) and
anthropogenic intervention in the form of blasting for road cutting, movement of
large number of vehicles through the fragile zone and alteration of hydrology due to
construction of unlined drains in slide areas have been the equally contributing factors
for large scale sliding activity.
Above case study of Varunavat Parvat landslide takes into account the monitoring
and assessment of sequence of landslide events and entire episode of landscape
obliteration and also the analysis of causative factors. It is not only Uttarkashi

township but many other habitations in Himalayan region which are prone to
landslides. On the basis of this case study of Varunavat Parvat landslide an attempt
has been made for reading the signs of large scale landslides and preparedness,
effective response and non structural mitigation are also discussed herein to minimize
the impact of such disaster in the future.
Prognosis for major landslide-prone areas and effective response
Emergence of large cracks or sudden widening of existing cracks (from few
centimeters to few meters) in the upper reaches of hill slope, particularly in the upslope
or immediate down slope of habitation, infrastructure (road, water supply line, power
line, telephone line or canal), agricultural land, wild life area and protected forest area
indicate that the ground is witnessing rapid stretching and immediate measures are
required to minimize the risk.
Emergence of small slide zones (in the vicinity of a large active slide zone) and their
head- ward shifting towards the neighboring large active slide zone is an indication of
an impending disaster in the form of gradual or sudden triggering of large scale
landslides in the area in near future. Best examples of this phenomenon are active slide
zones of Ramlila Ground, Masjid Mohalla-Horticulture colony, which have developed
in the year 2003 as a result of head-ward shifting of small slide zones and their
subsequent merging with the large active zone of Tambakhani slide.
Sudden disappearance of some seepage zones, fluctuation in the discharge of other
such zones and emergence of new springs and seepage zones in the close vicinity of
existing or abandoned seepage zones/springs are some other indications of gradual or
sudden changes in the hydrology as a consequence to the imperceptible or perceptible
slope movement.
Few days or hours before a major slope failure (in the from of debris rock slide or
subsidence) in an area of human habitation, the indications are sudden snapping of
fencing wires, electricity and telephone wires between pillars/poles and sudden
disruption of water supply due to breaking of pipe lines, displacement of canals (kools
in local parlance) and sewer lines. Finally the sudden tilting of walls of houses coupled
with the development of cracks on their roofs and walls and subsidence of floor and
baranda imply that the slope failure may take place any time, may be in a few days or
even few hours. Under the given circumstances the inhabitants of such localities
should immediately evacuate children and old persons to safer location and domestic
animals should be immediately untied and be allowed to go free. Furthermore, the
locality should be abandoned as early as possible in an effort to minimize the loss of
human and animal lives.
Under given conditions, incessant rains for hours or continuous rains for days
coupled with the flow of muddy water into the drains (gadera in local parlance) which
otherwise have fresh water and rolling of boulders and small scale debris flows are
strong indications that the area is at the verge of experiencing a major debris flow and
inhabitants of the area should immediately abandon their houses.
Preparedness and mitigation
Participatory rural appraisal
Local authorities should facilitate interactive sessions of NGOs with the villagers and
(women in particular) of high-risk prone habitations in order to disseminate the
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information pertaining to the presence or emergence of cracks in the upslope of
habitations/villages. It has been observed that the local villagers during day today
collection of animal fodder sometimes notice newly emerging small slide zones, cracks
and or sudden widening of existing cracks in the upslope areas of the village, but
unfortunately this crucial information about the initiation of sliding activity often goes
unnoticed by the Disaster Management Community due to lack of communication
between villagers and Disaster Management community.
Ban on construction activity in the vicinity of landslide zones
Complete ban be imposed on new constructions in the immediate upslope of active or
potential slide zones, as the active slide zones may cause gradual or rapid subsidence of
upslope habitation. Similarly, the areas in the immediate down slope of landslide zone
should also be avoided for construction activity as the debris flow and rock fall from
upslope area might cause damage in the near future.
Effective rehabilitation policy
Construction of new houses (in the safer areas) for the affected population is a better
option as compared to the distribution of money to the affected people for construction
of new houses. It has been observed that in many cases this money is utilized by the
affected people for repairing the same old houses which have already witnessed the
damage due to landslides. In some cases even new houses are constructed in the close
vicinity of landslide affected old houses or otherwise on an another unsafe site.
Strict implementation of land use regulations
Land use regulations should be strictly implemented to avoid unplanned cutting and
overloading of fragile hill slope for construction activity. Furthermore, in high risk
areas there should be complete ban on blasting for road construction or road widening,
instead cut and fill method of road construction should be adopted. In view of the high
cost of road construction through cut and fill method, restricted blasting can be
introduced but only in moderate to low risk areas, certainly not in the areas of high
risk. This regulation is necessary since the blasting in fragile terrain causes opening of
cracks of the rocks and in some cases even increases the joint aperture (opening) and
these openings serve as easy pathways for percolation of rainwater (into the rock mass)
which in turn increases sliding force and decreases resisting force and finally triggers
the failure.
Conservation of natural drains
On the pattern of forest conservation measures, there should be provisions for
conservation of the existing courses of natural drains and new constructions should
not be allowed within the active flood plains of perennial or seasonal steams and
furthermore, the constructions that block the natural drainage courses should be
removed. This can be done by time to time survey, identification and subsequent
demolition of residential, commercial or residential cum commercial or any other
construction that is blocking, narrowing or diverting the course of natural drains
(nala/gadera in local parlance) or is otherwise causing choking of sewerage/drainage
system of municipal body or local body or village.

Waste management
Clear-cut policy should be formulated for the waste management of hill slopes
particularly for the planned disposal of debris material generated from the slope cutting
or digging for construction activity. As the slope cut debris not only blocks the natural
drains butevengives rise tonewslide zones anddamages agriculture andforestresources
of the immediate down slope area. Separate funds for planned disposal of road cut debris
should be allocated to the agencies (such as Public Works Department) involved in the
road construction work. Furthermore, the expenditure to be incurred by the concerned
department for the disposal of slope cut/ road cut debris should be proposed in the project
estimate itself. This measure can substantially reduce the risk of landslides and
subsidence to the immediate upslope and down slope areas of newly constructed hill
roads and can also minimize the annual maintenance cost of hill roads.
Avoidance of ground-water harvesting structures in the old slide zones
Recharge wells and ground-water harvesting structures should be avoided in the
upslope areas of old and active slide zones wherein habitations or critical facilities are
located (over old slide zones).
Rainfall database creation
Detailed database for rainfall needs to be created in an attempt to workout the
threshold amount of rainfall that might cause slide or debris flow in the near future.
For this purpose there is an urgent need to increase the number of rain gaze stations in
hill districts.
Landslide risk mapping at municipality ward and village level
Landslide hazard zoning at municipality ward and village Level on 1:4000 and larger
scale should be carried out through conjunctive use of high resolution satellite image of
IKONOS, QUICKBIRD, CARTOSAT 1 and CARTOSAT 2 satellites and precision
ground surveys using Total Station. Furthermore, the GIS techniques can be best
utilized for vulnerability assessment by overlaying the thematic layers of population,
infrastructure, assets and natural resources over the landslide hazard zone maps of the
area. Risk maps at municipality ward and village Level should be created by relating
the landslide hazard potential and vulnerability of the area. Risk maps can provide
information about the likelihood, dimension, extent and degree to which the
communities in the area may be affected by landslides.
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Corresponding author
Aniruddh Uniyal can be contacted at: aniruddhauniyal@yahoo.com
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