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Attabad Landslide - Dam disaster in Pakistan 2010

Authors:
  • Diamer Basha Consultants Group (DBCG)

Abstract and Figures

On January 4, 2010, in the remote Hunza Valley of Northern Pakistan a massive landslide buried the village of Attabad, destroyed 26 houses and killed 20 people. The landslide dammed Hunza River and formed an extensive lake of 100m depth. Until the end of July 2010, 381 houses were ruined; out of which 141 were directly affected by Attabad landslide, others were submerged due to expansion of the lake. By the end of May 2010 local authorities excavated a spillway to guide the flow of impounding lake over the natural dam. Until August, 2010, the spillway is performing well but internal response of the loosely deposited debris is unknown.
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ABSTRACT
On January 4, 2010, in the remote Hunza Valley of Northern Pakistan a massive landslide buried the
village of Attabad, destroyed 26 houses and killed 20 people. The landslide dammed Hunza River and
formed an extensive lake of 100m depth. Until the end of July 2010, 381 houses were ruined; out of which
141 were directly affected by Attabad landslide, others were submerged due to expansion of the lake. By
the end of May 2010 local authorities excavated a spillway to guide the flow of impounding lake over the
natural dam. Until August, 2010, the spillway is performing well but internal response of the loosely
deposited debris is unknown.
INTRODUCTION
Attabad village is situated in the extremes of Northern Pakistan. It is located at a distance of 760km from
Islamabad, the capital of Pakistan.
Karakoram highway connects Islamabad to Gilgit and further passes through Hunza valley up to Khunjrab
Pass. The Karakoram Range of Himalayas passes through the Hunza valley in NW-SE direction. High snow-
covered mountains with steep cliffs and narrow valleys are topographic characteristics. The difference of
elevation between the valleys and the peaks ranges from 2200 m to 2700 m. Hunza and Hispar Rivers
control the drainage of the area. A very high mountain of Rakaposhi (7788m) lies to the South-West and
the Pasu Glacier lies in North of Attabad landslide area. Hunza valley rises from 1850 m to the peak of
Rakaposhi at 7788 m over a distance of 11 km which is the most contrasting relief in the world.
The highest areas of the valley have pyramidal peaks and sharp ridges without plateau features.
Weathering due to frost action is the cause of slope failures and mass movements. High peaks covered
with snow are common along with rock and scree slopes, and mud flows are present throughout Hunza
valley. The moraines have irregular topography. Attabad area have extreme climate in winter in which
temperature falls below 0°C; however, spring and summer are pleasant with an average temperature of
30°C. The area receives about 1 m of snow in winter; January is the coldest and snow melting causes
mudflows and rock falls during summer.
ISSMGE Bulletin: Volume 4, Issue 3 Page 21
Case History
Attabad Landslide- Dam Disaster in Pakistan 2010
Tahir Hayat, Vice President, National Engineering Services Pakistan
Imran Khan, Director General, Geological Survey of Pakistan
Hamid Shah, Director, Geological Survey of Pakistan
Mohsin U. Qureshi, Doctoral Student, The University of Tokyo
Sajjad Karamat, Master Student, The University of Tokyo
Ikuo Towhata, Professor, The University of Tokyo
Figure 1 Location plan of Attabad landslide disaster
GEOLOGY & TECTONICS OF THE AREA
The Northern areas are one of the most complex and difficult terrain in the world, exhibiting a great
variety of rock types and structures. The exposed rocks range in age from pre-Cambrian to Recent and are
composed of igneous and metamorphic rocks of various types. On the basis of regional tectonic set up, the
Main Karakoram Thrust (MKT) and Main Mantle Thrust (MMT) are the major tectonic features and these
mega-shears may affect the Attabad area during any seismic activity
ISSMGE Bulletin: Volume 4, Issue 3 Page 22
Case History (continued)
Attabad Landslide- Dam Disaster in Pakistan 2010
GILGIT
Image taken on March 16, 2010 by NASA
HUNZA
RAKAPOSHI
ATTABAD
GULMIT
SHISHKAT
ATTABAD
KARAKORAM
HIGHWAY
Figure 2 Geological map of Hunza valley and adjoining areas
The destroyed Attabad village was located on valley slope of glacio-fluvial deposits underlain by Gneissic
rocks (orthogenesis and Para-gneisses of Baltit Group); Baltit group consists of gneisses, schist, quartzite,
dolomite limestone and marble. Glacio fluvial deposits forming the site of Attabad village consist of
boulders, cobbles and gravels with some silt and sand as cementing materials. The rocks exposed at crown
and toe are highly fractured, sheared, jointed and weathered. A fault on the eastern side of the village is
passing through Hunza River trending almost North-South.
PRE-DISASTER PERIOD
Attabad village has been affected by very complex slope instability conditions due to denudation process,
effect of seismic activity, high slope angle, river cutting, lithological conditions, snow melt, rains and
irrigation for agriculture, and heavy overburden on bed rock in the form of glacio-fluvial deposits. In 2002
Astore earthquake of magnitude 6.3 was recorded as one of the major triggering factor, and cracks
appeared at the back-slopes of Attabad. The second major displacement was observed in 2004, when the
cracks extended longitudinally and transverse into the cultivated fields and populated areas of Attabad
and surface failure features appeared at the toe of the affected area. The 2005 Kashmir earthquake of
magnitude 7.6 accelerated the slope movement and networks of cracks destroyed several houses.
ISSMGE Bulletin: Volume 4, Issue 3 Page 23
Case History (continued)
Attabad Landslide- Dam Disaster in Pakistan 2010
ATTABAD
Figure 3 Site of Attabad landslide in pre-disaster period (August 2009)
Geological survey of Pakistan conducted a hazard analysis of the area in August 2009 and reported their
viewpoint as follows;
1. Unconsolidated overburden lies on the bed rock in the form of glacio-fluvial deposits ranging in
thickness from 3 to 12m. These deposits form the terraces and back-slopes of the affected area.
Clay and silt constitute major proportions of the overburden at the back-slope and terraces.
2. A fault is passing through the affected area having a strike NS and crossing the river. A huge
landslide has developed across the river (Fig. 3(b)). This landslide is associated with the fault. The
movement along this fault has weakened the shearing strength of the rocks and decreased the
angle of repose.
3. High slope angle is the major triggering factor of the eastern Attabad. A slope angle at terraces is
ranging from 30° to 40°, at the back-slope from 35° to 55° and toe of terraces is nearly vertical
(Fig.3 (a)).
4. The bed rock is highly fractured, sheared and jointed due to the tectonic activity in the area.
Blocks of rocks started to slide down in the form of wedge failure, while rockfalls and toppling are
observed at some places. The mass movement has weakened the base and results in widening and
vertical settlements of cracks and expanding the landslide phenomena in the areas.
5. Hydrological conditions of the affected area are further accelerating the slope failures, Water
from three sources are infiltering into the cracks and fissures, i.e. rain, snow melt and irrigation.
At many places water is directly infiltrating into the cracks and fissures and damaging the
mechanical behavior of failure planes, accelerating the underground movement that appears as
surface failures.
Based on those studies Attabad was declared as high hazard zone. Local authorities were suggested by
Geological Survey of Pakistan to take necessary action for the evacuation of dwellings from vulnerable
area. A suggestion was given to monitor the hazardous area during the winter and snow melt season.
ISSMGE Bulletin: Volume 4, Issue 3 Page 24
Case History (continued)
Attabad Landslide- Dam Disaster in Pakistan 2010
Karakoram
Highway
Attabad village
(a) Right ban
k
(b) Left ban
k
SALIENT FEATURES
On January 4, 2010 a huge mass failed, destroying the village of Attabad and damming the Hunza River.
Fig.4 shows the secondary landslide taking place at the site. The blocked length of the river was about 2
kilometers with the width of 500m. The landslide itself blocked 1.3km of Karakoram Highway. Till the end
of May 2010, the lake stretched to a length of 22km. The estimated potential storage of the lake, if it
impounds up to the maximum height of the dam, is 305 million m3.
Figure 4 Secondary landslide on January 22, 2010 at Attabad (image courtesy PAMIRTIMES)
The distribution of deposited debris is shown in Fig. 5. A longitudinal profile through the flow path of
Hunza River is shown in Fig.6. Deposited mass is mainly composed of non-cohesive rock flour (fine dust,
silt, silt gravels and cobbles) at the toe of the failed slope. Large boulders of granodioritic rocks with
intrusions of granite, pegmatite and apatite were deposited close to the left bank of Hunza River. The
deposit on the downstream side is composed of black clay with high plasticity and organic content.
Figure 5 Distribution of debris material
ISSMGE Bulletin: Volume 4, Issue 3 Page 25
Case History (continued)
Attabad Landslide- Dam Disaster in Pakistan 2010
Down stream Up stream
The longitudinal profile (Fig.6) indicates that the upstream shoulder of the natural dam has mild slope,
however downstream slope is quite steep. With such length (2 km) of the dam there are rare chances of
piping failure. Fig.7 shows drowned villages of Shishkat and Gulmit along with the stretches of Karakoram
Highway.
Figure 6 Topography and Longitudinal profile of failed deposited material
TIME HISTORY OF LAKE EXPANSION
NASA monitored the expansion of lake by taking satellite imageries as shown in Fig. 8. It was believed that
the lake expansion has direct relation with the increase in temperature which is the cause of snowmelt
and increased inflows. Timely evacuation of the inhabitants was carried out from the drowning villages of
Shishkat and Gulmit.
ISSMGE Bulletin: Volume 4, Issue 3 Page 26
Case History (continued)
Attabad Landslide- Dam Disaster in Pakistan 2010
Gulmit
Shishkat
Karakoram
highway
Figure 7 Drowning of villages due to expanding lake (image courtesy PAMIRTIMES)
CONTROLLED DRAINAGE FROM LAKE
A Dam breach study was conducted by NESPAK (National Consulting Firm). They reported the study in
March 2010 to National Disaster Mitigation Authority (NDMA) and proposed the excavation of spillway as a
safe way to drain the water. The recommended spillway was 24 m deep and 45 m wide. The excavation
works for the spillway were finished in the mid of May. As anticipated the overflow began on May 29,
2010. Time histories of stage over spillway crest and discharge that was measured downstream at the
Ganish Bridge (down stream of Attabad) show the performance of the spillway (Fig. 9). The consistency of
stage and discharge curves contradicts because the measured discharge also includes the seepage
allowance. However, inflow depends on the snowmelt which is directly related to the rising temperature
in summer. Data shown in Fig. 10 was reproduced from the daily pager reports given by NDMA. Fig. 10
shows the situations before and after over spilling of the downstream slope. The marks of erosion are
quite visible in Fig. 10(b). NASA satellite image shows the overflowing spillway in Fig.11.
ISSMGE Bulletin: Volume 4, Issue 3 Page 27
Case History (continued)
Attabad Landslide- Dam Disaster in Pakistan 2010
Figure 8 Images of lake expansion by NASA before it overspills
ISSMGE Bulletin: Volume 4, Issue 3 Page 28
Case History (continued)
Attabad Landslide- Dam Disaster in Pakistan 2010
(a) March 16, 2010 (b) May 2, 2010
(c) May 25, 2010
(d) June 1, 2010
0
3
6
9
Aug. 6July 27
July 17
July 7June 27June 17June 7
May 28
Stage (m)
0
200
400
600
Discharge (m3/s)
Figure 9 Time histories of discharge measured at Ganish Bridge and stage over spillway crest (drawn after
daily pager report supplied by National Disaster Mitigation Authority Pakistan; NDMA)
Figure 10 Performance of spillway (courtesy by PAMIRTIMES)
ISSMGE Bulletin: Volume 4, Issue 3 Page 29
Case History (continued)
Attabad Landslide- Dam Disaster in Pakistan 2010
(a) May 28, 2010 (b) June 17, 2010
Figure 11 Image of over spilling Attabad landslide dam on July 7, 2010
SOCIAL IMPACTS
The disaster has social impacts on the daily life of community other than the displacement of residence.
Karakoram Highway was the only route which connects the towns of Gulmit and Shishkat with Hunza,
which has been blocked by landslide and impounded water. Now the mode of transport changed from
vehicles to boat (Fig. 12). Directly or indirectly 25,000 peoples were affected by this disaster. The banks
of the lake are highly vulnerable and small mass movements are frequent which restricts the boat service
through the lake.
ISSMGE Bulletin: Volume 4, Issue 3 Page 30
Case History (continued)
Attabad Landslide- Dam Disaster in Pakistan 2010
More recently, the situation is being relaxed. Fig. 13 compares two images from NASA that were taken on
July 7 and August 23. These images compare the part of upstream edge of the lake. It is therein seen that
the inflow has been reduced. In the month of June and July, the temperature was high to produce more
inflow due to ice melting. In contrast in August, the temperature dropped, and thus the inflow decreased.
Figure 12 Modal change of transportation after the disaster from land to boat
Figure 13 Decreasing inflow of water into the lake in August, 2010 (NASA images)
REFERENCES
National Engineering Services Pakistan (NESPAK) (2010) Dam break study of Attabad landslide, Report to
National Disaster Mitigation Authority Pakistan, March.
S. Hamid Hussain and Adnan A. Awan (2009) Causative mechanisms of terrain movement in Hunza valley,
Geological Survey of Pakistan, August.
Daily pager reports from January to July 2010 from the database of National Disaster Mitigation Authority
Pakistan, http://ndma.gov.pk/AttaHunzaLandslide.html
Pamir Times http://pamirtimes.net/
APPENDIX. FLOODING IN AUGUST 2010
Pakistan suffered terrible flooding in August of 2010. This flooding was caused by an unprecedently heavy
rain fall in the northwest part of the country. All the early warning systems for floods have been installed
in the eastern rivers, and nothing has been monitored on the western and south western rivers, which are
the source of the terrible flooding in 2010. A flood from these channels do not have any evidence in the
recent history. Probably there will be a chance for this bulletin to report this flooding event.
ISSMGE Bulletin: Volume 4, Issue 3 Page 31
Case History (continued)
Attabad Landslide- Dam Disaster in Pakistan 2010
July 7th August 23rd
... A second period of displacement was observed in 2004, when the cracks extended longitudinally and transversely into cultivated fields and the populated area of Atta Abad Village. Surface failure features also appeared at the toe of the affected area(Hayat et al., 2010). The situation was exacerbated by the 2005 Kashmir earthquake, which destroyed several houses, damaged others and expedited slope movement. ...
Conference Paper
Full-text available
Natural processes, such as earthquakes, landslides and landslide-dam outburst floods, meteoric floods, and glacially-derived floods, have over even just the last few years within the Hindu Kush-Karakoram-Himalayan Region caused several billions of dollars' worth of damage to hydropower infrastructure alone, let alone wider societal losses, thousands of fatalities, and hundreds of thousands of displaced and homeless people. It is evident that the consequences of extreme hydro-meteorological and geological processes have not been considered adequately in the development of major infrastructure projects, such as hydropower schemes, in this region. Analysis of a number of notable natural disasters that have occurred within the last decade in the Hindu Kush-Karakoram-Himalayan Region has aided the understanding of the causes and behaviour of the responsible natural processes and their sequencing. Rather than examine each as an example of a specific type of event, it has been necessary to review a combination of geological preconditioning factors and the interaction with recent and current physical processes, including the effects of changing climate. Three disasters that have occurred between 2010 and 2016 are described from Pakistan, northern India, and Nepal to illustrate the combination of physical processes in each case. Lessons learned from each with respect to geohazard assessment will be highlighted. In addition, it is also germane to examine how Massive Rock Slope Failures influence active landslides and the development of future major rock instabilities. Many of these events and phenomena further demonstrate the role of the physical preconditioning of sites in shaping the nature and scale of subsequent natural disasters. Better understanding of the physical processes involved in destabilisation of steep mountain flanks and the role of climate change is helping to refine the way in which these mountain hazards can be assessed. The relationships between these physical processes and the timescales over which they operate are critical in framing appropriate Disaster Risk Management strategies for major infrastructure developments. It is by understanding better the interrelationships between preconditioning factors and ongoing geological and hydrological processes, including the effects of climate change, that integrated geohazard assessment methodologies can be developed. These in turn can be used to help inform Disaster Risk Management strategies and action plans. There is substantial ongoing and projected investment worth multiple-tens of billions of US dollars in especially hydropower and road infrastructure in high mountain environments in the Hindu Kush-Karakoram-Himalayan Region over the next decade and beyond. It is crucial to the performance and, in some cases, survival of these investment projects that robust integrated geohazard assessments are undertaken and incorporated into flexible forward-looking Disaster Risk Management plans.
Dam break study of Attabad landslide
National Engineering Services Pakistan (NESPAK) (2010) Dam break study of Attabad landslide, Report to National Disaster Mitigation Authority Pakistan, March.
Causative mechanisms of terrain movement in Hunza valley, Geological Survey of Pakistan
  • Hamid Hussain
  • Adnan A Awan
Hamid Hussain and Adnan A. Awan (2009) Causative mechanisms of terrain movement in Hunza valley, Geological Survey of Pakistan, August. Daily pager reports from January to July 2010 from the database of National Disaster Mitigation Authority Pakistan, http://ndma.gov.pk/AttaHunzaLandslide.html Pamir Times http://pamirtimes.net/