This page presents a second report on landslides in the Kashmir area of
Pakistan associated with the 8th October 2005 earthquake. It is an
addition to the earlier report, available
here. In
the first report I focussed in general upon the widespread levels of
damage associated with the earthquake. In this second report I
have focussed upon the serious concerns that I have about the likely
impact of the forthcoming (Summer 2006) monsoon on the stability of the
slopes in this area. This report focuses only on two small parts
of the earthquake affected area: Muzaffarabad and Hattian. It is
likely that similar problems to those at Muzaffarabad exist elsewhere in
Kashmir, but to date these are undocumented.Fortunately, the
authorities are also aware of the concerns and are acting to try to
mitigate the impact of them. The most impressive action is a
large-scale evacuation of the slopes around Muzaffarabad:
Pakistan
Times story
MUZAFFARABAD (AJK): Almost 55,000 earthquake survivors will be
relocated due to the danger posed by monsoon landslides in Azad
Kashmir, officials said on Saturday. “A strategy is being evolved to
relocate some 50 to 55 thousand people from areas prone to landslides
before the start of monsoon season,” the region’s top administrator
Kashif Murtaza said. Murtaza said that 18 villages were likely to be
affected. The government would work with the United Nations and other
aid agencies get the people out of harm’s way, he said. “It is a big
challenge to relocate the most vulnerable to safer places before the
monsoon starts,” Murtaza said. Depending on how many people need to be
resettled the government may have to buy land near Muzaffarabad, the
capital of Azad Kashmir, he added.
I believe that this is probably the most serious landslide threat
worldwide at present, and there is an urgent need to provide assistance
to the authorities in the assessment of the hazard and the relocation of
the affected population.
Muzaffarabad
Muzaffarabad is the largest city in the earthquake-affected area.
According to the AJK Government data, the Muzaffarabad district
had a population of 822,000 people in 2002. The following is a
montage of images taken from the south looking northwards across
the city. The mountains in the background are formed from Precambrian
limestones, whilst the more gentle slopes in the foreground are formed
mostly from colluvium (deposits of old landslides and slope processes).
Multiple shallow rock slides are visible in the limestones. The
bottom of these slides is mostly marked by a sharp beak where the slope
angle decreases and the slopes are vegetated and inhabited. This
is the line of the fault that caused the 8th October 2005 earthquake.
Note on the left side the steep, fresh limestone - this slope failed in
the earthquake, blocking the river for some hours. Immediately to
the right of this is an area in which the upper slope is limestone but
the lower slope has a reddish hue - the red rocks are the young
sandstones and mudstones of the Eocene and Miocene Murree Formation -
the fault is the boundary between the two formations.
Image 1:
This is an image of the city of Muzaffarabad, taken looking northwards.
Note the multiple shallow rockslope failures in the limestones at the
back of the city. However, the ongoing, serious landslide problems
lie in the more gentle slopes upon which the upper part of the city is
built.
During the earthquake and subsequently a number of landslides were
triggered in inhabited areas. In Images 1 and 2 two of these
slides are shown. In both cases they have caused considerable
disruption but no fatalities.
Image 2:
This is an image of the Botha landslide upslope from the city of
Muzaffarabad. This landslide was triggered by the earthquake and,
according to local people, developed over the following month. The
material is mostly colluvium. Note the earthquake shattered house
in the foreground. I have severe concerns about the stability of
the land to the right of the Botha landslide (see below).
Image 3:
This is an aerial image showing a small, earthquake-triggered,
rotational/translational landslide on the south side of Muzaffarabad.
Note that a substantial number of houses are threatened by this
landslide both in the crown (upper) area and at the toe. The
electricity pylons are also in a very hazardous location.
Whilst the landslides shown in images 2 and 3 are dramatic, I do not
believe that these constitute the main threat to the population in the
Muzaffarabad area. I believe that the principal hazard lies in the
incipient landslides that appear extensively across the landscape.
These are slopes. mostly within a few kilometres of the fault, which
have been extensively deformed but have yet to fail, probably because of
the dry weather since the earthquake. Most of these slopes would
seem to be highly vulnerable to failure in the forthcoming monsoon.
In image 4, an area of cracked slope in the Botha area of
Muzaffarabad is shown. In this case the cracks extend some 400 m
up the slope, covering an area of several square kilometres. This
area is that highlighted in image 2 to the right of the existing
landslide. The slope is still inhabited. In image 5 another
set of these cracks is shown, in this case at Upper Killha above
Muzaffarabad. Such cracks occur across the landscape in the
Muzaffarabad area. In images 6 and 7 the threat posed by these
landslides is clearly shown. In image 6, a ruined school can be
seen. Note the multiple arrays of cracks in the slope down from
the school. Unfortunately, as image 7 shows, despite is very
hazardous location, the school is still in use (albeit in very difficult
circumstances. The threat to the children when the monsoon starts
is very high. Therefore, considerable credit should go to the
authorities for their evacuation plans in this area.
Image 4:
Slope cracks, indicating incipient failure, in the hills near to Botha
near to Muzaffarabad.
Image 5:
A multiple crack array in the area of Upper Killha, near to Muzaffarabad.
Failure of these slopes in the forthcoming monsoon looks to be very
probable.
Image 6: An
earthquake-destroyed school in the Upper Killha area. Note that
this school is built on the back scarp of one of the incipient slides.
Image 7: The
earthquake-destroyed school in the Upper Killha area, as shown in image
6. Note that this school is still being used by a large number of
pupils, housed in a temporary classroom on the left side of the image.
Clearly there is a considerable threat here during the monsoon unless an
evacuation is completed. The Hattian
Landslide
The Hattian Landslide was a gigantic, valley-blocking landslide
triggered by the 8th October 2006 earthquake (Image 8). It may
represent the largest landslide that occurred in 2005.
The landslide scar is over 1.5 km long, and the width is about 500 m.
The deposit has blocked the valley to a depth of about 250 m (Image 9),
and two lakes are currently forming behind the deposit (Image 10).
Image 8: Overview image of
the Hattian landslide (image courtesy of Dr A.B. Kausar, GSP).
Image
9: The Hattian landslide deposit, taken from the downstream side,
showing the valley blockage to a depth of 250 m. Note that when
the water starts to flow through the spillway it will then flow down the
valley in the foreground. The slopes on the right, which are
already heavily undercut, as can be seen, consist of relict landslides
and have arrays of new cracks in the headscarp areas. To
address concerns about the potential for over-topping, and thus
collapse, of the lake during the monsoon the Pakistan Army have been
constructing a spillway across the top of the landslide deposit (Image
11). Whilst the spillway is large, it is perhaps surprising that
the spillway walls are so steep (Image 11) and that there is no channel
on the downslope face. We are assured that the absolutely
essential spillway lining will be in position before the monsoon.
Image 10: The larger of the
two Hattian landslide lakes, taken from the crest of the dam. Note
that the lake valley walls are highly asymmetric. On the left side (as
seen in this image) the slope is comparatively gentle. Note the
large shallow landslide however. On the right side the valley is
much steeper, and here the slopes show considerable signs of distress.
Image 11: The Hattian
landslide spillway under construction in late May 2006. Note that
the material forming the landslide is mostly silt sized particles of
sand and clay. In this context, the steep walls of the cut are
perhaps surprising. At the time of the visit the channel was
unlined, although we are assured that a lining is planned. Note
also that at the time of my visit the spillway ended at the location of
the excavator at the far end of the channel, and no structure was in
place to handle the water exiting the spillway.
The greatest threat to this site is probably posed by
the slopes above the larger of the two lakes, which are steep and show
many signs of historic landslide activity (Image 12). Close
examination of the slope itself suggests that there are many cracks and
lateral shears, suggesting instability (Image 13). I have some
serious concerns about the potential for this landslide system to slide
into the lake, with potentially disastrous consequences.
Image 12: The slope above
the Hattian landslide main lake (image courtesy of Dr A.B. Kausar, GSP).
Note that at the time of the photography
the lake was much smaller than at present. Note the multiple
indications of historic shallow- and deep-seated landsliding on this
steep slope. The Hattian landslide is at the far end of the lake,
and the source area is directly behind the ridge at the back of the
slope pictured.
Image 13: Cracks in the
slope above the Hattian landslide main lake. Cracks such as this
exist across the whole of the slope above the lake, suggesting that
there is a high level of hazard. In the monsoon, the combination
of intense, prolonged rainfall and increasing groundwater levels as the
lake fills presents a high level of hazard at this site.
This page was compiled by Professor David Petley of the International
Landslide Centre at the University of Durham. Please contact me
for any further information or assistance. Postal address:
Professor David Petley, International Landslide Centre, Department of
Geography, Science Laboratories, Durham DH1 3LE, United Kingdom
Telephone: +44 191 334 1909
Fax: +44 191 334 1801
Email: d.n.petley@durham.ac.uk
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