Gifts and Perils of Landslides

Ken Hewitt has written a wonderful article for Scientific American entitled "Gifts and Perils of Landslides", in which he examines the inter-relationship between the development of society and the occurrence of landslides in the Upper Indus valleys.  Ken is the guru of high mountain landslides in Pakistan, having spent many field seasons mapping rock avalanche deposits in the remote upper valleys of the Hindu Kush.  The article is available online at the following link:

http://www.americanscientist.org/issues/feature/2010/5/gifts-and-perils-of-landslides

His key point is that these giant landslides create both destruction and benefits to humans in this very rugged topography, the latter because they create terrain that is fertile (e.g. on lake beds formed behind landslide dams) and less steep. 

The piece will be accompanied in due course by a slideshow, which will be online here.  This is not yet available.

Meanwhile, the Pamir Times has an image of restarted works on the Attabad landslide, the aim of which is to widen and then, I understand, to deepen the spillway:

Potential landslides in California and the ongoing crisis in Hunza, Pakistan

Amongst the (appropriate) focus upon Haiti at the moment, we must of course remember that landslides do not stop elsewhere. So, here are two important ongoing stories:

1. Potential landslides in California this week:
The US National Weather Service has issued a series of warnings for very heavy rainfall in California this week, with the pontential for landslides, flash flood and debris flows. For example: ...Flash flooding and debris flows possible for recent burn areas In southwestern california late monday morning through monday night... .the first in a series of powerful pacific storms is expected to Move into southern california tonight into monday. Initially...rainfall Is expected to be fairly light...with rainfall coverage and intensities Expected to increase significantly by late monday morning through Monday evening. Rainfall rates between one half inch and three Quarters of an inch per hour will be possible monday afternoon Into monday evening. Local rates over one inch per hour will be possible Near thunderstorms and across favored south facing slopes...including The station and morris burn areas. Rainfall totals with this first Storm system through monday night are generally expected to range Between one and three inches across coastal and valley Areas...with three to five inches in the foothills and Mountains...except local amounts up to 6 inches possible across Favored south facing slopes. For the station burn area...rainfall Totals of 3 to 6 inches can be expected through monday night. Additional periods of heavy rain will be possible later in the Week as future storm systems move into the area...which may Require additional flash flood watches to be issued.

And:
...Wet weather to continue through much of the week... A series of storms...no fewer than six...are lined up across the Pacific all the way to asia. The first of these systems was moving Through the central california interior this afternoon...and will Spread light to moderate rain to the central and southern san Joaquin valley and the adjacent sierra foothills through tonight. Rain also will spread into the high deserts of kern county by late Afternoon and tonight. A second system is developing west of the California coast...and will move into california monday. It is This system that will spread occasional rain...heavy at Times...into the region. For the rest of the week...it is still too early to say when and How much each individual system will impact central california. But there will be periods of rain...heavy at times. Preliminary Indications are for another strong surge of moisture during the Day tuesday...again wednesday...and yet another thursday. Some Decrease in activity is now seen by the weekend...or at least Becoming more showery at times.

There is particular concern about the potential for debris flows in the Station Fire burn zone in the San Gabriel Mountains, as shown in this NASA satellite image:


However, as the La Conchita landslide showed five years ago, many areas in California have the potential for a landslides during very heavy periods of rainfall. It will be an interesting week.


2. The Attabad landslide in Hunza
The blockage of the Karakoram Highway by the Attabad landslide in northern Pakistan continues to cause major problems to that area. Meanwhile, the lake is continuing to fill. The Pamir Times continues to provide excellent coverage of this serious event. Over the weekend they posted a series of images of the slide. First, the lake:


Second the contact between the water and the dam sediment:


And finally the flow path once over-topping is achieved:

In some places the materials look worryingly fine grained and even muddy, but it is impossible to get a proper idea from these images. The report says that the water level is currently 10-15 m from the dam crest, which is of increasing concern. Various reports suggest that there is little government action to date in terms of creating a channel, although clearly this is unverified. It would be unwise to allow the water to flow over the top of the dam without being controlled. However, a report from the ICRC in Pakistan, dated 14th Jan, states that "According to the local government, a dam burst is very highly unlikely to occur."

Detailed information and amazing images of the catastrophic Attabad (Atabad or Atta Abad) landslide in Hunza, Pakistan

See update from 11th January 2010 here



Pamir Times image of the landslide

A few days I ago I posted on reports of the Attabad landslide (which is variously described as the Atabad landslide or the Atta Abad landslide) in Hunza, Pakistan. There has been very little information about this bar various reports that it was not as bad as had been feared. However, Reliefweb has today published a report from the Pakistan Red Crescent that paints a rather different picture.

The essence of the report is as follows:

• The slide occurred in two parts, the first at 13:00 (local time) on Monday 4th January, the second two hours later. The second slide was the larger of the two;
• To date 15 fatalities have been recorded; an unknown number of people are missing;
• Debris has covered a 4 km stretch of the Karakoram Highway, to a maximum height of 263 feet (80 metres) (!!!). The road is still closed;
• 1763 people have been displaced.

However, perhaps the most important part of the report states that:

"On 6th January Pakistan Red Crescent Society (PRCS) Gilgit-Baltistan branch reported that the Hunza River is still blocked and its level
had risen to 350 feet and still rising. The situation raises fears that low-lying areas across the
river would be inundated. The population of these red-zone areas is estimated to be around
20,000 people."

350 feet = 107 metres.

The Pamir Times has published a very high quality set of images of the landslide here. Two images are particularly useful - first, this one shows on an aerial image the area affected by the landslide:


Second, this image shows the slide debris and the lake, taken I assume from the top of the landslide debris pile:

The most extraordinary image though is this one, captioned "Huge clouds of dust arise as land sliding continued on second day of the Attabad disaster":

Dawn.com reports that towns up the valley from the blockage, especially Gojal, are facing real hardship due shortages of food and medicine caused by the road blockage. This is of course mid-winter in a high mountain location. They suggest that it may take a month to reopen the road. Meanwhile they also expressed concerns about the potential for failure of the dam, causing a catastrophe downstream, which judging by the images above must be a real concern.

Finally, an EEFIT report on the landslide site, dated 2003, is available online here:

http://www.istructe.org/EEFIT/files/Atabad%20Landslide.pdf

The report describes the existence of a very large tension crack, in places 1.5 metres wide, across the slope and through the village. This crack appeared in 2003.

The reports states, with an impressive level of prescience:

A sudden catastrophic failure of the size, and which not uncommon elsewhere in the Northern Areas, could have the following effects:
• Removal of fields over perhaps half the village area and also removing nearly 30% of the
farming properties.
• Destruction of the rough mountain road probably with no alternative route that could be
established at any time in the near future.
• A blockage of the Hunza River - of a temporary or permanent form. Dam breakage could
cause disastrous water wave effects down stream. The dam hypothesis should be compared
with the estimated 2Mm³ of scree soil that in 1980 formed a permanent dam across the
Ghizar River just up stream of Gupis, west of Gilgit.
• Creation of an adjacent unstable landform and which contains other houses and associated
fields.
• Knock-on effects of loss of tree stands in minor descending lateral Hunza Valley gorges.
• Destruction of buildings, farmed lands and water supply to Sarat village.

Comments and thoughts welcome. See update from 11th January 2010 here

Landslides in Darjeeling, India

In September 2007 intense monsoon rainfall in the Kalimpong region of Darjeeliing in Northern India triggered large numbers of landslides, killing at least seven people. This has brought to the fore the issue of environmental degradation and the consequent landslides in Himalayan environments. Darjeeling is a microcosm of problems arising throughout the Himalaya, with rapidly increasing numbers of landslides causing major problems.

Darjeeling is probably most famous for its tea plantations, which thrive there because of the rolling topography, moderate temperatures and high rainfall. These conditions are great for tea but bad for slope stability. Preservation of the landscape can minimise the occurrence of landslides, and indeed the tea plantations generally do this reasonably well if managed carefully. However, many Himalayan regions are currently facing a near perfect storm of conditions that promote landslides - rapid population growth (which means that there are more people needing more houses and more food), deforestation, uncontrolled building to low standards, intense monsoon rainfall, and the construction of low cost roads with poor engineering standards. The upshot is all too predictable - increasing numbers of landslides with a growing level of impacts. The image below from Google Earth shows the town of Kalimpong, located on a high ridge. The slopes below are scarred with active landslides, but more importantly much of the landscape is made up of old landslides and landslide scars. Kalimpong has been seriously affected by active landsliding in recent years.


Now, as the SW monsoon rains start to build, the issue of landslides in Darjeeling is becoming pressing once again. In Darjeeling though there is one glimmer of hope, which is a remarkable campaigning group called Save the Hills, led Wing Commander Praful Rao (Retired), who campaign to raise awareness of issues associated with slope instability in Darjeeling. They have a very detailed blog in which they document both the magnitude of the challenges and the range of their activities to reduce landslide occurrence and to increase preparedness and resilience. I thoroughly recommend taking a look as it represents a model of community-level action in response to landslide threats. The main blog is here:

http://savethehills.blogspot.com/

I particularly enjoyed their images of historic landslide events, which can be found here. Darjeeling is fortunate to have such an active group, and I hope that it is able to make a difference. Many other places would benefit hugely from the activities of such organisations.