6 May 2014
New photos of the Ab Barak landslide in Afghanistan
Posted by Dave Petley
Photographs of the Ab Barak landslide
The Atlantic has a wonderful gallery of images of the Ab Barak landslide in Afghanistan. There are 22 images to choose from, including this fantastic overview of the whole landslide:
There is a great deal to note from this. First, I think that the image confirms that the Ab Barak landslide is in loess (i.e. a deposit of windblown dust). All of the features visible, including the nature and colour of the material, the lack of boulders and the gullying in the areas around the landslide suggest that this is a loess landslide. Sue Kieffer has a very nice post on her blog about why loess is so susceptible to landslides. Second, the mobility of the landslide is clearly evident, and in particular the way that it has flowed up and down the main valley, and up the side valleys too. Third, the large, old landslide scar next to the recent one (on the right side) suggests that this is a material that is prone to landslides. And fourth, this other landslide scar probably indicates the likely future of the Ab Barak landslide site. The old scar extends almost to the ridge line, whereas the recent one has left a great deal of material intact on the slope. There is a partially detached mass on the left side of the new scar, but the remainder of the scar is over-steepened and is likely to fail in due course. If this occurred as another large landslide then the material would over-run the existing deposit and would threaten the houses in the surrounding area. I can see little alternative to relocation of those properties if the safety of the inhabitants is to be assured. The image below shows just how close some of these houses are to the landslide deposit:
Note also the lake building up on the left side of the landslide deposit. This of course poses an additional threat, although the height of the landslide deposit suggests that it will be a while before the lake over-tops. However, the landslide deposit is not as large as is the case for many landslide dams, and the material is of course highly erodible, suggesting that a rapid release might be possible. There is a need to mitigate the threat quite quickly, though fortunately we are now entering the dry season in this part of Afghanistan.
Lessons learnt from the Ab Barak landslide?
It is good to hear politicians indicating that disaster risk reduction is becoming increasingly important. Richard Bowden, UN Humanitarian Coordinator for Afghanistan, is quoted as saying:
“I think when you fly over the area itself, and see how the earth moved and the fragility of the environment here, it highlights the long-term risk to the population in this very vulnerable province and the need for long-term preventive measures.”
This is quite correct – I just hope that this is translated into something meaningful. Far too often these sorts of good intentions are not translated into a meaningful programme of work, unfortunately.
How much is this due to deforestation? There are no trees holding the soil in place.
Yep, I just googled it and deforestation is a HUGE problem there, and has been for decades…
“Deforestation has also made the country more prone to flash floods and landslides. Every year floods cause human deaths and loss of property in Nangarhar, Kunar and Laghman provinces, according to the Afghanistan National Disasters Management Authority.”
“‘Deforestation has contributed to the longstanding drought in the country,’ Ahmad Bakhtyar, an expert at the Ministry of Agriculture, told IRIN.”
Once-green mountainsides across Afghanistan are still being stripped of their trees as the long-running process of deforestation continues.
Deforestation has resulted in numerous landslides and extensive erosion, reducing the already limited area of arable land available.
I also note that there are a cluster of houses built within a slide scar above the creek in the upper left-of-center portion of the second photo. Living at the mouth of a cannon……..
This same process happened in central China (Shaanxi?) If I recall. Rugged debris flow prone canyonland w/ strips of agriculture on the remaining flat ground up top on what was the original ground surface centuries ago.
Desio (1975) mapped the area as blanket loess; presumably overlying a subcrop of Carboniferous intermediate intrusives mapped by the Soviets (dubious). A bit SW of here in the vicinity of the coal mines I noted many landslides in the marine Upper Jurassic (which is laterally restricted) or perhaps loess covering the marine J3. The major and very active fault systems of Laran and Eshkamesh/Darvaz straddle the slide area, and there was a small(?) quake with casualties in Rostaq on April 12.
The Boston Globe’s Big Picture Photo Blog has more images:
It is very premature to attribute any of this to deforestation. The terrain in question resembles lichen (rather than boreal) taiga. It is much different in terms of elevation, topographyy, precipitation, and geology/soils than the alpine areas of Nangarhar and Kunar. That is not to say that deforestation has not taken place, but particularly in the loes terrain, it needs to be documented.I tried to do this naecdotally while in Northern Afghanistan, with little success.
There are no trees at all on those hills, only a few around the houses. Are you suggesting that is natural – that no trees evolved to live on those slopes? I’ve been googling taiga and all I can find are links to high latitude locations (and even those have trees). Can you provide more information?
I’m not an expert on the climate of Badahkstan, but I got the impression that the climate of Badahkstan might be quite similar to that of the U.S. High Plains region where short grass prairie dominates and some trees eke out a living in riparian zones and around homesteads.
I did spot this article, not specific to the landslide zone:
To some degree i am suggesting that. There is anecdotal evidence that that there was once a wild pistachio-juniper cover in these areas (see ‘UNEP deforestation afghanistan’ or ‘vegitative potential maps afghanistan’). This is not my area of expertise; I did, however, notice incipient solifluction and landslides in the steep loess slopes which implied to me that it was possible these areas were never or only sparsely tree-covered. The only trees I saw anywhere in Afghanistan other than the alpine Hindu Kush were riparian. Field research will be necessary to assess the landslides in Afghanistan, and that will not be easy in the current security environement.