6 May 2014
Photographs of the Ab Barak 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.