27 April 2012
Before and after – the Hattian landslide in Pakistan
Posted by Dave Petley
I was looking at Google Earth imagery of the area affected by the 2005 Kashmir earthquake this week, and in particular focused in on the Hattian landslide. This was by far the largest landslide triggered by the earthquake in 2005. There is a detailed description of the landslide in a paper that we wrote for Engineering Geology, which can be downloaded here. This image, collected in September last year, shows the landslide scar and the deposit. Note that the main landslide lake breached in early 2010 – evidence of the higher water levels for ZalZal lake is clear upstream if the blockage:
An interesting comparison is the image from before the earthquake, in this case collected in 2002. Note that Google Earth retains the labels indicating the location of the two lakes, which in this case is quite useful for orientation:
The area that the landslide affected is clearly identifiable in this image, and the condition of the topography appears quite deformed. In particular, the streams are deeply incised in comparison with the adjacent areas. Of course this then asks the question as to whether this site could have been identified as a potential landslide before the earthquake from visual inspection alone. In fact I suspect that this would have been difficult, but I am interested hear the opinions of others.
Dunning et al paper on Hattian landslide
No shortage of older landslide deposits evident in the GE screenshots. Based on the pre- and post-EQ landslide images, it looks like the failure may have involved older landslide debris. Also, it appears that there may be landslide deposits (or at least very thick colluvium) underlying the houses in the swale to the north.
I used these images in a piece of work I did last year. While I wouldn’t be confident in predicting a site-specific failure in advance, I did find it fascinating (and terrifying) to notice the amount of resettlement that’s taken place on the high slopes to the north east of the 2005 failure. Surely those areas on the margin of the current scar are vulnerable, if not the whole slope due to another deep-seated failure. One wonders what is happening in the locale as far as mitigation and preparedness are concerned?
[…] of two girls being killed in a flash flood or debris flow Hattian Bala, 50 km from Muzaffarabad. Hattian Bala was the site of the largest landslide, a giant rock avalanche, triggered by the 2005 Kashmir […]