11 May 2015
Gorkha earthquake update
Posted by Dave Petley
Gorkha Earthquake update
The landslide situation in the aftermath of the Gorkha earthquake in Nepal is steadily becoming more clear due to the efforts of multiple parties. Importantly, the main groups working on mapping the landslides have now joined forces and are indeed generating a common dataset. There is a nice summary of their efforts on the ICIMOD Gorkha Earthquake portal, which notes that:
“To date, the response teams have identified over 3,000 landslides, and assembled a database of over 250 identified landslides and other large mass movements, focusing specifically on those that were generated by the earthquake and its aftershocks or other secondary effects.”
The Google Earth map of the 250 landslides is available to download as a kml file. The map looks like this:
As the BGS / EWF team noted earlier, the landslides are concentrated in the northern area of the earthquake affected region, and many are along highways. Apart from the high losses associated with Langtang moraine and ice avalanche, the most serious landslide identified to date seems to be a valley-blocking slide on the Marshyangdi River upstream of Lower Pisang. NASA have a nice post describing this landslide, including this satellite image. This work was undertaken by Dan Shugar from the University of Victoria in Canada:
As of 6th May this landslide dam had not breached.
Meanwhile, news reports are describing the impact of landslides at various locations. For example eKantipur has an article outlining the loss of life from landslides in Rasuwa:
“Scores might be missing in landslides triggered by the devastating earthquake on April 25 at Mailung, which lies between Dandagaun and Haku VDCs in Rasuwa district. Rescuers have fished out 12 bodies from the debris as of Sunday. The Mailung settlement has been buried by landslides. Locals said around 250 workers at the 60 megawatt Upper Trishuli III A hydroelectricity project, access road of Upper Trishuli I and locals have been buried in landslides…However, the construction company has the record of 32 workers missing. Sixteen workers are from Rolpa, two each from Dang and Bardiya. The address of 12 others is yet to be verified.
Two bodies of workers engaged in constructing the Upper Trishuli I road track, have been found. Project chief Uttam Amatya said they had recovered the body of one Chinese and another Nepali whereas eight others are still unaccounted for.
The District Administration Office said one each from Nepal Army and Nepal Police were also killed in landslides. Police found six bodies of people who had reached Mailung for a picnic. Eight other picnickers are missing.”
The magnitude of landslide damage to new and under construction hydroelectric stations in Nepal is the subject of an article in the Himalayan Times, which details extensive landslide impacts at a number of sites.
Finally, to date 120 bodies have been recovered from the Langtang ice and moraine avalanche.
Are there any plans to also assess the ice and debris cored terminal moraines that are retaining many supraglacial lakes? As I recall, there were several (including Rolpa Thso) that were categorised by ICIMOD as extremely high risk without the consideration of a seismic event of such magnitude.
I would think the reassessment is far more urgent now that a second quake has hit the Rolwaling Valley, some 15 miles west of Rolpa Thso.