27 February 2012
Updated (twice) with videos: Breaking news – the Attabad landslide spillway has been reopened
Posted by Dave Petley
http://pamirtimes.net/wp-content/uploads/2012/02/Attabad-Spillway-Hunza-1.jpg
The Pamir Times is reporting that the coffer dam at the Attabad spillway, shown in the above image from the Pamir Times, has been blasted today, allowing water to flow through the newly reopened spillway. At the time of writing that are reporting that the discharge is about 50,000 cubic feet per second (1415 cubic metres per second), which is amongst the highest flow rates recorded through the spillway to date. The lake level is reported to have dropped by about 45 cm so far.
Update 1: The following video has now been posted on Youtube. The flow looks to be impressive:
Update 2: A video of the blast is now available too:
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
It will be interesting to see how much the lake will fall after the initial discharge tails off. Any ideas how much the spillway was deepened?
From the first picture there still seams to be some large boulders in places that restrict flow.
However, there seems to be a fair amount of debris being eroded by the initial flow.
Why was the coffer dam constructed? Was it simply to allow the blasting engineers access to place the explosives in the best place?
Did it cause the head of water to increase prior to blasting?
It looks very fine grained, and I doubt there will be much of it left now.
Brian, the coffer dam was built to allow work to be done on the spillway below it. I think the intention is that the spillway will now erode naturally. The coffer dam raised the water level by 3 meters, but I’m not sure how that relates to the highest ever level, as the spillway did erode somewhat when it first breached after the landslide.
[…] effects of the excavation operations to lower the deepen the spillway at Attabad, which led to the removal of the coffer dam on Monday. So far this operation appears to have proceeded well – and credit is definitely due to the […]