18 May 2010
The final spillway at the Attabad landslide
Posted by Dave Petley
The GLOF into the lake behind the Attabad landslide yesterday appears to have raised the water level by something over two metres, in addition to the increase of about a metre from the normal inflow (please see the data on my monitoring site). The upshot is that the freeboard is likely be 4 metres or less. Inflow has increased substantially as well to about 93 cubic metres per second. It has not been possible to measure seepage in the last 24 hours as the site is now too dangerous.
All work on the spillway has ceased and the machinery has been withdrawn. The final form of the spillway is shown in this Focus image:
It pains me to say this, but I simply cannot see how this will resist the peak flow in the Hunza River. However, it has at least served the purpose of reducing the total volume of water involved in any flood that should occur.
The boat service has also now ceased as it would clearly be too dangerous should a breach start.
Water flow past the blockage may start through one of three key processes:
1. Overtopping and water flow through the spillway. In Tangjiashan the initiation of erosion started some hours after initial flow; this may or may not be the case here. Erosion may start on the downstream face or at the crest of the spillway, or there may be slope failures on the downstream face. It is also possible that the sides of the channel may fail, creating a new blockage, stopping water flow for a while.
2. A seepage induced failure. This is less likely than 1., but remains a distinct possibility;
3. Overtopping initiated by a landslide into the lake.
None of these can be ruled out at this stage, but 1. is the most likely. If so, the size of the resultant flood will depend upon the rate of erosion, if any.
I hope above all hopes that erosion happens slowly. My thoughts are with the people of Hunza.
Oh men! this is like a nightmare. It's unbelievable how the authorities can not listen the scientists, we have the same problem in my country, Peru.Best regards, and waiting for the inevitable and final post of this sad history.Patricio V
Well, we are all hoping that erosion will happen slowly! But today's significant episode of sliding at the Attabad site is very concerning! Now the lake will become even more massive… and I wonder if the spillway has been filled in by the new sliding.
The Sliding seems to have happened at May 12th though… so before work on the spillway ceased (if I got it right)…
The Sliding seems to have happened at May 12th though… so before work on the spillway ceased (if I got it right)…
This is not a spillway.It is just an old Hunza style channel which would get eroded in no time by the ever fierce Hunza River.This gigantic river is probably going to keep up its past reputation of cutting at everything coming in its way!!Prof Salman Ali
Well, it looks like there will be flooding in the end, which is a problem. That's a good video of the landslide that you have from youtube. Quite dramatic.