I do a fair bit of landslide work and so try to stay up with the science. I have been following the developments associated with a very large landslide in northern Pakistan. This slide took place in one of the most rugged landscapes inhabited by humans on the planet. It completely blocked the road between Pakistan and China. Its must be an amazing road to travel as it crosses just in front of huge valley glaciers, crosses very active alluvial fans and the entire valley is hemmed in by huge mountains.
I recently took a look at the satellite imagery accessed via Google and found that a newer high resolution view of the area shows the slide and the lake forming behind the slide. An older view of the river prior to being backed up can be seen on the right of the image. The yellow line is a rough approximation of the road route. The lake has inundated the bridge that formerly crossed the river to the northeast in the image.
The risk now is that the landslide dam will fail suddenly as the water levels behind the dam rise. Geologic evidence downstream indicates this sort of event has happened in the past and there are what appears to be lake terraces up stream from past landslide dammed lakes. Pakistan government has been excavating an emergency spillway to reduce the final height of the lake and reduce the risk of a catastrophic breach of the landslide dam. But this is an emergency effort with very limited time. It has been a heroic effort given the conditions and location. One worker was killed from further rockfalls on the slide. He was not able to hear the crashing boulders that were approaching as he was operating an excavator.
As the spring snow melt begins the lake will fill rapidly. The anticipated date of the dam being over topped is in about two weeks.
4 months ago