Most importantly, here is an overview image of the spillway:
It is helpful to compare this with the image of the spillway from 1st June (right hand image):
It is clear that the situation has developed considerably over the last few days. The flow along the spillway has increased greatly, and the lower part of the channel has widened and deepened. Flow appears to still be controlled by the large boulder in the middle of the channel, although the lowering of the channel downstream will be steadily undercutting this.The development of the spring on the channel edge is also interesting.
A closer view of the spillway clearly shows how widening is occurring:
The flow is undercutting the banks, which are then progressively failing. Note also just how much scour is occurring even though the bed of the channel is boulder-strewn - it is clear that at the moment the boulders are not armouring the channel.
A view from the downstream side of the channel is fairly dramatic:
This gives the impression that there is a huge volume of water flowing. However, a look downstream towards the old landslide deposit at Salmanabad (that is the big pile of debris upper right) shows that this is not really the case:
It is clear that the flow is still rather modest, despite the huge amount of erosion that the water has achieved.
thanks David its really nice analysis and the pics are too clear. if we look at the 3rd pic very closely near the entrance of the spillway it looks a huge erosion is gonna take place possibly tonight but it depends now on the rocks there how much could it create resistance.
ReplyDeletewe all pray for a smooth end of this lake.
Those boulders continue to be of particular interest. I can only hope there are enough to provide sufficient ballast. It's clearly a guessing game without a complete assay of the soil, but as long as there are sufficient boulders, and as long as the rate of flow remains below the entrainment velocity, this situation might not be as bad as many have predicted.
ReplyDeleteThe channel base is starting to look pretty bouldery. That seems like a good thing. It seems like the composition of this slide deposit is quite a bit coarser than the one in China that has been used for comparison a couple times here.
ReplyDelete