At the moment there appears to be little evidence from these figures that large-scale scour and erosion has been initiated - the increase in flow appears to be the consequence of the increasing lake level, plus perhaps some lateral erosion.
However, erosion at the toe of the slope remains the major concern, with reports suggesting that the gully is continuing to erode back through the channel. This remains the most likely failure mode of the dam, but this may take a few more days to initiate. In addition, the increasing channel discharge may cause the flow velocity to increase to the point at which basal erosion starts. This has not yet happened, but could begin at any stage.
There have been various comments on the blog that the dam is not behaving as expected - i.e. erosion is not initiating - and that as a result measures should be taken to encourage erosion. I want to stress that this is not correct - from the start we knew that it could be that it could take some time for erosion to initiate. So far I see nothing surprising in the behaviour of this system, and nothing to suggest that erosion will not allow a lowering of the lake level in the next few days. At the same time, it is important to emphasise that the probability of a rapid breach has not diminished, and may in fact have slightly increased due to the headward erosion of the lower gully.
There is no need to panic, but at the same time there is also no justification for lowering the alert status. We all need to be patient and alert - this has a long way to go yet. If you are in the area please pay attention to the local alert system.
Dave,
ReplyDeleteWell said! People must remain vigilant. The discharge through the spillway is still only about a tenth of the inflow to the lake, so the situation has a long way to go yet.
Thanks again for keeping us all informed with developments
i think there is a possibility that when erosion goes back towards the lake and when the spillway deepens, the debris from either sides or both sides may fall into the spillway and we may see another blockage in next few days..........situation is gonna be more alarming. The responsible authorities should take serious note of all the repercussions. The world knows they have created an absolute pandemonium for all of us in the region and for themselves as well. Come up people of Hunza-Nager and Gilgit Baltistan our leaders procrastinating and irresponsible behavior is drowning us and flooding us away.........its time to wake up.
ReplyDeleteMr Bashu Hunzai... you choose to be with your dearest pakistan !! now you understand how much the punjabis care for you folks.
ReplyDeleteHUNZA, has a all kind of access to all telecom communications like tv, internet, mobile, radio, cable etc, so i believe that mostly Hunza guys living within the country side or abroad, are following Dave;s web.
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