However, we must not lose sight of the potential for other failure mechanisms. Given that seepage appears to now be constant, the greatest concern may well be associated with the potential for a further landslide into the lake. The high water levels and (comparatively) warm temperatures render this a possibility (but not in any way a probable event). This remarkable set of images, taken at 6:14 to 6:16 pm last night (10th June) by the Focus geologists, clearly illustrates the ongoing threat:
From the pics it looks like this landslide is at the mouth of spillway. Do you think this could cause blockage of spillway and dam would remain intact?
ReplyDeleteFOCUS helicopter video over spillway uploaded June 11. Fallen boulder clearly has water flowing on both sides. Gives good sense of the spillway's profile, especially in the first 15 seconds.
ReplyDeleteDave posted a link to a report on the flow rates of the Hunza during the year:
ReplyDeletehttp://iahs.info/redbooks/a190/iahs_190_0139.pdf
See Dave's entry here:
http://daveslandslideblog.blogspot.com/2010/05/inflow-to-landslide-lake-at-attabad.html
According to the observations of the author, the Hunza's peak flow (cubic meters) will happen in July, with the flow going down starting around August 1. While there are many more forces than just flow at play, it should be noted that the lake's inflow is still increasing, so for the lake to remain at its current level, the spillway flow would also need to increase. Obviously this is about averages, not a specific day. There could be cold upper elevation temperatures that slow the glacial melt, and thus, the inflow could slow.
According to the report, the flow rate can be expected to go down greatly in August, so if the dam holds until mid-August, it's my guess that we will be clear of flow issues until next year.
This month, June, the inflow into the lake is still increasing.
Yes, I know I've made some assumptions, including one about flow rates at the observation point and the dam location.