8 August 2010
Meanwhile in Northern Pakistan…
Posted by Dave Petley
Amidst the appalling tragedies playing out in southern Pakistan and in China, Northwest Pakistan continues to grapple with its own problems. Unfortunately the problems at Attabad have not gone away as yet, even though the NDMA reports on the situation have now dried up completely. However, the Pamir Times are still on the case, with a somewhat concerning report yesterday that “Three more houses were dismantled in Gulmit Gojal due to sudden increase in water level of the dammed Hunza River…Rains and floods in different parts of Gojal valley have taken the water level up by around three feet during the last 36 hours, according to local people.”
That new houses are being dismantled suggests that the lake is at its highest level so far. I do hope that the spillway is being watched carefully.
Meanwhile, the Frontier Post reports two substantial landslides in Gilgit-Baltistan on Friday and Saturday. The first occurred at Qamrah village in Skardu district late on Friday night, reportedly killing 35 people. The second occurred in Shout village in Ghanche district, killing four people. Flash floods are also causing substantial problems.
The only near real time proxy that I have found is the Partab Bridge hydrograph. It's at peak values right now, mitigated by the thought that perhaps the other tributaries from Skardu et al are also high.Thus it looks like our low resolution view of an Attabad dam failure will be a profoundly scarey spike on the Partab chart — if you see a huge vertical jump, suspect the worst. Or if Partab drops off the charts altogether, worry. (Dave, do you have a comparative view of a dam failure vs the recent gilgit flood? What would the difference be?)The Gilgit max temperature graph has been in line with the seasonal averages. Without rainy (and therefore cloudy) weather, it looks like the glacier runoff is also high. Today's temperature graph suggests rain and cooling after 3 days of warmth. So perhaps the lake level will fall again. (But if rain comes in the form of downpours — or really, significant amounts; water does not stay on those mountains unless it's frozen — all bets are off.)As I understand the physics, at the current lake level the pressure is around 170 lbs per square inch at the bottom of the water column. And if a significant fraction of that pressure gets to place where it can be applied sideways, boulders move. (Limestone is only 163 pounds per square foot.) Fortunately, the very long profile of the landslide dam — remember that long upriver slope leading up to the spillway when it was being made? — have prevented so far a catastrophic failure. Currently, mu guess is that the spillway is just like an overflowing bathtub; the water we see going over the top is in a minimum pressure regime. But as the downstream side erodes and the long leading toe shortens, the potential pressure differential increases. Eventually the sideways force of the water may exceed the weight of the dam. And even a single point of flow may be enough to start the process.One hopes that there's at least one aware set of eyes watching that dam and that they have a hot line to the powers that be.
oops, 163 pounds per cubic foot.
There are also reports that landslides have "narrowed" the spillway, sugesting that the lake level is also being affected by outflow constriction. http://www.southasianow.com/47-dead-in-skardu-ghanchhe-flooding/
Pakmet issued this warning today: S.No.33Dated: 08th August2010Significant Flood Forecast For River Indus(Partab Bridge to Besham andTarbela). According to latest Hydrological conditions / observations River Indus from Partab Bridge to Besham and Tarbela is likely to flow ranging between 550000 to 650000 cusecs during next 24 hours. Due to this massive flow, the areas between Partab Bridge to Tarbela (Bunji, Chilas, Pattan, and Besham) and low level bridges over the river is likely to be damaged badly.Time of issue: 1515 hrs PST
Partab Bridge has missed its last two updates.If it's just a sensor failure, it may be weeks before it is repaired.
We had a "little" dam break last days here in middle Europe: After heavy rain the river Neisse (usual depth at this time of year in Görlitz/Germany 1.7m) the level rose on saturday to about 3m. Nothing extremly, highest historical levels were somewhere in the 6.7m.Then in the night to sunday a dam broke in Poland – dozends of km away. The water in Görlitz was rising for 3 hrs, marking an historical record of 7.07m on sunday morning. Later the same day the level began to drop, although it is still high… and rain continues…So in this "little" case the level of the river rose for more than 100% over the existing flood level. I do really not want to know, what would hapen, if similar things would happen at Attabad.Thanks to everyone keeping the world up to date!
The controlled blasting of the Attabad dam may be delayed indefinitely because of the unfolding floods in many parts of the country and the shortage of manpower to address the multitude of emergencies.Too bad nothing more was done while there was time. Too bad, Attabad!Brigitte
According to my sources in Hunza, the rise in Attababd lake level was 9 inches on 8th Aug and the flow at Ganish bridge was 35430 cusecs.But there are lot of flash floods in the area and FOCUS has also redeployed it's assets to other parts of GB province,Chitral and Sindh province.Engg. Hussain