----------------------- Posted on 05/27/2008 1:25:49 PM PDT by Danae
Excavators work at Tangjiashan Lake in Beichuan County in Sichuan Province yesterday. Some 1,800 soldiers, each carrying 10 kilograms of explosives clambered up mountain paths to reach the barrier lake and blast through debris to drain water. Dozens of dams created by landslides during the May 12 earthquake are posing a new threat in the disaster zone.
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Excavators work at Tangjiashan Lake in Beichuan County in Sichuan Province yesterday. Some 1,800 soldiers, each carrying 10 kilograms of explosives clambered up mountain paths to reach the barrier lake and blast through debris to drain water. Dozens of dams created by landslides during the May 12 earthquake are posing a new threat in the disaster zone.
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Excavators work at Tangjiashan Lake in Beichuan County in Sichuan Province yesterday. Some 1,800 soldiers, each carrying 10 kilograms of explosives clambered up mountain paths to reach the barrier lake and blast through debris to drain water. Dozens of dams created by landslides during the May 12 earthquake are posing a new threat in the disaster zone.
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A SMALL diversionary trough was started this morning to drain water from a barrier lake in quake-stricken Sichuan Province and ease a flooding threat to millions of people in the area.
At the same time, soldiers are using big earth-moving equipment to dig out a bigger channel to drain the lake.
Flood diversion of Tangjiashan Lake in Mianyang City, the largest of 35 barrier lakes that formed after the 8.0-magnitude earthquake hit on May 12, began at 10:30am today, China Central Television Station reported.
The diversion was small and will not pose a threat to dams or other places down stream, a CCTV reporter said.
The lake holds 130 million cubic meters of water, according to Liu Ning, chief engineer of the Ministry of Water Resources.
The lake's water level reached 725.3 meters yesterday, only 26 meters below the lowest part of the barrier, Liu said.
More than 30,000 people in the Tangjiashan area have already been evacuated as the lake begins to swell behind quake debris that now blocks the Jianhe River near Beichuan, one of the worst-hit towns areas in the disaster.
Around 600 engineers and soldiers, who gathered at the blockage late last night, are taking turns to dig out a channel to drain Tangjiashan.
Several Mi-26 helicopters have transported 15 earth-moving machines since 11am yesterday to the quake lake area as it is still inaccessible by road.
The soldiers, who hiked to the quake lake carrying dynamite, want to remove 100,000 cubic meters of debris.
The channel digging work will take about 10 days and is expected to be complete by June 5 if the weather is good, CCTV said.
Experts previously planned to blast the lake. However, the plan was dropped in fear that a blast may shake nearby mountains that are already extremely unstable.
Hard to imagine just how big the scope of it all is...
Kinda like Hurricane Katrina.
I’m certainly no fan of China, but I must say their response to the quakes has been about as good as could be expected.
They can’t claim they don’t have the money to do anything. What money of ours that the ragheads don’t have is in China.
Of course those landslides don't care about design codes (unless they are in areas with oversleep road cuts, etc.) - but it doesn't look like it for this one. And one nice thing - we would probably waste valuable time coming up with an environmental audit, engineering studies, etc. before we could get an excavator on the site to open the drain a little.
Hope these guys can let the water out safely and in time. I'm thinking of those other workers clearing a highway slide when a tremor let loose another one top of them and killed a couple hundred workers as I recall.
THe pics are incredible,,everything looks so huge.
When I was a kid, me and my brother used to build these mud and rock dams in streams near where we lived.
If you’re into it, you can build up some pretty impressive stuff. One time, we got one up to almost two and a half feet or so.
But the water keeps coming in, and the amount of material you have to move to keep going gets to be too much, even for a couple twelve year olds.
So eventually, it starts to overflow the top.
Slowly, at first, a tiny trickle.
Then you know what happens. The force of the water running over the top starts to erode the dam.
And then, all hell breaks loose.
So what is it they are doing that differs at all from what I described? That water starts running, and it won’t be long before it is a torrent, not a gentle release of water from behind.
Not much. Better to have a relatively small torrent wash it out early.
The term relatively, being relative, of course...
Yeah. I wrote up something about that based on my experiences during the Loma Prieta ‘quake.
If your mud dam had been 2 1/2 ft. high, 10 feet across, and 30 ft. from front to back, the result would have been somewhat different. Take another look at the pics... In this particular instance, a relatively controlled release looks to be possible.
Now, if there are other areas with relatively high blockages that are not “thick” (from front to back), those could be very problematic.
P.S. No, I never got past a “thin” 2 ft. dam myself...
:-)
Good point.
Well, I guess two and a half feet is probably a bit of an exaggeration.
But My dam is still bigger than your dam...
;-)
I’ll probably get in trouble with the Mods if I say “Oh, ### ##!”
One thing though (seriously), I have to wonder what could happen to some of those landslide formed dams if there is a large aftershock after the new lake has formed behind the “dam”. If the material is unstable or liquifies, the whole mess could go roaring downstream almost instantly. Not a happy thought.
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