10 June 2008
Tangjiashan – latest image
Posted by Dave Petley
This is a new image released by Xinhua of the collapse at Tangjiashan. It is clear that the dam has now effectively failed:
The rate of scour is clearly very fast and the lake level is still very high indeed (it has apparently dropped 10 m). CCTV has just reported that the smaller dams downstream have now been overtopped and washed away.
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
Impact downstream:http://uk.reuters.com/article/topNews/idUKPEK30372720080610BEICHUAN (Reuters) – Muddy lake water from a dangerously unstable “quake lake” rushed into the devastated Chinese town of Beichuan on Tuesday, covering about a third of the settlement where the water level was rising fast.Brown water, clumps of trees and occasional vehicles pushing against buildings were moving quickly into low-lying areas of the town, washing away remains of buildings, bodies and valuables left under the rubble.
The slide dam failed at its toe, and the uphill part of the slide mass is still saturated, and worse, its toe is being swept away. There will probably be a failure of the whole hillslope before this is over.
http://64.233.179.104/translate_c?hl=en&u;=http://news.sohu.com/20080610/n257396790.shtml
The channel bank is very steep. The failure of left or right banks (landslide mass) may again block the channel flow. If it happens it will help to reduce the outflow discharge.
The lake level was 737.51 m at 11 am.Is there any hope that fast decrease of water level will slow down the callapse of the dam?ah
Water level of lake is 734.3m at 12:00, discharge is dropped to 5200m3/s from 7300m3/sec (at what time??).
The water level of lake at 12:30 is 732.5m and outflow discharge is 5630m3/sec. Probably, the peak discharge is 6500m3/sec at 11:00.(http://news.sohu.com)
1pm, 5310 cumecs, 730.48 mhttp://news.sohu.com/20080610/n257397821.shtml
The peak flow rate was 12,000 cubic meters per second (cms) at 12:45 p.m. (Beijing time). The flow has come down and is now relatively stable at about 5,000 cms. I feel better now.Source: Xinhuanet
hi, Dave, the picture is dramatic, but without first hand data, i don’t think it’s wise to play the role of doom predictor, actually, the water level has dropped from 742.8 m (8am local time) to about 730m (1pm), the volume has peaked around noon at 9000 cubic meters per sec, now is stable at 5000, remaining water in the lake has also dropped to 0.16 billion m3 from around 0.25 bm3. engineers are hoping the current volume will hold for another several hours to lower the water level further to 720m, which they consider won’t pose much danger even the dam give away totally.the reuters report mentioned the town of beichuan, to be honest, the town has been destroyed in the quake, chinese troops had it sealed off after rescue work, no one was allowed in given the pending lake.as to the small dams downstream which collapsed, it is a bliss in disguise for local people, several little time-bombs now gone.there are lots of chinese web sites following the story 24/7, local tv has the whole situation live on air, if they need to run, they will know. please don’t create panic for people already suffer so much.thanksxuan
At 2 pm, the discharge was 3880m3/s and the level was 727.94m.ah
hi, Davedon’t know if you can read chinese, here’s the web site of china water resource ministry,http://www.mwr.gov.cn/xwpd/zxrd/2008053011492020a0aa.aspxdetailed data over there, updated hourly, way faster than their english version. the experts on the ground are hoping the water can carve a slice as wide as 300m (right now is 130m), as low as 720m above sea level. http://news.xinhuanet.com/newscenter/2008-06/10/content_8338676.htmxuan
Hi Dave,BBC has video of the army shelling the sluice channel:http://news.bbc.co.uk/2/hi/asia-pacific/7443568.stmWas this really a necessary step? Wouldn’t the water have been able to erode the channel at a more steady and presumably safer pace if they had just been patient? Interested in your opinion.More from BBC:http://news.bbc.co.uk/2/hi/asia-pacific/7404614.stmhttp://news.bbc.co.uk/2/hi/in_pictures/7444823.stm
Great blog, thank you everyone. I think the Chinese army have done what they could. No, they are not experts in this kind of thing.Here are two videos showing the army hiking into the area and setting up some dynamite blasts.http://tv.sohu.com/20080610/n257380355.shtmlhttp://v.youku.com/v_show/id_ca00XMzAwOTg0OTY=.html
brad,I think it was neccessary because at that time the water level was keeping rising(as the outflow well below 100m3/s). The later sudden massive discgarge(happened when outflow~100m3/s) seems invitable. Given that, it might be better let it happen sooner with a lower water level.Now it seems that the drama is over.
holl;Those two video are about another tiny quake lake, totally irrelevent to the topic of the blog.
OK, a bit late, but here is a dam being deliberately breached in Norway.http://tinyurl.com/4lyubpInteresting to note the very slow start and then the rather sudden rush!