10 June 2008
Tangjiashan – let's be a little careful here…
Posted by Dave Petley
I note from comments below that now that the landslide dam at Tangjiashan has failed the disaster is considered to be over. Please let’s be a little careful here. It is true that the flood waves has now passed through the upper parts of the river. Below is the graph of the reported discharges as per the comments left on earlier postings:
The water level is clearly dropping. However, the key issue is what happens downstream – it will take some time for the flood wave to reach these downstream areas. A wave of this size will inevitably cause considerable damage along the channel. We will know that the disaster has been averted when the flood wave disperses on the plains. Until we know this has occurred we must be careful. However, the Chinese government has been effective in moving people to date, so all the indications are that they are managing this crisis well.
Note that there is also a secondary risk that this wave will trigger further landslides.
Dear Dave:to 16:00 10 june, the discharge was 1680 cms, the water level was 725.8 m. A quick calculation on release volume was around 110 millions cm.since the discharge rising and falling so quickly, I guess that the dam breach was go to cut through model and stop it for a moment. From now on will be the most critical situation because the rest part of dam is still with 60 m height and dam breach can developed to second stage either to wider or collapse model which both model will send dramatical water to the downstream for the left 0.14 billions cm water.I hope the first breach was stoped and wait for a moment to second breach.