I would think other countries would try to replace any manufacturing lost. I realize it may take some time to fill the void but it seems many other nations would have some ability to do so. But I think you are right, initially it would be a gut punch to the world economy. Its like the world stuck all their eggs in the China basket. But I do believe American farmers would benefit almost immediately and (who knows?) perhaps a demand for American steel? No probably not, but the farmers I think so. And eventually, it seems, within a couple of years copper woud be in big demand. But thats morbid speculation. As much as I am not a fan of the Chinese govt and their style of govt, I do hope for the peoples sake they can get past this and the govt does actually fix the dam. And your anecdote related to the housing tracts in CA seems to be all to common. When I lived on the coast as a child there was a new middle/upper middle class neighborhood being built. Paperwork was pencil whipped, palms were greased and within 10 years the entire neighborhood had sunk a couple of feet into the bay, atleast most of it. And who can forget Love Canal? Ive seen that scenario played out a couple of times. Right now it continues to rain at Three Gorges (live feed)

https://www.youtube.com/watch?v=93w2Rq4abuE