Li Yifan and Yan Wu’s probing, but predictably lumbering documentary “Before the Flood” opens up a can of worms that the rest of the world would be well advised to um, swallow. Or at least digest a little.
Once completed, the Three Gorges Dam on the Yangtze River will be the largest hydroelectric dam in the world. Supplying a massive future source of electricity and an attempt to control the spontaneous and notorious floods of the Yangtze, the dam — built in between the spectacular series of canyons on the Yangtze known as the Three Gorges — will be a monumental colossus: one-and-a-half miles wide, 600 feet high and 400 miles long, the thing will be able to create as much energy as 18 nuclear power plants.