The worst flooding in six decades in China is displacing millions and straining the Three Gorges Dam. WSJ’s Jonathan Cheng explains how the natural disaster is hampering the country’s efforts to restart an economy already battered by the coronavirus pandemic. Photo: Hector Retamal/AFP (Originally Published July 21, 2020) Heavy rains that again swelled the Yangtze River are expected to hit the Three Gorges Dam with its largest-ever flood this week. The new rainfall at a time when summer rains usually have subsided threatens to prolong a crisis that has already caused billions of dollars in economic losses and displaced millions of people. In the city of Chongqing,…