In October 2013, the coastal Chinese city of Ningbo, which is home to 10 million people and the world’s fourth-largest port, was hit with a torrential flood. Wastewater systems and rivers overflowed. Five people were killed, and more than 100,000 houses were inundated with brown flood water polluted with sewage, industrial chemicals and heavy metals.  Flooding is a perennial problem in southern and central China, but in the last three decades it has gotten much worse. All along China�