Instead of putting in more drainage pipes, building flood walls and channeling rivers between concrete embankments, which is the usual approach to managing water, Mr. Yu wants to dissipate the destructive force of floodwaters by slowing them and giving them room to spread out.

Mr. Yu calls the concept “sponge city” and says it’s like “doing tai chi with water,” a reference to the Chinese martial art in which an opponent’s energy and moves are redirected, not resisted.