Comment by gozur88

Japan didn't (over)build that flood control system because they're worried about global warming or thousand year floods.

They did it to create jobs. In the same way the US is said to have a "military industrial complex", Japan has a "construction industrial complex", wherein the government builds a whole lot of infrastructure the country can't really justify or even maintain. Flood control, rail lines, airports, etc. It's all stuff an industrialized country needs, but the Japanese take it up to eleven in an effort to stimulate the economy.