A recent study conducted by the government’s disaster management council found that a flooding of the Arakawa River could cause an apocalypse of the meticulously interwoven Tokyo subway system. Every 200 years or so, it rains over 550 millimeters a year; if this ever happens again, the heavily dammed river could flood, causing 97 subway stations in the city to be destroyed. It would start with just a few stations, but then the subway tunnels would function as pipes and bring the water damage from one station to the next, destroying close to 100 within days. Needless to say, government officials are now hard at work trying to figure out how to make sure this doesn’t happen.
Link (Thanks, Vagrant!)