Catalyst

Season 1, Episode 23

Episode Title: Tokyo Flood Prevention

Air Date: 2014-01-01

Overview:

Fifty meters beneath the teeming mega-city of Tokyo is an underworld river system - 6.4km of tunnels, colossal water tanks, massive pillars, giant pumps that remove 200 tons of floodwater every second. It’s an engineering marvel built to protect Tokyo against the increasing threat of flooding.