Underground Discharge Channel To Prevent Greater Tokyo From Flooding

TOKYO, JAPAN - APRIL 08: Metropolitan Outer Floodway Management Office Subsection Chief, Takayuki Yabe is seen in the pressure-adjusting underground water tank during a tour of the Metropolitan Area Outer Underground Discharge Channel facility on April 8, 2015 in Tokyo, Japan. The Metropolitan Area Outer Underground Discharge Channel is the world's largest underground flood diversion facility. The facility takes water overflow from four rivers and redirects it 50 meters underground into a 6.3 kilometer tunnel before being pumped into the Edo river. Construction of the facility began in 1993 and became fully operational 13 years later in 2006. The gigantic pressure-adjusting water tank is one of the highlights of the facility, positioned 22 meters below ground level, it is 177 meters long, 78 meters wide, 18 meters high and each of the 59 pillars weighs 500 ton. The tank is connected to a drain pump facility, housing four gigantic pumps which are capable of pumping up to 200tons of water per second (The equivalent of a 25m pool) The facility, designed to drain flood waters from the surrounding areas after heavy storms or typhoons is used on average seven times a year and has also become a tourist attraction with the facility running guided tours three times a day allowing tourists to visit the massive underground water tank. (Photo by Chris McGrath/Getty Images)