The Japanese government has built one of the world’s largest underground floodwater diversion facilities, 50 meters below the ground.
WD News: Japan’s megalopolis region of Tokyo has a history of heavy rainfall and typhoons. But the days when the region used to be inundated with flooding are past. The pain of losing lives and livelihoods and seeing property worth billions of dollars being swept away by devastating floods, forced the region to turn to technology for a solution.
The $1.7 billion Metropolitan Area Outer Underground Discharge Channel was completed in 2006, after 13 years of construction.
The region is reaping the benefits of the system which has cut flooding by 90% even though rainfall has increased by 10% over the years. Put it this way, there is more rainfall but less flooding.
A delegation from the African Development Bank Group recently toured the facility. They were shown around the facility by two senior officials from the Ministry of Land, Infrastructure, Transport and Tourism, General Manager Kunihiro Moriyasu and the Director of International Affairs Konami Takahiro.
They explained that when the water level rises in small and medium sized rivers due to heavy rain, it automatically flows into the inflow facilities, travels down through a vertical shaft and is directed through a 10-meter wide and 6.3-kilometre-long tunnel into a bigger river (Edogawa River). A giant pressure-adjusting water tank is used to reduce the momentum of the water, ensuring it runs smoothly into Edogawa River. The water pump used is run by an engine like that of an aircraft.
Takahiro said since the facility became operational, “the region has saved more than $150 billion that would have been lost due to floods over the past 16 years.”
In the giant water pool are nearly 59 imposing pillars, 18 meters tall, each weighing 500 tons.
Quaynor noted that Japan has already recorded 90% reduction in the cost of damage caused by floods. “It’s a scalable model, which means we should be able to replicate it in lower scale in most of our coastal cities and in areas that are at a high risk of flooding.”
Source & image courtesy: AfDB
