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KASUKABE, Japan: It has been called Japan’s underground “Parthenon,” a cavernous complex tasked with protecting Tokyo and surrounding areas from catastrophic flooding, a risk experts warn is growing as climate change advances.
Above the ground, there is little to reveal the feat of cathedral-like engineering that forms the main reservoir of the Kasukabe flood tank, the largest facility of its kind in the world.
The immense structure, deep enough in places to house the Statue of Liberty, channels and redirects excess water from storms and typhoons, protecting one of the most populated capitals in the world.
Elevated piers weighing 500 tons each support the main tank, a bare concrete tank the length of two football fields.
Staff members at the facility in Saitama, north of Tokyo, are on constant alert, especially during the rainy and typhoon seasons in Japan, from June to late October.
It has been called Japan’s underground ‘Parthenon’, a cavernous complex tasked with protecting Tokyo and surrounding areas from catastrophic flooding – a risk experts warn is growing as climate change advances AFP / Charly TRIBALLEAU
“In this area, torrential rains, typhoons and even daily rains can cause damage by submerging houses and roads,” site chief Nobuyuki Akiyama told AFP.
The reservoir has helped reduce the number of homes affected by water damage in nearby areas by about 90 percent, he said.
In Tokyo alone, a city crossed by more than 100 rivers, there are another 10 underground reservoirs and three flood tunnels, and more flood protection structures are being built.
And in Osaka, in western Japan, a flood protection facility similar to the Kasukabe Reservoir is being built at a cost of 366 billion yen ($ 3.5 billion). Construction is scheduled to finish in 2044.
But experts warn that more may be needed, as global warming makes what were once once-a-century storms increasingly common and catastrophic.
“Japan … has a climate where floods and heavy rains tend to occur frequently,” says Kei Yoshimura, professor of meteorology at the University of Tokyo and an expert on river flooding.
“But on top of that, now global warming is advancing,” Yoshimura told AFP.
MORE TYPHONS
In recent years, the rainy seasons and typhoons have caused regular destruction.
Massive floods and landslides killed more than 80 people in western Japan this July, and a typhoon last year killed nearly 100 people in eastern Japan.
Japan’s Meteorological Agency says the number of typhoons a year that threaten Tokyo has multiplied by 1.5 in the past four decades.
Japan’s anti-flood systems are considered world-class, and the country learned bitter lessons from several gigantic disasters after World War II. (Photo: AFP / Charly Triballeau)
The Kasukabe reservoir is connected to a 6.3 km tunnel and the system can release the accumulated water in the nearby Edogawa River at a speed equivalent to discharging a pool of 25 m per second, with the power of a jumbo-jet engine .
Built in 2006 at a cost of 230 billion yen (US $ 2.2 billion), the facility kicks in about seven times a year.
Excess water flows out automatically and operators pump it out from the main tank when it approaches capacity, Akiyama said.
This year it had already been used seven times in September, and the water was discharged twice after an unusually long rainy season, he added.
Official studies credit the unique facility with saving 148 billion yen in disaster clean-up costs so far.
Japan’s anti-flood systems are considered world-class, and the country has learned bitter lessons from several major disasters after World War II.
But experts, including Yoshimura, say infrastructure alone is not enough, especially with advancing climate change, and Japanese authorities have stepped up their efforts in recent years to remind citizens to evacuate homes early when prompted.
The Kasukabe system accepts visitors when not in use, in part to promote the importance of disaster management.
“This underground facility is great, but it’s just a defense measure,” Toru Tamai, a 79-year-old retiree who attended a recent tour, told AFP.
“I live on low ground, so flooding is a clearer and more present danger than any other natural disaster,” he added.
“In the end, you can’t count on anyone but yourself.”
