How Japan is preparing for the great flood

Experts fear Tokyo’s flood defences are not enough to avoid calamity.

Just north of Tokyo, a network of gigantic subterranean cisterns, tunnels and industrial engines helps to protect the world’s largest metropolitan area from extreme flooding – the threat of which is rising because of climate change. The system’s five cylindrical shafts can each accommodate a space shuttle, and the main tank, known as “the temple”, is held up by rows of 500-tonne pillars. Built at a cost of $2bn in 2006, the Metropolitan Area Outer Underground Discharge Channel sucks in water from swollen rivers and pumps it
out towards the ocean using the type of engines used in jet airliners.

The project has so far done its job in protecting the Tokyo area’s 38 million residents. But many experts fear the capital’s flood defences – which also include extensive underground reservoirs – are not enough to avoid calamity. Japan is being afflicted by ever stronger typhoons, and rainfall levels rise every year. In one river breach scenario, the government projects more than 6,000 deaths. “To be frank, these measures are not enough,” says Nobuyuki Tsuchiya, the former chief civil engineer of Tokyo’s flood-prone Edogawa ward.

Mayumi Ootani, who sells pots and pans and cigarettes from her shop, puts things more bluntly: “We’re living side-by-side with death.”

Calamitous flooding wrought by extreme weather is becoming an international menace, as shown last year in Texas, Puerto Rico and the Philippines. In Tokyo, the threat is even greater because the city is already so vulnerable to natural catastrophes such as earthquakes, typhoons and tsunami.

Swiss Re, a reinsurer, described Tokyo and neighbouring Yokohama as the world’s riskiest metropolitan area in a 2014 study, citing extreme flooding as one of the perils. The Japan Meteorological Agency blames climate change for a 30 per cent rise in rainfall measuring more than two inches per hour – in what is already one of the world’s wettest cities. In recent times, Tokyoites have also been beset by man-made perils, such as the 2011 Fukushima nuclear disaster and North Korea’s recent threats to bring “nuclear clouds ” to Japan.

Such a confluence of worries might seem a recipe for mass-neurosis, or a flight to areas that do not lie on seismic or geopolitical fault lines. But while Japan’s overall population declines due to low birth rates, Tokyo’s is still growing, with young people migrating from stagnant rural areas. Meanwhile, the city continues to build more and more skyscrapers – testament to Japan’s superlative earthquake-resistance technologies.

Even in the districts of Tokyo most at risk from floods and earthquakes, people tend to go about life with an optimism partly born of resignation. “I don’t go around worrying about it – if disaster comes, it comes,” says Toshio Miyata, who runs a tempura restaurant in a wood-framed home. “We Tokyoites don’t give a damn, whether it’s earthquake, fire or flooding. You can’t expect to fight with nature and win.”

Miyata runs his business in the Edogawa ward – bordered and bisected by flood-prone rivers. It’s one of the areas that form what is known as the city’s shitamachi, or downtown, traditionally considered the authentic heart of Tokyo, where people are gruff, plain-spoken and on the hustle. It’s also the centre of so-called zero-metre zones that lie below sea level – and are doubly vulnerable because of the risk of inundation and buckling during quakes, a result of poor land quality. (One Edogawa resident described the ground beneath her home as “soft as tofu”.)

Yet it is precisely a centuries-old history of coping with disaster that explains how people here deal with the prospect, even likelihood, of natural calamity. “The consciousness that you may die in a natural disaster is something deeply-rooted among the Japanese,” says Kansai University disaster psychologist Tadahiro Motoyoshi. “There is a strong sense of the threat and the blessings of nature.”

Tsuchiya, the former Edogawa chief civil engineer, says these low-lying areas have been flooded at least 250 times in the past four centuries – causing countless deaths – but each time the survivors started over in the same place. Innovation came with the commitment to stay. Residents developed elevated structures called mizuya – literally “water houses” – where they could store necessities and escape to during flooding, as well as a sophisticated system of emergency boats that converted the submerged city into a floating one.

Engineering marvels such as the metropolitan discharge channel and a planned network of super-levees, more than 300 meters wide, are an extension of these early innovations.

Japan’s earthquake-resistance technologies also draw inspiration from the past. The Tokyo Skytree, the world’s tallest tower at 634 metres, completed in 2011, borrows from Japan’s traditional five-storey pagodas – which since medieval times have been resistant to the most powerful earthquakes. Skytree engineers adapted the pagoda’s central pole – called a shinbashira – that redistributes seismic vibrations to prevent collapse.

There is also a stock of resilience and community spirit that has managed to survive waves of rampant development and inward migration. Masanobu Namatame makes painted paper lanterns for traditional festivals. He squats on straw mats in his Edogawa workshop, carrying on a craft that has been handed down through generations. “The locals depend on me during festival time,” he says. “So I’m not thinking about running away.”

But the family business was not always in this location. During Namatame’s grandfather’s time it was in the more affluent Kojimachi district. Wartime air-raids that burned down the house forced the family to flee here with a few belongings on their backs.

“The bottom line is if some calamity happens you have to run,” says Namatame. “But until then you just stay put and get on with things.”