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Japan's sea defense

Julian Ryall, Tokyo
March 24, 2015

Four years after the Great East Japan Earthquake and the devastating tsunami that it triggered, work is under way to build better sea defenses for the communities of Tohoku. But will it work? And what is the cost?

A general view of Mihama nuclear power station No 1 reactor (R), No 2 reactor (C) and No 3 reactor (L) which is run by Kansai Electric Power Co, on March 8, 2012 in Mihama, Japan (Photo: Buddhika Weerasinghe/Getty Images)
Image: Getty Images

The view from Hisataka Haneda's home will never be the same again, he laments.

His home town of Minamisoma, on the coast of Japan's Fukushima Prefecture, used to be protected from the power of the Pacific Ocean by carefully sited blocks and breakers, he said, but they proved pitifully inadequate when the March 2011 magnitude-9 Great East Japan Earthquake triggered a tsunami that soared more than 20 meters high along some stretches of the northeast coast of the country.

The waves destroyed homes, businesses and a good part of what had previously been a close-knit community. The devastation was compounded by the meltdown of three reactors at the nearby Fukushima Dai-Ichi nuclear plant, which released massive amounts of radiation into the atmosphere and forced the evacuation of Minamisoma.

With most of the town now declared safe for residents to return, the focus is on building up the town's defenses from the sea.

Haneda, a 66-year-old member of staff of the International Association of Minamisoma, says he accepts that the colossal new sea wall is necessary, but he has reservations.

Local government officials and nuclear experts inspecting a monitoring well where high levels of radioactive materials were detected at Tokyo Electric Power's (TEPCO) Fukushima Dai-ichi nuclear plant in Okuma, Fukushima prefecture (Photo: JAPAN POOL/AFP/Getty Images)
The devastation was compounded by the meltdown of three reactors at the nearby Fukushima Dai-Ichi nuclear plantImage: AFP/Getty Images

"Quite a few homes were swept away in the disaster and I and the rest of the residents of the town do understand and accept that we need a new sea wall," he told DW with a shrug. "But it is so big and it has completely ruined the beautiful view we used to have of the ocean. I suppose we should be satisfied with what we have."

Worst disaster

In the immediate aftermath of the worst natural disaster to strike Japan in living memory, a tragedy that claimed around 19,000 lives, the government promised to rebuild the lives of the residents of Tohoku and protect them in the future. Part of that plan involved rebuilding sea walls that had been destroyed by the force of the tsunami or constructing new defenses in coastal areas that had previously not considered to be at risk.

The plan calls for the construction of an impressive 440 sea walls along the northeast coast of Japan at a cost of Y820 billion ($6.8 billion). In total, the defenses will cover nearly 400 kilometers and, in places identified at serious threat should another massive earthquake strike, rise to a height of five stories.

And while the Tohoku region is the priority because its sea defenses were destroyed or badly damaged four years ago, the government will extend the program once the work is completed in Tohoku to upgrade sea walls around the 35,000 km of Japan's coastline.

The scheme has not been without its critics, however, and not just the concerns of local residents who will lose their ocean views.

Many questions have been raised over the way in which funds set aside for the reconstruction of Tohoku have gone to projects elsewhere that are less urgent. One of those identified in an investigation by national broadcaster NHK was a Y500 million (€3.82 million) sea wall in Okinawa Prefecture, in the far south of Japan, that even the contractor admitted was "not really an essential project."

Other gripes are that the walls are simply a waste of taxpayers' money while even the best defenses would almost certainly have been overwhelmed by the 2011 tsunami.

Experts debate impact

Even the experts debate the effectiveness against the appearance and cost of the largest public works project presently under way in Japan.

Naoshi Hirata, a professor of earthquake science at The University of Tokyo, and an advisor to the government on the impact of major tremors, agreed that constructing massive new sea walls can only have a partly positive impact.

"If we have another huge tsunami, more than 10 or 20 meters high, then these new walls are still not high enough," he admitted. "And we now know that tsunami of that size are possible, even if they only occur once every 100 years or so.

"A wave of that size would top the sea walls and inundate the land behind.

"But on the other hand, smaller tsunami of between 3 and 5 meters are far more likely in a much smaller time frame, so a wall would be effective against a tsunami of that size," Professor Hirata told DW.

Japan's Prime Minister Shinzo Abe attends the national memorial service for the victims of the March 11, 2011 earthquake and tsunami, in Tokyo March 11, 2015 (Photo: REUTERS/Toru Hanai)
Experts debate the effectiveness against the appearance and cost of the projectImage: Reuters/T. Hanai

Weakening the wave

The walls are being designed to dissipate the power of the initial wave and, in combination with a nationwide education program of the actions to take in the event of a natural disaster, should give local residents more time to evacuate.

Professor Hirata points out that even small tsunami are dangerous because of the destructive power that they contain. A wooden house will be dislodged from its foundations by a wave just 1 meter high, he said. A tsunami of 30 cm can kill a person, he added.

"Not all residents fear losing their view over losing their towns," he said. "We do not believe that another magnitude-9 earthquake will happen anytime soon and it may be another few hundred years since we have something that serious, but we may very well have more tremors of magnitude seven or eight, each of which could cause a tsunami up to five meters high.

"We cannot prevent those tsunami; all we can do is to have the best defenses we can build in place to protect ourselves," he added.

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