Experts divided over anti-tsunami sea walls being built along Japanese coast

Four years after a towering tsunami ravaged much of Japan's northeastern coast, efforts to fend off future disasters are focusing on a nearly 400km chain of cement sea walls, nearly five storeys high in some places.

Opponents of the 820 billion yen (HK$53 billion) plan argue that the massive concrete barriers will damage marine ecology and scenery, hinder vital fisheries and actually do little to protect residents who are mostly supposed to relocate to higher ground. Those in favour say the sea walls are a necessary evil, and one that will provide some jobs, at least for a time.

In the northern fishing port of Osabe, Kazutoshi Musashi chafes at the 12.5-metre-high concrete barrier blocking his view of the sea.

"The reality is that it looks like the wall of a jail," said Musashi, 46, who lived on the seaside before the tsunami struck Osabe and has moved inland since.

Pouring concrete for public works is a staple strategy for the ruling Liberal Democratic Party and its backers in big business and construction. Local officials tend to go along with such plans.

The paradox of such projects, experts say, is that while they may reduce some damage, they can foster complacency. That can be a grave risk along coastlines vulnerable to tsunamis, storm surges and other natural disasters.

"There's a bit of an over belief in technology as a solution, even though everything we have learned demonstrates that people's own insights and instincts are really what makes a difference, and technology in fact makes us a bit more vulnerable," said Margareta Wahlstrom, head of the UN's Office for Disaster Risk Reduction.