World’s Deepest Breakwater Failed to Stop Tsunami
Several months ago, an award ceremony was held in the town of Kamaishi in Iwate prefecture. An official from the Guiness Book of World Records had come to proclaim that the Kamaishi Tsunami Protection Breakwater (63-meters deep) the title of world’s deepest breakwater. The event was described in a blog post:
The 1,960 m (6,430 ft 5 in) long breakwater was constructed at the mouth of Kamaishi bay to prevent from the threats of tsunami disaster from Pacific sea side. It reduces the bay-mouth opening to decrease tsunami run-up height as well as wind waves and swells. The construction work started in 1978 and it took amazing 31 years until it finally completed in March 2009.
To celebrate the much anticipated completion as well as the Guinness World Records achievement, Kamaishi city held the ceremony on the sightseeing boat, Hamayuri. I was honoured to be invited to present the certificate to the city mayor.
It was moving to hear from the people involved how much hard work had been spent for the construction. The citizens of Kamaishi are proud of their breakwater which protects their lives. It surely is an incredible world record!
Unfortunately, the record-breaking breakwater proved to be incapable of stopping the massive tsunami that hit the town on Friday:
…waves swelled over the barrier, engulfing buildings and cars and smashing everything in its path to smithereens in a matter of minutes.
The images from Japan’s Pacific coastline have been a scary reminder of nature’s power. Kamaishi thought it had built just the thing to keep the forces of nature at bay.
The concrete breakwater, nearly 207 feet deep, was designed to blunt an incoming tsunami. Its construction marked the culmination of decades of research on wave dynamics and dissipation. It stretches 6,430 feet and was completed in March 2009 after more than three decades of construction.
Videos of the tsunami destroying Kamaishi:
Norimitsu Onishi of the New York Times has written an article that is extremely critical of Japan’s use of sea walls:
The risks of dependence on sea walls is most evident in the crisis at the Daiichi and Daini nuclear power plants, both situated along the coast close to the earthquake zone. The tsunami that followed the quake washed over walls that were supposed to protect the plants.
Peter Yanev, one of the world’s best-known consultants on designing nuclear plants to withstand earthquakes, pointed out that the plants’ diesel generators were situated in a low spot on the assumption that the walls were high enough. That turned out to be a fatal miscalculation.
Critics have long argued that the construction of sea walls is a hubristic effort to control nature as well as the kind of wasteful public works project that successive Japanese governments used to reward politically connected companies. Supporters have said the sea walls increased the odds of survival in a quake-prone country.
In Kamaishi, 14-foot waves surmounted the sea wall — the world’s largest, erected a few years ago in the city’s harbor at a length of 1.2 miles and a cost of $1.5 billion — and eventually submerged the city center.
“This is going to force us to rethink our strategy,” said Yoshiaki Kawata, a specialist on disaster management at Kansai University in Osaka and the director of a disaster prevention center in Kobe. “This kind of hardware just isn’t effective.”
Onishi is infamous for skewed and misleading articles he penned back when he served as the main Tokyo correspondent for the paper, so I’m not sure what to make of his article. It does seem obvious that sea walls failed to protect several towns from Friday’s tsunami, but is it because the whole concept of sea walls is flawed, or because they were not built to stop waves from a magnitude 9.0 earthquake?