Coastal infrastructureJapan debating 400 km sea wall to protect coast from tsunami, floods
Four years after the Tōhoku earthquake and tsunami destroyed much of Japan’s northeastern coast, officials are reviewing plans for a $6.8 billion, 400 kilometer chain of concrete seawalls for protecting coastal towns from future flooding and tsunamis. Opponents say the project will harm fisheries and damage marine ecology and scenery, while offering little, if any, actual protection and creating unjustified complacency among coastal residents. Former prime minister Morihiro Hosokawa is leading a Green Wall coalition which calls for an alternative: planting mixed forests along the coasts on tall mounds of soil or rubble, creating a living green wall which would last long after the concrete walls have crumbled. The green wall project would not completely prevent flooding but it would slow tsunamis and weaken the force of their waves.
Four years after the Tōhoku earthquake and tsunami destroyed much of Japan’s northeastern coast, officials are reviewing plans for a $6.8 billion, 400 kilometer chain of concrete seawalls for protecting coastal towns from future flooding and tsunamis. Opponents of the plan argue that the seawalls, up to five stories high in some areas, will damage marine ecology and scenery, harm vital fisheries, and do little to protect residents who are mostly relocating to higher ground.
Leaders of Japan’s ruling Liberal Democratic Party say the plan will create jobs. The plan has received support from party backers in big business and construction. The project may reduce some damage from future tsunamis, but it may also encourage people living along coastlines vulnerable to flooding to ignore disaster warnings or efforts to move to higher ground. ABC News reports that some of the 18,500 people who died or went missing in the 2011 tsunami failed to heed warnings to escape in time. Tsuneaki Iguchi was mayor of Iwanuma, a coastal city with a 2014 estimated population of 43,897, when the 2011 tsunami flooded half of its area. A 7.2-meter high seawall built years earlier to stave off erosion of the city’s beaches slowed the wall of water, as did rows of tall, thin pine trees planted along the coast. The tsunami still swept up to five kilometers inland, and according to ABC News, passengers and staff at the local airport watched as waves carried off cars, buildings, and aircrafts.
The city repaired the broken seawalls, but does not plan to raise them any higher. Iguchi prefers to adopt a plan promoted by former prime minister Morihiro Hosokawa to plant mixed forests along the coasts on tall mounds of soil or rubble, creating a living “green wall” which would last long after the concrete walls have crumbled. The “green wall” project would not completely prevent flooding but it would slow tsunamis and weaken the force of their waves. “We don’t need the seawall to be higher. What we do need is for everyone to evacuate,” Iguchi said. “The safest thing is for people to live on higher ground and for people’s homes and their workplaces to be in separate locations. If we do that, we don’t need to have a ‘Great Wall,’” he said.
Overreliance on safeguards such as seawalls can lead communities to be too complacent, says Margareta Wahlstrom, head of the United Nation’s Office for Disaster Risk Reduction. “There’s a bit of an overbelief 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,” Wahlstrom said.
Tomoaki Takahashi is tasked with gathering support for the living “green wall” project in local communities, but he acknowledges that it has been difficult to get people to forego the concrete seawalls for Hosokawa’s “Great Forest Wall.” “Actually, many people are in favor of the seawalls, because they will create jobs,” said Takahashi. “But even people who really don’t like the idea also feel as if they would be shunned if they don’t go along with those who support the plan,” he said.
Prime Minister Shinzo Abe’s wife, Akie, has raised objections to the concrete seawall plan. In a speech in New York last September, she said the walls may prevent residents from being on alert for future tsunamis and coastal communities may find it costly to maintain the seawalls. “Please do not proceed even if it’s already decided,” she said.
In Rikuzentakata, a town with a population of 23,302 in 2010 and an estimated population of 19,449 in February 2014, the 2011 tsunami wiped out the downtown area. Officials there are now building a higher seawall, but also raising the land well above sea level. Local leader Takeshi Konno said no construction project will eliminate the need for coastal residents to protect themselves. “What I want to stress is that no matter what people try to create, it won’t beat nature, so we humans need to find a way to co-exist with nature,” he said adding that residents need to escape when there is danger.
