When trying to prepare for the next tsunami, building a bigger seawall isn’t the easy solution it sounds, writes Fletcher Howell.
For two weeks, I had the opportunity to travel the East Coast of Japan as part of the New Colombo Plan field course ‘Understanding Geologic Hazards’. The most compelling part of this journey was the time the group spent in the town of Otsuchi, two hours north of Tokyo by Shinkansen. Being a coastal fishing village, Otsuchi residents make their livelihood harvesting the oceans, but in doing so must live with the challenges of their chosen environment.
On March 11 2011, a magnitude 9.0 earthquake struck 70km off the east coast of Japan. This jolt caused a 20-metre-high tsunami wave that would inundate Otsuchi within 60 minutes. The tragedy resulted in 1,400 of the town’s residents being reported dead or missing, a loss of 10 per cent of the local population.
When we first arrived at Otsuchi, it was immediately evident that something had happened to this place. Even for a Japanese rural town, the housing was particularly low density. The limited residential and commercial buildings that were present were a mismatch of various shapes and styles. Everything was overly clean and tidy. All infrastructure had been built in the last three years.
Despite the sparsity of buildings at present, there has been much progress made in the town over the last eight years. From a pile of water-logged organic and anthropogenic rubble the landscape was painstakingly returned to a flat plain. At this point, the first of many future mitigation measures was implemented. Land within a few hundred metres of the coast was restricted from residential development, and beyond this, the level of the land was raised by two to four metres.
On top of the raised land, the town has also begun work on the reconstruction of a sea-wall. Following governmental and scientific consultation, town members were offered two choices: they could rebuild the six-metre sea-wall which was overcome and destroyed in the 2011 tsunami, or build a larger 14.6m sea-wall.
The original sea-wall was built to protect against most typical tsunamis. In the case of a rare event such as 2011, this height was clearly insufficient. A larger sea wall would likely reduce the effect of any foreseeable tsunami, but comes with an added cost of construction and maintenance, and the visual impact of an imposing concrete façade disrupting the coastal feel of the town.
Emotionally, it is easy to want to make decisions that will preserve lives, and to invest in the larger wall. Yet, a decision that centres on economics will focus more on the comparative costs of the larger wall against the likelihood of needing to use it.
Opinions on this choice amongst others facing the rebuilding town still divides residents. Particular clashes have occurred between working fishermen who want to preserve their waterways, and elderly residents preferring greater protection. Making the matter more difficult, the town has been left to make these decisions without any clear leadership structure after the tsunami.
Rather than evacuate in the minutes before the inundation, town officials held an emergency planning meeting outside the town hall. As a result, they and the onlookers who congregated to observe the happenings did not have time to escape the incoming waves.
Recovering from a natural disaster is a lengthy, complicated, and contentious process. Trying to rebuild and live again in an area after it has been so thoroughly ravaged leads people to demand accountability that progress has been made, and that they will be better protected in the future.
One approach being used in other locations moves the focus from a battle against the forces of nature. Rather than invest solely in sea-walls or diversion channels, which can lull people into a false sense of security, money is being spent on improving the means of escape. This includes building wider roads, signposting preferred evacuation routes, and building easily accessible evacuation mounds/towers. While these options would result in loss of property in the case of a large enough tsunami, they may save lives.
It is more difficult to convince people of the safety behind effective escape routes than it is to place a large concrete barrier in their eyeline, but public consultation to create informed solutions will ultimately lead to better outcomes than the government making unilateral decisions. Engaging locals in discussions about their situation will also lead to greater public education in disaster survival.
In Otsuchi, the residents want to be involved in the decision-making, and while it may cause conflict if poorly managed it is still preferable to relinquishing control over their town. Whatever the potential mitigation measures, an informed decision made by those whose lives may one day rely on it is the most effective solution to a deceptively complex problem.