How do you protect coastal areas from a once-in-a-millennium tsunami? You don't, planners in Japan have concluded. So they are rebuilding the coastal seawalls washed away by the 11 March 2011 tsunami to their original specifications.
This is not madness. Speaking at press conference in Tokyo today, Tatsuo Hirano, the government's minister for reconstruction, explained that the seawalls topped by last March's massive waves were designed to withstand tsunamis expected to recur once every 200 to 300 years. And they proved "quite effective" in protecting harbors and low-lying coastal areas from the routine tsunamis and storm surges that regularly hit Japan's Pacific Coast, he said. Building something to resist what experts have concluded is a once-in-a-thousand-years event is not cost effective. So current plans are to rebuild the seawalls pretty much as they were.
What to do about the coastal residential areas inundated last March is a thornier problem. Experts believe it would be best to move residential areas inland and uphill, and turn those low-lying lands into parks, forests, or farms. "People agree on the concept," said Hirano, a native of the hard-hit Iwate Prefecture. But as for where to rebuild and what kind of community to create, "it is very difficult to come to an agreement." So "you can see long stretches (of coast) where there is no reconstruction work at all," he said.
To protect lives, the "highest priority should go to training people to evacuate," Hirano said. Communities are also investigating escape towers—sturdy, tall buildings that could provide shelter on upper floors.
Japan is expecting to spend 10 years rebuilding the devastated Tohoku region. But Hirano pledged "to get as much done as possible in the first 5 years."