Concrete seawalls, breakwaters and other sea structures have been a linchpin of Japan's major initiative against earthquakes and tsunamis. But as the death toll from Friday's quake rises and the nuclear accident continues to play out, the devastation in coastal areas could push Japan to redesign its seawalls, or re-evaluate its reliance on them altogether.
At least 40 percent of Japan's 22,000-mile coastline is lined with seawalls, breakwaters or other structures meant to protect the coast from high waves, typhoons and tsunamis.
But the risks of depending on them were laid bare at the Daiichi and Daini nuclear power plants, which are both located along the coast close to the earthquake zone. There, the tsunami that followed the quake washed over the plant's protective walls, disabling the diesel generators that are crucial for maintaining power for the reactor's cooling systems during shutdown.
Malfunctions with the cooling system prompted overheating and partial fuel meltdowns at two reactors at the Daiichi plant, making it Japan's worst nuclear accident.
Peter Yanev, a world-renowned consultant on designing nuclear plants to withstand earthquakes, said there were major flaws in the Japanese plan. The plant's seawalls probably could not handle tsunami waves as high as the ones that struck them, he said. And the diesel generators were located in a low spot because it was assumed that the walls were high enough to protect against any tsunami that might hit.
These turned out to be a fatal miscalculations, Yanev said. In the near-term, increasing the heigh of tsunami walls is the obvious solution.
"The cost is peanuts compared to what is happening," he said.
Some critics have long argued that the seawalls are a mistaken effort to control nature and a wasteful public works project that rewards politically connected companies. They also say that, because they block the view of the sea, seawalls reduce coastal residents' understanding of the water and their ability to flee by watching for clues in changing wave patterns. But supporters say the seawalls increase the odds of survival in a country vulnerable to earthquakes whose mountainous interior has historically driven people to move to the coast (Norimitsu Onishi, New York Times, March 13). -- AS
