At least 40 percent of Japan’s 22,000-mile coastline is lined with concrete seawalls, breakwaters or other structures meant to protect the country against high waves, typhoons or even tsunamis...Along with developing quake-resistant buildings, the coastal infrastructure represents postwar Japan’s major initiative against earthquakes and tsunamis. But while experts have praised Japan’s rigorous building codes and quake-resistant buildings for limiting the number of casualties from Friday’s earthquake, the devastation in coastal areas and a final death toll predicted to exceed 10,000 could push Japan to redesign its seawalls — or reconsider its heavy reliance on them altogether.
Peter Yanev, one of the world’s best-known consultants on designing nuclear plants to withstand earthquakes, said the seawalls at the Japanese plants probably could not handle tsunami waves of the height that struck them. And the diesel generators were situated in a low spot on the assumption that the walls were high enough to protect against any likely tsunami. That turned out to be a fatal miscalculation. The tsunami walls either should have been built higher, or the generators should have been placed on higher ground to withstand potential flooding, he said. Increasing the height of tsunami walls, he said, is the obvious answer in the immediate term.
“The cost is peanuts compared to what is happening,” Mr. Yanev said.
Some critics have long argued that the construction of seawalls was a mistaken, 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 in flush times and to try to kick-start a stagnant economy. Supporters, though, have said the seawalls increased the odds of survival in a quake-prone country, where a mountainous interior has historically pushed people to live along its coastline.reports from affected areas indicate that waves simply washed over seawalls, some of which collapsed. Even in the two cities with seawalls built specifically to withstand tsunamis, Ofunato and Kamaishi, the tsunami crashed over before moving a few miles inland, carrying houses and cars with it.
In Kamaishi, 14-foot waves surmounted the seawall — the world’s largest, erected a few years ago in the city’s harbor at a depth of 209 feet, 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.”
Gerald Galloway, a research professor of engineering at the University of Maryland, said one problem with physical defenses protecting vulnerable areas was that they could create a sense of complacency. “There are challenges in telling people they are safe” when the risks remain, he said.
Whatever humans build, nature has a way of overcoming it.
If private companies spearheaded the development of quake-resistant buildings, the seawalls are the products of the same Japanese governments that built networks of unnecessary roads and bridges throughout the country, especially in the 1980s and 1990s.
The construction of seawalls continued in the last decade, and at least two massive antitsunami seawalls are under construction. One in Kuji, a city in Iwate Prefecture that was damaged in Friday’s tsunami, was scheduled to be completed soon.
Massive antitsunami seawalls tend to be located in harbors and number around a dozen nationwide, Mr. Kawata said. But smaller seawalls, often reaching as high as 40 feet, and other structures extend along more than 40 percent of the nation’s coastline, according to figures from the Ministry of Land, Infrastructure, Transport and Tourism.
The seawalls are typically built along the shoreline of inhabited areas. They tend to restrict access to the shore and block the view of the sea from inland, often casting shadows on houses built along the shore. Environmentalists and tourism officials have described them as eyesores; fishermen have also been among their fiercest critics, complaining that they need to see the sea from their homes.
Critics have said that the seawalls reduce coastal residents’ understanding of the sea and their ability to determine when to flee by looking for clues in changing wave patterns.