.Seawalls Offered Little Protection Against Tsunami’s Crushing Waves
JAKARTA, Indonesia — 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. They are as much a part of Japan’s coastal scenery as beaches or fishing boats, especially in areas where the government estimates the possibility of a major earthquake occurring in the next three decades at more than 90 percent, like the northern stretch that was devastated by Friday’s earthquake and tsunami.
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.
The risks of dependence on seawalls were most evident in the crisis at the Daiichi and Daini nuclear power plants, both located along the coast close to the earthquake zone. The tsunami that followed the quake washed over walls that were supposed to protect the plants, disabling the diesel generators crucial to maintaining power for the reactors’ cooling systems during shutdown.
Cooling system malfunctions caused overheating and partial fuel meltdowns at two reactors at the Daiichi plant, becoming Japan’s worst nuclear accident.
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.
A fuller picture of how seawalls protected or failed to protect areas beyond the nuclear plants will not emerge for at least a few more days. But 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.”
Mr. Kawata said that antitsunami seawalls were “costly public works projects” that Japan could no longer afford. “The seawalls did reduce the force of the tsunami, but it was so big that it didn’t translate into a reduction in damage,” he said, adding that resources would be better spent on increasing evacuation education and drills.
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. Mr. Galloway noted that New Orleans is getting a substantial upgrade of its hurricane protection system, but he said, “If all the new levees were in and we had a Katrina times two, a lot of people are going to still get wet.” Similarly, he said, some of the floodwalls in Japan, which can be almost 40 feet high, but vary from place to place, were simply too low for the wave.
“If a little bit dribbles over the top, you get a little wet inside,” he said. “If it’s a massive amount, then you get buildings washed away.”
Some Japanese experts said the seawalls may have played a useful role in this crisis.
“This time, almost everybody tried to flee, but many didn’t succeed in fleeing,” said Shigeo Takahashi, a researcher at the Asia-Pacific Center for Coastal Disaster Research in Yokosuka. “But because of the seawalls, which slowed the arrival of waves even just by a little, a lot of people who would not have otherwise survived probably did. Just one or two minutes makes a difference.”
As of Sunday, the Japanese authorities confirmed 1,300 casualties but expected that the final toll would exceed 10,000, with almost all the deaths resulting directly from the tsunami.
But it remains far from clear whether even such an elevated toll will damp Japan’s embrace of seawalls, whose construction over the years has fueled heavy investment in Japan’s public works, especially in rural areas with weak economies but dependable votes. 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.
The height of seawalls varies according to the predictions of the highest waves in a region. Critics say that no matter how high the seawalls are raised, there will eventually be a higher wave. Indeed, the waves from Friday’s tsunami far exceeded predictions for Japan’s northern region.
Seawalls also tend to be built in areas that have suffered tsunamis. But because seawalls cannot be constructed along all of a community’s shoreline, they tend to be clustered along stretches that have been directly hit, leaving other areas exposed.
“The perverse thing about tsunamis is that when they come again,” Mr. Kawata said, “they usually don’t come at the same place they did before.”
NYT
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.
The risks of dependence on seawalls were most evident in the crisis at the Daiichi and Daini nuclear power plants, both located along the coast close to the earthquake zone. The tsunami that followed the quake washed over walls that were supposed to protect the plants, disabling the diesel generators crucial to maintaining power for the reactors’ cooling systems during shutdown.
Cooling system malfunctions caused overheating and partial fuel meltdowns at two reactors at the Daiichi plant, becoming Japan’s worst nuclear accident.
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.
A fuller picture of how seawalls protected or failed to protect areas beyond the nuclear plants will not emerge for at least a few more days. But 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.”
Mr. Kawata said that antitsunami seawalls were “costly public works projects” that Japan could no longer afford. “The seawalls did reduce the force of the tsunami, but it was so big that it didn’t translate into a reduction in damage,” he said, adding that resources would be better spent on increasing evacuation education and drills.
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. Mr. Galloway noted that New Orleans is getting a substantial upgrade of its hurricane protection system, but he said, “If all the new levees were in and we had a Katrina times two, a lot of people are going to still get wet.” Similarly, he said, some of the floodwalls in Japan, which can be almost 40 feet high, but vary from place to place, were simply too low for the wave.
“If a little bit dribbles over the top, you get a little wet inside,” he said. “If it’s a massive amount, then you get buildings washed away.”
Some Japanese experts said the seawalls may have played a useful role in this crisis.
“This time, almost everybody tried to flee, but many didn’t succeed in fleeing,” said Shigeo Takahashi, a researcher at the Asia-Pacific Center for Coastal Disaster Research in Yokosuka. “But because of the seawalls, which slowed the arrival of waves even just by a little, a lot of people who would not have otherwise survived probably did. Just one or two minutes makes a difference.”
As of Sunday, the Japanese authorities confirmed 1,300 casualties but expected that the final toll would exceed 10,000, with almost all the deaths resulting directly from the tsunami.
But it remains far from clear whether even such an elevated toll will damp Japan’s embrace of seawalls, whose construction over the years has fueled heavy investment in Japan’s public works, especially in rural areas with weak economies but dependable votes. 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.
The height of seawalls varies according to the predictions of the highest waves in a region. Critics say that no matter how high the seawalls are raised, there will eventually be a higher wave. Indeed, the waves from Friday’s tsunami far exceeded predictions for Japan’s northern region.
Seawalls also tend to be built in areas that have suffered tsunamis. But because seawalls cannot be constructed along all of a community’s shoreline, they tend to be clustered along stretches that have been directly hit, leaving other areas exposed.
“The perverse thing about tsunamis is that when they come again,” Mr. Kawata said, “they usually don’t come at the same place they did before.”
NYT
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