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15 Jan 05 Tsunami: Will we be ready for the next one? By Jenny Hogan and Emma Young AS SURVIVORS along the coasts devastated by the tsunami on 26 December start to clear the debris, the world's attention is turning to how these communities are going to rebuild their towns and villages. When the unthinkable happens again, will they be any better prepared? "When you think of the hundreds of millions of dollars that have been lined up, there is a real chance that we simply rebuild the risky circumstances that we had before," warns Reid Basher of the UN's International Strategy for Disaster Reduction (ISDR) in Bonn, Germany. "This is often the case in earthquake situations. The rebuilding reinstates the risk in the big rush to get everything going again." But rebuilding also gives communities an opportunity to prepare for future tsunamis, and at little extra cost. The nations that border the Pacific, which are in most danger from earthquake-triggered waves, have pioneered ways to protect themselves. "Tsunami defence work consists of political, social, economic, cultural and engineering matters. Not one of them can be neglected," says Nobuo Shuto, a tsunami engineer at Iwate Prefectural University in Iwate, Japan. The first priority is to identify and map the areas at risk. In the US, there are inundation maps for many west coast cities. To create them, oceanographers run simulations of tsunamis generated by earthquakes, landslides or volcanic eruptions. Combining this with detailed measurements of the shape of the sea floor and the coastal topography reveals how far tsunamis might tear inland and where there will be flooding. Crude simulations can even be run in real time when a tsunami is detected to decide whether an alert should be issued. Such maps do not yet exist for the Indian Ocean. "We did a simulation, but we didn't get to a level of wave heights on the shores," says Phil Cummins, a seismologist with Geoscience Australia who was asked to study the tsunami risk in the Indian Ocean in October 2003 by Australian and Indonesian officials. "For that you need very high-resolution images of the sea floor." Now, sadly, a zone of devastation stretching for thousands of miles has done much of the mappers' job for them. Once the areas at risk have been identified, authorities can begin to plan for the worst. Japan, one of the countries most at risk, has resorted to building massive coastal defences to try to hold back waves or at least reduce their impact. Sea walls up to 5 or 6 metres high protect many towns around the coast, while the biggest breakwater in the world is being built in north-eastern Japan. Due to be completed in two years, it will be almost 2 kilometres long and 63 metres deep. The mega-engineering approach is not suitable for poorer regions where tsunamis are rarer, or for tourist areas known for their natural beauty. But conserving or replanting coastal belts of forest and mangrove swamps, which are rapidly being cleared in south Asia to make way for shrimp farms, can offer a degree of protection. Biswajit Mohanty, an environmentalist who runs the Wildlife Society of Orissa in India, says that a patch of mangroves near Nagrapattinam in Tamil Nadu helped protect the area. "This area was not as badly affected as the rest," he says. For many regions, though, creating effective sea defences is not practical. Instead, the residents of coastal villages in Papua New Guinea hit by a tsunami in July 1998 (see "Reconstructing a most deadly wave"), which killed more than 2100, chose the most drastic course of action. Several thousand moved a few kilometres inland. But even on this small scale, moving was problematic, says Lori Dengler of Humboldt State University in Arcata, California, who surveyed the damage in Papua New Guinea. Not all the tribes owned land away from the coast, sparking territorial disputes. The inland areas were also hotter and insect-ridden. Relocation is not going to work in south-east Asia. "The regions affected were so widespread and no one place was particularly dangerous, so it would seem unreasonable to get people to leave their homes," says Cummins. What's more, many of the people affected depend on the sea for their livelihood. "How can you tell a fisherman to move inland?" asks Nicole Rencoret, a spokeswoman for the UN ISDR. Even the less drastic measure of banning building right on the shore and moving existing villages and hotels further back from beaches is going to be unpopular, especially in tourist areas. "You'd be talking about sterilising the beach, for events that are pretty rare," says Russell Blong, a natural hazard specialist with the insurance risk advisory company Benfield Asia-Pacific in Sydney, who has surveyed the damage to hotels in Thailand. But it is possible to make large buildings like hotels tsunami-resistant. "What we see from the videos coming out of the Asia region is that people who were in reinforced concrete buildings, often hotels, survived as long as they were above the second floor," says Ian Robertson, a civil engineer at the University of Hawaii. Robertson and his colleagues are studying how buildings withstand tsunamis. The most important feature is for the ground floor to have walls that break away from supports, he says, with windows or wall panels that wash out. "If you build a solid wall the force on that will be enormous, it will take down the whole building," he says. Small, cheap buildings will never stand up to a tsunami as strong as the one that struck Aceh. But simple measures, such as raising buildings on stilts and tying the struts together with ropes can provide some protection. A few specially reinforced buildings, such as schools and hospitals, can be designated as evacuation centres in villages and towns where residents cannot easily escape to higher ground, as in the densely populated Banda Aceh. In Japanese cities there are specially built towers for just this purpose. If residents know where to go as soon as they feel an earthquake, they can reach such safe havens even if the tsunami arrives without warning only minutes after the quake, as in Aceh. Planning is crucial, too. Local authorities can try to ensure that all critical infrastructure, such as water plants and hospitals, are located outside the tsunami danger zone. This would avoid problems like those in Kalpakkam in India, where a nuclear power plant was closed down for days after the tsunami sent salt water gushing into its pumping station. In the end, even well-fortified countries like Japan are likely to suffer widespread damage if a powerful tsunami strikes. But while property will always be vulnerable, people can save themselves if given a chance. That means getting warnings to people on the ground as quickly as possible. For instance, even cash-strapped Nicaragua, whose coast was smashed by a tsunami in 1992, now uses radios to alert fishing villages if a big wave is approaching. It also means planning and signposting evacuation routes, so people know which way to go to get to higher ground or tsunami-proof buildings. Most important of all is education. There are newspaper reports of a 10-year-old British girl sending a hundred people on one Thai beach to higher ground after seeing the sea recede, because she had been taught about tsunamis in school. The UN wants disaster reduction to be included in school curricula worldwide. "There's no question that the absolute least expensive, most effective, most bangs-for-the-buck mitigation effort is education," says Dengler. "Even without a warning system, even in places where they didn't feel the earthquake, if people had simply understood that when you see the water go down, when you hear a rumble from the coast, you don't go down to investigate, you grab your babies and run for your life, many lives would have been saved." But if all the mitigation efforts focus on the Indian Ocean, there is a danger of history repeating itself. The Pacific warning system was set up after the Chilean tsunami of 1960. Now one will be set up for the Indian Ocean. In the Atlantic, Lisbon was hit by a 12-metre-high tsunami in 1775 and a 10-metre high tsunami hit the Azores in 1855. Will a warning system be in place before the next one arrives? links Related articles on Tsunami and the environment |
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