When disaster strikes

South-east Asia had barely got going on its major rebuilding operation after the tsunami of 26 December 2004, when disaster struck again. This time it was an earthquake in Indonesia that killed an estimated 1800 people, just three months after the tsunami. With an increasing number of disasters worldwide, the need for construction technologies that reduce their impact has never been greater.

But a recent report says we should pause before automatically throwing up new buildings in south-east Asia. The study, Major incident management with particular reference to the recent south Asian tsunami disaster, written by consulting engineers Dr Philip Esper and Bill Keane, says rebuilding in response to one, narrow type of threat – whether a natural disaster such as an earthquake, tsunami or hurricane, or a man-made catastrophe such as a chemical or gas explosion – is not desirable.

Instead, it calls for an integrated, flexible approach to disaster management that can be adopted in a range of threats, including flooding and terrorism. In the USA, this integrated approach – known there as the national mitigation strategy – has already been adopted for floods, hurricanes and earthquakes. It is implemented by the Federal Emergency Management Agency, which considers “mitigation strategies” for different risks simultaneously. For example, the agency looks at developing construction standards for projects that are at risk from both flooding and earthquakes. The hope is that this integrated approach will be more effective at reducing the effect of any future disasters and therefore cutting the cost of reconstruction. The report’s authors recommend that this approach be extended to regions such as those devastated by the Boxing Day tsunami.

Any disaster management strategy needs to encompass political, social, economic, cultural and engineering issues, and the report makes a number of suggestions on how to achieve this. As a first step, it suggests mapping the areas at risk from future tsunamis. South-east Asia is one of the many parts of the world for which flood inundation maps do not exist. However, oceanographers can simulate tsunamis and consider factors such as the shape of the sea floor and coastline, as well as the cause of the tsunami. An inundation map of this region could then reveal how far a tsunami might go inland.

In the recent tsunami, water surged up river channels, breached sea defences and refracted around projecting coastlines to affect areas that appeared to be protected by large land masses. The money to construct civil engineering-led sea defences may not exist in this part of the world, but politicians could prevent coastal belts of forest and mangrove swamp, which offer some protection from a tsunami, from being ripped up for, say, shrimp farming. An inundation map highlighting areas at risk could be used to persuade politicians of the need to act.

The next stage is to draw up strategies for specific locations. An understanding of local geology could help prevent foundations being undermined by floodwater, or buried services such as sewers being ripped up. High-risk areas could be surveyed to identify poorly built or poorly maintained buildings in danger of collapsing in a tsunami. Crucially, this information could inform new building design, too.

The Boxing Day tsunami should hold valuable lessons for those designing new buildings. Detailed surveys of damage, particularly of smaller domestic buildings, could yield valuable information on areas where there is little research – for example, about how buildings perform compositely in a tsunami, the interaction between non-structural and structural elements.

A key issue is the need to make buildings resistant to more than one type of disaster – as the earthquake in Indonesia three months after December’s tsunami made clear. Heavy roofs, for example, are considered a good anti-hurricane measure where there is a risk of the roof being blown off by high winds. Yet this type of heavy construction is potentially lethal in an earthquake. With a more flexible approach, building codes could be developed that specifically address the whole spectrum of dangers particular to a high-risk location.

Smaller buildings could feature a variety of tsunami-resistant features, such as windows or even walls that break away from the structure in a tsunami. This would greatly reduce the surface area of the building subjected to water pressure, so that the structure is far more likely to stay standing. Where money is very limited, cheap, localised solutions could be adopted. One example would be to raise small buildings on stilts and tie these together with ropes for increased lateral stability.

Larger buildings could be made tsunami- resistant and act as refuges if other, smaller buildings are unstable, or where there is no nearby high ground to escape to. In the recent tsunami, many reinforced concrete buildings were left standing amid the surrounding devastation, notably hotels in tourist areas. New public buildings could be built to the same standards to function as designated refuges, and some key buildings (such as water treatment plants and hospitals) should be located away from high-risk areas.

Some of these measures rely on having some kind of early warning system to give people time to get to the upper storeys of refuges or to high ground. The tragedy of the Boxing Day tsunami was that scientists were unable to communicate their concerns to those countries that were about to be hit. Poor countries could follow Nicaragua’s example: after it was hit by a tsunami in 1992, it introduced a radio alert warning system to warn villages of an impending tsunami. It surely also makes sense to teach people to recognise the early signs: typically, seismic vibrations and the sea receding rapidly and dramatically before the powerful waves strike.

The success of disaster management is ultimately down to political will – and money. There has to be a concerted effort, consisting of both enforcement measures and incentives, to put all these measures in place. Enforcement is crucial: it has been suggested that many lives could have been saved in tsunami-affected countries if a law banning development in coastal areas had been enforced. Incentives could include tax breaks or cheap loans for constructing buildings to disaster-resistant standards.

The report stands far enough back from the devastation to make valuable suggestions on the need for a more integrated approach when considering and managing future disasters. But the big question is whether its vision can be implemented before the next one strikes.

• For more information on the report, visit www.ebi-engineering.com