|Natural Disasters - Be Prepared! (UNESCO, 1997, 50 p.)|
What individuals and societies can do to cut the toll of human and economic loss
BY BARBARA CARBY
The European Laboratory for Structural Assessment In Ispra (Italy). [© Enzo Signorelli/Gamma, Paris]
The most effective disaster mitigation measure that can be taken at community level is for people not to build in high-risk areas such as unstable slopes, river beds or flood plains. Local knowledge about these hazards is usually good, especially among older people. Sometimes though, a hazard such as a geological fault is not obvious or visible, and surveyors and geologists have to be called in.
People can also ensure they reduce risks in their houses. Roofs should be secured against hurricanes. Roof shape is important for wind resistance. A flat roof is much more likely to be blown off than a pyramid-shaped one. Some worry about the cost of such measures, but they are no more than a small percentage of the total cost of the building and are well worth the investment.
Map showing earthquake monitoring centres in southern California (U.S.A.). [© Eric Sander/Liaison/Gamma, Paris]
- Earthquake mitigation focuses on building codes, including correct use of steel and the strength of concrete mixes. Wooden buildings can be reinforced by braces and tying corners so as to make the structure react as a box.
Hazards in the home are not all structural. If you live in an earthquake-prone area, you should check the following:
- Are heavy objects like cabinets, TV stands and entertainment centres attached to the wall?
- Are heavy objects on the lowest shelves?
- Are water heaters and gas cylinders bolted to the wall?
- Do household members know how to turn off the gas, electricity and water supply?
- Are hanging objects such as fans and ceiling lights securely fastened?
- Are shelves fitted with wire or board to prevent objects falling off them during tremors?
- Are dangerous substances like fuel, poisons and chemicals secured against spillage?
- Are plate-glass windows and doors covered with safety film to prevent shattering?
At the national level, governments should include mitigation in their disaster management policies. Zoning and land use laws should ensure there are no buildings in an area likely to be flooded, say, once every thirty years. Golf courses and parks could be built there instead. Steep slopes would be left as wooded areas.
But planners and policy makers do not usually have this freedom. Many rivers already flow through towns, so mitigation will take the form of reducing loss of life and damage after a flood. Ground floors can be designated non-sleeping areas, levees can be built and flood warning systems and evacuation plans can be developed.
Building codes should be drafted and where they already exist, should be reviewed and strengthened. They should ensure that buildings can survive a 7 magnitude earthquake or 200 km/h winds.
Standards of safety
Many buildings were put up before codes were drafted, so they need to be retrofitted by strengthening. This is more expensive than building to resistant standards. Large public buildings and bridges are prime candidates for retrofitting. But small traditional buildings should be strengthened too. Much work has been done on this in India and Peru. Chicken mesh and mortar has been effective in reinforcing walls of adobe-type buildings against earthquake damage.
Vulcanologist Maurice Krafft measures the temperature of a lava flow using a device called a thermocouple. [I. And V. Krafft © Hoa Qui, Paris]
Emergency facilities such as hospitals, police stations and shelters, along with water, electricity and sewage systems, must also be able to remain functional after a disaster. They should be designed to a higher standard of safety than other buildings and retrofitted where necessary. This especially applies to hospitals - crucial after a disaster - as they can be knocked out of action without structural damage. So non-structural mitigation measures are vital.
Cost is one of the reasons cited for lack of mitigation measures in poor countries. But one could say that such countries cannot afford not to take measures. Tropical Storm Debby set off extensive flooding and landslides in the small Caribbean island of St. Lucia in 1994. Agricultural losses alone were about 12 per cent of the islands 1993 Gross Domestic Product (GDP).
Even reducing direct damage by one per cent through mitigation would have been worthwhile. But political support for mitigation is hard to drum up because little work has been done on quantifying the benefits of mitigation as opposed to cost.
Bangladesh is a mitigation success story however. Improved warning systems and the building of cyclone shelters has sharply cut loss of life and livestock. In Jamaica, Hurricane Gilbert in 1988 showed the benefit of roofs shaped for wind resistance. Many specially-designed buildings which went up after a hurricane in 1951 kept their roofs in 1988, while more modern and expensive structures with fashionable flat or slightly-sloping roofs which went up in the 1970s and 1980s, did not.
A Sri Lankan engineer inspects coastal hurricane defences south of Colombo. [© Peter Barker/Panos Pictures, London]
Damage in a San Francisco (U.S.A.) store after an earthquake in October 1989. [© C. Charles/Liaison/Gamma, Paris]
Recent earthquakes in California and Japan have successfully tested earthquake-proof buildings. In California, many old masonry structures which had been retrofitted survived. But little is heard about this success since news is about buildings which collapse. However the media can do a lot to publicize the advantages of mitigation, especially just after a disaster when mitigation measures should be included in repair work.
Mitigation is also very important in the natural environment. Action taken in watersheds in the mountains will eventually affect the marine environment, especially in small countries where the distance between water shed and sea is small. Eroded soil washing down into the ocean results in silting which kills off coral and fish. Coral reefs help control beach and coastal erosion, and if they are damaged the coast is more vulnerable to flooding which will in turn cause more erosion. Coral reefs are also important fish hatching grounds, so loss of reefs will harm the fishing industry, especially in island states. Destruction of reefs and beaches also harms countries which live off tourism. Chemical spills into waterways eventually reach the sea and also damage coral reefs and marine life. Damaged or stressed reefs are more vulnerable to natural hazards because they are less resistant to wave action.
Dialogue between environmental and disaster managers is essential. For mitigation to work, the entire society must be involved. Programmes should ensure local communities take part in planning at the same time as they ensure political and financial support at national and international level. Mitigation must be part of our daily life. If the present century invented mitigation and moved disaster management beyond mere response, the next must see that mitigation becomes an integral part of planning at all levels of society.