A global review of disaster reduction initiatives - Welcome to the ...

Understanding the nature of hazardsRisk awareness and assessment2Understanding the nature of natural hazards involves a consideration of almost every physical phenomenon on theplanet. The slow movements in the earth’s mantle – the convection cells that drive the movement of continents andthe manufacture of ocean floors – are the starting point and also the sticking point. They lift mountains and shapelandscapes. They also build volcanoes and trigger potentially catastrophic earthquakes. Like those other invisiblemovements that take place on a vast scale through the atmospheric medium – the carbon cycle and the water cycleand the nitrogen cycle – volcanoes and earthquakes, along with technological advancements, provide the bedrock ofstrong nations, rich industries and great cities. They do, of course, have the potential to destroy them. This is alsowhat happens with technological hazards and environmental degradation.While most natural hazards may be inevitable,disasters are not. By seeking to understand andto anticipate future hazards by study of the pastand monitoring of present situations, a communityor public authority is poised to minimizethe risk of a disaster. It is a measure ofpeople’s wisdom and a society’s values if acommunity is able to learn from the experiencesof others, rather than to suffer its own.There is a wealth of knowledge about thenature and consequences of different hazards,expected frequency, magnitude and potentialgeographical impacts, but many fewer examplesof lessons learned from them.Hazards are increasingly dynamic and withhighly varying potential impacts. Due tochanging environments, many countries andregional organisations call for a greater knowledgeof hazard characteristics. Such knowledgerequires additional, more focussed research onhazards and a greater understanding of theirnature, effects and history.A wide range of geophysical, meteorological,hydrological, environmental, technological,biological and even socio-political hazards,alone or in complex interaction, can threatenliving and sustainable development. Hazardshave often been divided into natural, humaninducedtechnological and increasingly negativeeffects of environmental degradation isbeing added to this list.While natural hazards can be divided into threebroad categories -hydrometeorological, geologicaland biological- the variety, geographical coverageand types of impacts are huge. Forest fires,for example, are recognised as a natural hazardbut are often referred to as environmental, alongwith pest infestation and desertification. Inorder to distinguish between different hazardtypes, many institutions have developed hazardcatalogues. A table has been prepared by ISDRto summarise the current thinking (see next page).The strong compound relation between differenttypes of natural hazards may give theimpression that attempts to catalogue them arefatuous. At what stage does a landslide, recognisedas a geological hazard, becomes a mudflow,which is often classified as a hydrologicalhazard? In the same vein, primary hazardsoften give rise to a myriad of related potentialcollateral or secondary hazards. In many cases,these cause greater threat to a community thando the primary hazards. Tropical cyclones cantrigger other hazards, in particular stormsurges, flash foods and landslides. Often themost serious impact of a tropical cyclone comesfrom the associated coastal and river floods.Similarly, damages related to earthquakes areoften caused by landslides, fires, tsunamis, andfloods.All communities – urban or rural – are vulnerableto most hazards. However, different regionswill be more prone to certain types of hazardsthan others. Floods and windstorms are the hazardsthat most frequently lead to disasters inAsia, the Pacific, Europe and North America,while it is droughts and epidemics that arereported in African countries. In contrast, Pacificand Caribbean islands are most vulnerable tothe effects of tropical cyclones. El Niño events,floods, volcanic eruptions and earthquakes affectin greater degree the Andean and Meso-Americancountries. Even within a specific region,such as the Pacific, the frequency and intensity ofspecific hazards varies from one country toanother. Hydrometeorological hazards are mostcommon and floods alone account for two-thirdsof people affected by natural hazards.In the same way, different levels of income groupsare more or less vulnerable to certain types of haz-43