What is a natural disaster?

A natural disaster or catastrophe is an event produced by high-energy phenomena forming part of the planet’s natural dynamics, which cause large-scale material and personal damage in a certain geographical area and at a given moment.

What natural phenomena are catastrophic?

The range of phenomena that can produce catastrophes on our planet is ample and varied. Broadly speaking we can classify them in two main groups according to their origin:

Internal geodynamic phenomena, which have their origin in the Earth’s interior and which have obvious repercussions on the surface. These are earthquakes (which can also result in tsunamis) and volcanic eruptions. Although any part of the Earth can be affected at a given moment by an earthquake, we know that they are mainly produced in the areas bordering on the tectonic plates. Volcanism and its geographical distribution are also directly related to the edges of these plates.

External geodynamic phenomena, which have a hydro-meteorological origin, are tied to atmospheric dynamics and make themselves clearly felt in geological processes we call external or superficial (erosion, transport and sedimentation). These include especially floods (spates, river floods, flash floods, coastal floods and lake floods). It is also worth mentioning landslides, rockfalls and subsidence; avalanches; storms that cause damage to the coastline, and those forest fires which do not have their origin in man. Many of these phenomena are linked to storms or hurricanes that cause heavy rain and strong wind.

Most external geodynamic phenomena have a climatic control, which also conditions their geographical distribution. Some can affect a large geographical area, such as floods and landslides caused by a tropical hurricane or cyclone (remember Central America’s Hurricane Mitch in October 1998), while others can be almost local (remember the river flood of the Barranco de Aràs which took place in Biescas on 7 August 1996).

The socio-economic impact of natural disasters

UN resolution 4/169-1987 contains this international body’s decision to declare the International Decade for Natural Disaster Reduction (IDNDR) for the period 1990-1999. The origin of this decision lies in the concern to halt the rise in the socio-economic impact of natural catastrophes in recent decades.

During this ten-year period each member state of the United Nations set up a Decade Committee (IDNDR) to promote and coordinate actions in favour of reducing natural disasters.

By the end of the nineties the global balance for the impact of natural catastrophes on the planet is not very hopeful. Earthquakes, for one thing, and floods and landslides caused by large storms or hurricanes, for another, are the phenomena which have caused most victims and the greatest economic losses. According to the statistics of the insurance companies, the number of natural disasters in the nineties trebled those of the sixties, and if we make the same comparison referred to economic losses, the figure is multiplied by eight.

This year (2000), a report on catastrophes in 1999, the last year of the Decade (IDNDR), reproduced in a publication by the prestigious insurance company Swiss Re (Sigma, No. 2/2000), reveals the following:

Since 1970, when systematic data gathering on the impact of natural disasters began, 1990 was the second most expensive year in the history of insurance (28,600 million $US; 24,400 million corresponding to catastrophes brought about by natural phenomena and 4,200 million corresponding to disasters caused by man). With regard to natural disasters, in 1999 there were more than 90,000 deaths (there were 50,000 in 1998, the year of Hurricane Mitch), which represents the fifth worst year in the last thirty years.

The problem is therefore obviously still with us and a long way from being solved. The UN Secretary-General, Kofi Annan, speaking of this problem in the closing address for the International Decade for Natural Disaster Reduction, suggested the following solution: “In the fight against natural catastrophes that may not be so natural,...we know what we need to do; all that is needed is to put the political will into practice”.

It’s obvious then that this problem raises a series of questions:

• Are natural phenomena getting more severe?
• Has their frequency increased?
• Has society become more vulnerable?
• What is changing in the relationship between man and natural phenomena?

Natural risk

Risk analysis is applied in the study of natural catastrophes to evaluate their impact and establish mitigating strategies. In evaluating the natural risk, three basic factors are taken into account: the danger level of the natural phenomenon in question (earthquake, flood, landslide, avalanche, etc.), which is defined according to the probability the phenomenon will occur and its energy (magnitude or severity); exposure of territorial elements to the phenomenon (such as people, buildings, infrastructures, etc.), and vulnerability --that is, the degree of damage each of these elements can suffer from a natural phenomenon that is considered dangerous.

If we define the natural risk as the product of danger level and vulnerability of the elements exposed, we can easily understand that an increase in the risk --that is, the social and economic impact of catastrophic natural phenomena-- does not depend only on an increase in the frequency of events or on an increase in their size. It also depends on the increase in a society’s vulnerability. And what does that mean? Quite simply, that man, society, and especially that of the less developed countries, has occupied areas where high-energy phenomena have always taken place. What is more, he has occupied them with very fragile settlements and in a disorderly fashion. Obviously, in the Third World, population increase and population movements --but especially poverty-- are prime factors.

If we take a look at just a few of the great catastrophes of recent years on a world level, as well as those mentioned above we can pick out: Hurricane Mitch in Central America (October 1998), flooding on the Yangtze (China, 1998), the Afghanistan earthquake (1998), avalanches in the Alps during the winter of 1999, the series of tornadoes that swept the American states of Oklahoma and Kansas (May, 1999), strong winds in France (December, 1999), flooding in Mozambique (February 2000).

And if we look around our immediate geographical surroundings, we can see that in recent years there have been a number of particularly striking scenarios and risk situations in Spain: the flood of the Barranco de Aràs in Biescas caused 87 dead in August 1996; flooding in a working-class neighbourhood in the city of Badajoz killed 24 people in autumn 1997; very recently (10 June 2000), heavy rain in Central Catalonia caused the loss of five human lives and considerable material damage. The problem is here, too; political will needs to be put into practice here, too.

As regards the danger level, and on the basis of the data analysed in recent decades, scientists are agreed that destructive natural phenomena have not increased either in frequency or energy.

In this graph we can see the evolution of the number of “strong” earthquakes --of magnitude M7 or above-- during the last 40 years. The Richter scale of magnitude expresses the energy released by an earthquake and is measured on the basis of the seismogram. The Richter scale is an open scale --that is, it has no upper limit, and each unit of the scale represents a 10-fold increase in the amplitude of the seismic wave. One of the biggest earthquakes in recent history is the one in Alaska in 1964 (magnitude 9.2), which released the same amount of energy as that produced by 25,000 atom bombs like the one that destroyed Hiroshima in 1945.

What must be done to fight against natural disasters

Mitigating the natural risk involves reducing some of the three factors of risk (danger level, exposure and vulnerability) and of all three at once whenever possible.

The question “What must be done?” has several answers, all of them complementary, which can be summed up in a policy of prevention combining prediction and protection.

Research and new technologies will allow us to be prepared for catastrophic events with improved prediction techniques (unfortunately, we are still a long way from making a good temporal prediction for all types of phenomenon) and to reduce their magnitude whenever possible.

Research and technological development will also help design what we call structural defence strategies (civil works). But this is not enough; real prevention must begin by redirecting man’s attitude to natural phenomena in his occupation and use of land.

Once and for all, regional administrators and political leaders must realise they need detailed zoning risk maps if their policies are to work.

Education and social organisation, the pillars of prevention

The basis for a good preventive strategy involves education and proper social organisation. There are examples of countries affected by catastrophes where in spite of a lack of financial resources, proper social organisation, supported by a policy of basic environmental education for civil society, allows a considerable reduction in vulnerability. This is the case in Cuba, which during the Hurricane Mitch crisis demonstrated a high capacity for reaction, evacuating areas threatened by the storm without worse consequences.

Teaching society, at school, to live with natural risks affecting its geographical area means having a population that is aware of the problem and therefore demands a successful policy of risk management from its leaders.

Natural catastrophes are socially and economically very expensive and it is obvious that they make development unsustainable. Prevention is not expensive; prevention means basically educating and organising society; prevention means, above all, rational planning of the territory and its uses. For this to work, we need especially one thing more than ever: political will.