The wind, waves and all the natural dynamics show us the complex interrelation between the lithosphere, hydrosphere, atmosphere and biosphere. Much of this dynamic is almost imperceptible, such as erosion or sedimentation caused by wind, rivers, glaciers, and so on. However, in other cases, the behavior is violent natural elements, such as earthquakes and volcanic eruptions, threatening the companies, their assets or activities.
An earthquake, hurricane or other extreme event of nature becomes a disaster or catastrophic when human losses or economic causes. That is, natural disaster is called only when the social or economic problem is triggered by a phenomenon of nature. loe Golden said "a potential danger becomes disaster if it occurs where people live."
The consequences of natural disasters must be viewed not only from the point of view of the lives lost, but also from an economic standpoint, they constitute an obstacle to economic and social development of the region, especially in countries development. In them, a disaster can result in a reduction of gross national product for several years, for example, flood drag the topsoil and takes years to recover. It has been estimated that the gross national product losses due to disasters can be, proportionally, 20 times higher in developing countries than in developed nations.
The FAO has estimated that the drought in the 70s in the Sahel (Africa) reduced to half the gross national product (GNP) of the region's countries: Burkina Faso, Chad, Mali, Mauritania, Niger and Senegal.
Disasters can have consequences later, ie can only be evaluated over several years. A drought or flood can affect the economy of the region or a country in a way that affects the quality of life or health of its population for several years. According to the Office of the Coordinator of United Nations Disaster Relief (UNDRO), floods in the Philippines in 1972, delayed the development efforts between three and five years.
A major cause of the slow recovery and reconstruction in developing countries after a disaster, you do not have property seized as many developed countries. Hurricane Andrew, which struck the U.S. in 1992, led to 30,000 million dollars in losses, but 75% were carried out by insurance companies. By contrast, floods and landslides that swept China in 1996, caused an economic loss of 24.000 billion dollars, but their insurance did not reach 2% of losses.
In addition, after the phenomenon, the victims need not only material assistance but also psychological support: studies show an increase in depression, alcohol consumption and to increase the suicide rate.
A point to note is that disasters or disasters caused by natural events are increasing and entail losses in the millions, but scientists who observe, record and analyze the natural dynamic state that the frequency of extreme cases has not increased significantly. This is due in large part to rising world population and poverty, as the where and how man built their homes may increase the risks for both physical (injuries and deaths) and social and economic, which are slow to recover.
Currently, at least one fourth of humanity lives in areas vulnerable to disasters, especially in developing countries. In them, people settled their homes in areas prone to such disasters, for example on the slopes of the mountains, where avalanches can drag entire villages, as happened in El Nevado del Ruiz (Colombia), or in the beds of rivers that when they increase their flow, overflow and cause serious flooding.
Another element to consider is that many of the actions of human beings as deforestation and pollution compound the effects of natural phenomena. Cleared forests on the slopes of the mountains favor avalanches or landslides, the sediment fill in riverbeds, causing overflow more frequently