ABSTRACT:
Volcanic disaster mitigation in densely populated areas is based on the emergency plans or the guidelines of interdisciplinary systems integration. An emergency plan is primarily designed to wait for a volcanic eruption and manage its evacuation, whereas an interdisciplinary approach mainly aims at reorganizing the territory to minimize the impact of future eruptions and evacuation. The latter approach is advantageous for a densely populated area because of our inability to forecast future eruptions more than several days or weeks in advance and evacuate a very large number of people who are ignorant about the risk or who do not wish to evacuate, because of the difficulty in confronting the political and socio-economic consequences caused by a massive or false evacuation, due to the impracticality of protecting a rich territory from speculators after the eruption for a long time; or due to the unwillingness of the population or the nation to accept the destruction of its culture by a failure to evacuate or evacuate to faraway places.
BACKGROUND:
There are places around the world where people dwell and work in the proximity of dangerous volcanoes, and where the problems of declining these volcanic risks caused by future eruptions are becoming more an arduous task to solve because of the increasing population density. A volcanic risk is defined in terms of the degree of vulnerability of people, potential hazard produced by that eruption and the infrastructures and value of the territory exposed by the future eruptions. This hazard is measured in terms of the time in which the extreme situations can be effusive and the probability of an eruption event occurring at a given place, when a volcano induces slow moving lava, and explosive, when it produces great rising volcanic clouds of gas and ash and pyroclastic flows which move very fast along the slopes of the volcano. People, transportation, houses and communication systems, such as the layout of roads, train and bus routes, sewers, electrical power and telephone lines, water supply lines and archaeological sites are all vulnerable in different intensities to different eruptions and it is defined in terms of the probability of its vulnerability. Each of these infrastructures has a different intensity value which may be difficult or not possible to estimate the proper calculation of its risk. The volcanic risk thus constantly changes not only because of its hazardous nature but also because of the changing socio-economic conditions of the people exposed to this hazard. Further, the population surrounding a volcano may consider the preservation of its culture as an important factor, which complicates the risk balancing equation.
Thus, it is mandatory to possess reliable data which will define its risk before concluding that the population around a hazardous volcano needs to be resettled or the area separated from the future developments. More fear and confusion about this problem are often created from the ignorance of the danger instead of confronting it and actively finding its solution. Educated people living in high risk areas and who carry the necessary educational background about the risk are often the better judges of reality of this risk than the people who tend to be biased by their own interests, and by those who want to conquer the region for their own interest and gains. An ordinary person dwelling in a volcanic eruption prone area is not very much concerned about the future eruptions and its effect on that area, for from the person’s often limited exposures, he has learned that the dangerous volcanic eruptions in that area are very rare and that the problem of risk mitigation should be passed on to the future generations who are ready to live in this territory. As a result, many people tend to adopt or live in harmony with these volcanoes and they move only when the volcanoes begin showing signs of unrest or when they tend to alter their lives in one or the other concrete manner. Therefore, the basis for volcanic risk reduction in highly populated areas should involve an interdisciplinary scientific approach in which the political, science and social and economic factors of the region play significant roles in the risk mitigation.
The main purpose of this activity is to discuss the two various approaches of volcanic risk mitigation in the highly populated areas. The first approach which is practiced by volcanologists does not represent an advisable strategy when dealing with highly populated areas, because of the unavailability of necessary and sufficient data to produce the reliable eruption forecasts and evacuate hundreds of thousands of people on time. So another alternative is based on interdisciplinary systems integration which aims at creating different options for the region which are necessary for making decisions by the people whether to live and work on the region or how to behave during future eruptions.
PROSPECTS OF FUTURE CATASTROPHES:
A volcanic catastrophe is an eruption which is devastating enough to alter the social and economic order of an entire territory. It is thus not possible today to forecast such an incident because it may occur from a volcano which was inactive for hundreds or thousands of years. But, we can classify several of the well-known volcanoes as being appropriate candidates for the future catastrophes, for each of them can induce a significant change of social and economic order of a nation.
A volcano named Vesuvius in Italy has been erupting for the last 17,0000 years by producing explosive eruptions every thousand years and medium explosive eruptions every hundred years. The seventy nine plinian eruption buried the Greco-Roman cities of Pompei and Herculaneum, devastating the surrounding territory, and made the area unproductive for several centuries. In 1631, about a few hundred years later, the subplinian eruption induced an even higher damage on the territory because of the much higher population density which killed about ten thousand people. Post this eruption, Vesuvius was in a phase of strombolian and eruptions in which some of them also produced a great deal of damage, such as the eruption of 1794 that devastated Torre del Greco, and the eruption of 1944 which devastated San Sebastiano al Vesuvius. It is now preparing for its next awakening which may be large in intensity, and which can cause an unimaginable human and environmental catastrophe due to the higher population density near the crater of the volcano. A small eruption could even induce tens or hundreds of thousands dead and affect at least thirty lakh people who dwell in the 30 km radius of this volcano where the infrastructures are totally not adequate for the region of such a high risk. There are nearly ten lakh people in the 7 km radius of the volcano with population density as high as fifteen thousand people per square km (Portici, San Giorgio) .To worsen the things; the Italian volcanologists convinced the government to introduce an unreliable Emergency Plan for the Vesuvius area that portrays a false sense of security.
The above said volcanoes are only several illustrations which can produce environmental and human catastrophes, because of the influential nature of the word catastrophe and the degree of intensities that can be associated with this word. A catastrophe can imply the loss of most of the members for a family, the loss of several hundred or thousand people for a town, the loss of hundreds of thousands for a region, and the collapse of the government for a country. The word catastrophe also imprints upon our mind our inability to face these problems and finding appropriate solutions to them.
ERUPTION FORECASTING:
The data obtained from monitoring of seismicity,deformation of the volcanic cone,gas emissions, and magnetic, electric and gravity fields help the volcanologists to predict the eruption forecast .The seismicity of a volcano does not, of course, always lead to the conclusion that a volcano has become restless, because a seismic signal can also be produced by the tectonic motions in the region which may have nothing to do with the volcano.The changes in the groundwater level or temperature, lake levels, snow and ice accumulation,and the transport of sediments in the stream can also be useful signals for the issuance of eruption forecasts.Delayed eruption forecasts can produce a catastrophic consequence in a densely populated area, since its unpractical to evacuate hundreds of thousands of people on a very short notice and possibly in a state of panic.The evacuation order must be given weeks or months in advance.The end result of this conflict between the uncertainity of eruption forecasting and interest of avoiding a false forecast, as well as the interest of local politicians to keep the population ignorant about the risk in order to govern them, can only produce a tragedy for those who have left their destiny in the hands of those who are no better equipped with the facts than they are.
VOLCANIC RISK MITIGATION BASED ON EMERGENCY PLANS:
Intense urbanization and inadequate planning contributes towards an increasing risk of living and working in the area.The lack of forecasting an eruption is based on our ignorance of the substructural characteristics of the volcano, such as the composition of magma , location and size of the magma reservoir, magma supply rate to the volcanic system, and mechanical, structural, and thermophysical characteristics of the volcanic edifice.The cost of a false alarm , cost of evacuation reentry, cost to avoid speculation and protect the area during and after evacuation, cost to maintain the command and control centres in the area and the cost of making the plan reliable when its proponents refuse to discuss it at scientific meetings are the factors that does not make the plan economically reliable.
INTERDISCIPLINARY VOLCANIC RISK MITIGATION:
Our inability to predict on time the eruptions of explosive volcanoes such as Vesuvius , Popocatepetl, and others, and evacuate on short notice hundreds and thousands of people,socio-economic and political consequences caused by the evacuation to far away places, peoples inability to leave their homes , large costs on false alarms , and possible destruction of the culture and and speculation caused by the evacuation, its necessary to manage the catastrophe and substitute this with a plan for the prevention of a catastrophe and development of the area. Such an objective may only be achieved after solid scientific , technological ,sociological, educational, and urban planning feasibility studies .
ROLE OF THE NATION:
The ultimate goal of civil nations must be the prevention of catastrophes. An effective volcanic risk reduction plan for a densely populated area should have the central objective of providing the basic elements or guidelines to reduce this risk through an interdisciplinary effort involving volcanologists, geophysicists, seismologists, physicists, engineers, computer scientists,historians, urban planners, sociologists, educators, telecommunication experts, economists, environmentalists,civil protection volunteers, and the exposed population. Such a plan should aim at creating a multitude of different options for the risk area which are necessary for taking decisions by the population whether to live and work on the territory or how to behave during the future reawakening of the volcano.
CONCLUSION:
Mitigation of volcanic risk through an emergency plan which tends to wait for an eruption and then try to manage it through evacuation is not a viable option for a densely populated area because of our limited ability to forecast future eruptions, deal with the evacuation of very large number of people, or protect an evacuated and rich territory for a long time. A more realistic approach of volcanic risk mitigation should involve the prevention of a disaster where the territory is reorganized for the purpose of confronting future eruptions with minimum panic and necessity to destroy the culture and leave the area to the speculators.
