Estratto dal libro: Principles of Emergency Planning and Management David Alexander
In the context of disasters, a scenario is a hypothetical progression of circumstances and events designed to illustrate or reveal the consequences of any decision, action or impact. Usually the scenario is set up to provide a consistent and logical answer to the question "what if ...?" However, rather than aim for the future, sometimes using the method of scenarios to look back (a positive and constructive way to use hindsight) as a tool for debriefing to better learn the lessons of an event's happened before.
A scenario is a model of conditions and circumstances. It is usually designed to reveal the link between these two things (that is, how the conditions affect the circumstances and conditions as circumstances change). The method of the scenarios can be used, for example, to reveal the consequences of the impacts of disasters, or a certain range of mitigation works, or certain strategies of search and rescue of survivors. The scenarios may explain the vulnerability interacts with dangerousness to create special forms of risk and impact. The scenarios for losses due to disasters can be modified according to certain measures to reduce the risk and in relation to how they work during the disaster.
It is clearly essential to build the scenarios as chains of events that are plausible and reliable. One of best ways to do this is to use a systems approach (systems approach). The entries are specified in the form of a series of conditions and forces that cause changes in fundamental variables (such as a river flood wave interacts with the strength of a bank). Further conditions are specified within the compass of the system: some of these limitations, and other guides, the mechanisms of change in the situation as it evolves. Together, the conditions act as a forcing function, or motive of the events. The emission model is the scenario, as constructed, and its changes over time taken into account.
The scenarios are useful to contingency planning, given that the method can be used to clarify the conditions that need a plan (ie, the presence of dangerous phenomena and their likely effects), that the impact of preparation in terms of how it can reduce risk. In fact, detailed studies of hazard, vulnerability and risk exposure can be integrated into the development of the scenarios that are created to investigate the losses and injuries in disasters. As a result, they may form the basis of emergency planning and measures to mitigate the risk.
The first step in building a scenario is to specify the initial entries and the limitations (Boundary conditions). For example, you could develop a scenario for a magnitude 7 earthquake, which constitutes the danger of fires dl emission scenario and soul. The initial conditions are given the vulnerability of the built heritage, dall'inquadramento activity at the time of the earthquake, people living in the area at risk, and the ability of the emergency forces to respond quickly to disaster. The development scenario is based on the temporal progression of events. The vulnerability data indicate that a number of houses could collapse and a number of people could die. Under this scenario can be used to judge the probabile efficacia delle operazione di soccorso o per stimare la riduzione dei danni e degli infortuni avuta con un potenziamento dell'intervento immediatamente dopo il sisma.
Lo scenario procede attraverso una serie di fasi, le quali vengono solitamente definite dagli eventi (ad esempio, può estendersi dall'isolamento delle vittime all'inizio dell'emergenza all'arrivo delle forze incaricate con la ricerca e il salvataggio dei superstiti, e poi all'inizio dei processi di ripristino). Alla fine di ogni fase si può "congelare il tempo" e trarre la somma degli eventi successi, delle azioni e le decisioni prese. Così si ottiene una "sezione trasversale" del disastro, un quadro del progresso fatto e dei problemi affrontati dai principali actors (disaster managers, relief workers, firefighters, volunteers, doctors, paramedics, etc.).. When you explicate the entire progression of events, and was once the final outcome, you can change the scenario by searching for answers to a series of questions like "what happens if we double the number of rescuers?" or "what will happen if the earthquake caused landslides that hinder the main roads into the disaster area?" The answers to these questions are based on a number of changes to the outcomes of the scenario.
is particularly important that the emergency planning construct scenarios in written form, if necessary with the help of relevant experts, for all major risks and dangers that come within its competence. These will serve to illustrate the situations that must be planned and will help to establish the parameters of the process of emergency planning at the local level.
In many cases the construction of scenarios a priori there are no means to verify the result, if a disaster does not happen like that in the near future (thus making the scenario a kind of prophecy!). So we look for the verisimilitudine the plausibility of the facts, conditions, mechanisms and outcomes represented by the scenario. While going on the progression of events must continually ask themselves: is this possible? " or: "Is likely to happen this way?" It is best to avoid scenarios or improbable events, and also, of course, the injury, the excesses of fantasy, irrationality, excessive detail. A good scenario writing takes the reader with clarity, transparency and logic through a series of events will demonstrate the framework for decisions, illuminate the reasons for actions taken, describe the outcomes, and justify the different events with a credible and logical explanation . The present exemplary scenario the large picture of the situation and not be encumbered by the invention of large amounts of detail. Its bases are collected data on hazards and risks, and also the trend di eventi simili che sono veramente accaduti in passato (quindi è essenziale studiare meticolosamente i dati che possono aiutare la formulazione dello scenario). Così, l'esito finale sarà interamente plausibile, sebbene non necessariamente immune al dibattito.
Come esempio consideriamo lo scenario costruito per una ripetizione del grande terremoto di Kanto, che avvenne in Giappone nel 1923, il quale è raccapricciante. Si aspetta tra 40.000 e 60.000 morti, fino a US$1.200 miliardi di danni al patrimonio edilizio, danni per $900 miliardi all'infrastruttura, e perdite di $1.000 miliardi dovute all'interruzione delle attività redditizie. Comunque, il vero esito dipende dalle assunzioni su cui è basato questo scenario: some researchers have considered exaggerated sums of money found here. However, it is clear that many important things are at stake: the final figure of losses could be equivalent to half of GDP and Japanese financial markets may force the world to suffer a serious downturn.
Of course, most of the scenarios are less grand than this, and so now we will consider a hypothetical example that has the merit of being very simple. To be brief, to exclude most of the details of the fund.
Around 16.00 a normal Friday afternoon in a case of May an earthquake measuring 6.7. The strong shaking lasts 33 seconds and generates horizontal accelerations the surface reaching 31% of gravity (0.31 g). Among the architectural heritage of the city hardest hit (50,000 inhabitants) the damage is serious but not universal. Most spectacular of all, a 200 m long section of a highway viaduct collapsed on a parking machine, crushing several cars and maybe some of their occupants. Secondly, the facade of brick and concrete of a department store in the mall of the city collapsed and blocked the main road with its rubble. Again, as there may be victims. In third place in a shed, in use at the time of the quake, with a steel frame collapsed in the industrial zone, while in the residential you had the partial collapse of a 4-story building occupied by the elderly. In three points of the city breaking gas pipes has resulted in fires that are violent but fortunately located. Elsewhere in the rupture of water pipes has led to a series of small floods and a severe loss of pressure of water supply in the city. The lack of mutual assistance indicates that neighboring communities have to deal with serious damage. Finally, in the area there is only one hospital with emergency room, and its functionality and efficiency are limited by severe structural damage and the absence of several members of the medical and support of some officials.
The scenario goes on the basis of a rational approach managing a situation that is currently full of unknown, uncertainties and limits on the capacity to act. The damage described above is clearly based on appraisals of vulnerability that are made in "times of peace" in mind with a certain magnitude of earthquakes and other seismic parameters of the specification. The description refers to a time point about half an hour after the earthquake: it is not complete at this time because you will not have a complete range of information on the disaster. For example, the number of deaths and injuries is not known. The further development of scenario depends on a number of assumptions of how it will continue the rescue operation, and shows how the situation than people who remain homeless and injured survivors and trapped. The end result is a graphic of the immediate need for massive resources, a problem that the planner will face a very serious emergency.
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