A new classification of catastrophes based on “Complexity Criteria”

Summary

A classification system of catastrophic events is a methodology assembling all the catastrophe groups. There are many classifications of catastrophes. The most widely known are classified into: nature, consequences of the event, duration, affected territories and areas of the destroyed zone, and at last into the needed intervention measures. It is difficult to study the complexity of catastrophes with these classifications. We propose a new system of classifications of catastrophes based on “Complexity Criteria”.Within the scope of this paper, we focus first on organization, self-organization and emergence of the event, and then on spatial and temporal scales of the catastrophes. The organization is a key concept of complexity. In the catastrophe field, complexity of organization results essentially from the self-organization of the systems (the system develops its internal constitution and its behaviour because of the interactions between its various components and not because of an external strength). Phenomena as different as mantels of snow, seismic hazards, behaviours of the persons and the crowd have characteristics of self-organization allowing the emergence of new events: snow avalanches, earthquakes, collective panic. A particular attention will be given to the emergence of collective panic in a context of catastrophe. We observe that emergent properties appear after the interactions between the individuals and the crowd happened It means that we need to take into account the multi-scales aspect in order to be able to study the behaviours. The complex systems of catastrophe have characteristics able to emerge at higher or lower levels of scales. It allows us to study the complexity of the disasters through the scales. The disasters belong to the various temporaland space scales.

First, the disasters cannot be classified in a single category of spatial scale. Some of them appear on the scale of a territory, a region, a country or the planet. If we speak about a natural or technological disaster, none of them will be automatically associated with a spatial scale. Furthermore, a local disaster can have large-scale impacts. Various events (for example, the earthquake in the Chinese province of Sichuan in 2008, the hurricane Katrina which destroys New-Orleans in 2005, the tsunami which ravaged the South of Asia in December 2004, the catastrophe of September 11th, 2001 in New-York) remind us that the catastrophe is not always an event within a restricted area. A catastrophe have often impacts outside this area. The complexity of catastrophes can result from the interactions between different spatial levels and from systemic relations between these levels.

The complexity also results from various temporal scales of the risks and the disasters. There are three temporal phases. The first one is relative to the temporality of the potential risk I mean what takes place before the disaster. The second phase refers to the temporality of the disaster I mean all what happens during the catastrophe. During the disaster, the temporalities of hazards, vulnerabilities and domino effects rarely happen together. The third and last phase refers to the time after the disaster and to the experience feedback for the risk management. These three temporal phases are based on two scales of time: a short time, I mean a time - action, inherent to the functioning of any dynamic system [1] and a long time. The study in each of the scale gives some information about the whole of the catastrophe, or about some of its components (hazard, vulnerability and domino effects).