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A GIS-based modeling of environmental health risks in populated areas of Port-au-prince, Haiti

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par Myrtho Joseph
University of Arizona - Master in Natural Resources Information System 1987

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Often the terms risks, hazards, and vulnerability are not well understood and consequently are repeatedly misused or used with different meanings (Schmidt-Thomé et al. 2006). In that vein, it is worthy to elucidate these concepts, which will further clarify the phenomenon we intend to assess.

2.1 Risk

A risk is perceived as: the losses derived from a specific hazard to a defined element at risk, over a certain time period (UNDRO 1979); the chance that a particular hazard will actually occur or the probability of experiencing loss from a hazard (Smith 1996); or simply the product of the vulnerability of a community or people to the effects of a specific event, and the potential for the occurrence of that event (Ferrier and Haque 2003). From these approaches, it is possible to express risk either as an average expected number of deaths, economic loss, or physical damage to property, or as the probability of the occurrence of an event. This probability is then dependant on social, physical, economic and environmental factors or processes, which increase the likelihood for people or communities to be harmed.

2.2 Hazards

Common definitions offered in the literature describe a hazard as a physical event, natural or man-made, that may cause damages to human life, property, assets and generate social and economic disruption or environmental degradation. It is also perceived as conditions that increase the probability of losses (UNISDR 2004, UNDP 1994, Smith 1996, Corvalan et al. 1999, City of Long Beach 1998). These definitions imply that natural hazards are normal phenomena that do not set nature necessarily to risk (Schmidt-Thomé 2006a). Risks and hazards are linked through vulnerability.

2.3 Vulnerability

The social, physical, economic, and environmental parameters that we referred to earlier and which boost the chance for the occurrence of a disaster embody the characteristics of the elements at risk, i.e. their vulnerability. The Stockholm Environment Institute (SEI) (2005) characterizes vulnerability as a lack of security from environmental threats and as the result of a mixture of processes that profile the exposure to a hazard, susceptibility to its impacts, and ability to recover in the face of those effects. As Schmidt-Thomé (2006a) noticed, vulnerability must be seen in a human perspective, since human beings put themselves at risk by their exposure to hazardous areas. Other definitions adhere to the concept of exposure to hazard but go one step further by adding the coping ability of people to adjust and reduce the negative impacts. Shortly, it is the potential for a geographic area and its belonging to experience losses from events (Hossain and Singh 2002, UNDP 1994, Chambers 1989, Cutter 1996, Clark et al. 1998, Liverman 2001). Though three categories of vulnerability are suggested (Cutter 2003, Weichselgartner 2001), namely the risk/hazard exposure, the social response, and the vulnerability of places, our perspective in this study is limited to the first and third approach. Yet the social response determined by the characteristics of the population studied can not be dissociated from the other elements (Cutter et al. 2003).

The concepts above suggest that hazards and vulnerability represent the two components of risk. How risk is assessed is another methodological aspect that we want to bring forward.

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