Description of effects and vulnerability

How are effects and vulnerability described?

The way in which vulnerability and the effects of hazards are described will depend on the scope of the vulnerability assessment. If a community is assessed, a standard set of parameters to describe the effects (e.g. extent and number of services disrupted, number of homeless persons) can be used. For a hospital, however, other parameters (e.g. effect of loss of service on the community, emergency medical demands on the hospital, effects on staff, and cost of and time required for repairs) would be useful. Table 14 shows some possible parameters for describing community vulnerability and the effects of hazards on a community.

These possible parameters should be discussed with the planning group and modified if necessary. Each hazard should then be examined in detail, parameter by parameter, to estimate the degree of loss in relation to each parameter in the community. The differential vulnerability of parts of the community in respect of these parameters can also be described, and the results of the entire examination should be documented immediately. The planning group should also realize that one emergency may provoke others. There is usually, in fact, a cascade effect, more and different emergencies following the original. These, too should be planned for. There are also specific needs that can be predicted for different types of emergencies (12). In addition:

· Volcanic eruptions. Possible needs (and secondary effects) are similar to those for earthquakes within the area directly affected by the eruption; there may be population displacements.

· Tsunamis (tidal waves caused by earthquakes). Possible needs are similar to those of tropical storms plus floods, with the added complication of contamination of wells and agricultural land by salt water.

· Epidemics. Needs usually include specific drugs, transport, surveillance, improvement of water supplies, personal hygiene and sanitation; reinforcement of health service management may also be required.

Table 14. Descriptive parameters for the potential effects of hazards^a

^a Reproduced from reference 10 by permission of the publisher.

Effects and vulnerability mapping

On vulnerability maps, those aspects of the community (and often of the environment) that are vulnerable or at risk are overlaid with hazard information. This allows an estimate of the degree of harm or loss that may occur. The simplest way to produce such a map is to use a transparent, removable overlay on a base map. Even if a preparedness programme lacks the time and financial resources for vulnerability maps, the concept of mapping can still be used as an analogy. In determining the likely effects of hazards it is worth considering how the community is spatially related to the hazard.

It is equally possible to map the vulnerable aspects of the environment. This can be useful in the following areas:

· Fire. Which areas contain forest resources that might be destroyed? Are there fauna and flora that would be severely affected?

· Hazardous materials. Are there fishing areas downstream of industrial outfalls that might be affected by acute spills? Are there breeding grounds for waterfowl or fish downstream?

· Oil pollution. Are there fauna and flora likely to be affected by oil spills or by the use of oil dispersants? Are there areas that are used for recreation and tourism that may be affected adversely?

Geographical information systems

Geographical information systems (GIS) will be widely used in the future for hazard and vulnerability mapping. They are computer programs that combine a relational database with spatial interpretation and output. A more technical definition is “A system for capturing, storing, checking, integrating, analyzing and displaying data about the Earth that is spatially referenced. It is normally taken to include a spatially referenced database and appropriate applications software.” (11).

It is possible to enter a variety of types of data, and relate them through formulae, or overlap them in a graphic presentation, either on screen or as a printed map. Use of GIS is increasing for the everyday administration of communities, and existing systems and information can be used for emergency management purposes. GIS allow the rapid analysis of large quantities of related data and can also be used as a predictive tool. When applied to hazard and vulnerability information, GIS can be employed for all aspects of emergency management.

An example of the use of GIS in preparedness and response is in the recording and analysis of data on large stores of hazardous materials. Government organizations often collect data on these stores for the purposes of licensing and public safety. If the data are entered into a GIS, the following information can rapidly be displayed in graphic form:

- locations of the largest stores;
- distances to the nearest fire station;
- who owns a particular storage area and their after-hours contact details;
- what material is stored, where on the site, etc.

GIS can be combined with a gas- or smoke-modelling program to determine the possible concentrations of gas, fumes, or smoke following an accidental release of hazardous material or a fire. The shortest routes from a given fire station to a given store can be calculated and possible evacuation routes plotted. This information can be used both for emergency planning in relation to the storage of hazardous materials and in the response to accidents involving hazardous materials.