II. ASPECTOS DEMOGRÁFÍCOS Y SOCIALES
3. Educación
3.5 Educación Secundaria y Diversificada (III y IV Ciclos)
Evacuation planning with regard to flood risk management means dealing with the possibility that an evacuation may not be followed by a flood or that a flood happens unexpected. An evacuation followed by a flood might even be an exception. Evacuation policy is therefore risk averse.
Previous experiences are only relevant to people in the area who have had such experiences and if these experiences are relevant. For example, when the expected frequency of an evacuation is less than a (large part of) a lifetime, it is questionable whether this experience will influence the response of authorities and citizens in a subsequent event. A survey among Dutch evacuees of the area of Rivierenland ten years after the mass evacuation (in hindsight, the flood did not occur, although a preventive evacuation was conducted) and Zeeland (50 years after the flood) shows that inhabitants’ the willingness to evacuate is almost equal to that of the inhabitants of other areas (NIPO 2006). In New Orleans, where people evacuated more frequently, the willingness to evacuate is related to previous events.
The ‘professional lifetime’ of the decision makers and their advisors and crisis managers is even shorter (for example about a decade or even less). Therefore, the willingness of evacuation is related to different lifetimes.
For low frequent events as in the Netherlands it can however be questioned if learning of previous events is relevant for citizens because the frequency of such events compared to an average life of a human. For authorities however learning is relevant and explicit attention is needed as citizens in a democratic society expect of public leaders also to take responsible measures in case of a crisis based on the available information and knowledge (Boin et al. 2005).
As research shows that training and exercises that has to stimulate the correct response have to be based on a plausible scenarios (Alexander 2000). These scenarios and possible responses have to be recognized and accepted in planning.
Preparation for evacuation is often related to the frequency of the disaster (such as a flood or nuclear incident) and not the frequency of the evacuation itself or even the decision-making process. The frequency of early warnings, activating emergency teams and other measures could be (significantly) greater than the frequency of flooding, as shown in the case study. Figure 22 shows a conceptual figure that illustrates the relation between frequency and impact of measures. Because of these different frequencies, it can be concluded that:
1. The activation of emergency planning will occur more often than the implementation of operational measures and calls for evacuation;
2. Evacuations will occur more often than floods.
Figure 22: The frequency of decision making, evacuations and disasters
4.6
Concluding remarks
A flooding scenario for emergency management includes the lead time as well as the size of a flood. Because of uncertainty in the lead time and the size of the event, a ‘one scenario fit’s all’ approach excludes other possible scenarios and can create blindness for these events (Boin et al. 2005). When planning is related to a design scenario and measures are implemented as foreseen in the planning documents, this could create additional damage and loss of life or be less effective as foreseen when the actual event is not equal to the planned (or pre designed) event.
The matrix of threat and impact scenarios can be seen as a ‘design set for scenarios’. This matrix covers classes that represent all possible and known scenarios, taking uncertainty in the size and lead time into account. The matrix also contains a class for worst case scenarios with a role to identify how systems fail in a stress test.
The number of classes can be defined using probabilistic analyses. When the consequences of uncertainties are limited only one scenario can be used to represent all; however this is not the case for flooding in the Netherlands.
During top strategic decision making information is required of possible scenarios. This requires the combination of possible events and identification of the risk taken the probability and consequences into account.
The role of a scenario for top strategic decision making for evacuation is only relevant when it is considered in relation with other possible scenarios. Top strategic decision will be made during the transition phase. Decisions have to be made quickly to become effective for evacuation. The location of breaches is still unknown and also uncertainty in forecasts (and therefore hydraulic loads) will exist. The threatened area and evacuation zone has to be based on multiple scenarios and can take the probability into account. Top strategic decision makers will focus on the risk.
The addition of new developed scenarios during the crisis to the scenarios that represent a class in the matrix in using the actual conditions does not improve the effectiveness of the evacuation when the available time is limited. The additional information in the new scenario is limited compared to the earlier defined classes. Multiple scenarios have to be developed as part of the risk assessment. Also because of uncertainty in the parameters defining the boundary conditions of the scenario the additional information related to the earlier defined class is limited. The development of a new scenario also requires time for calculation, visualisation and interpretation by experts (including validation) and decision makers. The use of new scenarios will also introduce complexity and increase the risk of ambiguity or linguistic problems as well as the time needed for decision making.
In the case of event-driven scenarios, the development of a new scenario might result in better information when the actual conditions are known. However, the availability of the required information to develop the scenario and the uncertainty in this information gives the new scenario less additional value compared to the defined scenario. A new scenario that describes deterministic the expected flood pattern does not contribute to the performance of evacuation, this is because of the uncertainty in the parameters about the actual situation. This is also because the limited possibility of influencing the on-going response using command and control structures, especially when the operation is on-going. The scenarios in the matrix of scenarios offer enough information for the emergency response. Using the matrix of scenarios, the risk for an overload of information is reduced; all stakeholders use the same information (which reduces ambiguity). However, new flooding patterns remain useful for evaluation purposes.
The motive of emergency planning is often related to the frequency of a flood. However, the motive should be related to the frequency of evacuation or when the thresholds are exceeded. The frequency of activating emergency planning (because of defined thresholds) is far greater than the frequency of evacuation. Additionally, the frequency of evacuation is far greater than the frequency of a flood. Emergency preparation should therefore also focus on situations in which measures are taken but a disaster does not occur and on situations when crisis teams and decision makers meet but in the end it is decided to continue normal activities. This better-safe-than-sorry policy is the cornerstone of emergency preparation. However, most planning documents and almost all exercises focus on the situations when a flood does occur and people are trained to implement measures.
This also implies that an evacuation not followed by a flood is not always a false alarm; in fact it can be good planning when it is based on earlier defined criteria and procedures. A false alarm can occur when forecasts are made incorrectly based on information that is used in the wrong way.
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