2. CONCEPTS 1: A BRIEF OVERVIEW OF CLIMATE CHANGE AND THE
3.4 Risk Management
3.4.2 Risk mitigation and control
Risk mitigation and control constitute the second major component of risk management (Figure 3.4). “Risk mitigation considers setting up alternative measures to reduce the impacts of a hazard by minimising its destructive and disruptive effects, thereby lessening the scale of the disaster. It attempts to find practical and workable strategies and solutions for minimising risk at scales ranging from international to national to local (Schulze, 2003d).”
Risk may be reduced by decreasing the extent of any one or more of the contributing variables. From the equations relating to risk and hazard in Box 3.1 and Section 3.1, respectively, the risk equation can be expanded so that
Risk = Physical Event x Exposure x Vulnerability
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This can be illustrated by assuming the ‘dimension’ of each of the three variables represents the side of a triangle, with risk represented by the area of the triangle (Granger, 2000). In Figure 3.5, the larger (yellow) triangle portrays each of the variables as being equal, whilst in the smaller (green hatched) triangle the risk has been mitigated by the reduction of both exposure and vulnerability. The reduction of any one of the three factors to zero would consequently eliminate the risk (Granger, 2000).
It follows that the main mitigation strategies would involve physical event modification, i.e. modifying the physical processes that create or constitute the hazard, involving some degree of direct confrontation; as well as vulnerability modification, i.e. reducing the impact of the event by rendering the human environment less vulnerable to, and more prepared for the event; and exposure modification, which is usually achieved as a result of the first two mitigation strategies.
Figure 3.5 A schematic illustration of risk mitigation through modification of the components of risk (adapted from Granger, 2000)
Exposure Vulnerability
Physical Event
(e.g. Flood)
RISK
44 3.4.2.1 Physical event modification
The objective of physical event modification is to reduce the damage potential associated with a particular event by means of some extent of physical control over the primary processes of the event involved (Schulze, 2003d), e.g. the stimulation of cumulus clouds to reduce rainfall intensity and increase rainfall duration. However, owing to technological deficiencies and the uncertainty involved, the suppression of natural events such as those causing large scale flood events is not yet possible (Schulze, 2003d).
A more common approach to event modification is via manipulation of the secondary processes that cause a hazard (Schulze, 2003d). In the case of floods, for example, instead of attempting to manipulate the rainfall event, the runoff generation processes could be manipulated through the restoration and rehabilitation of wetlands, or by increasing the efficiency and capacity by which floodwaters are conveyed through channel improvements (Smith and Ward, 1998). Hazard resistance is another form of event modification, this involving the construction of defensive engineering structures such as levees for flood proofing or dams to contain floodwaters (Smith and Ward, 1998; Alexander, 2001; Schulze, 2003d).
3.4.2.2 Vulnerability modification
Vulnerability modification is a more complicated process that involves the interaction of several different interrelated factors, and is concerned with human reactions toward a potential hazard (Schulze, 2003d). Risk mitigation through vulnerability modification may be achieved through the implementation of several different measures, which include community preparedness programmes, forecasting and warning systems, and legal and financial measures such as insurance, which ideally should be linked into one interrelated programme (Schulze, 2003d).
Preparedness reflects the extent to which a community is provided with the necessary decision support system for the case where the above-mentioned physical event modification has failed (Smith and Petley, 2009). No technical solution is absolutely safe; therefore there is always a residual risk (Plate, 2002a). It is the
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purpose of preparedness to reduce the residual risk through widespread and ongoing community awareness programmes based on risk history, effective risk communication, evacuation strategies, the provision of medical and food aid as well as shelter for evacuees (Granger, 2000; Schulze, 2003d).
An important step in improving an existing flood protection system is the provision of better warning systems. An effective forecasting and warning system, combined with a high level of community awareness and risk appreciation, is one of the most potent mechanisms by which to achieve risk reduction (Granger, 2000). The basis for a warning system has to be an effective forecasting system, which permits the early identification and quantification of an imminent hazard (Plate, 2002a). Although typically taken to mean short term warnings, longer term estimates of the
‘hazardousness’ of a region can also be generated (Granger, 2000), for example those resulting from climate change scenario analyses. For these longer term estimates, however, it is important to note that warnings are based on predictions (e.g. design flood probability) or projections (e.g. scenarios of climate change), rather than forecasts (Schulze, 2003d).
A governing factor in the decision process for risk mitigation and control measures is the availability of legal and financial resources (Plate, 2002a). Legal and financial measures are designed to either avoid the settlement of individuals or communities into areas of high risk, or to provide aid that is able to accelerate the recovery of affected communities (Schulze, 2003d). However, it is important to note that financial resources for risk mitigation are often sourced from public funds and are in competition with other needs of society (Plate, 2002a).