|Introduction to Hazards - 1st Edition (Department of Humanitarian Affairs/United Nations Disaster Relief Office - Disaster Management Training Programme - United Nations Development Programme , 1992, 168 p.)|
This part of the module is designed to supply some fundamental concepts for hazard mitigation and preparedness in regard to:
assessment of vulnerability and risk
types of disaster mitigation options
choosing disaster mitigation options
relationships between disasters and development.
Vulnerability and risk assessment
Effective risk management requires information about the magnitude of the risk faced (risk assessment) and on how much importance society places on the reduction of that risk (risk evaluation). Quantification of the level of risk is an essential aspect of both preparedness planning and mitigation planning.
Risks are often quantified in aggregated ways (e.g. a probability of 1 in 23,000 per year of an individual dying in an earthquake in Iran). Such gross risk estimates can be useful for comparative purposes, but usually conceal large variations in the risk to individuals or different regions. There are 3 essential components to the quantification of risk:
Hazard occurrence probability - the probability of occurrence of a specified natural hazard at a specified severity level in a specified future time period.
Elements at risk - an inventory of those people or things which are exposed to the hazard.
Vulnerability - the degree of loss to each element should a hazard of a given severity occur.
The probability of occurrence of the extreme levels of natural hazards which can cause a disaster may be estimated by statistical extrapolation from data on the normal levels of occurrence. The accuracy of such estimates depends on the amount and completeness of data and the period of time over which it has been collected. Historical records can be an invaluable source of information.
Recurrence frequency and intensity of most natural hazards varies from place to place - hazard mapping may be used to show this variation. For some, notably geological hazards, detailed local mapping (micro-zoning) can be used to establish local variations and assist land-use planning decisions. For others only coarse mapping of geological areas at risk is possible, such as desertification and deforestation.
Vulnerability assessment involves first identifying all the elements which may be at risk from a particular hazard. Local knowledge and census data may be used to complete the inventory.
Loss functions in the form of vulnerability curves or damage probability matrices may be obtained for some elements at risk (buildings, people) based on past experience elsewhere.
Many aspects of vulnerability cannot be described in monetary terms, such as personal loss of family, home, income and related human suffering and psychosocial problems, but these should not be overlooked.
Because hazards tend to be uncontrollable, much mitigation work is centered on reducing vulnerability. Improved economic conditions reduce many aspects of vulnerability and a sound economy may in many cases be the best defense against disaster.
Risk is compiled from hazard and vulnerability data and from the inventory of elements at risk. A variety of ways of presenting risk are available such as f:N curves, scenario mapping, potential loss mapping and annualized risk.
The importance a community places on the risk of a hazard is likely to be influenced by the types and level of other everyday risks it faces. For example, village communities living in the mountain valleys of Northern Pakistan are regularly afflicted by floods, earthquakes and landslides and do not perceive disaster mitigation to be a priority. Instead they choose to protect themselves against the greater risks of disease and irrigation failures. In contrast, in the state of California, where people and their houses are much less vulnerable to natural disasters and the risk of disease is low, communities choose to initiate disaster mitigation programs against natural disasters.
The process of economic development needs to incorporate a risk mitigation strategy because traditional ways of coping with environmental risks are otherwise likely to be lost.
Risk is perceived differently by different individuals and different groups. Those with regular access to news media are likely to be more aware of the environmental risks they face than others, but they may, as a result, overestimate the likelihood of uncommon risks such as natural disasters.
The acceptability of a level of risk to individuals and societies appears to increase with the benefits that are obtained from exposure to it, and to be much greater where exposure to the risk is voluntary (as in sports) than where it is involuntary (like natural disasters). The acceptable level of risk also appears to decrease over time as more people become exposed to particular types of risk.
For many risks, mitigation can only be handled at the level of the community because the exposure of the community may be greater than that of the individual, and because protection often requires collective, sometimes large scale action.
Disaster mitigation options
The essential first step in any mitigation strategy is to understand the nature of the hazards which may be faced. Understanding each hazard requires comprehension of:
- its causes
- its geographical distribution, magnitude or severity and probable frequency of occurrence
- the physical mechanisms of destruction
- the elements and activities most vulnerable to destruction
- the possible economic and social consequences of the disaster
Mitigation involves not only saving lives and injury and reducing property losses, but also reducing the adverse consequences of natural hazards to economic activities and social institutions. Where resources for mitigation are limited, they should be targeted where they will be most effective - on the most vulnerable elements and in support of existing community level activities.
Vulnerability assessment is a crucial aspect of planning effective mitigation. Vulnerability implies both susceptibility to physical and economic damage and lack of resources for rapid recovery. To reduce physical vulnerability, weak elements may be protected or strengthened. To reduce the vulnerability of social institutions and economic activities, infrastructure may need to be modified or strengthened or institutional arrangements modified.
For most risks associated with natural hazards, there is little or no opportunity to reduce the hazard. In these cases the focus of mitigation policies must be on reducing the vulnerability of the elements and activities at risk. For technological and human-made hazards, reducing the hazard is, however, likely to be the most effective mitigation strategy.
Actions by planning or development authorities to reduce vulnerability can broadly be classified into two types - active and passive.
Active measures are those in which the authorities promote desired actions by offering incentives - these are often associated with development programs in areas of low income.
Passive measures are those in which the authorities prevent undesired actions by using controls and penalties - these actions are usually more appropriate for well-established local authorities in areas with higher incomes.
"Although they may cost more to initiate, active measures may produce better results in some communities because they 1) tend to promote a self-perpetuating safety culture, 2) do not rely on the economic capability of the affected community, and 3) do not rely on the ability of the local authorities to enforce controls."
The range of mitigation actions which might be considered can include:
Engineering and construction - Engineering measures range from large-scale engineering works to strengthening individual buildings and small scale community based projects. Codes of practice for disaster protection are unlikely to be effective unless they are accepted and understood by the community. Training of local builders in techniques to incorporate better protection into traditional structures - buildings, roads, embankments - is likely to be an essential component of such measures.
Physical planning measures - Careful location of new facilities - particularly community facilities such as schools, hospitals and infrastructure plays an important role in reducing settlement vulnerability; in urban areas, deconcentration of elements especially at risk is an important principle.
Economic measures - The linkages between different sectors of the economy may be more vulnerable to disruption by a disaster than the physical infrastructure. Diversification of the economy is an important way to reduce the risk. "A strong economy is the best defense against disaster." Within a strong economy, governments can use economic incentives to encourage individuals or institutions to take disaster mitigation actions.
Management and institutional measures - Building disaster-protection takes time. It needs to be supported by a program of education, training and institution-building to provide the professional knowledge and competence required.
Societal measures - Mitigation planning should aim to develop a "safety culture" in which all members of society are aware of the hazards they face, know how to protect themselves, and will support the protection efforts of others and of the community as a whole.
Any successful mitigation strategy should include a range of measures from the menu of possible actions. To obtain political acceptability, the ultimate deciding factor, a mitigation strategy may need to contain a mixture of immediately visible improvements and of less visible but long-term sustainable benefits.
The selection of an appropriate strategy should be guided by evaluating and considering the costs and benefits (in terms of future losses saved) of a range of possible measures. In conducting a cost benefit analysis, either a minimum cost or a maximum benefit/cost ratio criterion may be used. However, this method poses difficulty in assessing the monetary value of human lives.
Alternatively, an acceptable risk may be defined in relation to other risks to individuals or society, the balanced risk criterion. This method is not dependent on the cost element. The most sophisticated approach is to quantify the costs and different types of benefits separately (economic, human) and also calculate the cost effectiveness of each strategy in relation to different objectives of mitigation. This approach is more in keeping with the social and economic realities of decision-making.
Mitigation strategies are much easier to implement in the immediate aftermath of a disaster or near-disaster. Awareness of the impact of similar natural hazards elsewhere can also assist in obtaining public and political support for disaster protection.
Empower the community by promoting planning and management of its own defences and obtaining outside assistance only where needed.
Assessments must be planned for, systematically implemented and regularly conducted during the recovery process, as a critical component of the disaster preparedness and management continuum. It is through assessment that decision-makers can identify needs that lead to appropriate types of assistance. Equally important, assessment indicates what types of assistance are not needed, thereby decreasing inappropriate assistance. Further, assessments can provide feedback on how the recovery is progressing which will allow for correction of programs that may be falling short of their objectives.
Assessment is most effective when it is pre-designed as part of an overall preparedness plan which is tested and refined. The assessment process will vary with different types of hazards and must take into account the range of possible situations the country might encounter. Information for assessment is best gathered through well designed observation and survey methods. Assessments should be coordinated efforts, taking into account the ideas of a range of "relief actors".
The relationship between disasters and development
Disasters can destroy development inputs and years of development initiatives. Disasters can delay future development due to loss of resources, need to shift resources to emergency response and depressing the investment climate.
Development can increase vulnerability to disasters through, for example, dense urban settlement, development of hazardous sites, environmental degradation, technological failures or imbalance of pre-existing natural or social systems.
Development programs can reduce vulnerability by, for example, strengthening of urban utility systems, use of hazard resistant building techniques, institution building, and agricultural and forestry programs.
Disasters can provide development opportunities by:
creating a social and political atmosphere of acceptance to change
highlighting the sources of underdevelopment that exacerbated the disaster
focussing international attention and aid on the disaster area.
Recovery programs should be designed to reduce vulnerability by:
targetting areas of high risk
supporting the private and nonformal sectors
enhancing management training programs.