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Techniques Used in Disaster Risk Assessment

The following list is not meant to be all-inclusive, but rather to present and explain a few of the wide range of techniques used to develop and apply disaster assessment tools.
 
  • Access model
    • A model that explores how an individual or groups relative resilience to disasters is impacted by differences in access to the economic or political resources needed to secure a livelihood.
    • The strengths of the model are that it provides a broad view of vulnerability including root causes, it gives weight to natural hazards, and it provides a framework for looking at livelihoods and vulnerability.
    • The limitation of the model, is that it is a tool for explaining vulnerability, not for measuring it. The model cannot be applied operationally without a great deal of data collection and analysis.
  • Computer assisted techniques
    • The use of computer software programs to automate steps of the risk management process.  For example the use of GIS and remote sensing has allowed hazard mapping to become more comprehensive.
    • The limitations vary by technique; however in general there is a reliance on equipment and expertise, which may not be readily available in the communities undertaking the assessments which may widen the breach between the information produced by technical risk assessments and the understanding of risk by people.
  • Cost-benefit analysis
    • A process used to select countermeasures, by balancing the costs of implementing each option against the benefits derived from it. In general, the cost of managing risks needs to be equal to the benefits gained from putting the countermeasures in place.
    • The benefit of this technique is the attempt to ensure public investment is directed toward those activities producing the greatest benefits for the best value for money.
    • The limitations of the technique include the lack of data collection and methods that are required to capture indirect and intangible costs and benefits, legal and social responsibility requirements may override simple financial cost benefit analysis, and the possibility that its application may disadvantage certain measures or people.
  • Disaster risk indexing
    • A quantitative analysis technique that uses statistical indicators to measure and compare risk variables.
    • Benefits of the technique are efficiency in measuring key elements of risk, repetitive application of the indictor system may allow the monitoring of disaster risk reduction progress, and because the system can be applied rapidly and with little cost it is also a useful tool for the national level to identify risk exposed communities.
    • Limitations of the technique include the use of indicators that may not reflect the complex reality; local and sub-national databases are not currently using uniform data collection and analysis frameworks; lack of availability of data with a suitable coverage and accuracy; and while indexing allows a comparison of relative risk between geographic areas, it cannot be used to depict actual risk for any one area.
  • Environmental impact assessment (EIA)
    • A policymaking tool that provides information on the environmental impacts of activities.
    • The benefits of an EIA are encouraging the private sector and individuals to consider the impacts of their actions on vulnerability factors; as part of a detailed risk assessment it can provide alternative solutions, and it could be used to reorient disaster impact assessments as planning tools.
    • Limitations of the technique include the current focus on post-event impact assessment and not promoting its use as part of the planning process, although the results can feed into future planning.  In addition, there is still some way to go before EIA processes are fully mastered.
  • Event-tree analysis (ETA)
    • A consequence based analysis in which an event either has or has not happened or a component has or has not failed. An event tree begins with an initiating event. The consequences of the event are followed through a series of possible paths. Each path is assigned a probability of occurrence and the probability of the various possible outcomes can be calculated.
    • The benefits of the technique are its value in analyzing the consequences arising from a failure or undesired event.
  • Failure modes and effects analysis (FMEA)
    • An analytical technique, which explores the effects of failures or malfunctions of individual components in a system - i.e. "If this part fails, in this manner, what will be the result?" The level of risk is determined by: Risk = probability of failure x severity category
    • An FMEA can be used for a single point failure but can be extended to cover parallel failures and is valuable for future reviews and as a basis for other risk assessment techniques
    • The limitations to the technique are that it can be a costly and time-consuming process.
  • Fault-tree analysis (FTA)
    • This is a graphical technique that provides a description of the combinations of possible occurrences in a system, which can result in an undesirable outcome. The most serious outcome is selected and called the Top Event. The analysis proceeds by determining how these top events can be caused by individual or combined lower level failures or events.
    • The benefits of the approach are the identification of the basic causes of failures, and the investigation of the reliability and safety of complex and large systems.
    • The limitations of the approach is that it does not measure probability, therefore counter measures identified by the process may not be those with the greatest potential for reducing risk.
  • Geographic information system (GIS) mapping
    • The use of a geographic information system, a computer-based tool, for risk or hazard mapping. GIS technology integrates database operations with the geographic analysis benefits offered by maps.
    • The benefits of the technique are the increase in productivity of hazard-mapping technicians, it can give higher quality results than can be obtained manually and it can facilitate decision-making and improve coordination among agencies when efficiency is at a premium.
    • The limitations of the technique include the lack of trained personnel; difficulties in exchanging data between different systems; difficulties in including social, economic and environmental variables; variability in access to computers and the quality and detail of the data required by GIS analysis.
  • Geospatial analysis
    • Analysis of risk information by distance, area, volume or any other spatial characteristic within geographic boundaries through GIS and hazard mapping techniques.
    • The benefits of the technique are the identification of hazards and dangerous locations at varying scales from local (less than 100,000 km2), through regional (100,000 to 10 million km2) to continental (10 to 100 million km2) and a view of risk not only from a singular hazard point of view, but also from an orientation to the relative levels of exposure.
    • The limitations of the technique are the same as those for GIS techniques with the added requirement for well-defined geographic boundaries (e.g., counties, municipalities, and health districts).
  • Hazard mapping
    • The process of mapping hazard information within a study area of varying scale, coverage, and detail.
    • Mapping can be of a single hazard such as fault maps and flood plain maps or several hazard maps can be combined in a single map to give a composite picture of natural hazards.
    • The benefit of the individual mapping technique is a visual form of information for decision makers and planners, which is easily understood. Multiple hazard maps provide the possibility of common mitigation technique recommendations; sub-areas requiring more information, additional assessments, or specific hazard-reduction techniques can be identified; and land-use decisions can be based on all hazard considerations simultaneously.
    • The limitations of the technique are that the volume of information needed for natural hazards management, particularly in the context of integrated development planning, often exceeds the capacity of manual methods and thus drives the use of computer assisted techniques.
  • Historical analysis
    • The analysis of historical information to determine levels of risk based on past experiences.
    • The benefits of this technique are the identification of dynamic aspects involved in vulnerability and providing the criteria to assign relative weights to different dimensions of vulnerability in risk assessment exercises.
    • The limitations to the approach are the reliance on historical disaster databases and the requirement for refinement, maintenance and systematic feeding of disaster data sets.  In addition, statistics on previous disasters’ impact can be unreliable and rarely cover socio-economic aspects of the disaster; data on vulnerability is likely to be restricted to physical vulnerability, and reliance on historical assessment alone can create a false expectation of preparedness if hazards, which may not have previously occurred in the area of analysis have not been considered.
  • Impact analysis
    • The practice of identifying and evaluating the negative and positive consequences of disasters on natural and human systems (i.e., environment, economic, financial, and social). Includes methodologies and standards for damage and needs assessments.
    • The benefits of the technique are the identification of linkages between disaster vulnerability and disaster impact and the ability to then create measures to reduce vulnerabilities to those disasters.
    • The limitations of the technique include a reliance on historical disaster data (limitations as stated in historical analysis); the current focus on post-event impact assessment and not promoting it’s use as part of the planning process, although the results can feed into future planning; and finally the need for social and economic analysis of disaster impacts.
  • Inductive analysis
    • The analysis of risk by integrating layers of information (e.g., visualizing disaster information in relation to other socio-economic parameters by geographical features such as administrative units, ecological zones, towns and streets) in GIS techniques.
    • Data can be presented on maps, with the variable of interest divided into classes or categories, and plotted within each geographic unit.
  • Participatory analysis
    • A risk analysis which includes the affected people in defining problems and needs, deciding solutions to them, implementing agreed activities to achieve those solutions and/or evaluating the results.
    • The benefits of the technique are the growth of capacity, the creation of disaster risk management attitudes and behavior, and a greater insight into the communities enabling better results. In addition participatory analysis may be more cost-effective in the long term, than externally-driven initiatives, partly because they are more likely to be sustainable and because the process allows ideas to be tested and refined before adoption.
    • The limitations of the technique are a poor fit within rigid timetables; impact will be limited at best if only some parts of the community are involved and where participation involves real social change it leads to the possibility of confrontation and conflict with those who traditionally hold power and influence.
  • Pressure and release model
    • The starting point of the pressure and release model is that a disaster is the intersection of two opposing forces: the process generating vulnerability on one side, and the physical exposure to hazard on the other.  Increasing pressure can come from either side but vulnerability has to be reduced to relieve the pressure.  Vulnerability is considered in three levels: root causes, dynamic pressures and unsafe conditions.
    • The strengths of the model are that it provides a broad view of vulnerability, it gives weight to natural hazards, and it provides a framework for looking at livelihoods and vulnerability.
    • The limitation of the model, is that it is a tool for explaining vulnerability, not for measuring it.  The model cannot be applied operationally without a great deal of data collection and analysis.
  • Qualitative analysis
    • Analysis that uses words rather than numbers to describe and measure the magnitude of potential consequences and the likelihood that those consequences will occur.  These scales can be adapted or adjusted to suit the circumstances, and different descriptions may be used for different risks.
    • Qualitative indicators are preferred as a way to engage as many parties as possible. In addition they may be used:
      • As an initial screening activity to identify risks which require more detailed analysis
      • Where this kind of analysis is appropriate for decisions, or
      • Where the numerical data or resources are inadequate for a quantitative analysis
    • Qualitative analysis should be informed by factual information and data where available.
  • Quantitative analysis
    • Analysis that uses numerical values (rather than the descriptive scales used in qualitative and semi-quantitative analysis) for both consequences and likelihood.  The quality of the analysis depends on the accuracy and completeness of the numerical values and the validity of the models used.
    • Quantification does have limitations and clearly it is not possible to measure all human experience. One of the major criticisms regarding the creation of indicators is that they attempt to encapsulate complex and diverse processes into numerical form.
  • Remote sensing
    • Remote sensing refers to the process of recording information from sensors mounted either on aircraft or on satellites. The technique is applicable to natural hazards management because nearly all geologic, hydrologic, and atmospheric phenomena are recurring events or processes that leave evidence of their previous occurrence.
    • The benefits of the technique are that revealing the location of previous occurrences and/or distinguishing the conditions under which they are likely to occur makes it possible to identify areas of potential exposure to natural hazards.  It additionally provides comprehensive displays of disaster information to assess vulnerability, enhance mapping, and monitor threatened areas.
    • The limitations of the technique include the requirement for expert science writers and graphics designers to translate and package the resulting information into images and explanations that can be easily understood by a wide variety of users; and while space technology has advanced rapidly in recent years, a number of countries still lack the human, technical and financial resources required to conduct even the most basic space-related activities.
  • Risk mapping
    • A risk map is a map of a community or geographical zone that identifies the places and the structures that might be adversely affected in the event of a hazard.
    • The production of a risk map requires consideration of areas and features threatened within the community or geographical zone, consultation with people and groups of varying expertise, and the discussion of possible solutions to reduce risk.
    • The benefits of this technique are that it helps to locate the major hazards; they can create shared criteria for decision-making, they can provide a record of historical events that have had a negative impact on the community, and they identify risks so a community may find solutions or take precautions.
  • Semi-quantitative analysis
    • In semi-quantitative analysis, qualitative scales are given values. The objective is to produce a more expanded ranking scale than is usually achieved in qualitative analysis, not to suggest realistic values for risk such as is attempted in quantitative analysis.  However, since the value allocated to each description may not bear an accurate relationship to the actual magnitude of consequences or likelihood, the numbers should only be combined using a formula that recognizes the limitations of the kinds of scales used.
    • The limitations of the approach are that the numbers chosen may not properly reflect relativities and this can lead to inconsistent or inappropriate outcomes and semi-quantitative analysis may not differentiate properly between risks, particularly when either consequences or likelihood are extreme.
  • Social survey
    • A survey to provide information to establish the context in which the risk assessment will take place and the criteria against which risk will be evaluated. Decisions concerning whether risk treatment is required may also be based on operational, technical, financial, legal, environmental, humanitarian or other criteria for which additional surveys will be required.
  • SWOT analysis
    • A tool used in the assessment of organizations to capture and identify the organization’s geographic and programmatic scope of action, perceived effectiveness and level of acceptance and support by community members and local institutions. The analysis is broken down into Strengths, Weaknesses, Opportunities and Threats.
    • The benefits of the technique are the identification of the links between each of the perceived “threats” to related organizational “weaknesses”, the “weaknesses” to related “opportunities”, and the “opportunities” to related “strengths”. The items at which the most lines (links) converge indicate the priority threats to be mitigated, weaknesses to be corrected, opportunities to be seized, and strengths to be reinforced.
  • Temporal analysis
    • The basis of a temporal analytical technique is the assumption that observed patterns arise from an underlying process. Modeling this underlying process allows for the estimation of impacts which best transform a map at time t into that at time t + 1.
    • Time series analysis is suited to monitoring tasks such as looking at the influence of climatic and other environmental time series on the occurrence of events. Scales may range from seasonal to geological (up to hundreds of millions of years). Maps can reveal the changing nature of vulnerability, and the effectiveness of previous preparedness or response measures.
  • Vulnerabilities analysis matrix
    • A practical and diagnostic tool in the form of a simple matrix which measures vulnerabilities and capacities in three broad and interrelated areas (i.e., physical/material, social/organizational, and motivational/attitudinal) Other factors are added to the matrix to reflect a complex reality such as disaggregation by gender or economic factors, changes over time, different scales etc.)
    • The benefits of the matrix are that it is practical and broad-based, linking the many different aspects of vulnerabilities and capacities.
    • Limitations to the approach include that on its own the matrix does not provide indicators of vulnerabilities and capacities but only an overarching framework, and that applied alone, it tends to underestimate the significance of natural hazards by concentrating on human aspects of disaster.
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