CHAPTER 2

HAZARD AND RISK ASSESSMENTS

Decisions that affect vulnerability to natural hazards are made almost daily by individuals, businesses, and communities. If these decisions are to be made wisely, decision-makers must know that hazard and risk information exists, and it must be readily available to them in a clear and usable format.

Hazard assessments identify where a drought, wildfire, landslide, tornado, or other event is likely to occur, how frequently it may occur, and how severe its physical and/or biological effects may be. Although the precision of scientific knowledge varies from hazard to hazard — the recurrence of large floods and major wildfires in a particular area is better understood than the timing and location of major earthquakes, for example — the principal natural hazards facing the nation and the world have been identified. Advances in the basic understanding of hazards will provide more accurate and complete information.

Risk assessments combine hazard information with information on human activity, structures, and natural resources to determine the likely impacts of a hazardous event. They provide estimates of the number of deaths and the extent of injuries, damage, and economic losses that are likely to result. Because activities and environments are continually changing, risk assessments must be updated regularly.

Armed with hazard and risk assessments, individuals, businesses, and communities can make informed decisions on implementation of disaster reduction strategies. The world will never be hazard-free, but choices can be made that will reduce vulnerabilities. The actions taken should be determined by an understanding of the hazards faced, the willingness to take risks, and the resources available for reducing the risks.

The Committee recommends that state and local jurisdictions review, update, and improve their hazard and risk assessments with the assistance of the federal government and use this information in their decision-making processes.

To achieve this goal, the Committee proposes that:

  • state governments work with the Federal Emergency Management Agency (FEMA) and other relevant federal agencies to ensure that adequate hazard and risk assessments within their boundaries are produced;

  • states, with assistance from the federal government, develop mechanisms for providing hazard and risk information to local decision-makers; and

  • the federal government continue to support physical, biological, and social science research on hazard and risk assessments as well as methods for making this information available to decision-makers and practitioners.

A program for enhancing the nation's hazard and risk assessment capabilities should include:

  1. Development of multihazard geographic information systems. Recent advances in computer communications and geographic information systems (GIS) offer innovative ways to provide hazard and risk information to decision-makers. Information traditionally provided on paper maps and charts and in volumes of text can now be computerized. It can then be retrieved, analyzed, and displayed in two-



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A SAFER FUTURE: Reducing the Impacts of Natural Disasters CHAPTER 2 HAZARD AND RISK ASSESSMENTS Decisions that affect vulnerability to natural hazards are made almost daily by individuals, businesses, and communities. If these decisions are to be made wisely, decision-makers must know that hazard and risk information exists, and it must be readily available to them in a clear and usable format. Hazard assessments identify where a drought, wildfire, landslide, tornado, or other event is likely to occur, how frequently it may occur, and how severe its physical and/or biological effects may be. Although the precision of scientific knowledge varies from hazard to hazard — the recurrence of large floods and major wildfires in a particular area is better understood than the timing and location of major earthquakes, for example — the principal natural hazards facing the nation and the world have been identified. Advances in the basic understanding of hazards will provide more accurate and complete information. Risk assessments combine hazard information with information on human activity, structures, and natural resources to determine the likely impacts of a hazardous event. They provide estimates of the number of deaths and the extent of injuries, damage, and economic losses that are likely to result. Because activities and environments are continually changing, risk assessments must be updated regularly. Armed with hazard and risk assessments, individuals, businesses, and communities can make informed decisions on implementation of disaster reduction strategies. The world will never be hazard-free, but choices can be made that will reduce vulnerabilities. The actions taken should be determined by an understanding of the hazards faced, the willingness to take risks, and the resources available for reducing the risks. The Committee recommends that state and local jurisdictions review, update, and improve their hazard and risk assessments with the assistance of the federal government and use this information in their decision-making processes. To achieve this goal, the Committee proposes that: state governments work with the Federal Emergency Management Agency (FEMA) and other relevant federal agencies to ensure that adequate hazard and risk assessments within their boundaries are produced; states, with assistance from the federal government, develop mechanisms for providing hazard and risk information to local decision-makers; and the federal government continue to support physical, biological, and social science research on hazard and risk assessments as well as methods for making this information available to decision-makers and practitioners. A program for enhancing the nation's hazard and risk assessment capabilities should include: Development of multihazard geographic information systems. Recent advances in computer communications and geographic information systems (GIS) offer innovative ways to provide hazard and risk information to decision-makers. Information traditionally provided on paper maps and charts and in volumes of text can now be computerized. It can then be retrieved, analyzed, and displayed in two-

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A SAFER FUTURE: Reducing the Impacts of Natural Disasters and three-dimensional maps for use by a wider rangeof recipients. Several GISs could be adapted to process multihazard information. Such systems would make upto-date hazard and risk assessments available to local decision-makers throughout the nation. This information would enable planners, emergency managers, and other public officials to identify potential disaster vulnerability by integrating data on locations of population, essential facilities, natural resources, and hazards. It would be possible to project the consequences of new development, alternate land uses, and other actions. Business and industry could also benefit from natural hazard information systems when planning for safety and capital investment. Research on the physical and biological nature of disasters. Further understanding of the physical and biological processes that cause hazardous events — such as the solid earth processes that generate earthquakes or the ecosystem changes that cause wildfires and outbreaks of insect pests — would contribute to more accurate and useful hazard assessments and to improved prediction capabilities. Risk assessments could be enhanced by research on how a single hazardous event can trigger a sequence of disasters. (See Figure 1.) The interrelationships of natural hazards and short- and long-term environmental changes should be given special emphasis. Federal agencies and academic researchers currently conduct such research. Business should participate actively in this research because its actions have profound environmental impacts, many of which increase vulnerability to hazards. In addition, the United States would benefit from collaborating on the excellent work being done in Canada, Japan, Mexico, the United Kingdom, Australia, and other nations. Research on the social factors that govern response to natural hazards. As previously noted, lack of technical knowledge is rarely the primary obstacle to disaster reduction. Social, political, administrative, legal, and economic factors are the greatest barriers to implementing loss reduction strategies. Research on means to overcome these barriers will be critical to improving risk assessments and reducing vulnerability. Among the areas that should be studied are the ways that individuals and organizations discover, produce, and use hazard reduction information; barriers to use of disaster information; economic and other incentives to action; and means for marshaling political support for hazard reduction. Factors that govern communication and collaboration among physical, biological, and social scientists and engineers should also be studied. Research on technological and societal strategies for disaster reduction. Improved hazard reduction practices should result from understanding incentives for and barriers to technological innovation; incorporating physical, biological, and social science knowledge into the initial stages of development planning; and reducing the costs of implementing technical and social strategies. Different disasters can produce similar damage. Though it looks like an earthquake rocked this interstate to pieces, this Maine roadway was damaged by floodwaters and the resultant landslides. As is often the case for local-level response, the local National Guard Engineering Group mobilized for cleanup and repair during the state-declared emergency.

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A SAFER FUTURE: Reducing the Impacts of Natural Disasters Figure 1. NATURAL HAZARDS SEQUENCE A sequence of disastrous results can be triggered by a single hazardous event. For example, an intense thunderstorm can cause flash flooding that may lead to power outages, disruption of water supply and telephone service, fire, and environmental contamination. (Source: F. May, University of Utah.)

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A SAFER FUTURE: Reducing the Impacts of Natural Disasters Flexible and resilient, youngsters are often eager volunteers for community-aid projects. Children need to learn about hazards they can face at home and school to make preparation, response, and recovery less traumatic, and to provide valuable lessons that can be applied throughout their lives.