This lesson describes a methodology that can be used by communities to determine what hazards potentially threaten a community. Once completed, a community has valuable data to use as the basis for the hazard mitigation plan, emergency plans, and other long-term community planning mechanisms.

Objectives: At the end of this lesson, you should be able to:

• Define important risk assessment terms.
• Describe the four step multi-hazard risk assessment process.
• Determine what hazard risks potentially threaten a community.
• Explain how a community uses this risk assessment as the basis for developing hazard mitigation and emergency plans.

This lesson should take approximately 20 minutes to complete.

Click this link to access a printable version of this lesson.

Before we proceed, there are some important risk assessment terms that are sometimes misunderstood and therefore will be defined, namely hazards, vulnerability, exposure, and risk.

• Hazard
• Vulnerability
• Exposure
• Risk

Click each term to learn more.

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A hazard is something that is potentially dangerous or harmful, often the root cause of an unwanted outcome. Hazards exist with or without the presence of people and land development. Earthquakes, hurricanes, tornadoes, and other geological and meteorological events have been occurring for a very long time, and the natural environment adapted to their impacts. Hazard identification is the process of identifying hazards that threaten a given area.

Vulnerability is the susceptibility of people, property, industry, resources, ecosystems, or historical buildings and artifacts to the negative impact of a disaster. Vulnerability assessment provides the extent of injury and damages that may result from a hazard event of a given intensity in a given area.

Exposure is the people, property, systems, or functions that could be lost to a hazard. Generally, exposure includes what lies in the area the hazard could affect.

Risk is the probability of an estimated impact a hazard event would have on people, services, facilities, and structures in a community. It refers to the likelihood of a hazard event resulting in an adverse condition that causes injury or damage.

Risk Assessment is the process of measuring the potential loss of life, personal injury, economic loss, and property damage resulting from hazards. This process is accomplished by completing four steps, which are described in FEMA’s planning guide entitled, “Local Mitigation Planning Handbook".

• Step 1: Describe hazards.
• Step 2: Identify community assets.
• Step 3: Analyze risk.
• Step 4: Summarize vulnerability.

This step answers the question: "What kind of hazards can affect your community, and how badly?"

There are many ways to find hazard information. Review existing plans, such as emergency operations plans or State Hazard Mitigation Plans; hazards may be described there. Search old newspapers and other historical records. Involve the Whole Community and talk to the experts in the community, State, Tribe, or region. Gather information such as hazard maps on Internet websites of agencies such as FEMA, Department of Homeland Security, U.S. Geological Survey (USGS), the National Oceanographic and Atmospheric Agency (NOAA), and the U.S. Forest Service.

If preliminary research reveals that your community, State, or Tribe has been directly affected by a specific hazard, or that your area is threatened by one, address it in greater detail later in the process. If the area has not been affected by a hazard event in several years, but it is identified as a possible threat, confirm that the hazard type is relevant by going to the websites of the agencies listed above.

Completion of this step will produce a list of hazards that could affect the community. Another benefit of this research is to begin to foster relationships with experts at the State, Tribal, and community levels, and to begin involving the stakeholders in the community to take the Whole Community approach.

Profiling hazards is necessary because each hazard type has unique characteristics that can cause different types of damage. In addition, the same hazard events may affect communities in different ways because of various community characteristics, such as geography, development trends, population distribution, and age and type of buildings.

A hazard profile includes:

• The location or geographical areas that would be affected.
• The hazard extent (magnitude or severity). For hazards not geographically determined, like tornadoes, recorded intensities of previous events are used.
• The probability, likelihood, or frequency of the event occurring.
• Any past occurrences of the hazard events in or near the community.

The best way to show areas affected by hazards is to record the data on a base map. A base map is used for designated and identified areas to show specific information (for example, specific hazards). A base map should be as complete, accurate, and current as possible.

Depending on community resources, it can be as sophisticated as a digital display or as simple as a paper map of the community.

For example, transfer flood boundaries and base flood elevations (BFEs) from a FEMA Flood Insurance Rate Map (FIRM) onto the base map. If there is an earthquake risk, transfer the Peak Ground Acceleration (PGA) zones from a USGS map onto the base map. Completion of this step will produce a map showing the area impacted by each hazard type.

Click this link to access a larger view of the example base map: https://www.douglas.co.us/wp-content/uploads/2014/11/community-base-map.jpg

Step 2 answers the question: "What assets will be affected by the hazard event?"

Assets are the people, property, and activities in a community. The product of this step is a list of the assets in the community. This enables hazard mitigation planning teams to understand what can be affected by different hazard events. The level of detail in this step will determine the quality of the loss estimate in the final risk assessment step.

Incorporate in the asset inventory an overview, or summary, of the impact on the community's vulnerable structures. Include, by type of hazard, a general description of the types of structures (e.g., buildings, infrastructure, and critical facilities) affected by the hazard. For example, flooding will affect all structures whose lowest floors are built below the base flood elevation. Include a general description of the extent of the hazard's impact to vulnerable structures. This description can be presented in terms of dollar values or percentage of damages.

Continue to use the Whole Community approach to involve various stakeholder groups who are invested in the community and are knowledgeable about the assets associated with them. It may be helpful to consult the representatives selected or considered to build the Hazard Mitigation Planning Team.

Critical Facilities

Among the most urgent and important assets within the community are critical facilities. The community will be able to make better decisions about how to expend resources to protect critical facilities as a result of this type of assessment. Critical facilities include the following:

• Essential facilities for the health and welfare of the whole population (e.g., hospitals, police and fire stations, emergency operations centers, evacuation shelters, and schools).
• Transportation systems, including airways, highways, railways, and waterways.
• Lifeline utility systems, such as potable water, wastewater, oil, natural gas, electric power, and communication systems.
• High potential loss facilities, such as nuclear power plants, dams, and military installations.
• Hazardous material facilities, producing industrial/hazardous materials (e.g., corrosives, explosives, flammable materials, radioactive materials, and toxins).

If the community has the resources to take the inventory to a greater level of detail, it is possible to determine the proportion of buildings, the value of buildings, and the population of hazard areas. Keep track of the inventory data gathered for each hazard being assessed.

This step should also include a look at the location(s) of expected growth in the community. This information can be found by referring to the local comprehensive plan, or talking with community officials to determine where future growth is expected to take place. Are those areas located within hazard areas?

The FEMA criteria for approval of a local hazard mitigation plan requires identification of hazard areas.

The following questions will help you determine how much more information to collect, if any.

Do you have enough data to determine:

• Where greatest damages may occur?
• Which critical facilities will be operational after an event?
• Which assets are subject to greatest potential damages?
• If historic, environmental, or cultural resources are vulnerable?
• Severity, repetitiveness, or likelihood of particular hazard?
• Benefit of mitigation actions?

If the planning team decides to proceed, it will gather information on the assets that can be damaged by a hazard event. Characteristics of different hazards create the need for different types of data. For example, for flooding the following data are needed:

• Building type/type of foundation
• Building code design level/date of construction (i.e., before or after the adoption of floodplain ordinance?)
• Topography
• Distance from hazard zone (flood zone)

Step 3 answers the question: "How will the community's assets be affected by the hazard event?"

This step provides the community and the State or Tribe with a common framework in which to measure the effects of hazards on vulnerable structures. Steps 1 and 2 of the risk assessment phase involve gathering data on the hazards that may affect the community and the assets that can be damaged by the hazard event. All that information will be put to analyze risk.

This step is not required for approval of a local hazard mitigation plan by FEMA. If it is completed, it does provide a greater degree of dependability upon which to base the hazard mitigation strategy. The list of activities at right provides only a brief synopsis of how to complete a loss estimate:

Create a composite map of the risk assessment data that have been collected and mapped, and create a composite loss map. A composite map overlays the results of individual hazard maps to determine areas with relatively more assets at risk than others.

FEMA has developed a loss estimation model that is useful in estimating losses from earthquakes, floods and hurricane winds. HAZUS-MH is a geographic information system (GIS) software package that uses census data and other existing databases to estimate damage and losses, including:

• Physical damage: damage to residential and commercial buildings, schools, critical facilities, and infrastructure;
• Economic loss: lost jobs, business interruptions, repair and reconstruction costs; and
• Social impacts: impacts to people, including requirements for shelters and medical aid.

During the past decade, HAZUS-MH has evolved into a powerful tool for mitigation and recovery planning and analysis. An increasing number of States, Tribes, and localities are using HAZUS-MH in the preparation of risk assessments and mitigation plans. HAZUS-MH is also being used to support post-disaster planning for recovery from hurricanes, earthquakes, and floods.

States, Tribes, and communities may obtain free HAZUS-MH software and training from FEMA. Information is available at www.fema.gov/hazus.

HAZUS-MH can be used by individuals and organizations with limited knowledge of hazard analysis, as well as by those with extensive expertise in the earth, building, and GIS sciences due to its diverse range of options.

This lesson presented the following topics:

• Important Risk Assessment Terms
• Risk Assessment Steps
• Step 1: Describe hazards.
• Step 2: Identify community assets.
• Step 3: Analyze risk.
• Step 4: Summarize vulnerability.