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Frequently Asked Questions

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What is the National Risk Index?

The National Risk Index is a dataset and online tool to help illustrate the United States. communities most at risk for 18 hazard types: Avalanche, Coastal Flooding, Cold Wave, Drought, Earthquake, Hail, Heat Wave, Hurricane, Ice Storm, Landslide, Lightning, Riverine Flooding, Strong Wind, Tornado, Tsunami, Volcanic Activity, Wildfire, and Winter Weather.

It was designed and built by FEMA in close collaboration with various stakeholders and partners in academia; local, state, and federal governments; and private industry. The Risk Index leverages available source data for natural hazard and community risk factors to develop a baseline relative risk measurement for each United States county and Census tract. The National Risk Index is intended to help users better understand the natural hazard risk of their communities.

Who is the National Risk Index for?

The National Risk Index is intended for planners and emergency managers at the local, regional, state, and federal levels, as well as other decision makers. It is made publicly available for any interested members of the general public seeking to better understand the risk from natural hazards in their community.

Learn more about how the National Risk Index can help

Which parts of the United States are included in the National Risk Index?

The National Risk Index provides Risk Index scores and ratings for counties and Census tracts for all 50 states and Washington, DC.

It does not provide Risk Index scores and ratings for United States territories (e.g., Puerto Rico). The goal is to include these communities in the future as data become available.

For tribal areas, the National Risk Index has data resources available to help identify the spatial relationships between tribal areas and the National Risk Index data.

How were natural hazards selected for the National Risk Index?

State mitigation plans from all 50 states were reviewed, and the most common natural hazard types profiled in all plans were identified. If a hazard type was profiled by at least 25 states, then it was included in the National Risk Index. Regionally significant hazards (e.g., hurricanes, tsunamis, or volcanic activity) were also included.

The National Risk Index includes 18 hazard types:

  • Avalanche
  • Coastal Flooding
  • Cold Wave
  • Drought
  • Earthquake
  • Hail
  • Heat Wave
  • Hurricane
  • Ice Storm
  • Landslide
  • Lightning
  • Riverine Flooding
  • Strong Wind
  • Tornado
  • Tsunami
  • Volcanic Activity
  • Wildfire
  • Winter Weather

Manmade hazards, such as dam and levee failure, are profiled by some state mitigation plans. However, the data required to calculate Expected Annual Loss, a component of the National Risk Index, for such hazards are not nationally or publicly available.

Hazard mitigation plans for tribes and territories were not reviewed due to their limited availability, and as a result, tribes and territories were not included in the hazard analysis.

Who provided source data for the National Risk Index?

Source data for the National Risk Index were provided by many different organizations.

  • Data for Expected Annual Loss were provided by a mix of federal and state agencies, academia, and other research institutions. The types of data used vary across hazard types, as do the periods of record. For some hazard types, multiple data sources were used, while others rely on only a single dataset. Visit the natural hazard-specific pages for more details.
  • The Social Vulnerability component of the National Risk Index is supported by the Social Vulnerability Index (SoVI), and Community Resilience is supported by the Baseline Resilience Indicators for Communities (BRIC). Both indices are provided by the Hazards and Vulnerability Research Institute (HVRI) at the University of South Carolina.

What are the National Risk Index scores and ratings? How are they calculated?

The National Risk Index provides relative Risk Index scores and ratings based on data for Expected Annual Loss due to natural hazards, Social Vulnerability, and Community Resilience. Separate scores and ratings are also provided for each component: Expected Annual Loss, Social Vulnerability, and Community Resilience. For the Risk Index and Expected Annual Loss, scores and ratings can be viewed as a composite score for all hazards or individually for each of the 18 hazard types.

Scores are calculated using the equations:

Risk Index = Expected Annual Loss × ÷ Community Resilience

Expected Annual Loss = Exposure × Annualized Frequency × Historical Loss Ratio

A community’s score describes its relative position among all other communities at the same level for a given component. For example, a county’s Risk Index score and rating is relative to all other counties in the United States, and a Census tract’s Risk Index score and rating is relative to all other Census tracts in the United States.

All scores are constrained to a range of 0 (lowest possible value) to 100 (highest possible value). To achieve this range, the values of each National Risk Index component are rescaled using min-max normalization. For Expected Annual Loss specifically, a cube root transformation is applied before min-max normalization.

For every score there is a qualitative rating that describes the nature of a community’s score in comparison to all other communities at the same level, ranging from “Very Low” to “Very High.” To determine ratings, a methodology known as k-means clustering or natural breaks is applied to each score.

For comprehensive details about National Risk Index scores and ratings, see the National Risk Index Technical Documentation.

How can I view scores and ratings for the National Risk Index and its individual components?

Use the National Risk Index Map to view color-coded map layers that visualize ratings and select a county or Census tract on the map to view ratings, scores, and other details. The map’s reporting feature enables you to generate printable reports containing National Risk Index scores and ratings for one or more communities. For help with using the National Risk Index Map or reporting feature, review the User Guide.

Users can also access several National Risk Index data resources, including downloadable datasets.

How do I find the highest risk hazard type in a county or Census tract?

Find the county or Census tract of interest using the National Risk Index Map and select it to open the information panel. In the Risk Index view, review the Hazard Type Risk Ratings section. You could also create a printable report for the community using the National Risk Index Map's reporting feature. Identify the hazard type with the highest Risk Index score—this is the community's highest risk hazard type. This measure should not be interpreted as the hazard type that is most likely to occur. Rather, it represents the hazard type with the highest potential for negative impacts.

For help with using the National Risk Index Map or its reporting feature, review the User Guide.

How do I find the county or Census tract with the highest natural hazard risk?

Find the area of interest on the National Risk Index Map. Use the reporting feature to select the counties or Census tracts you want to compare and create a Community Risk Comparison Report. Review the communities sorted by Risk Index scores (high-to-low), and the community listed first with the highest Risk Index score has the highest natural hazard risk of those selected. The resulting table should not be interpreted as a comparison of which county or Census tract has the highest likelihood of a hazard occurring. Rather, the data represent which county or tract has the highest potential for negative impacts from a given hazard type.

For help with using the National Risk Index Map or its reporting feature, review the User Guide.

How can a county have a high Risk Index score, but its Census tracts have low Risk Index scores?

Census tracts are subdivisions of counties based on a population criteria of approximately 4,000 people. The number of Census tracts in a county vary widely. Some rural counties have only one Census tract while urban counties may have hundreds or even thousands of Census tracts.

A community’s Risk Index score and rating, for either a county or Census tract, describe its relative position among all other communities at the same level for a given component. A county’s Risk Index score and rating is relative to all other counties in the United States, and a Census tract’s Risk Index score and rating is relative to all other Census tracts in the United States.

Thus, it is possible for a county with a large number of Relatively Low or Very Low risk rated Census tracts to have a Relatively High or even Very High risk rating. Conversely, it is possible for a county with a few Relatively High or Very High risk rated Census tracts to have a Relatively Low or Very Low risk rating.

Why are some data missing for my county or Census tract?

All data supporting National Risk Index risk components were required to be nationwide in scope and able to be measured at the Census tract level. Hazard type data sources were also required to have location and time information. For some counties and Census tracts, data that met these requirements were simply not available.

The National Risk Index uses specific ratings to communicate if a community is missing data:

  • Not Applicable indicates there is no historical record in the National Risk Index source data for a hazard type and the hazard type is not geographically possible ( i.e., Coastal Flooding in inland areas). Therefore, there is no perceived probability of the hazard impacting a community.
  • Insufficient Data indicates that one or more required components for a calculation are not available.
  • Data Unavailable indicates source data are not available for an National Risk Index component. This is specific to Social Vulnerability and Community Resilience only.
  • No Rating indicates there is an National Risk Index component with a score of 0, and the Risk Index score cannot be calculated for that hazard or community.
  • No Expected Annual Losses indicates one of the Expected Annual Loss factors has a value of 0 and Expected Annual Loss cannot be calculated for a hazard type. If a community has No Expected Annual Loss for a hazard type, then the hazard type does not contribute to the composite Expected Annual Loss score for all 18 hazard types.

Why does my county or Census tract, which is known for a natural hazard type, have a low Risk Index score for that hazard type?

Even if a community has well-known activity for a hazard type, the community’s risk for that hazard type may be low because its people or assets are less vulnerable to the hazard type’s impacts and/or more resilient when impacted. In terms of the National Risk Index, a community’s Expected Annual Loss score for a hazard type may be high, but its Risk Index score may be low because it has lower Social Vulnerability and/or higher Community Resilience scores.

Also, the National Risk Index leverages the best available nationwide datasets. Nationwide datasets used as inputs for the National Risk Index are in many cases not as accurate as available local data. Users with access to local data for any National Risk Index risk factor should consider deferring to that data to calculate a more accurate risk measurement.

What types of consequences are factored into the National Risk Index? Are all types of consequences considered for each hazard type?

Natural hazard loss is represented by the Expected Annual Loss component of the National Risk Index. Expected Annual Loss is based on three consequence types: buildings, population, and agriculture.

Not all consequence types are considered for all hazard types. Building and population exposure are modeled for all hazard types except Drought, which only modeled agriculture exposure. Agriculture exposure was also modeled for Cold Wave, Hail, Heat Wave, Hurricane, Riverine Flooding, Strong Wind, Tornado, Wildfire, and Winter Weather.

What is the source of geographic/administrative boundaries in the National Risk Index?

The source of geographic/administrative boundaries used by the National Risk Index is the U.S. Census Bureau’s 2017 TIGER/Line Shapefiles. According to the U.S. Census Bureau, geography in the 2017 TIGER/Line Shapefiles generally reflects the boundaries of governmental units in effect as of January 1, 2017, and other legal and statistical area boundaries adjusted and/or corrected since the 2010 Census. The TIGER/Line Shapefiles include United States territories and some large bodies of water, which the National Risk Index does not currently evaluate, so these are either manually removed or clipped based on the USA County Boundaries shapefile provided by Esri.

For comprehensive details about how geographic/administrative boundaries are defined by the National Risk Index, see the National Risk Index Technical Documentation.

What is missing from the National Risk Index?

The National Risk Index is missing the following source data:

  • Landslide source data for Alaska and Hawaii
  • Lightning source data for Alaska and Hawaii
  • Tsunami source data for the East Coast, Gulf Coast, and Great Lakes regions
  • Wildfire source data for Alaska and Hawaii

What are the limitations of the National Risk Index?

Please review the Disclaimer for an official statement on the National Risk Index’s limitations. limitations.

Also, the National Risk Index and its scores, ratings, and methodology do not explicitly consider or account for:

  • Natural hazard forecasts
  • Climate change and its projected impacts *
  • Dependencies between hazard types or interrelated hazard types (e.g., Coastal Flooding and Hurricanes)
  • Secondary hazard types (e.g., ash fall from Volcanic Activity or flash flooding after Wildfire)
  • Previous, ongoing, or future natural hazard mitigation efforts
  • Levees, dams, or other flood control structures **
  • Manmade hazards †
  • Historical, priority natural disaster response coordination
  • A community's evacuation efficiency
  • Changes in a community over time (e.g., a county having more farmland in the past than now)
  • Impacts to infrastructure
  • Impacts to transportation
  • Impacts to critical facilities (e.g., hospitals)
  • Supply chain impacts
  • Economic damages from the disruption of business

* To some extent, some of the listed aspects of natural hazard risk may be included in the source data used by the National Risk Index. Please refer to information by source data providers for more information on what is included in their datasets.

** Levees, dams, or other flood control structures are factored into the Coastal or Riverine Flooding hazards of the National Risk Index only if the manmade features are incorporated into the source datasets.

† The data required to calculate Expected Annual Loss for manmade hazards, such as dam and levee failure, are not nationally or publicly available. Also, such hazards should not be discussed separately from traditional, natural hazard risk assessment.

How can I use the National Risk Index to reduce my natural hazard risk?

There are many ways you can leverage the National Risk Index to better understand your natural hazard risk and use this understanding to reduce your risk. Visit the Take Action section of the website to learn how.

Can I use the National Risk Index data with geographic information system (GIS) or other software? How?

The National Risk Index data are available for download in spatial (GIS) format as geodatabases and shapefiles and table format (CSV). You can download complete National Risk Index datasets for all 50 states in all formats. Individual state datasets are available in table format only. Datasets are available at both the county and Census tract level. Once you download the data, you may use the data in your tool or software of preference.

National Risk Index GIS web layers and services are also available through the National Risk Index Group on FEMA’s Hazards GeoPlatform.

When will the National Risk Index data be updated?

The National Risk Index Team intends to continuously update the National Risk Index as new data become available and improved methodologies are identified. At this time, we are unsure when the National Risk Index will be updated next.

Learn more about the latest updates to the National Risk Index data and website