Comprehensive Risk-Based Approach toward a Secure and Resilient Nation

Comprehensive Risk-Based Approach toward a Secure and Resilient Nation

The Strategic National Risk Assessment in Support of PPD 8: A

Comprehensive Risk-Based Approach toward a Secure and Resilient Nation


The Strategic National Risk Assessment (SNRA) was executed in support of Presidential Policy

Directive 8 (PPD-8), which calls for creation of a National Preparedness Goal, a National

Preparedness System, and a National Preparedness Report. Specifically, national preparedness is

to be based on core capabilities that support ―strengthening the security and resilience of the

United States through systematic preparation for the threats that pose the greatest risk 1 to the

security of the Nation, including acts of terrorism, cyber attacks, pandemics, and catastrophic

natural disasters.‖

As part of the effort to develop the National Preparedness Goal and identify core capabilities, the

Secretary of Homeland Security led an effort to conduct a strategic national risk assessment to

help identify the types of incidents that pose the greatest threat to the Nation’s homeland

security. Representatives from the offices of the Director of National Intelligence and the

Attorney General, as well as other members of the Federal interagency, supported this effort.

The assessment was used:

To identify high risk factors that supported development of the core capabilities and capability targets in the National Preparedness Goal;

To support the development of collaborative thinking about strategic needs across prevention, protection, mitigation, response, and recovery requirements, and;

To promote the ability for all levels of Government to share common understanding and awareness of National threats and hazards and resulting risks so that they are ready to act

and can do so independently but collaboratively.

The subsequent pages provide an overview of the unclassified findings and the analytic approach

used to conduct the SNRA. It should be emphasized, however, that although the initial version

of the SNRA is a significant step toward the establishment of a new homeland security risk

baseline, it contains data limitations and assumptions that will require additional study, review,

and revision as the National Preparedness System is developed. These limitations are discussed

below, and future iterations of the assessment are expected to reflect an enhanced methodology

and improved data sets.

Strategic National Risk Assessment Scope

To inform homeland security preparedness and resilience activities, the SNRA evaluated the risk

from known threats and hazards that have the potential to significantly impact the Nation’s

homeland security. These threats and hazards were grouped into a series of national-level events

with the potential to test the Nation’s preparedness.

1 The DHS Lexicon defines risk as the potential for an unwanted outcome resulting from an incident, event, or occurrence, as

determined by its likelihood and the associated consequences. Accessed at:


Strategic National Risk Assessment December 2011


SNRA participants – including Federal agencies, DHS Components, and the intelligence

community, among others – developed a list of national-level events (see Table 1) for assessment

in the initial SNRA. The events are grouped into three categories: 1) natural hazards; 2)

technological/accidental hazards; and 3) adversarial, human-caused threats/hazards. For the

purposes of the assessment, DHS identified thresholds of consequence necessary to create a

national-level event. These thresholds were informed by subject matter expertise and available

data. For some events, economic consequences were used as thresholds, while for others,

fatalities or injuries/illnesses were deemed more appropriate as the threshold to determine a

national-level incident. In no case, however, were economic and casualty thresholds treated as

equivalent to one another (i.e., dollar values were not assigned to fatalities). Event descriptions in

Table 1 that do not explicitly identify a threshold signify that no minimum consequence

threshold was employed. This allows the assessment to include events for which the

psychological impact of an event could cause it to become a national-level event even though it

may result in a low number of casualties or a small economic loss. Only events that have a

distinct beginning and end and those with an explicit nexus to homeland security missions were

included. This approach excluded:

Chronic societal concerns, such as immigration and border violations, and those that are generally not related to homeland security national preparedness, such as cancer or car

accidents, and;

Political, economic, environmental, and societal trends that may contribute to a changing risk environment but are not explicitly homeland security national-level events (e.g.,

demographic shifts, economic trends). These trends will be important to include in future

iterations of a national risk assessment, however.

Table 1: SNRA National-Level Events






National-level Event Description


Animal Disease


An unintentional introduction of the foot-and-mouth disease

virus into the domestic livestock population in a U.S. state

Earthquake An earthquake occurs within the U.S. resulting in direct

economic losses greater than $100 Million

Flood A flood occurs within the U.S. resulting in direct economic

losses greater than $100 Million

Human Pandemic


A severe outbreak of pandemic influenza with a 25% gross

clinical attack rate spreads across the U.S. populace

Hurricane A tropical storm or hurricane impacts the U.S. resulting in

direct economic losses of greater than $100 Million

Space Weather The sun emits bursts of electromagnetic radiation and energetic

particles causing utility outages and damage to infrastructure

Tsunami A tsunami with a wave of approximately 50 feet impacts the

Pacific Coast of the U.S.

Volcanic Eruption A volcano in the Pacific Northwest erupts impacting the

surrounding areas with lava flows and ash and areas east with

smoke and ash

Wildfire A wildfire occurs within the U.S. resulting in direct economic

losses greater than $100 Million

Strategic National Risk Assessment December 2011







National-level Event Description



Biological Food


Accidental conditions where introduction of a biological agent

(e.g., Salmonella, E. coli, botulinum toxin) into the food supply results in 100 hospitalizations or greater and a multi-

state response

Chemical Substance

Spill or Release

Accidental conditions where a release of a large volume of a

chemical acutely toxic to human beings (a toxic inhalation

hazard, or TIH) from a chemical plant, storage facility, or

transportation mode results in either one or more offsite

fatalities, or one or more fatalities (either on- or offsite) with

offsite evacuations/shelter-in-place

Dam Failure Accidental conditions where dam failure and inundation results

in one fatality or greater


Substance Release

Accidental conditions where reactor core damage causes

release of radiation




Aircraft as a Weapon A hostile non-state actor(s) crashes a commercial or general

aviation aircraft into a physical target within the U.S.

Armed Assault A hostile non-state actor(s) uses assault tactics to conduct

strikes on vulnerable target(s) within the U.S. resulting in at

least one fatality or injury

Biological Terrorism

Attack (non-food)

A hostile non-state actor(s) acquires, weaponizes, and releases

a biological agent against an outdoor, indoor, or water target,

directed at a concentration of people within the U.S.


Food Contamination

Terrorism Attack

A hostile non-state actor(s) acquires, weaponizes, and disperses

a biological or chemical agent into food supplies within the

U.S. supply chain

Chemical Terrorism

Attack (non-food)

A hostile non-state actor(s) acquires, weaponizes, and releases

a chemical agent against an outdoor, indoor, or water target,

directed at a concentration of people using an aerosol,

ingestion, or dermal route of exposure

Cyber Attack against


A cyber attack which seriously compromises the integrity or

availability of data (the information contained in a computer

system) or data processes resulting in economic losses of a

Billion dollars or greater

Cyber Attack against



An incident in which a cyber attack is used as a vector to

achieve effects which are ―beyond the computer‖ (i.e., kinetic

or other effects) resulting in one fatality or greater or economic

losses of $100 Million or greater

Explosives Terrorism


A hostile non-state actor(s) deploys a man-portable improvised

explosive device (IED), Vehicle-borne IED, or Vessel IED in

the U.S. against a concentration of people, and/or structures

such as critical commercial or government facilities,

transportation targets, or critical infrastructure sites, etc.,

resulting in at least one fatality or injury

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National-level Event Description

Nuclear Terrorism


A hostile non-state actor(s) acquires an improvised nuclear

weapon through manufacture from fissile material, purchase, or

theft and detonates it within a major U.S. population center


Terrorism Attack

A hostile non-state actor(s) acquires radiological materials and

disperses them through explosive or other means (e.g., a

radiological dispersal device or RDD) or creates a radiation

exposure device (RED)

The SNRA participants identified the events listed in Table 1 as those with the potential to pose

the greatest risk to the security of the Nation and formed the analytic basis of the SNRA. In

some cases, tornados may also become national-level events that pose significant risk. Table 1 is

not a complete list of risks that exist and will be reconsidered in future iterations of the

assessment. Additional threats and hazards, such as droughts, heat waves, winter storms, rain

storms, and different types of technological/accidental or human-caused hazards, can also pose a

risk to jurisdictions across the country and should be considered, as appropriate, in preparedness

planning. Non-influenza diseases with pandemic potential and other animal diseases should also

be considered. In addition, assessment participants identified a number of events for possible

inclusion in future iterations of the SNRA, including electric grid failure, plant disease outbreak,

and transportation system failure.

Overarching Themes to an All-Hazards Approach

The results of the SNRA are largely classified and include a comparison of risks for potential

incidents in terms of the likelihood (calculated as a frequency—i.e. number of events per year)

and consequences of threats and hazards, as well as an analysis of the uncertainty associated with

those incidents. 2 The assessment finds that a wide range of threats and hazards pose a significant

risk to the Nation, affirming the need for an all-threats/hazards, capability-based approach to

preparedness planning. Overarching themes include:

Natural hazards, including hurricanes, earthquakes, tornadoes, wildfires, and floods, present a significant and varied risk across the country.

A virulent strain of pandemic influenza could kill hundreds of thousands of Americans, affect millions more, and result in economic loss. Additional human and animal

infectious diseases, including those previously undiscovered, may present significant


Technological and accidental hazards, such as dam failures or chemical substance spills or releases, have the potential to cause extensive fatalities and have severe economic

impacts, and the likelihood of occurrence may increase due to aging infrastructure.

2 The full results of the SNRA are classified.

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Terrorist organizations or affiliates may seek to acquire, build, and use weapons of mass destruction. Conventional terrorist attacks, including those by ―lone actors‖ employing

explosives and armed attacks, present a continued risk to the Nation.

Cyber attacks can have their own catastrophic consequences and can also initiate other hazards, such as power grid failures or financial system failures, which amplify the

potential impact of cyber incidents.

These findings supported the development of the core capabilities, as well as the establishment

of capability targets for the Goal. In addition to the above findings articulated in the National

Preparedness Goal, the SNRA found that:

Many events have the potential to occur more than once every 10 years, meaning that the Nation’s preparedness will likely be tested in this decade.

Although historic events provide a useful perspective on homeland security risks, the changing nature of society and the risk landscape means that the Nation must also be

prepared for new hazards and threats or for events that result in greater consequences

than have occurred in the past.

Within an all-hazards preparedness context, particular events that present risk to the Nation—such as nuclear attacks or chemical releases—require additional specialized

response activities.

Some events, such as explosives attacks or earthquakes, generally cause more localized consequences, while other events, such as human pandemics, may cause consequences

that are dispersed throughout the Nation, thus creating different types of impacts for

preparedness planners to consider.

Analytic Approach

The SNRA drew data and information from a variety of sources, including existing Government

models and assessments, historical records, structured analysis, and judgments of experts from

different disciplines. The information was used to assess the risk of identified incidents as a

function of frequency 3 and consequence—specifically, With what frequency is it estimated that

an event will occur, and what are the consequences of the incident(s) if it does occur?

The SNRA examined the consequences associated with six categories of harm: loss of life,

injuries and illnesses, direct economic costs, social displacement, psychological distress, and

environmental impact. This multi-faceted view of potential consequences draws attention to the

broad and often interdependent effects of incidents that require whole of community preparation

and cooperation across the homeland security enterprise. For instance, community resilience

relates to both mitigating human and economic consequences and addressing the psychological

and social distress caused by the incident within the community. Similarly, other types of

resilience involve withstanding environmental and infrastructure degradations to ensure that

essential services continue to be delivered.

3 Frequency was used in the SNRA to capture likelihood because some events have the potential to occur more than

once a year.

Strategic National Risk Assessment December 2011


The SNRA relied on the best available quantitative estimates of frequency and consequence from

existing Government assessments, peer-reviewed literature, and expert judgment. Where

sufficient quantitative information was not available—such as data related to the frequency of

high-consequence space weather—events were assessed qualitatively. The estimates of the

frequency and consequences for each of the events considered were compared where

appropriate. No effort was made to create a single ―risk judgment‖ for any event type because it

was deemed infeasible to aggregate all consequence types into a single metric. Instead, the

assessment treated consequence categories separately (i.e., economic consequences are reported

separately from fatality consequences). This allowed stakeholders to apply their own expert

judgments to the findings and decide how those findings should inform core capability targets in

the Goal.

All sources and estimates were documented to promote credibility, defensibility, and

transparency within the assessment. Uncertainty in frequency and consequences was explicitly

included in the analysis by representing low and high bounds in addition to best estimates.

Examples of sources of uncertainty include incomplete knowledge of adversary capabilities and

intent, variability in possible event severity and location, and lack of historical precedence.

Because the assessment was performed at a strategic national level, it provided the ability to

draw rough comparisons of the assessed events—within an order of magnitude—to view the

broad differences in risk across events. Given the uncertainty inherent in assessing risks at a

national level and the lack of information about some of the events included—many of which are

likely to occur very infrequently—the assessment was designed to avoid false precision. Instead,

the assessment identifies only those differences in risk that are still significant despite the

associated uncertainties.


The analysis of available information—even if that analysis is imprecise and contains a wide

degree of uncertainty—supports better decision making, as long as key limitations and

assumptions are noted. Participants designed the SNRA to capture the best information the

Nation has about homeland security risks to support the development of the National

Preparedness Goal while recognizing the limitations of conducting such analysis in a shortened

time frame.

This is a strategic national risk assessment. As such, it does not present a full view of the risk facing local communities. To complement preparedness planning, it is necessary to

consider national and regional risks, many of which differ from region to region.

Given PPD-8’s emphasis on contingency events with defined beginning and endpoints (e.g. hurricanes, terrorist attacks), the current SNRA does not explicitly assess persistent,

steady-state risks like border violations, illegal immigration, drug trafficking, and

intellectual property violations, which are important considerations for DHS and the

homeland security enterprise.

Information about the frequency and consequences of the events included in the SNRA is at varying stages of maturity, with additional work required in some areas to ensure that

event data can be appropriately compared. Where substantial additional research is

warranted, events are discussed qualitatively and are not compared with other events.

Strategic National Risk Assessment December 2011


The SNRA methodology does not explicitly model the dynamic nature of some of the included hazards. For example, terrorists’ evolving tactics in response to changes in

defensive posture are not included.

Experts consulted about psychological consequences emphasized caution in the application of the SNRA’s measure of psychological distress, and stressed the need for

additional research. The Department of Homeland Security and its partner organizations

leveraged previously funded social and behavioral research to better understand how to

anticipate, prepare for, counteract, and mitigate the effects of terrorist acts, natural

disasters, and technological accidents. Additional research is required to further explore

psychosocial factors that enable resilience in individuals, organizations, and communities

and at the societal level.

For national-level events where historic data was used as the basis of analysis, the risk from low-likelihood, high-consequence incidents may not be adequately captured. This

is particularly true for technological/accidental hazards. Further study is needed to better

characterize these risks at the national strategic level.

Impacts and Future Uses

The SNRA was executed in support of PPD-8 implementation and has served as an integral part

of the development of the National Preparedness Goal, assisting in integrating and coordinating

identification of the core capabilities and establishing a risk-informed foundation for the National

Preparedness System. Participants mapped the core capabilities identified in the Goal to the

events assessed in the SNRA to identify any additional core capabilities that may need to be

included. In addition, the SNRA can be used to inform discussions on priorities for capability

investment decisions. Finally, the SNRA results will be used to drive other preparedness

priorities at the national level.

In addition, conducting a Strategic National Risk Assessment will support the National

Preparedness System by providing a consolidated list of ―national level events‖ for consideration

and augmentation for Threat and Hazard Identification and Risk Assessment processes at

multiple jurisdiction levels.


Although the development of the SNRA is an important first step, further analysis through the

execution of regional- and community-level risk assessments will help communities better

understand their risks and form a foundation for their own security and resilience. The Nation’s

preparedness is dependent on a whole-of-community understanding of risk and comprehensive

consequences at and across all levels of government. In conjunction with Federal, state, local,

tribal, and territorial partners, the SNRA will be expanded and enhanced and will ultimately

serve as a unifying national risk profile to facilitate preparedness efforts.

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