Infrastructure Resilience

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Infrastructure systems have been major contributors to the growth of the United States. Hoover Dam helped desert regions in the west to bloom. The Interstate Highway System spanned the states and opened up the country to growth and provided corridors for trade. As the country grew, new technologies developed, and infrastructures developed around them that are integral to our daily lives. These infrastructures can be vulnerable to a variety of disruptions, including human events, earthquakes, extreme weather events and climate change impacts. The creation of the President’s Commission on Critical Infrastructure Protection (PCCIP) in 1996[1] resulted in the development of a national plan to identify the critical infrastructure sectors and how to identify and reduce their vulnerabilities to natural or deliberate threats. Subsequent extreme natural disasters like Hurricanes Katrina and Sandy pointed out additional limitations in the resilience of infrastructure due to the interconnected nature of infrastructure systems. Infrastructure cannot be made totally immune to disruptive events, but it can be made more resilient by considering the dependencies and interdependencies within and between systems and by taking a system-of-systems view of the vulnerabilities and threats to them.

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Contributor(s): Dr. John Hummel and Dr. Frederic Petit

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Infrastructure systems have always been an important aspect of the United States and signature elements of the country’s growth—examples such as Hoover Dam, Grand Central Station, and the Interstate Highway System. As the country grew and evolved, other infrastructure elements took on important aspects of everyday life, such as Global Positioning System (GPS) and the World Wide Web (WWW). Vulnerabilities in these systems were largely taken for granted until terrorist events such as the Tokyo sarin gas subway attacks, the 1993 terrorist bombing of the U.S. World Trade Center, and the bombing of the Federal Building in Oklahoma City demonstrated the reality of threats from human elements. The subsequent creation of the President’s Commission on Critical Infrastructure Protection (PCCIP) in 1996[1] resulted in the development of a national plan to identify the critical infrastructure sectors and how to identify and reduce their vulnerabilities to natural or deliberate threats. Subsequent extreme natural disasters like Hurricanes Katrina and Sandy pointed out additional limitations in the resilience of infrastructure due to the interconnected nature of infrastructure systems. In its October 1997 report, the PCCIP[3] defined an infrastructure as “a network of independent, mostly privately owned, man-made systems and processes that function collaboratively and synergistically to produce and distribute a continuous flow of essential goods and services.” In the original PCCIP assessments considered eight critical infrastructures whose “…incapacity or destruction would have a debilitating impact on our defense and economic security”[1]. The U.S. Department of Homeland Security has subsequently increased the number of critical infrastructures to the 16 sectors[4], listed in Table 1, and detailed a plan to strengthen and maintain, secure, functioning, and resilient critical infrastructure.[2]

Table 1. DHS Critical Infrastructure Sectors[4]
Chemical Commercial Facilities Communications Critical
Dams Defense Industrial
Emergency Services Energy
Financial Services Food and Agriculture Government Facilities Healthcare and Public
Information Technology Nuclear Reactors, Materials,
and Waster
Transportation Systems Water and Wastewater

Analyzing Infrastructure Vulnerabilities

Early studies on critical infrastructure vulnerabilities focused on physical threats, and the strategies to mitigate those vulnerabilities focused primarily on providing physical protection with “guns, gates, and guards.” As the array of potential threats expanded to include factors such as cyber, chemical, biological, radiological, and nuclear attacks, the vulnerability assessment methodologies evolved and expanded to include the consideration of the dependencies and interdependencies within and between infrastructure assets. The myriad of interdependencies in infrastructure systems can result in a disruption in a component of one infrastructure cascading through a network of dependencies and resulting in the taking down of a larger infrastructure, such as the northeast blackout in August 2003. The cause of the blackout was attributed to a software bug in a control room alarm system in Ohio, which made operators unaware of a need to redistribute the electrical load after transmission lines drooped into foliage. Events like this demonstrate that protecting infrastructure from all hazards is impossible. Instead, one must understand the dependencies and interdependencies in infrastructures, and how they differ, so they can be designed to be resilient to disruptions when they inevitably occur.

System View of Infrastructure Resilience

Numerous definitions can be found for resilience that depends upon the perspective of the problem being addressed, such as material physics, ecosystems, engineering, and psychological well-being, to name just a few. For the study of infrastructure resilience and how it contributes to regional and community resilience, the following definition is used[5]: “Resilience is the ability of an entity—e.g., asset, organization, community, region—to anticipate, resist, absorb, respond to, adapt to, and recover from a disturbance from either natural or man-made events.” Analyses of the resilience of infrastructure should be taken from an integrated systems perspective[2] of the infrastructure and the community and region being supported. Figure 1 provides a schematic representation of the systems that support resilience[6]. The high-level systems shown in Figure 1 can be expanded to finer scale system as needed. The Governing System in Figure 1 is deliberately not called a Government System because the intent is to be able to represent governing systems at multiple levels of population granularity—groups, villages, tribes, communities, countries, etc. These groups have different ways in which they organize themselves, and the organizing details may or may not be formalized and may or may not be codified. Organized criminal networks, for example, have strong governing and enforcement mechanisms that members clearly understand, but these mechanisms are not codified in any written form.

Figure 1. Schematic Representation of the Interconnected Systems that Contribute to Resilience[6].

The Human Landscape System is often the most overlooked system in resilience assessments of communities and infrastructure, yet it is probably the most important. It represents the actors who are the decision makers, the implementers of plans and activities, and the groups in the general population that will be impacted by the plans and the external forces that can disrupt the community [7]. The Human Landscape is also the system where the measures of effectiveness of resilience activities are assessed. For example, during the COVID-19 pandemic, the efforts to reduce the spread of the virus depended upon the collective behaviors of people to shelter in place, practice social distancing, and wear facial masks in public. The basic measures of the effectiveness of the efforts to control the spread of the virus were the number of cases of infection hospital strain and lives lost. The Natural Environment system in Figure 1 consists of the terrain, air, ocean, and space environments where the infrastructure and community systems are located and operated. The natural environment can be a driver for where an infrastructure is located and will be the source of the natural forces to which it must respond.

Assessing and Mitigating Climate Impacts on Infrastructure

The DHS Regional Resiliency Assessment Program[8] (RRAP) has conducted analyses of the vulnerabilities of infrastructure to a variety of disruptions, including earthquakes, climate impacts, and extreme weather events. These assessments utilize a variety of models and tools in the resiliency assessments, depending upon the context of the study. For example, an RRAP study done in the Casco Bay Region of Maine examined the disruptions to infrastructure from projections of coastal flooding triggered by sea level rise and heavy precipitation. In that study, inundation models driven by sea level and precipitation projections generated areas of flooding in the Casco Bay area. Overlays of the existing infrastructure elements were then used to identify the locations of electric power assets that could be disrupted by the projected flooding.

Figure 2. Potential Impacts from Flooding of Electric Assets in the Casco Bay Region of Maine.

In California, an integrated water system was developed in the second half of the 20th century, the California State Water Project (SWP), to collect and store water from the northern portion of the state and deliver it to communities in the central and southern regions of the state. The SWP was developed based on the climatic conditions of the time and the locations of the dams, reservoirs, canals, and aqueduct were selected based on the historic precipitation patterns of the mid-20th century. The effectiveness of the SWP to continue to collect and deliver water under projected climate conditions has been studied by combining high-resolution climate projections and overlaying the results against the SWP elements. The projections of 21st mid-century and end-of-century climate conditions[9] indicate changes in the timing of precipitation in California and how it falls (rain or snow). The changes in timing indicate that more of the precipitation may fall earlier in the year and in the form of rain, when the existing SWP is least able to collect and store the water because the reservoirs are required to have lower storage levels for flood control purposes. This could result in a requirement for significant investment in new reservoirs at new locations better able to capture and store the precipitation.

The 2021 power crisis in Texas pointed to the importance of the role of the natural environment in energy system planning. Energy grids are a combination of numerous nodes and links and disruptions in any component can potentially cascade through the system. Energy planning in Texas has traditionally considered only historical environmental factors when planning for future energy needs in terms of estimating future energy loads and did not include the consideration of extreme weather events—hot or cold—in planning. The extreme cold weather event resulted in two significant issues for the energy planners. First, many natural gas wells and pipelines were not winterized and failed or shutdown, depriving the electrical generating facilities of the natural gas to power the facilities. Second, it takes far more energy to warm households up from near freezing temperatures than it does to cool them down from a summer heat wave, increasing the demand load on the electric grid. Tools such EPfAST [10] and NGFast [11] can be used to study integrated electric power and natural gas system interdependencies.

In many coastal areas of the country, transportation systems are having to contend with disruptions from storm surges and high-tide flooding [12], which occurs when local sea level rises above a given threshold in the absence of storm surge or riverine flooding. This type of flooding is occurring on a regular basis along portions of the U.S. east coast and portions of the south Florida coast and is expected to worsen as sea levels rise. In south Florida, the problem is made worse because much of the area sits on porous limestone which allows the ocean to seep up from the ground – meaning that residents face the climate impacts from storm surges from the sea and rising ground waters from below. The intrusion of ocean water into the aquifers can impact the availability of potable water from aquifers as well as reduce the ability of the ground to absorb runoff, so floodwaters will remain longer[13]. In developing mitigation strategies for climate change impacts, infrastructure developers look at ways to protect or retrofit existing systems and how to develop new systems that take into account potential climate change impacts. As an example, the predictions of higher summer temperatures from climate change can mean that the operating ranges for heat, ventilation, and air-conditioning systems may change and require new designs for such systems. These changes may also result in changes in building codes in different areas[14][15][16]. Hurricane Sandy provided a number of critical lessons for infrastructure developers. One major lesson learned was that basements in building should not be used for any back-up or critical systems – power, computers, or telecommunications. Many of the hospitals in New York City lost power because their reserve generators were in basements which flooded. Another one was that waterproof doors should be installed at entrances to subway stations. One of the major challenges facing developers is what environmental conditions should they build for. The majority of building codes are based on analyses based on historical environmental conditions and are not representative of current conditions. The Federal Emergency Management Agency (FEMA) has the responsibility to update floodplain maps every five years. These maps are used to identify flood prone areas and locations where flood insurance is required. However, it was estimated in early 2020 that only one-third of nation’s 3.5 million miles of streams and 46% of shoreline have had maps generated[17]. In addition, climate projections are pointing towards more frequent severe precipitation events and in urban areas where developments are changing runoff patterns, the chances for flooding events may increase.

Climate Change and National Security

The CNA Military Advisory Board, a group of retired three- and four-star military officers, stated in 2007[18] and reaffirmed in 2014[19] that climate change will impact U.S. national security interests by increasing the chances for conflict around the world and by threatening U.S. military facilities. These assessments were also noted in a report from the National Intelligence Council in 2008[20]. As an example, a prolonged drought that hit the Mediterranean area near Syria from 2006 to 2011 is now felt to have been the precursor of factors that led to the civil war in Syria. As crops were destroyed, rural residents moved to the cities where tensions over lack of food and jobs ultimately triggered the political tensions that led to the Syrian civil war[21].

The Department of Defense (DoD) conducted a survey in 2018[22] to determine which DoD facilities have experienced negative effects from past extreme weather events in order to identify facilities that might be vulnerable to future extreme weather event. The impact of extreme weather events on military operations was demonstrated in October 2018 when Hurricane Michael, a Category 5 hurricane, devastated Tyndall AFB, damaging or destroying 95% of the base’s 1,300 structures and forcing the primary support missions to be relocated to other military installations. Tyndall AFB is home to two F-22 fighter squadrons, and it was estimated that about 10% of the U.S. F-22 inventory was damaged or destroyed by Hurricane Michael[23]. In addition to the U.S.-based facilities, DoD operates a number of facilities around the world. Some of them involve unique facilities located at strategic locations. One example is Diego Garcia, an island in the British Indian Ocean Territory that is part of Chagos Archipelago. Diego Garcia is home to U.S. naval and air facilities that provide critical force projection activities in the Asia Pacific region. Analyses of the impact of climate change indicate that many Pacific atolls could be rendered uninhabitable by sea level rise and wave-driven flooding[24]. U.S. based military facilities are already facing climate change impacts. In 2019, the U.S. Government Accountability Office (GAO) released a report to Congress detailing how DoD installation managers need to assess the risks from climate change to their facilities and to incorporate those risks into the master plans for the facilities (GAO, 2019)[25].

Naval Station Norfolk in Virginia has been on the front line of climate change impacts, having dealt with high tide flooding for a number of years in which low-lying areas are flooded during high tides. This problem is not unique to the Norfolk area but is being felt in a number of areas along the east coast of the United States. The majority of the Norfolk area is under 10 feet (ft) above sea level and the worst-case scenario estimates that sea level rise by the end of the century could be on the order of 6 ft. Under these conditions, portions of the Norfolk area could experience flooding during any high tide. This flooding could result in land loss as the flooded area become part of the tidal zone. The high sea level could also expose previously unexposed areas to storm surge flooding[26].


  1. ^ 1.0 1.1 1.2 1.3 Executive Order 13010. Critical Infrastructure Protection, 61 Fed. Reg., No. 138, July 17, 1996
  2. ^ 2.0 2.1 2.2 Presidential Policy Directive – Critical Infrastructure Security and Resilience. The White House Office of the Press Secretary, February 12, 2013.
  3. ^ President’s Commission on Critical Infrastructure Protection, 1997. Critical Foundations: Protecting America’s Infrastructures. Washington,DC. Report pdf
  4. ^ 4.0 4.1 U.S. Department of Homeland Security, Cybersecurity & Infrastructure Security Agency, “Critical Infrastructure Sectors”.
  5. ^ Hummel, J. R. and Lewis, L.P., 2013. Analytical Support for Societal and Regional Resilience in Support of National Security. Phalanx, 46(3), pp 10-17. Article
  6. ^ 6.0 6.1 Hummel, J.R., 2016. The Last Word Resilience: Buzz Word or Critical Analytical Issue? Phalanx, 49(3), pp. 60–63. Article
  7. ^ Hummel, J.R. and Schneider, J.L., 2016. The Human Landscape – The Functional Bridge between the Physical, Economic, and Social Elements of Community Resilience. Center for Infrastructure Protection and Homeland Security Report. Report pdf
  8. ^ U.S. Department of Homeland Security, Cybersecurity & Infrastructure Security Agency, “Regional Resilience Assessment Program”.
  9. ^ Reich, K.D., Berg, N., Walton D.B., Schwartz, M., Sun, F., Huang, X., and Hall, A., 2018. “Climate Change in the Sierra Nevada: California’s Water Future. UCLA (University of California at Los Angeles) Center for Climate Science. Report pdf
  10. ^ Portante, E.C., Craig B.A., Talaber Malone L., Kavicky, J., Folga S.F., and Cedres S., 2011. EPfast: A model for simulating uncontrolled islanding in large power systems. Proceedings of the 2011 Winter Simulation Conference (WSC), pp. 1758-1769. doi: 10.1109/WSC.2011.6147891
  11. ^ Portante, E. C., Kavicky J.A., Craig B.A., Talaber L.E., and Folga, S.M., 2017. Modeling Electric Power and Natural Gas System Interdependencies. Journal of Infrastructure Systems, 23(4), 04017035 doi:10.1061/(ASCE)IS.1943-555X.0000395 Article pdf
  12. ^ U.S. Federal Government, 2021. High-Tide Flooding. U.S. Climate Resilience Toolkit.
  13. ^ A 20-Foot Sea Wall? Miami Faces the Hard Choices of Climate Change, New York Times. Article
  14. ^ Ministry of Environment of Denmark/Environmental Protection Agency. Climate Change Adaptation, Climate Change Impact on Buildings and Constructions
  15. ^ Enker, R.A., and Morrison G.M., 2020. The potential contribution of building codes to climate change response policies for the built environment. Energy Efficiency, 13, pp. 789-807. doi:10.1007/s12053-020-09871-7
  16. ^ Myers, A., 2020. Building Codes: A Powerful yet Underused Climate Policy that Could Save Billions. Forbes. Article
  17. ^ Association of State Floodplain Managers. 2020. Flood Mapping for the Nation: A Cost Analysis for Completing and Maintaining the Nation’s NFIP Flood Map Inventory. Madison, WI. Report pdf
  18. ^ CNA Military Advisory Board, 2007. National Security and the Threat of Climate Change. CNA Corporation, Arlington, VA. Report pdf
  19. ^ CNA Military Advisory Board, 2014. National Security and the Accelerating Risks of Climate Change. CNA Corporation, Arlington, VA. Report pdf
  20. ^ National Intelligence Council, 2008. Global Trends 2025: A Transformed World. US Government Printing Office, Washington, DC. Report pdf
  21. ^ Polk, W. R., 2013. Understanding Syria: From Pre-Civil War to Post-Assad. The Atlantic. Article
  22. ^ Department of Defense, 2018. Climate-Related risk to DoD Infrastructure Initial Vulnerability Assessment Survey (SLVAS) Report. Office of the Undersecretary of Defense for Acquisition, Technology, and Logistics. Report pdf
  23. ^ Panda, A., 2018. Nearly 20 Percent of the US F-22 Inventory Was Damaged or Destroyed in Hurricane Michael. The Diplomat. Article
  24. ^ Storlazzi, C.D., Gingerich, S.B., van Dongeren, A., Cheriton, O.M., Swarzenski, P. W., Quataert, E., Voss, C. I., Field, D. W., Annamalai, H., Piniak, G. A., and McCall, R., 2018. Most atolls will be uninhabitable by the mid-21st century because of sea-level rise exacerbating wave-driven flooding. Science Advances, 4(4). doi: 10.1126/sciadv.aap9741 Article pdf
  25. ^ United States Government Accountability Office, 2019. Climate Resilience, DOD Needs to Assess Risk and Provide Guidance on Use of Climate projections in Installation Master Plans and Facilities Designs, GAO-19-453. Report pdf
  26. ^ Kramer, D., 2016. Norfolk: A case study in sea-level rise. Physics Today, 69(5), pp. 22-25. doi: 10.1063/PT.3.3163 Article pdf

See Also