Resilience for Compounding and Cascading Events
Not long ago, disasters would strike one at a time. The disaster would occur, and the disaster relief assembly line would kick into high gear: first responders would help stabilize the local situation, and local community members, people from surrounding areas, and even volunteers from around the nation—second responders—would pitch in to start the recovery process. The disaster would be named and declared, and Congress would pass funding for the next several years. Eventually, the affected communities would reassemble their broken pieces, and America would move on.
Today, there is a new normal—most disasters do not occur as isolated events and instead seem to pile on one another, disaster after disaster, often unleashing new devastation on a community before it has had a chance to recover from the prior disaster. Furthermore, acute events can be compounded by chronic deteriorating conditions, such as an acute, intense rain event causing mudslides and flash flooding in an area that had been experiencing extreme drought. Compound disasters—two or more extreme events occurring simultaneously—are typically the outcome of multiple causes and can generate multiplicative damage and losses. Because of climate change, compound disasters are increasingly likely. According to the Intergovernmental Panel on Climate Change’s 2021 report, examples include “concurrent heatwaves and droughts, compound flooding (e.g., a storm surge in combination with extreme rainfall and/or river flow), compound fire weather conditions (i.e., a combination of hot, dry and windy conditions), or concurrent extremes at different locations” (IPCC, 2021, p. 9). Additionally, long-term pandemics, such as COVID-19, further compound the situation.
A cascading hazard refers to a primary event (trigger), such as heavy rainfall, seismic activity, or rapid snowmelt, followed by a chain of consequences that may range from modest (lesser than the original event) to substantial. Also, the type of cascading damage and losses may be more severe than if they had occurred separately. A classic example is the major earthquake that struck Japan in 2011, which triggered a tsunami that led to failure of the Fukushima nuclear reactor. More recently, the war in Ukraine during the COVID-19 pandemic highlighted the importance of supply chain problems, which are cascading by their very nature as they represent the ripple effects of an initial bottleneck across sectors and regions over time.
Currently, research on disasters has focused largely on those triggered by natural hazards interacting with vulnerable human systems (e.g., populations and organizations) and the built environment. This report has taken a broader view of possible disaster scenarios. Recent events have highlighted how compounding and cascading natural hazards, whether acute or chronic in nature, can be further amplified by other events, such as public health outbreaks, supply chain
disruptions, and cyberattacks. For example, an increasing number of possible disaster scenarios involve “bad actors” who leverage an emergent or existing disaster context to cause additional harm through a cyberattack on a hospital, banking system, port, or other critical facility.
Regardless of the cause of a disaster, the nation’s disaster mitigation, response, and recovery system in its present form can no longer keep pace. “Cascading disasters are the new normal,” said Susan Cutter, the Carolina distinguished professor and director of the Hazards Vulnerability & Resilience Institute at the University of South Carolina, in her keynote address at the workshop designed to inform this report.1 The nation has two options for addressing what is becoming an untenable situation: The first is to make the disaster system as it currently exists work faster and harder. The second is to take a step back and rethink and redesign the system so that it has the capability and capacity to work on multiple disasters that are interconnected in multiple physical and social ways, at multiple locations, and on multiple scales, all at the same time (Moddemeyer, 2022).
While pondering which of these two options to pursue, the nation should consider the real possibility that the way communities have designed and built their infrastructure, including building codes and land use regulations, contributes or even amplifies the effects of cascading disasters on those communities. In that regard, the nation needs greater understanding of the dense entanglement between natural disasters, vulnerability, land ownership, and property rights with the legacies of racism, redlining, and disinvestment that can cause social disasters (NASEM, 2022; van Straalen et al., 2018). Recovery requires more than getting back to normal, especially when what is considered normal may be a major contributor to a community’s vulnerability to cascading disasters. How can communities recover from disasters when the normal they have lost was a major contributor to the disaster itself (Haggerty, 2020)? How can recovery efforts acknowledge a changing climate, shifting economic and cultural expectations for social equity, and the imperative for climate-smart economic development?
Answering these questions requires rethinking what is appropriate today and going forward in terms of disaster preparedness, emergency response, and recovery actions (Román, 2022). Fostering resilience and the governance of recovery appears to require integrated capabilities and skills that the nation has yet to deploy (Román, 2022). Specifically, the nation has yet to stand up the networks, measures, and tools that can help communities navigate their biophysical, political, and cultural crosscurrents so that they can recover and reduce their vulnerability to avoid cascading disaster upon disaster.
While humans have the capacity to adapt, that capacity is not unlimited in the face of compounding and cascading events. Human adaptive capacity contributes to resilience, and while there is a proliferation of methods to assess human adaptive capacity, there has been no definitive assessment of the best approach(es). Better understanding of human adaptive capacity can help improve the design of equitable policies and ensure that policies can be targeted to support those with less capacity to prepare for and respond to hazard events. Codevelopment of
1 The workshop agenda, video, and slides are available at https://www.nationalacademies.org/event/05-312022/hazard-mitigation-and-resilience-applied-research-topics-workshop-2-compounding-and-cascading-events.
solutions focused on governance, land use planning, and decisions about relocating infrastructure has been shown to be effective for addressing the growing number of compounding and cascading events and for building community resilience (Schoch-Spana et al., 2019a,b).
GOALS OF THE COMMITTEE
As part of its efforts to reduce the immense human and financial toll of extreme events, in 2020, the Federal Emergency Management Agency (FEMA) asked the Resilient America Program of the National Academies of Sciences, Engineering, and Medicine to convene the Committee on Hazard Mitigation and Resilience Applied Research Topics (see Box 1-1 for further information on the Resilient America Program). FEMA charged the committee with identifying “applied research topics, information, and expertise that can inform action and collaborative opportunities within the natural hazard mitigation and resilience fields.” In 2021, the first committee held two workshops on applied research topics—Social Capital and Social Connectedness for Resilience, and Motivating Local Climate Action—and prepared two brief consensus reports that identified and summarized key research topics for the applied research community in the specific areas discussed at the workshop and in open discussions of the Resilient America Roundtable.
In 2022, a second committee selected two additional themes—Equitable and Resilient Infrastructure Investments, and Compounding and Cascading Events—and held public workshops to explore each of these themes. This report examines the second theme, focusing on strategies that would enable the nation to be better prepared for and respond to compounding and cascading disasters so that affected communities can not only rebuild, but do so in a manner that increases their resilience to future disasters. As was true for the previous three reports produced by this project, this report contains findings but no recommendations and is limited to the topics covered in the public workshops and in open discussions with the Resilient America Roundtable. The full statement of task is as follows:
A committee of the National Academies of Sciences, Engineering, and Medicine will identify applied research topics, information, and expertise that can inform action and collaborative opportunities within the natural hazard mitigation and resilience fields. The committee will convene two public workshops as the primary source of information for its work, supplemented by background materials collected for the workshops and discussions at public sessions of the Resilient America Roundtable.
Each workshop will focus on distinct hazard mitigation and resilience issues and research questions, such as compound and cascading hazard incidents; risk communication and decision making in a changing risk landscape; nature-based solutions, buyouts, and managed retreat options for coastal risks; and equity and social vulnerability considerations in risk and decision metrics. Following each
workshop, the committee will prepare a brief consensus study report that identifies and summarizes key research topics for the applied research community in the specific areas discussed at the workshop. Each report will contain findings but no recommendations and will be limited to the topics covered at that workshop.
To meet this charge for the second theme—compounding and cascading events—the committee organized a public, 1-day workshop featuring diverse voices and expertise on this topic to survey existing knowledge and practice. Based on information the committee gained at this workshop and committee members’ backgrounds and experience with hazard mitigation and resilience, the committee focused on (1) drivers, systems, and relationships that impact understanding of compounding and cascading disasters; (2) solutions and avoiding unintended consequences; and (3) effective implementation of and governance for solutions and strategies.
This report’s primary audience is the applied research community in the fields of hazards, vulnerability, risk reduction, and resilience. This community includes hazard-specific and general resilience research centers, as well as cooperative institutions engaged with states and local communities on related challenges. Broader audiences include public, private, nongovernmental, philanthropic, and academic organizations at the local, regional, state, tribal, and federal levels that seek to reduce the impacts, losses, and suffering from disasters as a result of natural or technological hazards, public health emergencies, and other significant threats to communities and the nation. The committee’s activities intend to inform applied research programs that will strengthen capacities for hazard mitigation and resilience.
On May 31, 2022, the committee held a workshop on the theme of compounding and cascading events. The agenda for the workshop, developed in part based on input the committee received during an open session of the Resilient America Roundtable on April 11, 2022, appears in Appendix B, and biographical sketches for the workshop presenters are in Appendix C. Workshop panelists included individuals from the public and private sectors; organizations involved in various resilience and social justice activities across the United States; community-based organizations; and the research, community engagement, infrastructure, transportation, housing, and policy communities. While the voices included in the workshop were not exhaustive, and additional voices and inputs would continue to educate and bring attention to equity issues, the workshop panelists were diverse in their perspectives and orientations, and they reinforced the need for continued research on equity in resilience. The workshop highlighted the urgency of the current moment that requires rethinking disaster preparedness, emergency response, and recovery actions. As Miguel Román noted in his keynote address, “The choice before us is clear: We can either accept the status quo and allow this unique moment to bring equity, transparency, and accountability to pass, or we can promote transformative ideas around disaster science and fund them and implement them in a responsible manner so that we can serve and protect all Americans. This is the choice before us, and the stakes have never been higher” (Román, 2022).
The workshop presentations and discussions following the keynote address focused on answering the following questions:
- How can the nation build the ability of its communities, states, tribes, and territories to recover and thrive given increased likelihood, severity, and complexity of disasters in the midst of all the types of more general change coming in their direction?
- How can the resilience, mitigation, and disaster recovery communities step back and reframe the governance for recovery and resilience efforts, to take off the regulatory blinders and look clearly at the complex interplay of “acts of humans” that expose, situate, and perpetuate losses from compound and cascading disasters?
- What is an emergent applied research agenda that can help the nation and the disaster recovery community step up, respect, and re-envision the challenge the nation is facing regarding compound and cascading disasters?
The committee acknowledges that challenges this broad and complex defy easy answers. Nonetheless, the thought leaders tasked with addressing these challenges at the workshop provided the committee with four themes to guide its work, as noted in the statement of task, on identifying and summarizing key research topics for applied research. Several terms used in this report are defined in Box 1-2.
Theme 1—Compounding and Cascading Disasters Are the New Normal
As noted above, recurrent acute disasters are happening with more frequency, intensity, periodicity, and harm (Román, 2022). The COVID-19 pandemic, as an obvious example, compounds with other disasters and complicates recovery efforts. Climate change, an ongoing disaster, increases the likelihood and intensity of extreme weather events and natural hazards including wildfire, extreme heat, drought, and their natural follow-on events, including flooding,
landslides, and ecosystem collapse (Masson-Delmotte et al., 2022; Olsson et al., 2014; Siders, 2022). Heavy rainfall, for example, can lead to lush plant growth, which, if followed by a drought that dries out the ground cover, makes the area more prone to fires, which can then destroy the ground cover that holds the soil together. If another heavy rain falls, the denuded landscape will be vulnerable to mud- and rockslides. Climate change has also added significant uncertainty to future events and has reduced confidence levels in predictions of their frequency and magnitude (Kunreuther et al., 2014). These kinds of cascading events were seen in California when the record-breaking Thomas Fire burned through Santa Barbara County in December 2017, leaving behind barren hillsides that collapsed into mudslides during the subsequent January rainstorms, killing more than 20 people and destroying more than 100 homes.2
These cascading disasters affect response and recovery, yet the protocols, governance, regulatory underpinnings, and funding do not yet account for this new normal. For example, hurricane evacuations during the COVID-19 pandemic increase exposure of vulnerable people to infection, and seniors vulnerable to extreme heat must choose between sheltering at home without air conditioning or cooling at a shelter with increased exposure to infection (Zaitchik, 2022).
The United States as a nation has immense capabilities for responding to multiple disasters. However, while the national financial capacity to address losses is high, even a singular event can exceed the local capacity of vulnerable communities to absorb the associated losses (Cutter, 2022). Exacerbating the situation, the current condition of much of the U.S. infrastructure is inadequate to resist increasingly extreme natural hazards, as a result of siloed decision making, inadequate design parameters, poor construction quality, lack of maintenance, or aging effects, leading to avoidable disasters. In most cases, disasters are created by decisions that make a system brittle (ShelterBox, n.d.).
Legacy conditions, extreme hazards, and opaque response and recovery bureaucracy can overwhelm local communities already suffering from an extreme event. Moreover, communities may also have unrecognized cumulative risk when considered across the life expectancy of their infrastructure assets. For example, when engaging in water and climate risk management and planning, many risk managers continue to model risk assuming that they can calculate the statistical likelihood of extreme events by looking at past climate records (Churchill, 2022). This assumption, however, no longer holds as greenhouse gas emissions increase thermal energy and resulting water vapor in the atmosphere makes measurable probabilities of extreme events inadequate for long-range infrastructure design (Milly et al., 2008).
During recovery, cumulative risk compounds when a community replaces the brittle systems that failed in the previous disaster with a similarly brittle system, condemning survivors to continued risks in a time of changing climate. The nation’s approach to climate resilience will remain fundamentally flawed if it continues to focus on short-term horizons and singular major events. In fact, treating each event as discrete and short-lived, and without considering
2 See https://news.caloes.ca.gov/remembering-the-montecito-mudslides-two-years-later.
compounding or cascading impacts, undermines efforts to value and increase resilience (Churchill, 2022).
Theme 2—Legacy Conditions Need to Be Assessed, Evaluated, and Addressed
Legacy conditions are caused by a combination of ongoing stressors (hunger, poverty, etc.), socioeconomic conditions, and impacts from prior and ongoing events. When one disaster follows another in the same locale, the impacts from the first event can be amplified by legacy conditions and continue to affect the outcome of the subsequent disaster. Driven in part by a combination of climate change, population growth in at-risk locations such coastal communities, historic inequities and underinvestment in certain communities, and inadequate disaster preparedness, these compounding and cascading disasters pose an increasing threat to environmental quality, economic activity, public safety, national security, and health. A better understanding of how compounding and cascading disasters interact with and affect critical resources and social systems (see Figure 1-1) has the potential, then, to advance disaster science, improve disaster response, build resilience to future disasters, and save lives (Machlis et al., 2022; Román, 2022).
In fact, many workshop speakers were clear in stating that the current understanding of social, investment, and legacy conditions in communities is poor, and what is known cannot be characterized adequately. One approach to addressing this knowledge deficit would be to establish a long-term resiliency and vulnerability observatory network to gather and share relevant, near-real-time information about response, recovery, and mitigation. This disaggregated network, with standards for data collection, analysis, and archiving, would support applied research, information, and actionable insight for recovery (Cutter, 2022). The data this network generates could enable researchers to develop and validate informative indicators in addition to models for understanding the disparities in impact and recovery for communities affected by compounding and cascading disasters (Averyt, 2022).
An additional challenge is to develop a better understanding of how damage to all infrastructure networks and their interdependencies extend the impact of disaster and incurred losses (Figure 1-2). Addressing this challenge will require a better understanding of the interdependencies between systems and jurisdictions, digital assessment platforms and operations, and natural systems and urban water supply, along with the codependency of each of these with natural ecosystems (DeFlorio, 2022; Elhami-Khorasani, 2022).
Theme 3—Codesign with Communities: Examine Pain Points and Opportunities, Reverse the Design Process, and Start from the Impacts
There are many pain points in the nation’s response to disasters in general and to compounding and cascading disasters specifically. These include a disaster management system designed for singular events, a regulatory and governance model that has yet to adapt to compounding and cascading events, and a lack of meaningful and actionable data for recovery. As is increasingly recognized, failing to address these pain points or to leverage existing community strengths and opportunities can increase a community’s vulnerability and fragility. Without seeking out and receiving the views and standpoints of underrepresented minority communities, inequitable outcomes may increase. One approach is to create a modeling system based on current community conditions and capabilities that not only works backward from that point to the disaster, but also engages those potentially affected individuals, including local decision makers, and communities in codesigning pragmatic strategies that eliminate or reduce pain points and leverage a community’s strengths and opportunities (Zaitchik, 2022). Although they are normally left out of such conversations, including these voices affected by planning activities is important because they can provide a different perspective and greater local ownership in acceptable trade-offs that might be associated with a solution (Siders, 2022). Many of these historically excluded voices also belong to those who provide the services on which much of the economy is built, such as operating public transit or restocking groceries, and their inclusion can contribute to better outcomes across the economy.
Codesign, or meaningful and collaborative end-user engagement in the design of research, should occur across all stages of the research process. Community member engagement can range in intensity from relatively passive involvement to being highly interactive. For example, a project for extreme weather preparedness codeveloped materials with unhoused community members so that the information accounts for people’s life circumstances (Every and Richardson, 2017). The codesign approach resonates with a prior report from this committee on equitable and resilient infrastructure investments (NASEM, 2022), which describes codevelopment as taking into account voices from underserved and underrepresented minority communities that have been ignored previously and works directly with people impacted by disasters and redevelopment. That report documented that consultation and inclusion at the community level can help build trust in the engagement relationships that are essential for place-based disaster recovery.
When codesigning a solution, it is important to consider that most mitigation and recovery funding programs are too complex, and that most states, counties, and municipalities lack the capacity to implement them. These barriers are particularly high in rural areas where the tax base and local government staffing may be limited, as illustrated in Headwater Economics’ Rural Capacity Index.3 As a result, communities may miss the opportunity to make the most of
3 See https://headwaterseconomics.org/equity/rural-capacity-map.
the significant funding available to repair and improve damaged infrastructure because of a lack of capacity at the federal level to provide technical assistance and at the state and local levels to implement programs (Sprayberry, 2022). Another challenge arises as a result of multiple state and federal agencies having different rules and procedures and varied comfort levels in working across agencies. Addressing that challenge requires creating protocols for combining information about hazards with relevant vulnerability information (Zaitchik, 2022).
The workshop discussions generated four proposals for action (Cutter, 2022):
- Create a long-term resiliency and vulnerability observatory network.
- Fix the current governance bifurcation of recovery by providing a formal legislative or legal structure for disaster recovery and resilience on par with the Stafford Act,4 which constitutes the statutory authority for most federal disaster response activities, especially as they pertain to FEMA and FEMA programs.
- Reform the National Flood Insurance Program to reflect future climate risks and disproportionate risks to underserved communities.
- Create and fund a FEMA Office of Applied Research to conduct action-oriented research on social and behavioral science as a means of providing the evidentiary basis for disaster mitigation and resilience policy and practice.
Theme 4—The Importance of Relentless Resilience
When a series of earthquakes struck Puerto Rico over 2 days in early January 2020, the resulting devastation compounded difficulties the island was already experiencing: a 9-month drought had ended only 2 months earlier, and hurricanes Irma and Maria had struck 2 weeks apart in September 2017. One individual, Dr. Enid Santos Cintron of Guayanilla, refused to leave her community, even though her home was destroyed, and worked to supply medical care continuously through the resulting crisis. Hailed as a heroine of Puerto Rico, her steadfastness and support for her community demonstrate relentless resilience.
Relentless resilience may become the seed of a deeper antidote to the new normal of cascading events (Román, 2022). This emerging concept can be described as creating cultures, mindsets, tools, and insights that help people, both individually and collectively, to handle the diversity of challenges our country is facing, including the ability to function throughout a series of disruptive events. A bottom-up approach to relentless resilience starts with codesign involving vulnerable community members who face compounding and cascading disasters. The codesign process would examine the ability of legacy programs, existing governance procedures, and available funding streams to enable relentless resilience. Working together, communities would codesign adaptive protective systems, programs, social norms, and mechanisms to reduce suffering and accelerate recovery when design events are exceeded—as they almost always are.
4Robert T. Stafford Disaster Relief and Emergency Assistance Act of 1988, Public Law 100-707, 100th Congress (November 23, 1988), 42, 68.
Some may worry that the concept of relentless resilience places stress on individuals and communities from a constant need to be resilient in the face of never-ending, and often externally imposed, stressors (Mahdiani and Ungar, 2021). The committee believes that resilience is about more than coping and surviving in the face of negative events. Rather, socioecological resilience is about creating cultures, mindsets, tools, and insights that help people individually and collectively handle the diversity of challenges individuals and communities face (Anderson, 2015; Khalid, 2019).
The false certainty that stationarity has offered for designers of infrastructure needs to be replaced, as it is insufficient and inhumane in a world of changing baseline conditions. Indeed, at a time of climate uncertainty, it is no longer acceptable for infrastructure designers to believe that it is sufficient to resist events up to a certain design event. Instead, the goal should be to pick a design event and then design systems, programs, cultures, and mechanisms to reduce suffering and accelerate recovery when those design events are exceeded.
The workshop discussions identified a series of cross-cutting questions through which applied research could supply important information to drive the codesign process:
- How could we restructure boundaries and organizations to focus funding on people first?
- Can we create a long-term resiliency and vulnerability network with real-time response, recovery, and mitigation?
- How can we create a new formal legal structure for disaster recovery?
- How can we improve monitoring, evaluation, and learning approaches to adapt, learn, and promulgate community resilience?
- How can we make funding simple, synchronized, and integrated?
- How can we account for shifting baseline conditions and stop relying solely on stationarity thinking?
In response to these broadly framed questions, the committee identified a series of specific approaches to prioritizing applied research. These applied research priorities can begin to inform new parameters for governance, mitigation, response, and recovery that embrace a broader, more equitable approach to compounding and cascading disaster management.