International Journal of Disaster Risk Reduction 63 (2021) 102464
Contents lists available at ScienceDirect
International Journal of Disaster Risk Reduction
journal homepage: www.elsevier.com/locate/ijdrr
The practical use of social vulnerability indicators in disaster management
Erik Wood *, Monica Sanders, Tim Frazier, Phd
Georgetown University School of Continuing Studies, Emergency and Disaster Management Master’s Program, 640 Massachusetts Ave NW, Washington, DC, 20001, USA
A R T I C L E I N F O
A B S T R A C T
Keywords:
Poverty
Vulnerability
Indicator model
FEMA
SoVI
SVI
Sendai
As climate change focuses more frequent and intense disasters on vulnerable communities across the globe,
mitigation and response resources need to be allocated more efficiently and equitably. Vulnerability assessments
require time, skill, and cost money. In the United States (US), these assessments are mandated by the Federal
Emergency Management Agency (FEMA) to qualify for federal funding. However, new trends in the literature
clearly question their practical value. This study begins with a focused literature review which demonstrates that
popular social vulnerability indices that create a single vulnerability score can diminish the significance of a lone
variable, overlook the relevancy of all interconnected variables, and can result in contradictory policy recommendations. Next, existing case studies that used popular vulnerability assessment frameworks were compared to
maps generated of the same study area that employed the single variable of poverty. These case study comparisons demonstrated how considering this greatest common variable among different vulnerable groups can
often - quickly, efficiently, and inexpensively - reveal close to the same county and sub-county level community
vulnerabilities detailed in costly assessments. Finally, a national survey of emergency managers was conducted to
determine how much current social vulnerability indices were actually governing the ongoing distribution of
resources to the communities being served. Results indicate that, while these indicator models may be underused
nationally, those who do find them effective tend to be from higher income areas. This study questions the
practical value of these indices for emergency management practice in the US and for meeting the goals of the
Sendai Framework and other compacts.
1. Introduction
Differential vulnerability, where different groups in varying spatial
contexts are not equally predisposed to risk from a natural or humanmade disaster, is well established in the literature [1]. The term risk in
this context involves the probability of a disastrous event harming “what
humans value” as defined by their degree of vulnerability [2]. The International Federation of the Red Cross (IFRC) defines vulnerability as a
state most often associated with poverty and based on the relative ability
of an individual or community to cope with, resist, and recover from a
hazard [3]. The term social vulnerability connects the characteristics of
that individual or group to their inability to resist the forces of the
hazard [76]. Since the social vulnerability index (SoVI) was introduced
[4], there have been several similar vulnerability frameworks developed
globally [5] which employ a composite or aggregation of multiple
vulnerability indicators to derive a single measure of vulnerability.
Some of those include the Spatially Explicit Resilience-Vulnerability
(SERV) model [6], the Natural Hazards Index developed at Columbia
University [7], FEMA’s National Risk Index [8], and the Health
Vulnerability Index [9]. After SoVI, one of the next most widely used
indicator models is the Center for Disease Control’s (CDCs) social
vulnerability index (SVI) [10]. The main focus of this project was limited
to these two widely used and impactful indices.
The use of SoVI and SVI is facilitated by FEMA grant programs. This
includes the Emergency Management Performance Grants (EMPG), the
Homeland Security Grant Program (HSGP), and the Urban Areas Security Initiative (UASI), which require these kinds of vulnerability assessments as part of their funding application. Additionally, much of the
post-disaster assistance outlined by the Stafford Act of 1988 [11]
available to communities in the US is contingent upon having a current
Hazard Mitigation Plan (HMP) which includes an assessment of vulnerabilities of the population being served [12].
While there is little peer-reviewed research on what county and subcounty resource allocation is directly driven by social vulnerability
indices, one can find related academic studies and state or county level
technical documents. Flanagan et al. [13] is an example of a typical
* Corresponding author.
E-mail addresses:
[email protected] (E. Wood),
[email protected] (M. Sanders),
[email protected] (T. Frazier).
https://doi.org/10.1016/j.ijdrr.2021.102464
Received 17 May 2021; Received in revised form 9 July 2021; Accepted 10 July 2021
Available online 17 July 2021
2212-4209/© 2021 Elsevier Ltd. All rights reserved.
E. Wood et al.
International Journal of Disaster Risk Reduction 63 (2021) 102464
academic study in this space. Cited over 700 times, this well documented
research examines a historic disaster (in this case Hurricane Katrina)
and, using SoVI, determines what could have been done differently and
how vulnerability could be mitigated in the future in the face of similar
shocks. Directed by the 2013 FEMA Mitigation Planning Toolkit, many
states, like Georgia, also use SoVI to develop a snapshot of the social
vulnerability conditions across their counties and documented in their
HMPs [14]. “This comparison can be used by state, regional, federal
authorities in the allocation of pre and post disaster resources to better
ensure that these are delivered where most needed” [14].
Many states and counties in the US opt to hire private consultants to
meet these federally mandated assessment deadlines. Meanwhile, the
efficacy and efficiency of SoVI and other popular social vulnerability
assessments, like SVI, have been challenged in recent literature [5,
15–22]. Yet the number of studies that challenge the validity of leading
vulnerability assessments is still extremely low [19]. “SoVI and the SVI
are the most prominent social vulnerability configurations and are being
promoted for use by public health officials and planners to identify socially vulnerable places and populations. Our empirical analysis raises
questions about their construct validity” [19]. Within this context, this
study will explore how much these vulnerability indices are facilitating
the actual distribution of disaster mitigation and recovery resources to
the most vulnerable populations.
distribution of disaster mitigation and response resources at the county and
sub-county level? Search terms included: vulnerability, disaster, index,
and/or SVI and/or SoVi in multiple Booleen arrangements. Articles
considered “slightly relevant” or “likely relevant” were read completely
for further assessment. Initially, 19 abstracts and conclusions of potentially related articles were reviewed.
Next, only 11 core, peer-reviewed articles were retained for being
significantly relevant to this subject matter. This confirms the scarcity of
research on this topic mentioned in Rufat et al. [19]. While several of the
11 core citations also discuss the key variable of poverty (e.g. Refs. [16,
27], 13 additional citations were added to further establish the
connection between vulnerability and poverty. Finally, additional citations were considered and added by searching those core articles’ citations to look backward in time for additional relevant sources and by
looking more recently at where those core works had themselves been
cited. Three citations were added outside of this matrix to support the
use of a focused literature review for this type of study. With two expert
book author additions and two contextual citations (e.g. Ref. [4] this
resulted in a total of 30 citations related to the focused literature review.
2.2. Case studies methodology
The case studies in section 4.0 were chosen based on being readily
available and that they employed one of the more popular social
vulnerability indices previously discussed. In each case, areas of these
studies were enlarged to accommodate comparison at the graphic size
generally suited for publishing in an academic journal. Through visual
inspection of each map product, the goal was to prove or disprove
whether the single variable of poverty would produce similar assessment
results that the multi-faceted and multiple variable SoVI and SVI-style
studies produced. While the visual comparison approach to model
convergence has been criticized as a means of in-depth analysis, this
type of analysis has been shown to support basic correlations (e.g. Refs.
[28–30], that then require support from other qualitative and/or
quantitative sources to increase plausibility. Therefore, this method was
deemed appropriate for the purposes of exploring a potential correlation
between the Poverty Vulnerability Map (PVM) outputs and widely
known outputs.
Additionally, the single variable PVMs had to be produced in 15 min
or less using ESRI’s ArcGIS Online (AGOL) by a modestly skilled operator and not by an advanced technician using ArcGIS Pro or ArcMap.
Authors reasoned that this more closely resembled the average skill,
technology, time availability, and budget constraints experienced by
existing emergency management bodies at the county and sub-county
level in the planning and mitigation phases. A total of six case studies
were conducted. In each of the PVM case studies, two complimenting
data layers were used. This included “Low Income Community Census
Tracts - 2016 ACS” which contains US Census data from 2012 to 2016 at
the Census Tract level related to poverty and median family income. The
second, complimentary data layer was “ACS Poverty Status Variables Boundaries” which contained 5-year poverty estimates (2014–2018) by
tract, county, and state. Here again, these layers were chosen, not with
experience of an advanced technician, but by searching data layers
within AGOL’s Living Atlas content and using the search term “US
Census, Poverty.” These two layers were the first two results in that
search and their metadata indicated good quality. While timeframes for
the poverty data were close to those in the case studies, our goal was to
use data that was the same vintage or slightly newer as poverty trends
tend to continue in the same locations [31].
In each case study, the author/operator attempted to quickly adjust
the color range of the PVM to, as closely as possible, resemble the
existing social vulnerability map. This would accommodate comparison
without sacrificing the 15 min or less rule. Finally, it is important to note
that each case study was chosen for its SoVI or SVI-based map result of
an easily defined area in the US to determine if the 15-min PVM would
display vulnerability patterns that were highly similar, somewhat
2. Methodology
2.1. Focused literature review methodology
This research is based on a mixed methods approach synthesizing
data outputs from both qualitative and quantitative data to answer a
research question [23]. This included a focused literature review, a
comparison of single indicator versus more complex vulnerability
mapping outputs, and a nationwide pilot survey targeting practicing
emergency managers (see Fig. 1).
The introduction to this study includes a focused, qualitative literature review of relevant work. This method is common within peerreviewed literature to establish the plausibility of new ideas, approaches, or to encourage additional research (e.g., Refs. [24–26]. The
main research question for this study was: What is the accuracy of existing
vulnerability assessments and how are these studies influencing the actual
Fig. 1. Data sources and synthesis.
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International Journal of Disaster Risk Reduction 63 (2021) 102464
similar, or not similar at all when compared to the much more complex
frameworks. The intent is not to be critical of any of these existing
studies or their contributions to the literature. In fact, one of the six
studies [19] is also a supporting citation for this study. Furthermore, the
purpose of this study is not to argue against the use of the multi-indicator
approach. However, analyzing the speed, access, and low-cost when
employing a dominant, single variable like poverty can and should make
the argument for improved utility of and access to vulnerability assessments - especially within the most vulnerable and poorest
communities.
Table 1
The four core survey questions and Likert-type, five option response range.
2.3. Survey methodology
A national email survey directed at public agency emergency managers working at the state, county, or sub-county level was conducted.
Amassing email contacts where the individual either carried the title of
emergency manager (EM), emergency services coordinator or similar
was the goal. This included adjoining titles such as director, deputy
director, chief, and specialist. Filtering potential recipients to make sure
the person is an emergency manager or acting in this capacity for that
area was a priority. For example, to obtain EM email addresses from
California, a Google search led to the CalOES Regional contacts page
[32] where 41 current email addresses were collected. Two potential
email addresses from this website were not added to the list as they
carried the sole title of Government Program Analyst which did not
qualify as likely to carry EM decision-making responsibilities. A total of
2128 contacts were gathered from every state across the United States
using this method. Next, the publicly accessible directory of members in
the International Association of Emergency Managers (IAEM) website
was filtered using the aforementioned criteria and 1074 current email
addresses were added to the list. These were compared to the other list of
Google search contacts using Qualtrics software to ensure duplicate
emails would not be sent out which is likely to lower participation. The
final contact list, without duplicates, totaled 3108 contacts.
This was a cross sectional survey as all data were collected at once
using survey software from Qualtrics to distribute the survey via email to
the 3108 total contacts. To avoid compromising the data with social
desirability (participants wanting to be perceived well), all questions
were answered anonymously. This anonymous method directed at prescreened professionals was also considered low risk without ethical
challenges opposite the institutional review board (IRB) standards [33].
Two gateway questions began the survey to further qualify respondents.
The first of these questions asked the participant to simply confirm their
role in emergency management. The second gateway question (“Does
your agency use a community vulnerability assessment tool like SoVI or
SVI?“) employed the Qualtrics skip logic feature and only allowed
participants who answered in the affirmative to participate in the next
four core survey questions. Those who answered “No” or “Do Not Know”
had completed their survey. This gateway question helped ensure that
those answering the next four key vulnerability assessment questions
were not, for example, responding in the negative answer range because
they did not use this assessment or did not know what it was.
The Likert-based structure to the survey questions is common when
measuring attitudes toward a specific subject [34]. Five response options were provided so that respondents had a neutral response choice
and would not feel they were being compelled to either answer positively or negatively [35]. All four Likert-type questions revolved around
a single theme of “vulnerability assessments” and avoided extreme
language that could elicit a tendency toward a central or neutral
response (see Table 1). The intent was to make this as short a survey as
possible (rated at 1-min) to increase response rates from a historically
and presently extremely busy group of professionals. The simplicity of
the survey was intended to yield easily interpreted results that would
help answer the main study question stated in section 2.1. Qualtrics did
anonymously provide Internet service provider (ISP) address respondent
location data (latitude and longitude) which would facilitate further
Four core Likert-type survey questions
Five response option
range
How likely are you to refer to your current vulnerability
assessment on a monthly basis?
How likely are you to refer to your current vulnerability
assessment to help allocate resources to the community
you serve?
How likely would you support your agency budget
paying for your current vulnerability assessment if it
was not required by DHS/FEMA?
If you do use a vulnerability assessment (like SoVI or
SVI), please rate how effectively it helps you allocate
resources to the community you serve from “very
effective” to “not effective at all"
Very unlikely to Very
likely
Very unlikely to Very
likely
Very unlikely to Very
likely
Not effective at all to
Very effective
analysis of the responses. The assumption was made that, especially
during the height of the coronavirus travel restrictions when the survey
took place, US emergency managers ISP location would likely mimic the
location of the community they serve in.
3. Focused literature review
The current state of vulnerability assessments accepts the aggregation of indicators without knowing which variable is most associated
with that community’s vulnerability or which variable may actually be
masking this correlation, potentially skewing the equitable distribution
of resources which is defined here by three main categories including
financial, policy, and technical assistance [36]. Subjectively weighting
one of the 30 or more socioeconomic variables like age, residential
property, or occupation [37] higher than another, potentially more
locally relevant variable, like poverty, can produce misrepresentative
results [5,19]. Additionally, it is not evident which variable contributes
most to community vulnerability or that one vulnerability assessment is
compatible with another which could be a significant impediment to the
Sustainable Development Goals of the Sendai Framework [5]. This same
study found conflicting outputs at a national and international level
between comparative vulnerability index studies (e.g., SoVI or SVI) that
use qualitative methods and self-assessment studies that use qualitative
inputs.
While composite indicators used in vulnerability indices may provide a smaller scale digest of complex issues, they can also result in
misleading or overly simplistic policy conclusions [15]. The amount of
data needed to compile vulnerability indices may be out of reach of
many local resilience bodies without the expense of a consultant or team
of consultants. Supporting mapping software expenses (direct or via
consultant fees), from an industry leader like ESRI, can exceed US$12,
000 with annual maintenance fees of US$3000 or more [38]. However,
statisticians may consider an aggregation of indicators that result in a
single measure to carry minimal practical significance. Saisana et al.
[15] describe the ease with which a single output like this to quickly
form policy is irresistible. Others question the applicability of these
indices for hazard mitigation. “These benefits of indices make it likely
they will continue to be attractive to stakeholders, practitioners, and
decision makers, despite counterarguments that generalized aggregated
indices are too blunt an instrument to be used for specific hazard mitigation interventions” [16]. Chang et al. [1] determined that the
assessment of vulnerability factors has shown little value for local
disaster managers attempting to equitably allocate resources.
Ilbeigi and Jagupilla [21] concluded that SoVI has “critical shortcomings” and “might be misleading.” These authors also note that not all
vulnerable populations occupy physically vulnerable locations. Large,
scenic US coastal cities, for example, tend to attract higher income
groups despite the physical exposure to shocks [21]. This relates to the
concept of resilience which is defined here as ‘‘the ability to prepare and
plan for, absorb, recover from, and more successfully adapt to adverse
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events” [39]. This also speaks to two divergent frameworks of disaster
resource distribution: equal versus equitable. Higher-income individuals
occupying scenic coastal areas have access to insurance, bureaucratic
and political agency, and attractive options for temporary or even permanent living alternatives (e.g., second homes) [31]. Therefore, equitable emergency management resource allocation may need to give
more to those who appear to be impacted less than those who absorb the
greater physical impact but are intrinsically more resilient due to their
income. Equal distribution of resources (or even weighted to address the
‘greatest physical impact’), on the other hand, may disproportionately
benefit those already more resilient while areas of ‘lesser physical
impact’ may represent the greatest assault on short and long-term,
whole-community resilience.
Today, however, resources are often directed towards the greatest
physical damage and not necessarily the most vulnerable [6,40] which
implies vulnerability mapping may not be connecting to disaster management efforts on the ground or that the mapping is flawed. “While we
found flood recovery assistance to be strongly associated with physical
damage overall the relationship was more tenuous in places with higher
social vulnerability” [40]. The current state of social vulnerability
literature has numerous studies that demonstrate the inequitable distribution of resources through all phases of the disaster management
cycle [40].
Validating the efficacy of social vulnerability indices has also proven
to be difficult, yielding mixed or inconclusive results [16]. Subjectivity
is also inevitable since all models require the model builder to choose
between variable levels and weighting [16]. Additionally, different assessments of the same location have been shown to produce noticeably
different results [22]. “To a naïve observer, these latent variable
methods might seem like voodoo, that is, via the magic of statistics, one
can generate a quantitative description of something that they otherwise
could not observe” [22]. A more complex index can, in fact, be counterproductive to the efficient and equitable distribution of mitigation
resources when a critical variable, like poverty, is not singled out for
analysis. This variable might relate more clearly to the type of vulnerability an organization is attempting to address [17]. “SoVI® implicitly
weighs old age, making some tracts more socially vulnerable than they
should be. CDC SVI exhibits homogenous patterns of social vulnerability, so uniquely vulnerable tracts may go unnoticed” [17]. Higher
income directly correlates to increases in life expectancy [41] which
must also be considered when weighting the age variable.
The coronavirus pandemic has demonstrated the interconnectivity of
variables and how that can impact index outputs. Racial bias, for
example, is associated with age-based generalizations related to risk. In
the US, the age-based pandemic mortality rate for Blacks was 3.4 times
higher than for Whites [42]. Pandemic data are also demonstrating a
strong correlation between age, race, and income - revealing distinct
differences in infection rates and deaths at the county and zip code level
[43]. “Use of distinct social metrics (rather than summary indices) is
important to guide action: data on household crowding, poverty, and
residential segregation by race/ethnicity and income are all informative
and needed to communicate the social burdens of COVID-19” [43]. And
while SoVI and SVI consider income as one of 20, 30, or even 40 other
variables including age, race, and income, they do not, for example,
consider income distribution within neighborhoods and households. A
single parent household will have a different level of vulnerability than a
dual earner household. A single-income household led by a Latina or
African American woman will be more vulnerable than most other
households located in the same area [44]. Furthermore, neither popular
index (SoVI or SVI) includes homeless populations which can greatly
impact response and recovery [17]. Frazier et al. [20] points out two key
SoVI drawbacks. First, exposure, sensitivity, and adaptive capacity are
not included and second, SoVI is not differentially weighted for all indicators that, in turn, impact the resulting vulnerability score [20]. And
yet all of these types of indicator models, including others like the SERV
framework, are themselves vulnerable to the subjective weighting of
variables which can result in inaccurate geospatial assessments of
community vulnerability.
These models also require a complete buy-in from the emergency
management team that the aggregation of vulnerability factors produces
a metric that speaks to the specific block-level risk and resilience goals of
that community over, for example, a single variable – like poverty.
Barrett and Constas [74] maintain that the ability of an individual,
household, or community to avoid poverty is the single greatest
component of resilience. “Our work complements a flurry of recent
notes, white papers, and policy briefs on resilience, all offering measurement tools, policy and programming prescriptions, etc., but
conspicuously without any explicit theory of resilience as might be
applied to the lives of the poor” [74]. This connection between poverty
and vulnerability opposite the threat of disasters has already been well
established in the literature (e.g., Refs. [3,45–48]: [27,31,49–53].
“Poverty is an important aspect of increased social vulnerability because
of its direct association with access to resources which affects coping
with the impacts of disasters” [27]. The ongoing coronavirus pandemic
is providing further, visceral evidence about the causal relationship
between poverty and communal vulnerability. In one national pandemic
epicenter, Los Angeles County Public Health Department reported
mortality rates in areas of 30%–100% poverty that are 3.7 times higher
than areas of less than 10% poverty [54].
Glynn and Fox [55] found a direct causal relationship between rent
increases and increases in homeless populations in several major US
cities. “Communities where people spend more than 32% of their income on rent can expect a more rapid increase in homelessness” [56].
Today there is no place in the United States where full-time, minimum
wage earners can afford a two-bedroom rental. Ninety-five percent of
this same group cannot afford a one-bedroom rental [57]. In terms of
disaster mitigation and response, an increasing homeless population
directly translates into an increase in whole-community vulnerability
[56]. A Rand Corporation study revealed that, since 1975, $2.5 trillion
per year (in 2018 dollars), which is approximately 12% of GDP per year,
has been redistributed from the bottom 90% of earners to the top 1% of
Americans [75]. Between 1944 and 1974 all worker incomes in the US
rose at an even pace (or 100%) with US GDP. The rising economic tide
essentially lifted all boats. Since 1974, however, those same incomes
only increased by 17.4% of GDP [75].
A review of related literature by Hallegatte et al. [51] found that
disasters consistently increase poverty levels and reduce income levels,
and that the field of disaster management should be a part of poverty
reduction policy. For example, Hallegatte et al. [58] states that “in
relative terms, poor people always lose more than non poor people from
floods and storms” [58]. The processes that exploit poverty during disasters will only be exacerbated by climate change [48,58,59]. However,
the inability to connect post-disaster economic impacts, including
increased poverty and homelessness, to disaster management mitigation
practices prevents any kind of meaningful resiliency evaluation of those
same practices [60].
3.1. Evaluation of law and policy frameworks
The complexity of matching an accurate measure of vulnerability
with the appropriate tools to achieve successful mitigation is complicated by the law governing hazard mitigation funding and operations.
For example, Public Law 106–390, or the Disaster Mitigation Act of
2000, brings consideration of social vulnerability into hazard mitigation
planning. This bill amended the Stafford Act with the intent to streamline predisaster mitigation and control and/or lower the costs of federal
assistance. In drafting the statute, policy writers placed “effective
community partnerships’’ and reduction of loss of life, property, economic impact and disaster assistance costs as a priority. The writers also
heavily weighted the term “small impoverished communities’’ defined
in the law as “… a community of 3000 or fewer individuals that is
economically disadvantaged, as determined by the State in which the
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International Journal of Disaster Risk Reduction 63 (2021) 102464
community is located and based on criteria established by the President”
[61]. Reading these sections together, along with the Senate Report on
the legislation, it is clear that FEMA has funds designated to use technical tools to improve the assessment of community vulnerability,
generally speaking and specifically for these kinds of communities
(Senate Report PL 106–390). Based on the interpretation of the Disaster
Mitigation Act of 2000 and other barriers noted herein (e.g., time, skill,
and cost), where social vulnerability assessment tools are needed, the
agency should elect to use the most specific, time sensitive, accessible,
and cost-effective tool available. This is particularly critical when
working with those which qualify as “small impoverished communities.”
Six years later, Congress would deepen its focus on impoverished
communities and the broader issue of social vulnerability. In the aftermath of Katrina, the “Post-Katrina Emergency Reform Act of 2006” [62]
was written to address the harsh lessons learned about poverty,
vulnerability, and governance from that event. In particular, the legislation focused on understanding and serving the disabled, providing
temporary “social safety net” assistance related to housing, rental payments, and unemployment, as well as eliminating the denial of other
government benefits based on receiving this assistance. The bill added
additional emphasis on assistance to communities, both financial and
technical, while also ensuring more agency involvement in recovery. In
short, addressing poverty and vulnerability became more important in
emergency management [62]. When considering the need to assess
communities’ that have been hit hard by a disaster, assessors have to
consider pre-existing vulnerabilities alongside other damage caused by
the event. Expediency, availability, and cost-effectiveness should
dominate the consideration of assessment tools. Knowing this is the
intent of the law, how does the use of these relatively expensive tools
realistically fit within the framework of disaster mitigation?
This is a question not only being posed at the state and local level in
the United States, but at the international level as well. Referring to the
growing sets of social vulnerability assessment tools, the United Nations
Development Programme (UNDP) offers a cautious description of their
implementation in its own handbook:
analytical tools and in planning generally. This is an area ripe for further
research as this matrix tends to support that existing poverty and
vulnerability begets sustained or even increased poverty and
vulnerability.
In the international context, the term “impoverished” could be
about: funding, income levels, the harms of poor governance regimes in
the country, as well as neo-colonial attitudes within aid agencies. The
outcome for those managing and planning for catastrophic events will be
similar in terms of having to make difficult decisions about tools and
planning. The specific contextual analysis, again, is ripe for further
research. Here, we discuss whether, with respect to SoVI and SVI,
renewed consideration about the variables, availability, and uses will
yield uses and outcomes closer to the Sendai Framework goal of “freely
available and (widely) accessible”.
3.2. SoVI and SVI
The home of the Social Vulnerability Index (SoVI) is the Hazards and
Vulnerability Institute at the University of South Carolina. This institute
also houses the International Centre of Excellence in Vulnerability and
Resilience Metrics (ICoE-VaRM). The website indicated that it “collaborates with the International Digital Belt and Road (DBAR) Research
Program through their Center of Big Earth Data for Coasts (ICoE-Coasts),
NOAA’s Carolinas Integrated Sciences and Assessments (CISA) program,
and the University of South Carolina’s Artificial Intelligence Institute.”
Just within the University of South Carolina, there is an abundance of
opportunity to proliferate the index for academic purposes. In theoretical discussions, the indicators are used to broadly describe social
vulnerability in the context of resource mapping or to help with machine
learning and artificial intelligence development. SoVI is an index created
by Dr. Susan Cutter and other academics at the University of South
Carolina’s Hazards and Vulnerability Institute. It was developed as
“Social Vulnerability to Environmental Hazards” and intended for use by
stakeholders at the county level [17]. This index is about managing
disaster risk or developing tools for disaster risk reduction via the lens of
social vulnerability.
The CDC’s SVI was created by the Centers for Disease Control Agency
for Toxic Substances and Disease registry to identify populations that
would need more resources in the event of a disaster or emergency
(CDC’s Social Vulnerability Index (SVI), 2020). This is a public good,
released freely online and updated in a biannual report. It uses 15 variables from the U.S. Census. Those variables are ranked by impact on
vulnerability to come up with a vulnerability index and subsequent
‘scores’ for communities. Most of the data used by these two vulnerability assessment frameworks comes from the US Census, which is
common but not perfect, demonstrating margins of error consistently
over 10% (US Census Bureau, n.d.) and often over 30% [22]. The key
differences are that SVI is a public good and SoVI comes with a cost; one
is about resource allocation (or other creative uses by those using the
information) and the other is about disaster risk reduction. Despite their
broad use, both indices have inconsistencies as demonstrated in recent
literature and detailed in section 3.0 of this study.
“A number of issues and challenges arise in defining and mapping the
socially vulnerable population within climate change adaptation and
disaster risk assessment frameworks. The variety of parameters used to
determine social vulnerability includes, but is not limited to, income
disparity, gender, age, disability, language, literacy or family status.
However, personal characteristics can be linked to vulnerability, but not
define it. Group approach is widespread because it is easy to administer
and use for targeting the population, but it largely ignores the internal
heterogeneity of groups” [63].
Further, the Sendai Framework for Disaster Risk Reduction [64],
which encompasses both the risk reduction and vulnerability planning
goals of both SoVI and the CDC’s SVI, requires actors “… to systematically evaluate, record, share and publicly account for disaster losses and
understand the economic, social, health, education, environmental and
cultural heritage impacts, as appropriate, in the context of event-specific
hazard-exposure and vulnerability information.” Additionally, this
framework requires stakeholders to “make non-sensitive hazard-exposure, vulnerability, risk, disaster and loss-disaggregated information freely available and accessible, as appropriate” [64]. Looking at the
international perspective offered from both organizational and principled perspectives, it is important to ask about the heterogeneity of the
variables as suggested by the UNDP, but also to question the meaning of
“freely available and accessible.” For those in emergency management
related positions in the United States, particularly within these “small
impoverished communities” contemplated in the Disaster Mitigation Act
of 2000, this could be a budget question. Current emergency management and disaster science thinking rarely delves into the commonsense
nexus between poor communities, lack of tax revenue, and the difficult
decisions the two create for emergency managers when choosing
4. Results: case study comparisons
4.1. Case study 1: Roane County, Tennessee
In their article titled Developing a Climate-Induced Social Vulnerability
Index for Urban Areas: A Case Study of East Tennessee, Omitaomu and
Carvalhaes [65]. developed a social vulnerability assessment using the
CDC’s SVI model. The authors ultimately use this assessment to analyze
climate change vulnerability in the same area. See Appendix 10.1 for
more detail on this study’s methodology. In terms of resource allocation,
Omitaomu and Carvalhaes [65] focused on the equitable development
of greenspace within more vulnerable communities. The study also
points out that green space development can have the opposite effect on
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International Journal of Disaster Risk Reduction 63 (2021) 102464
poorer communities by inviting gentrification and higher taxes which
ultimately displaces those communities [65]. Fig. 2 shows an excerpt
from one of the counties this study analyzed during their SVI map
generation. Scores closer to 1 represent greater social vulnerability
while those closer to 0 represent lower vulnerability.
With reference to Fig. 3, results of this case study indicate an unequivocally strong similarity between, not only the two distinct areas of
high vulnerability within Roane County, Tennessee but also those areas
of lesser vulnerability. There were no notable areas of dissimilarity.
case, the 15-min PVM displayed patterns of vulnerability that were
highly similar to the more complex models. In some cases, small areas on
the PVM only showed patterns that were somewhat similar, but this was
generally attributable to the more refined gradations that the SoVI/SVI
map legends showed. When, for example, the top two highest levels of
vulnerability were matched to the PVM’s Low Income category, any
minor dissimilarities would lessen. Notably, there was not a single PVM
created that displayed areas that were not similar at all to the more
complex map products. This demonstrates the significance of the
poverty variable when determining vulnerability while raising concerns
(noted in the literature review) that aggregated indices may average out
this significance. This is combined with the concern that the related
policy frameworks (section 3.1) are encouraging the use of these indices.
4.2. Case study 2: US regional SoVI
In their article titled Risks of sea level rise to disadvantaged communities
in the United States, Martinich et al. [66] used SoVI in their study of four
key US regions to analyze social vulnerability opposite the effect of
climate change and sea-level rise (SLR). Fig. 4 shows one of four regions
analyzed using SoVI. See Appendix 10.2 for more detail on this study’s
methodology. In terms of resource allocation, Martinich et al. [66]
attempt to determine if populations displaying higher social vulnerability have the ability to harden their communities against SLR or if
relocation may be a more viable use of available resources. “In effect,
areas at risk of SLR, but with low levels of social vulnerability, should be
able to effectively respond to this risk by fortifying shores or nourishing
beaches, while more socially vulnerable populations would be more
likely to have fewer resources within their communities to respond in
this manner [66].
Fig. 5 shows the same region using the 15-min PVM method. Results
of this case study again indicate a strong similarity between patterns of
vulnerability seen within this regional scale map product and no obvious
areas showing a strong dissimilarity. In particular, areas south of the
Philadelphia, Baltimore, and Washington labels are strikingly similar.
The SoVI map product represents a finer granularity in vulnerability
classifications, showing a five-level vulnerability range whereas the
related PVM only shows two (Low Income and Not Low Income).
However, the similarity tended to increase when the highest two SoVI
vulnerability levels were compared to the Low Income areas from the
PVM.
A total of six of these case studies were conducted. The two comparisons chosen for publication had the highest resolution and represented the results of all six case studies. The other four included:
Flanagan et al. [67,68]; Rufat et al. [19]; and Lehnert et al. [69]. In each
5. Results: survey OF US emergency managers
A nationwide survey was emailed to 3108 emergency managers or
those acting in an emergency management role for their US state,
county, or sub-county public agency. From this contact list, 267 contacts
“bounced” indicating those emails were no longer valid or active. This
left a total survey pool of 2841 contacts from which 485 responded
equaling a 17% response rate. The first two gateway questions further
reduced the participant size. Question 1 (Can you confirm that you are an
emergency manager, coordinator, or work in a related role for the community
you serve?) yielded 19 “No” responses which left 466 to potentially
respond to the four core survey questions. However, 100 potential respondents dropped out of the survey after Question 1, possibly realizing
they did not qualify or for other reasons like connectivity. This left a net
pool of 366 participants. Question 2 (Does your agency use a community
vulnerability assessment tool like SoVI or SVI?) yielded 247 “No” responses
and 52 “Do Not Know” which, combined, represented 81% of the
remaining participants. This left 67 US EM professionals and seven of
those failed to continue, leaving a group of 60 for the final four questions. This moved this survey classification to that of a pilot survey
which has been shown to have value in advancing the literature (e.g.,
Refs. [70,71].
Location data provided by Qualtrics were overlaid onto the response
locations from the questions in Table 2 to attempt to identify any
poverty-related trends. Again, using AGOL software with the Low Income
Community Census Tracts - 2016 ACS data layer (reference section 2.2),
each response location was analyzed to determine if responses came
Fig. 2. Roane County, Tennessee vulnerability using SVI from Omitaomu and Carvalhaes [65].
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International Journal of Disaster Risk Reduction 63 (2021) 102464
Figs. 3. 15-min PVM of Roane County, Tennessee that matches Fig. 2 study area.
Fig. 4. One of regional SoVI maps produced by Martinich et al. [66].
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International Journal of Disaster Risk Reduction 63 (2021) 102464
Figs. 5. 15-min PVM of US region that matches Fig. 4 study area.
from a “Low Income” area or a “Not Low Income” area. Trends were
recognized in Questions 4 through 6 (See Table 3).
While the sample size of this pilot survey is not robust enough to
support standalone claims, it is reasonable to infer from the trends noted
in Table 3 that the popularity of the available vulnerability assessments
tends to lean toward areas that are “Not Low Income.” This result is
supported by the literature review that suggests that the nationallydriven vulnerability framework may not be supporting the most
vulnerable communities. These survey findings also support the call for
a more comprehensive nationwide survey.
practice of emergency management within poorer communities.
Meanwhile the efficacy of the most popular indicator models has also
come into question. “Present practice has two key limitations that may
restrict their use or potentially lead to poor decisions being made in their
implementation – low use of direct measures of disaster resilience and
low use of sensitivity and uncertainty analysis” [5]. The aggregation of
multiple variables can dull the complicity of a single one. All indicator
models are susceptible to the subjectivity of input and weighting of
variables [22] which can result in conflicting mitigation policy recommendations based on the framework that was used [18]. As stated
earlier, the aim of this study is not to discount the historic and potential
future value of the indicator approach. Before the advent of these
models, social vulnerability was rarely discussed and, moving forward,
their value could be more widely utilized with their limitations in plain
sight. However, it is clear from the literature alone that there needs to be
better utility of, and access to, vulnerability assessments - especially
within the most vulnerable communities.
The strong correlation between poverty and social vulnerability was
not only evident in the literature but also in the case study map comparisons from section 4.0. The PVM examples executed in a short time
span by a moderately experienced operator demonstrated how significant a single variable can be in determining vulnerability. The operator
experience and time allotment also attempted to address (or at least
acknowledge) the access poorer communities have to mitigation resources like more complex, time consuming, and costly vulnerability
modeling. Simply considering poverty as a common denominator to
many forms of vulnerability in many communities may ironically lead to
a more freely available and widely accessible means for those very
communities to mitigate their own vulnerability. The PVM case studies
were not conducted to advocate for whole community risk reduction
based on the single variable of poverty but to provide a lens from which
6. Discussion
This study conducted a focused literature review, reviewed legal
frameworks, produced comparative geospatial vulnerability map case
studies, and conducted a nationwide pilot survey of emergency management professionals. The results of the focused review clearly show
flaws in the current vulnerability assessment indices that are federally
mandated. Whether it is the issue of variable heterogeneity, oversimplified outputs discussed by the UNDP, or the lack of free availability
and wide access called for by the Sendai Framework, the literature
points to problems with each. Next, previous research supports a troubling, and increasingly plausible, connection between the lack of tax
revenue in poorer communities leading to less access to tools by emergency managers to assess and mitigate vulnerability. FEMA may be
unknowingly contributing to a cycle that moves the true potential of the
indicator approach further and further away from influencing mitigation in the poorest, most vulnerable communities. The maxim that
vulnerability begets vulnerability may, in turn, be supported by FEMA
grant programs that encourage the inclusion of vulnerability assessments (often by paid consultants) that are less and less accessible to the
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International Journal of Disaster Risk Reduction 63 (2021) 102464
might be underused nationally. Additionally, those that were using the
SoVI or SVI models and found it to be either effective or very effective
tended to be from areas that were “Not Low Income.” In fact, Questions 4
through 6 demonstrated this trend where communities that were “Not
Low Income” tended to be the ones favoring these popular assessment
tools. (see Table 3). While the literature supports the plausibility of this
connection, additional research that captures a larger sample size from
the emergency management community is required to verify and add
depth to this relationship. As the first-known survey of its kind, the
overall results also point to the need for a more robust sample size that
might include follow up, semi-structured interviews to determine, for
example, in what manner vulnerability assessments are being used and
how that use benefits the vulnerable populations in that community.
This could perhaps be conducted anonymously by FEMA but as part of
the grant program process discussed in section 3.0.
Assessments should drive mitigation and the simplicity of access to
the poverty variable, as shown in this study, points to how key variables
can be accessed and used for mitigation in the most underserved and
poorest areas in the US. While looking at a single variable may be less
complex, time consuming, and costly, it also ensures that this variable is
not averaged out. SoVI and SVI are not necessarily the wrong tools but
their normalization within the DHS/FEMA agency structure may also be
normalizing higher income community access to less accessible indicator driven assessments. This inadvertently leads to vulnerability in
poorer communities begetting higher vulnerability to future shocks in
those same communities.
Table 2
Aggregated core question results.
Question
Number
Question Text
Very
Unlikely +
Unlikely
Neither
(Neutral)
Likely +
Very Likely
3
How likely are you to
refer to your current
vulnerability
assessment on a
monthly basis?
How likely are you to
refer to your current
vulnerability
assessment to help
allocate resources to
the community you
serve?
How likely would
you support your
agency budget
paying for your
current vulnerability
assessment if it was
not required by DHS/
FEMA?
Question Text
38%
29%
33%
18%
15%
67%
35%
12%
53%
Not
effective at
all þ Not
very
effective
Neither
(Neutral)
Effective
þ Very
Effective
If you do use a
vulnerability
assessment (like SoVI
or SVI), please rate
how effectively it
helps you allocate
resources to the
community you serve
from “very effective”
to “not effective at
all"
13%
28%
59%
4
5
Question
Number
6
7. Conclusion
Thinking through the variety of uses for which these indices are
deployed and why, in addition to suggesting more accessible routes to
their benefits is one approach. Another is to review the policies which
incentivize the use of these indices and suggest changes that can help
socialize and operationalize some alternative approaches. Many times,
they are used in mitigation planning and for participation in FEMA’s
Hazard Mitigation Grant Program, which in 2020 was renamed the
Building Resilient Infrastructure and Communities (BRIC) Grant Program. The program funds mitigation projects as well as capacity building and management costs. In the mitigation eligibility section,
identifying and developing programs that impact “underserved” communities and populations rates high with the first updated activity
language reading, “Updating the risk and vulnerability assessment based
on new information, including supporting studies, such as economic
analyses, mapping, risk assessment, and planning” [72]. Much like the
preceding program, this one will require or incentivize the use of
vulnerability assessment tools for the grant program itself and to be
incorporated into other planning activities. Thus SoVI, CDC’s SVI, and
similar tools are in play in this program as a matter of policy. FEMA
could add flexibility into the program by moving beyond a focus on risk
and vulnerability to one which considers equity, as it has done in the
“Handbook on Expanding Equity” which focuses on operationalized
equity internal to the agency and externally. This handbook acknowledges the CDC’s SVI as part of their approach [73].
Looking at this framework, there are suggestions which address some
of the root causes of the vulnerabilities and how to overcome them. One
suggestion is simply working in concert with community leaders. The
agency should encourage this engagement, which will reveal more
practical truths about vulnerability than mapping and point data alone,
as a qualifier for the grant program. For applicants in disaster prone
states where assessments have consistently been done in the past, and
are still within a reasonable period of the last assessment (10 years for
census based indicators); those applicants should be allowed to base
assessments on factors that reflect the greatest community need and be
able to qualify. For example, a community in a hurricane prone state
that was also hit hard by COVID-19 may want to view hazard mitigation
from the lenses of increased poverty because of the pandemic’s
Table 3
Low income versus not low income response trends.
Question
Number
Question Text
Trend Noted
4
How likely are you to refer to
your current vulnerability
assessment to help allocate
resources to the community you
serve?
How likely would you support
your agency budget paying for
your current vulnerability
assessment if it was not required
by DHS/FEMA?
If you do use a vulnerability
assessment (like SoVI or SVI),
please rate how effectively it
helps you allocate resources to
the community you serve from
“very effective” to “not effective
at all"
67% of respondents answered
Likely or Very Likely of those,
32.5% were in Low Income areas
and 67.5% were in Not Low
Income areas
54% of respondents answered
Likely or Very Likely of those,
34% were in Low Income areas
and 66% were in Not Low
Income areas
59% of respondents answered
Effective or Very Effective of
those, 26% were in Low Income
areas and 74% were in Not Low
Income areas
5
6
a less discriminatory national vulnerability assessment model can form.
However, it is also evident from the results that poverty is a strong indicator of vulnerability and should be considered, at a minimum, as a
means to test aggregated outputs.
The national pilot survey called attention to several items. First, the
fact that 81% of respondents answered “No” or “Do Not Know” to the
second gateway question (Does your agency use a community vulnerability
assessment tool like SoVI or SVI?) suggests that these indicator models
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E. Wood et al.
International Journal of Disaster Risk Reduction 63 (2021) 102464
economic impact and population loss from the same or as a result of
severe weather. In short, the policy could be more flexible and community focused. This will give emergency managers the flexibility, time
savings, and cost to consider the best tools for their needs as opposed to
the ones favored by agency policy.
And while several studies like Rufat et al. [19] found that “there is a
mismatch between the rising application of social vulnerability models
and understanding of their empirical validity,” perhaps the emergency
and disaster management community can agree that there is an
increasing need to connect those vulnerability models to mitigation particularly in underserved communities. The necessary shift may begin
simply with an acknowledgement of the national mitigation framework’s limitations and the consideration of SoVI because it is good
enough, or the CDCs SVI because it is free and widely available. This
study demonstrated that another consideration should be checking a
single output of vulnerability derived from an aggregation of variables
against the poverty exposure indicator which takes little or no time or
cost. That irresistible temptation to jump to policy formation would
require this additional criteria that represents the poorest and most
vulnerable populations. Internationally, this could provide a practical
example that could meet the goals of the UNDP and the Sendai
Framework.
Declaration of competing interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
APPENDIX. (Case study methods)
10.1 - Omitaomu and Carvalhaes [65]
Indicators used in Omitaomu and Carvalhaes [65] are shown below in a table from that study. It is important to note that these authors weighted
each indicator equally in an attempt to avoid subjectivity. “This subjectivity would require a tortuous justification for each weight given as a
comprehensive reference for weighing these components is not yet clear” [65].
Table 2
List of the 15 ACS 2008–2012 variables used as indicators for the SVI and calculation methods to obtain final indicators to be used in the index. Colors correspond to the
workflow diagram in Fig. 2.
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International Journal of Disaster Risk Reduction 63 (2021) 102464
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International Journal of Disaster Risk Reduction 63 (2021) 102464
10.2 - Martinich et al. [66]
Martinich et al. [66] display the dominant variables used in their study’s Table 1 graphic below. The authors state that weighting for each regional
component in their study is available upon request but mention that they employ an equal weighting of components as seen in Cutter et al. [4]. “The
authors find that the manner in which the components are combined to create the final index does have a substantial impact on the end results, but
they make no alternative weighting recommendation” [66].
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International Journal of Disaster Risk Reduction 63 (2021) 102464
Table 1
Components for each regional analysis in the contiguous United States. The table displays the Social Vulnerability Index components, including the dominant variables
and their associated variance explained for each regional principle components analysis
North Atlantic
South Atlantic
Gulf
Pacific
Component
Percent
Variance
Explained
Component
Percent
Variance
Explained
Component
Percent
Variance
Explained
Component
Percent
Variance
Explained
Poverty
Rural/Urban
Age (elderly)
Foreign- born
Age (children)
Occupation
Female
22.5
11.4
10.5
8.8
7.4
5.4
5.0
Poverty
Family structure
Rural/Urban
Foreign-born
Native American/Female
Occupation
20.3
17.5
11.4
10.0
6.6
4.8
Poverty
Labor force participation
Foreign-born
Wealth
Rural/Urban
Occupation
Female
22.4
16.6
12.3
8.2
5.6
4.4
4.0
Poverty
Age (children)
Rural/Urban
Labor force participation
Female
Occupation
21.6
13.1
11.7
8.7
7.5
5.6
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