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Citation: Lu, S.; Huang, J.; Wu, J.
Knowledge Domain and
Development Trend of Urban Flood
Vulnerability Research: A
Bibliometric Analysis. Water 2023,15,
1865. https://doi.org/10.3390/
w15101865
Academic Editor: Ataur Rahman
Received: 10 April 2023
Revised: 4 May 2023
Accepted: 11 May 2023
Published: 15 May 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
water
Review
Knowledge Domain and Development Trend of Urban Flood
Vulnerability Research: A Bibliometric Analysis
Shuang Lu 1, Jianyun Huang 1, * and Jing Wu 2
1Design School, Shanghai Jiao Tong University, Shanghai 200240, China
2School of Urban Design, Wuhan University, Wuhan 430072, China
*Correspondence: jianyunhuang@sjtu.edu.cn
Abstract:
Floods have become the most prevalent and catastrophic natural hazard that plagues cities
worldwide. As an inherent characteristic of an urban system that reflects the degree of effect of
flooding and the capacity to cope with it, urban flood vulnerability is of great significance when
analyzing and managing flood disasters. To produce a better profile of the current status and the
development trend of urban flood vulnerability research, this study conducted a bibliometric analysis
using CiteSpace software based on 1134 articles sourced from the Web of Science Core Collection
database. The results showed that the annual publication number exhibited an ascending trajectory,
which was characterized by three stages: the sprouting stage, the stable development stage and
the rapid development stage. The United States, China and England were the most productive
countries. Among the top co-cited journals were Natural Hazards,Natural Hazards and Earth System
Science,Global Environmental Change and the Journal of Hydrology. In addition, the focus of this research
can be succinctly summarized as vulnerability assessments and mapping, the impact of climate
change and urbanization on urban flood vulnerability and the integration of urban flood vulnerability
with flood risk and urban resilience. This study presents a comprehensive analysis of the current
status and development trends of research related to urban flood vulnerability, and it contributes an
understanding of the key areas of focus in this field as well as insights into potential prospects for
future investigation for researchers and practitioners.
Keywords: urban flood; vulnerability; knowledge structure; bibliometrics; CiteSpace
1. Introduction
Under the combined effects of global climate change and rapid urbanization, natu-
ral disasters caused by extreme weather events increasingly threaten the environmental
security and sustainable development of cities [
1
–
3
]. Among various natural disasters,
floods are the most frequent and costly hazard worldwide, resulting in massive losses of
life and property [
4
–
7
]. According to statistics provided by the United Nations Office for
Disaster Risk Reduction (UNDRR), floods have accounted for approximately 43% of natural
disasters in the past two decades, affecting the largest population, exceeding 2 billion indi-
viduals, and resulting in substantial economic losses of USD 656 billion [
8
]. Cities, as the
centers of populations, valuable assets and economic activities, are more susceptible to the
adverse impacts caused by flood hazards [
9
–
12
]. The causes and influencing mechanisms of
flood risk are also more complex in urban areas [
13
–
15
]. Thus, it is increasingly recognized
that focusing solely on the hazard is insufficient in terms of disaster risk reduction [
16
]. In
this context, urban flood vulnerability, as an inherent feature of an urban system, which
reflects the degree of the effect of flooding and the capacity to cope with it, has become a
crucial concept for understanding and managing flood disasters [17–19].
Vulnerability, considered “the root cause of disasters” [
20
], has become a central focus
that has garnered increasing attention from academic communities focusing on disaster
management and climate change issues in recent years [
17
,
21
–
25
]. Investigating vulnerabil-
ity can assist in understanding the structural weaknesses that make a system susceptible
Water 2023,15, 1865. https://doi.org/10.3390/w15101865 https://www.mdpi.com/journal/water
Water 2023,15, 1865 2 of 23
and identifying the effectiveness of adaption and management
strategies [26,27]
. Although
there is no universal definition for vulnerability, various organizations and scholars have
tried to define vulnerability from their perspectives. For instance, Turner et al. [
28
] defined
vulnerability as “the degree to which a system, subsystem, or system component is likely
to experience harm due to exposure to a hazard, either a perturbation or stress/stressor”.
Adger [
29
] suggested that vulnerability is “the state of susceptibility to harm from exposure
to stresses associated with environmental and social change and from the absence of capac-
ity to adapt”. The IPCC describes vulnerability as “the propensity or predisposition to be
adversely affected” [
30
]. A growing number of studies have endeavored to augment the
understanding of vulnerability. Vulnerability is commonly conceptualized by scholars as a
tripartite function comprising hazard exposure, sensitivity to perturbation and adaptive
capacity to perturbation [
17
,
21
,
22
,
29
,
31
–
33
]. Additionally, vulnerability is considered to be
affected by the environmental, socio-economic, cultural and policy factors of a system, and
it should be considered to be a dynamic variable [
27
,
34
]. Srinivasan et al. [
35
] suggested
that vulnerability is spatially heterogeneous and scale-dependent.
As a distinct facet of the general concept of vulnerability, flood vulnerability in
urban areas has been extensively addressed by academic communities. According to
Balica et al. [
36
], flood vulnerability refers to “the susceptible extent of a system to floods
due to exposure, perturbation and its ability to cope, recover, or adapt”. Li et al. [
37
]
describe flood vulnerability as a combination of the flood-disaster-driver risk, the environ-
mental stability during the time of the disaster and the sensitivity of the disaster bearer.
In general, previous studies have deepened our understanding of flood vulnerability, with
contributions from various disciplines, such as hydrology, ecology, geography, landscape
science and socio-economics [
17
,
22
,
38
–
40
], and research methods and technologies have
also been evolving rapidly [
9
]. Timely reviews and summaries of the existing literature
can assist researchers and practitioners in comprehending current research hotspots and
frontiers in this field while also providing valuable insights to guide the direction of fu-
ture studies. Although many scholars have attempted to review the research progress
concerning flood vulnerability, the majority of their efforts have focused on scrutinizing
research approaches and methodologies [
9
,
31
,
41
,
42
]. There remains a lack of an inclusive
review that analyzes the overall knowledge structure and evolutionary trends of urban
flood vulnerability research.
In recent years, bibliometrics has been widely conducted as a quantitative analysis
approach in order to reveal the distribution and development of publications, discipline
characteristics, major contributing authors and institutions and research hotspots and
frontiers in a specific field of study. In the field of urban studies, bibliometric analysis has
been utilized to analyze a range of research topics, including urban resilience [
43
], urban
metabolism [
44
], healthy urban planning [
45
] and social vulnerability [
46
]. Due to the
escalating challenge of urban floods, many studies have employed bibliometric methods
to explore various aspects such as flood risk management [47], urban flood resilience [13],
sponge city [
48
] and stormwater management [
49
]. However, the studies mentioned
above did not specifically address urban flood vulnerability, and there has been limited
exploration of the temporal evolution of research hotspots and frontiers.
To fill the aforementioned research gaps, this paper aims to conduct a comprehensive
bibliometric analysis to comprehensively profile the status and development trends of
research on urban flood vulnerability. The remainder of this paper is structured as follows:
Section 2introduces the literature retrieval and bibliometric method applied in this study.
Section 3presents the results of the bibliometric analysis, including publication volume
and trend, cooperation network and research hotspots. The current status and prospects
concerning urban flood vulnerability research are discussed in Section 4. Section 5provides
a conclusion to this study.
Water 2023,15, 1865 3 of 23
2. Data and Methods
2.1. Data Acquiring and Cleaning
The Web of Science (WoS) Core Collection was selected as the literature database
to be analyzed in this study. The WoS Core Collection is the most comprehensive and
authoritative literature search engine, including the Science Citation Index Expanded
(SCIE), the Social Sciences Citation Index (SSCI) and the Arts & Humanities Citation Index
(A&HCI). It has been widely used for literature reviews and bibliometric analyses in various
fields [45,46,50–52].
In this study, the literature was searched based on the retrieval type of “Topic”,
including the title, abstract, author keywords and the keyword plus of the literature.
The topic of urban flood vulnerability includes three elements, namely “vulnerability”,
“flood” and “urban”, and the relevant terms to these three elements should be taken into
consideration when making the paper search strategy. Consequently, the following search
formula was used: TS = (“flood” OR “waterlogging”) AND TS = (“vulnerability” OR
“vulnerabilities”) AND TS = (“urban” OR “city” OR “cities”). The literature types were
limited to “article” and “review”. In addition, the literature retrieval was conducted on
29 November 2022, and the retrieval time span was unlimited (1900 to present). The
retrieval obtained 1722 documents. By manually reviewing the titles and abstracts of the
papers, irrelevant and reduplicative documents were filtered. Finally, 1134 documents were
retained and used for the subsequent analysis in this study.
2.2. Bibliometric Software and Method
The selection of the bibliometric software to be used was based on three key criteria.
To begin with, the software should be able to extract the information from the literature
automatically. Second, the software should have a variety of functions to support the
comprehensive analysis of the collected literature from multiple perspectives. Third, the
software should have a strong visualization feature to show the results. Consequently,
CiteSpace (Version 6.1.R4) was selected as the tool to be used for the bibliometric analysis
in this study. CiteSpace is a widely used multifunctional citation visualization analysis
software developed by the team of Prof. Chaomei Chen from Drexel University. This
piece of software can analyze and display a specific research field through data mining, the
processing of information and knowledge measurement. By using visualization technology,
it can generate visual knowledge maps named “mapping knowledge domains” to display
the research development process and knowledge structure.
In this study, CiteSpace was used to analyze and visualize the research status and
development trend on urban flood vulnerability in terms of research disciplines, cooper-
ation networks, and research hotspots. The multi-perspective goals were accomplished
by selecting different Node Types in the CiteSpace software. Specifically, the disciplines
involved in the urban flood vulnerability research were identified by using the Node Type
of “Category”. By setting the Node Type to “Country”, “Institution” and “Author”, the
cooperation networks at the corresponding levels in this field were explored. “Term”,
which refers to the noun phrases extracted from the title, abstract, author keyword (DE),
and the keyword plus (ID) of the literature, was selected as the Node Type to investigate
the research hotspots in different development stages during the whole study period.
3. Result
3.1. Overview of Urban Flood Vulnerability Research
3.1.1. Publication Volume and Trend
The variation in the annual publication volumes of articles related to urban flood
vulnerability is shown in Figure 1. The first article was published in 1997, and the annual
number of publications on this topic generally shows an upward trend. Based on the
annual publication numbers, the study period can be divided into three stages:
Water 2023,15, 1865 4 of 23
Water 2023, 15, x FOR PEER REVIEW 4 of 23
The sprouting stage (1997–2010): in this stage, a total of 60 articles were published,
only accounting for 5.29% of the total publications. It shows that the research on urban
flood vulnerability was in its initial stages, and scholars did not pay sufficient attention to
this field. However, there was a slight increase observed in the number of articles, from
two articles in 1997 to fifteen articles in 2010, indicating a slowly growing research interest
in this field during this stage.
The stable development stage (2011–2015): from 2011 to 2015, the number of articles
significantly increased compared to the previous stage, maintaining a relatively stable an-
nual publication number of around 36 on average. During this period, urban flood vul-
nerability began to attract stable attention from academic communities.
The rapid development stage (2016-present): the number of published articles in 2016
(66 articles) was almost twice as much as that of 2015 (38 articles), and the publication
volume showed a dramatically increasing trend, reaching a peak in 2022 (199 articles). A
total of 891 articles were published at this stage, accounting for 78.57% of the total. There-
fore, it is inferred that the field of urban flood vulnerability has attracted substantial at-
tention from academic communities and has reached a stage of flourishing development.
Figure 1. Annual publication volumes on urban flood vulnerability.
3.1.2. Discipline Categories
The participation and integration of different disciplines in the development of a cer-
tain research field can be revealed by generating a discipline co-occurrence network. Fig-
ure 2 shows the distribution of the disciplines involved in research related to urban flood
vulnerability. Each node represents a discipline, and the size of the node corresponds to
the contribution of this discipline. In addition, the dense links between various nodes in-
dicate frequent intersections between multiple disciplines. Table 1 lists the top 15 disci-
plines related to urban flood vulnerability in terms of occurrence count and the years of
their first occurrence. Five disciplines with a number of publications exceeding 200 were
identified, namely water resources (414 articles), environmental science (315 articles), ge-
oscience (289 articles), meteorology and atmosphere science (250 articles) and environ-
mental studies (205 articles). In addition, geography, civil engineering, urban studies, re-
gional and urban planning, environmental engineering and multidisciplinary science
were also significant disciplines involved in this field.
Figure 1. Annual publication volumes on urban flood vulnerability.
The sprouting stage (1997–2010): in this stage, a total of 60 articles were published,
only accounting for 5.29% of the total publications. It shows that the research on urban
flood vulnerability was in its initial stages, and scholars did not pay sufficient attention to
this field. However, there was a slight increase observed in the number of articles, from
two articles in 1997 to fifteen articles in 2010, indicating a slowly growing research interest
in this field during this stage.
The stable development stage (2011–2015): from 2011 to 2015, the number of articles
significantly increased compared to the previous stage, maintaining a relatively stable
annual publication number of around 36 on average. During this period, urban flood
vulnerability began to attract stable attention from academic communities.
The rapid development stage (2016-present): the number of published articles in 2016
(66 articles) was almost twice as much as that of 2015 (38 articles), and the publication
volume showed a dramatically increasing trend, reaching a peak in 2022 (199 articles).
A total of 891 articles were published at this stage, accounting for 78.57% of the total.
Therefore, it is inferred that the field of urban flood vulnerability has attracted substantial
attention from academic communities and has reached a stage of flourishing development.
3.1.2. Discipline Categories
The participation and integration of different disciplines in the development of a
certain research field can be revealed by generating a discipline co-occurrence network.
Figure 2shows the distribution of the disciplines involved in research related to urban flood
vulnerability. Each node represents a discipline, and the size of the node corresponds to the
contribution of this discipline. In addition, the dense links between various nodes indicate
frequent intersections between multiple disciplines. Table 1lists the top 15 disciplines
related to urban flood vulnerability in terms of occurrence count and the years of their
first occurrence. Five disciplines with a number of publications exceeding 200 were identi-
fied, namely water resources (414 articles), environmental science (315 articles), geoscience
(289 articles), meteorology and atmosphere science (250 articles) and environmental studies
(205 articles). In addition, geography, civil engineering, urban studies, regional and urban
planning, environmental engineering and multidisciplinary science were also significant
disciplines involved in this field.
Water 2023,15, 1865 5 of 23
Water 2023, 15, x FOR PEER REVIEW 5 of 23
Figure 2. Distribution of main research disciplines.
Table 1. Top 15 main disciplines.
No. Discipline Count Year
1 Water Resources 414 1997
2 Environmental Science 315 1999
3 Geoscience, Multidisciplinary 289 1999
4 Meteorology and Atmosphere Science 250 1999
5 Environmental Studies 205 2006
6 Geography 91 2005
7 Green and Sustainable Science and Technology 80 2008
8 Engineering, Civil 78 2000
9 Urban Studies 61 2006
10 Regional and Urban Planning 42 2007
11 Engineering, Environmental 39 2000
12 Geography, Physical 33 1999
13 Public, Environmental and Occupational Health 29 2008
14 Remote Sensing 22 2008
15 Multidisciplinary Science 19 2013
3.2. Cooperation Network Analysis
3.2.1. Cooperation Network of Countries
The cooperation network of the countries contributing to research related to urban
flood vulnerability is depicted in Figure 3. The size of each node represents the publication
number of a country, and the links between the nodes indicate the correlation of the coun-
try with each other. The major contributing countries mainly included the United States,
China, England, Germany, Italy, Netherlands, etc. Table 2 lists the top 10 most contrib-
uting countries in the field of urban flood vulnerability and the years of their first occur-
rences. Three countries with more than 100 publications were identified. The United States
was the country with the most publications, totaling 213 articles, followed by China and
England, which published 112 and 101 articles, respectively. Table 2 also shows the be-
tweenness centrality of each country. The betweenness centrality of a node refers to the
Figure 2. Distribution of main research disciplines.
Table 1. Top 15 main disciplines.
No. Discipline Count Year
1 Water Resources 414 1997
2 Environmental Science 315 1999
3 Geoscience, Multidisciplinary 289 1999
4 Meteorology and Atmosphere Science 250 1999
5 Environmental Studies 205 2006
6 Geography 91 2005
7Green and Sustainable Science
and Technology 80 2008
8 Engineering, Civil 78 2000
9 Urban Studies 61 2006
10 Regional and Urban Planning 42 2007
11 Engineering, Environmental 39 2000
12 Geography, Physical 33 1999
13 Public, Environmental and
Occupational Health 29 2008
14 Remote Sensing 22 2008
15 Multidisciplinary Science 19 2013
3.2. Cooperation Network Analysis
3.2.1. Cooperation Network of Countries
The cooperation network of the countries contributing to research related to urban
flood vulnerability is depicted in Figure 3. The size of each node represents the publication
number of a country, and the links between the nodes indicate the correlation of the country
with each other. The major contributing countries mainly included the United States,
China, England, Germany, Italy, Netherlands, etc. Table 2lists the top 10 most contributing
countries in the field of urban flood vulnerability and the years of their first occurrences.
Three countries with more than 100 publications were identified. The United States was the
country with the most publications, totaling 213 articles, followed by China and England,
which published 112 and 101 articles, respectively. Table 2also shows the betweenness
Water 2023,15, 1865 6 of 23
centrality of each country. The betweenness centrality of a node refers to the number of
times a node serves as the intermediary ‘bridge’ between the other nodes in the network,
and it is considered to be an indicator of the node’s importance. England, the United States,
Germany and Italy were the four countries with a betweenness centrality of more than 0.1.
Water 2023, 15, x FOR PEER REVIEW 6 of 23
number of times a node serves as the intermediary ‘bridge’ between the other nodes in
the network, and it is considered to be an indicator of the node’s importance. England, the
United States, Germany and Italy were the four countries with a betweenness centrality
of more than 0.1.
Figure 3. Cooperation network of countries.
Table 2. Top 10 major contributing countries by number of publications.
No. Country Publication Centrality Year
1 USA 233 0.31 1997
2 PEOPLES R CHINA 132 0.06 2008
3 ENGLAND 111 0.34 2005
4 GERMANY 75 0.10 2000
5 ITALY 75 0.10 2012
6 NETHERLANDS 64 0.08 2009
7 SPAIN 58 0.03 2006
8 FRANCE 57 0.05 2000
9 INDIA 55 0.05 2010
10 CANADA 51 0.06 2007
3.2.2. Cooperation Network of Institutions
Figure 4 exhibits the cooperation network and the distribution of institutions related
to urban flood vulnerability research. Each node represents an institution, and the node
size corresponds to the number of publications. The top 10 institutions with the most sig-
nificant contributions and the years of their first occurrences are listed in Table 3. Texas
A&M University, Asian Inst Technol and Arizona State University were the top three in-
stitutions with the most publications (22, 18 and 18 articles, respectively), followed by
Delft Univ Technol (16 articles) and the Chinese Academy of Science (16 articles). Regard-
ing the betweenness centrality, the Chinese Academy of Science ranked first place, with a
centrality of 0.13, and Arizona State University (0.09) and East China Normal University
(0.08) were in second and third place.
Figure 3. Cooperation network of countries.
Table 2. Top 10 major contributing countries by number of publications.
No. Country Publication Centrality Year
1 USA 233 0.31 1997
2 PEOPLES R CHINA 132 0.06 2008
3 ENGLAND 111 0.34 2005
4 GERMANY 75 0.10 2000
5 ITALY 75 0.10 2012
6 NETHERLANDS 64 0.08 2009
7 SPAIN 58 0.03 2006
8 FRANCE 57 0.05 2000
9 INDIA 55 0.05 2010
10 CANADA 51 0.06 2007
3.2.2. Cooperation Network of Institutions
Figure 4exhibits the cooperation network and the distribution of institutions related to
urban flood vulnerability research. Each node represents an institution, and the node size
corresponds to the number of publications. The top 10 institutions with the most significant
contributions and the years of their first occurrences are listed in Table 3. Texas A&M
University, Asian Inst Technol and Arizona State University were the top three institutions
with the most publications (22, 18 and 18 articles, respectively), followed by Delft Univ
Technol (16 articles) and the Chinese Academy of Science (16 articles). Regarding the
betweenness centrality, the Chinese Academy of Science ranked first place, with a centrality
Water 2023,15, 1865 7 of 23
of 0.13, and Arizona State University (0.09) and East China Normal University (0.08) were
in second and third place.
Water 2023, 15, x FOR PEER REVIEW 7 of 23
Figure 4. Cooperation network of institutions.
Table 3. Top 10 major contributing institutions by number of publications.
No. Institution Publication Centrality Year
1 Texas A&M Univ 22 0.05 2016
2 Asian Inst Technol 18 0.06 2011
3 Arizona State Univ 18 0.09 2010
4 Delft Univ Technol 16 0.06 2009
5 Chinese Acad Sci 16 0.13 2008
6 Univ Tehran 13 0.04 2014
7 Vrije Univ Amsterdam 12 0.05 2011
8 Univ Lisbon 12 0.02 2013
9 East China Normal Univ 11 0.08 2017
10 Univ Nacl Autonoma Mexico 11 0.04 2011
3.2.3. Cooperation Network of Authors
The cooperation network of authors was established, as shown in Figure 5. Each node
represents an author, and the size of the node represents the contribution of the author.
The most contributing authors and the years of their first occurrences are listed in Table
4, showing that 15 authors published five articles or more. Specifically, Irfan Ahmad Rana,
who was the leading author with the most publication (eight articles), followed by Siyu
Yu and Shangjia Dong, who both published seven articles, respectively.
Figure 4. Cooperation network of institutions.
Table 3. Top 10 major contributing institutions by number of publications.
No. Institution Publication Centrality Year
1 Texas A&M Univ 22 0.05 2016
2 Asian Inst Technol 18 0.06 2011
3 Arizona State Univ 18 0.09 2010
4 Delft Univ Technol 16 0.06 2009
5 Chinese Acad Sci 16 0.13 2008
6 Univ Tehran 13 0.04 2014
7 Vrije Univ Amsterdam 12 0.05 2011
8 Univ Lisbon 12 0.02 2013
9 East China Normal Univ 11 0.08 2017
10 Univ Nacl Autonoma Mexico 11 0.04 2011
3.2.3. Cooperation Network of Authors
The cooperation network of authors was established, as shown in Figure 5. Each node
represents an author, and the size of the node represents the contribution of the author.
The most contributing authors and the years of their first occurrences are listed in Table 4,
showing that 15 authors published five articles or more. Specifically, Irfan Ahmad Rana,
who was the leading author with the most publication (eight articles), followed by Siyu Yu
and Shangjia Dong, who both published seven articles, respectively.
Water 2023,15, 1865 8 of 23
Water 2023, 15, x FOR PEER REVIEW 8 of 23
Figure 5. Cooperation network of authors.
Table 4. Top 15 major contributing authors by number of publications.
No. Author Publication Year
1 Rana, Irfan Ahmad 8 2016
2 Yu, Siyu 7 2019
3 Dong, Shangjia 7 2019
4 Jamshed, Ali 6 2019
5 Birkmann, Joern 6 2018
6 Mostafavi, Ali 6 2019
7 Amoako, Clifford 6 2016
8 Park, Kiyong 6 2019
9 Zahmatkesh, Zahra 5 2014
10 Farahmand, Hamed 5 2019
11 Miguez, Marcelo Gomes 5 2019
12 Karamouz, Mohammad 5 2014
13 Oulahen, Greg 5 2015
14 Yu, Dapeng 5 2017
15 Eakin, Hallie 5 2010
3.3. Co-Citation Analysis
3.3.1. Co-Cited Journals
Journal co-citation analysis can reflect academic contribution and influence in the re-
search field of urban flood vulnerability in terms of various journals [52]. The network of
co-cited journals was generated, and it is visualized in Figure 6. Each node represents a
major cited journal of which the size reflects the co-citation frequency of the correspond-
ing journal. Table 5 shows the top 10 journals in terms of co-citation frequency, their im-
pact factors and their publishers. Natural Hazards was the most frequently cited journal in
terms of research relating to urban flood vulnerability, with a co-cited frequency of 624.
Other major influential journals included Natural Hazards and Earth System Science (417
citations), Global Environmental Change (410 citations), the Journal of Hydrology (388
Figure 5. Cooperation network of authors.
Table 4. Top 15 major contributing authors by number of publications.
No. Author Publication Year
1 Rana, Irfan Ahmad 8 2016
2 Yu, Siyu 7 2019
3 Dong, Shangjia 7 2019
4 Jamshed, Ali 6 2019
5 Birkmann, Joern 6 2018
6 Mostafavi, Ali 6 2019
7 Amoako, Clifford 6 2016
8 Park, Kiyong 6 2019
9 Zahmatkesh, Zahra 5 2014
10 Farahmand, Hamed 5 2019
11 Miguez, Marcelo Gomes 5 2019
12 Karamouz, Mohammad 5 2014
13 Oulahen, Greg 5 2015
14 Yu, Dapeng 5 2017
15 Eakin, Hallie 5 2010
3.3. Co-Citation Analysis
3.3.1. Co-Cited Journals
Journal co-citation analysis can reflect academic contribution and influence in the
research field of urban flood vulnerability in terms of various journals [
52
]. The network of
co-cited journals was generated, and it is visualized in Figure 6. Each node represents a
major cited journal of which the size reflects the co-citation frequency of the corresponding
journal. Table 5shows the top 10 journals in terms of co-citation frequency, their impact
factors and their publishers. Natural Hazards was the most frequently cited journal in terms
of research relating to urban flood vulnerability, with a co-cited frequency of 624. Other
major influential journals included Natural Hazards and Earth System Science (417 citations),
Global Environmental Change (410 citations), the Journal of Hydrology (388 citations) and the
International Journal of Disaster Risk Reduction (308 citations). The above top journals were
Water 2023,15, 1865 9 of 23
cited most frequently, indicating that these journals have made significant contributions to
urban flood vulnerability research.
Water 2023, 15, x FOR PEER REVIEW 9 of 23
citations) and the International Journal of Disaster Risk Reduction (308 citations). The above
top journals were cited most frequently, indicating that these journals have made signifi-
cant contributions to urban flood vulnerability research.
Figure 6. Network of co-cited journals.
Table 5. Top 10 journals by co-cited frequency.
No. Journal Citation IF (2021) Publisher
1 Natural Hazards 624 3.158 SPRINGER
2 Natural Hazards and Earth System Sciences 417 4.58
COPERNICUS
GESELLSCHAFT
MBH
3 Global Environmental Change 410 11.16 ELSEVIER
4 Journal of Hydrology 388 6.708 ELSEVIER
5 International Journal of Disaster Risk Reduction 308 4.842 ELSEVIER
6 Climatic Change 277 5.174 SPRINGER
7 Water 260 3.53 MDPI
8 Journal of Flood Risk Management 258 4.005 WILEY
9 Science of The Total Environment 253 10.754 ELSEVIER
10 PNAS 226 12.779
NATL ACAD SCI-
ENCES
3.3.2. Co-Cited Literature
Literature co-citation analysis can be used to identify the most influential documents
and summarize the primary academic achievements in the research field [53]. Figure 7
shows the network of co-cited articles in the field of urban flood vulnerability. Each node
represents an article, and the node size represents the citation frequency of the article.
Table 6 lists the top 10 most influential articles in this field by citation frequency, their
authors and the years of their publications. The article by E.E. Koks et al. (2015) [54]was
the most-cited, with 30 citations, which was followed by the article by S.F. Balica et al.
(2012) [55]and the article by S. Rufat et al. (2015) [56].
Figure 6. Network of co-cited journals.
Table 5. Top 10 journals by co-cited frequency.
No. Journal Citation IF (2021) Publisher
1Natural Hazards 624 3.158 SPRINGER
2Natural Hazards and Earth
System Sciences 417 4.58
COPERNICUS
GESELLSCHAFT
MBH
3Global Environmental Change 410 11.16 ELSEVIER
4Journal of Hydrology 388 6.708 ELSEVIER
5International Journal of Disaster
Risk Reduction 308 4.842 ELSEVIER
6Climatic Change 277 5.174 SPRINGER
7Water 260 3.53 MDPI
8Journal of Flood Risk Management 258 4.005 WILEY
9Science of The Total Environment 253 10.754 ELSEVIER
10 PNAS 226 12.779 NATL ACAD
SCIENCES
3.3.2. Co-Cited Literature
Literature co-citation analysis can be used to identify the most influential documents
and summarize the primary academic achievements in the research field [
53
]. Figure 7
shows the network of co-cited articles in the field of urban flood vulnerability. Each node
represents an article, and the node size represents the citation frequency of the article.
Table 6lists the top 10 most influential articles in this field by citation frequency, their
authors and the years of their publications. The article by E.E. Koks et al. (2015) [
54
] was
the most-cited, with 30 citations, which was followed by the article by S.F. Balica et al.
(2012) [55] and the article by S. Rufat et al. (2015) [56].
Water 2023,15, 1865 10 of 23
Water 2023, 15, x FOR PEER REVIEW 10 of 23
Figure 7. Network of co-cited references.
Table 6. Top 10 highly cited references.
No. Title Authors Citation Year
1
Combining hazard, exposure and social vul-
nerability to provide lessons for flood risk
management [54]
Koks, E. E et al. 30 2015
2
A flood vulnerability index for coastal cities
and its use in assessing climate change impacts
[55]
Balica, S. F et al. 23 2012
3 Social vulnerability to floods: Review of case
studies and implications for measurement [56] Rufat, S et al. 23 2015
4 Future flood losses in major coastal cities [57] Hallegatte, S et al. 22 2013
5
Application of GIS-Interval Rough AHP Meth-
odology for Flood Hazard Mapping in Urban
Areas [58]
Gigović, L et al. 19 2017
6 The impact of flooding on road transport: A
depth-disruption function [59]
Pregnolato, M et
al. 18 2017
7 Integrating human behaviour dynamics into
flood disaster risk assessment [60]
Aerts, J. C. J. H et
al. 18 2018
8
Evaluating the impact and risk of pluvial flash
flood on intra-urban road network: A case
study in the city center of Shanghai, China [61]
Yin, J et al. 17 2016
9
Urban flood risk mapping using the GARP and
QUEST models: A comparative study of ma-
chine learning techniques [62]
Darabi, H et al. 17 2019
10 Framing vulnerability, risk and societal re-
sponses: the MOVE framework [16] Birkmann, J et al. 16 2013
From the perspective of research hotspots, the majority of the top 10 most cited arti-
cles focused on evaluating the holistic risks and impacts caused by flood disasters. Koks
et al. [54] proposed a framework for a joint assessment of flood hazard, exposure and
vulnerability to evaluate the effects of flood risk management strategies. Gigović et al. [58]
and Darabi et al. [62] produced a flood risk map by adopting a GIS multi-criteria
Figure 7. Network of co-cited references.
Table 6. Top 10 highly cited references.
No. Title Authors Citation Year
1
Combining hazard, exposure and social
vulnerability to provide lessons for flood
risk management [54]
Koks, E. E et al. 30 2015
2
A flood vulnerability index for coastal
cities and its use in assessing climate
change impacts [55]
Balica, S. F et al. 23 2012
3
Social vulnerability to floods: Review of
case studies and implications for
measurement [56]
Rufat, S et al. 23 2015
4Future flood losses in major coastal
cities [57]Hallegatte, S et al. 22 2013
5
Application of GIS-Interval Rough AHP
Methodology for Flood Hazard Mapping
in Urban Areas [58]
Gigovi´c, L et al. 19 2017
6
The impact of flooding on road transport:
A depth-disruption function [59]Pregnolato, M et al. 18 2017
7Integrating human behaviour dynamics
into flood disaster risk assessment [60]Aerts, J. C. J. H et al. 18 2018
8
Evaluating the impact and risk of pluvial
flash flood on intra-urban road network:
A case study in the city center of
Shanghai, China [61]
Yin, J et al. 17 2016
9
Urban flood risk mapping using the
GARP and QUEST models: A
comparative study of machine learning
techniques [62]
Darabi, H et al. 17 2019
10 Framing vulnerability, risk and societal
responses: the MOVE framework [16]Birkmann, J et al. 16 2013
Water 2023,15, 1865 11 of 23
From the perspective of research hotspots, the majority of the top 10 most cited
articles focused on evaluating the holistic risks and impacts caused by flood disasters.
Koks et al. [54]
proposed a framework for a joint assessment of flood hazard, exposure and
vulnerability to evaluate the effects of flood risk management strategies. Gigovi´c et al. [
58
]
and Darabi et al. [
62
] produced a flood risk map by adopting a GIS multi-criteria method-
ology and machine learning technologies, respectively. Hallegatte et al. [
57
] quantified
present and future flood losses and identified the most vulnerable cities where the most
significant losses were expected. Balica et al. [
55
] developed a flood vulnerability index
for coastal cities, and Birkmann et al. [
16
] outlined a systematic vulnerability assessment
framework to conceptualize the multi-faceted nature of vulnerability.
On the other hand, the other articles mainly focused on a certain specific issue related
to urban flood vulnerability. Rufat et al. [
56
] profiled the leading factors influencing social
vulnerability to flood disasters. Aerts et al. [
60
] emphasized that integrating societal behav-
ior can be conducive to more accurately assessing flood risk and management strategies.
Pregnolato et al. [
59
] and Yin et al. [
61
] investigated the impacts of floods on road transport
networks. By reviewing the top 10 cited articles, a consensus can be drawn that vulnera-
bility is regarded as a crucial aspect of flood risk analysis and management. The scholars
endeavored to enhance the effectiveness of flood risk assessment and response strate-
gies coping with flood disasters by promoting a comprehensive understanding of urban
flood vulnerability.
3.4. Term Analysis
3.4.1. Term Co-Occurrence Analysis
Term co-occurrence analysis can provide insights into the thematic focuses of the
research field [
43
,
44
]. Based on the statistical analysis using CiteSpace software, 252 terms
with an occurrence frequency of five or more were detected. Figure 8visualizes the term
co-occurrence network during the whole study period, in which each node represents a
term, and the size of the node represents the occurrence frequency of the term. In addition,
each link between the different nodes denotes the strength of the co-occurrence between the
two terms. Table 7summarizes the top 20% of newly emerged terms in three different stages
and the years of their first to explore more detailed information concerning the research
hotspots and reveal the temporal evolution of research topics. From 1997 to 2010, the
research in this field was in its initial creative period, with the most high-frequency terms,
totaling 122, accounting for 48.41% of the total. From 2011 to 2015, although the number
of publications increased significantly, the number of new terms inversely decreased to
107 (42.46% of the total). Since 2016, the emergence of new terms has significantly reduced
in spite of the exponential growth of publication numbers. This phenomenon may be
explained by the fact that most of the relevant terms have already been defined during the
previous stages. Based on the high-frequency terms, the research focuses can be reflected
from multiple perspectives, including research content, research methods, research subjects
and research contexts.
Water 2023,15, 1865 12 of 23
Water 2023, 15, x FOR PEER REVIEW 12 of 23
Figure 8. Term co-occurrence network of urban flood vulnerability research.
Table 7. Top 20% new terms in three stages by occurrence frequency.
Term Frequency Centrality Yea
r
Sprouting Stage (1997–2010)
climate change 270 0.01 1999
flood risk 258 0.01 2004
urban area 164 0.02 2004
flood hazard 135 0.03 2005
geographic information system 110 0.01 2007
social vulnerability 95 0.02 2009
sea level rise 90 0.03 1999
urban flooding 76 0.02 2000
vulnerability assessment 74 0.01 1999
flood risk management 61 0.01 2009
natural hazards 57 0.01 2007
urban planning 56 0.01 2004
risk assessment 55 0.01 2010
adaptation 52 0.14 1999
coastal flooding 49 0.07 1999
coastal area 48 0.03 2008
urban development 42 0.03 1997
flood risk assessment 42 0.03 2009
coastal cities 39 0.05 2008
vulnerable area 38 0.01 2010
flood damage 35 0.02 2009
developing countries 35 0.01 2010
Stable Development Stage (2011–2015)
resilience 54 0.02 2011
analytical hierarchy process 40 0.02 2013
disaster risk reduction 38 0.03 2012
urban resilience 30 0.02 2012
spatial distribution 26 0.02 2011
sensitivity analysis 23 0.01 2012
spatial analysis 22 0.01 2013
extreme weather event 21 0.01 2012
flood impacts 18 0.01 2013
urban growth 17 0.01 2011
Figure 8. Term co-occurrence network of urban flood vulnerability research.
Table 7. Top 20% new terms in three stages by occurrence frequency.
Term Frequency Centrality Year
Sprouting Stage (1997–2010)
climate change 270 0.01 1999
flood risk 258 0.01 2004
urban area 164 0.02 2004
flood hazard 135 0.03 2005
geographic information system 110 0.01 2007
social vulnerability 95 0.02 2009
sea level rise 90 0.03 1999
urban flooding 76 0.02 2000
vulnerability assessment 74 0.01 1999
flood risk management 61 0.01 2009
natural hazards 57 0.01 2007
urban planning 56 0.01 2004
risk assessment 55 0.01 2010
adaptation 52 0.14 1999
coastal flooding 49 0.07 1999
coastal area 48 0.03 2008
urban development 42 0.03 1997
flood risk assessment 42 0.03 2009
coastal cities 39 0.05 2008
vulnerable area 38 0.01 2010
flood damage 35 0.02 2009
developing countries 35 0.01 2010
Stable Development Stage (2011–2015)
resilience 54 0.02 2011
analytical hierarchy process 40 0.02 2013
disaster risk reduction 38 0.03 2012
urban resilience 30 0.02 2012
spatial distribution 26 0.02 2011
sensitivity analysis 23 0.01 2012
Water 2023,15, 1865 13 of 23
Table 7. Cont.
Term Frequency Centrality Year
spatial analysis 22 0.01 2013
extreme weather event 21 0.01 2012
flood impacts 18 0.01 2013
urban growth 17 0.01 2011
metropolitan area 17 0.01 2011
rapid urbanization 15 0.01 2011
global south 15 0.02 2011
road network 15 0 2014
global climate change 12 0.01 2013
flood depth 12 0 2013
census data 11 0 2013
physical vulnerability 11 0.01 2014
population density 10 0.01 2011
Rapid Development stage (2016-present)
community vulnerability 11 0 2018
land use planning 9 0 2018
hydraulic model 9 0 2018
land cover 9 0 2021
machine learning 8 0 2021
Note(s): To emphasize the more representative terms, the terms with broad meanings (e.g., vulnerability and
flood) were removed from the term list. For the duplicated terms (e.g., sea level rise and sea-level rise, geographic
information system and gis), only one term was kept.
From 1997 to 2010, the term that most frequently occurred was Climate change, with
an occurrence frequency of 270, and it is the term with the highest occurrence frequency
throughout the entire study period. On the one hand, research relating to urban flood
vulnerability developed in the context of increasing frequencies and intensities of flood
events caused by climate change. On the other hand, climate change can be regarded as
the most important factor influencing urban flood vulnerability. Several terms related
to natural hazards (e.g., flood hazard and sea level rise) and those related to urbanization
(e.g.,
urban development
) can also be considered influential factors. Social vulnerability and
vulnerability assessment indicated that the research mainly focused on the social aspect of
urban flood vulnerability and the evaluation of urban flood vulnerability at this stage.
The information related to research methods was also reflected. Geographic information
system was widely adopted in this stage. Vulnerability index,social vulnerability index and
flood vulnerability index, which were not included in the top 20% of terms, as shown in
Table 7, also emerged, indicating that an indicator-based approach was a mainstream
method during this stage. In addition, the research subject and geographic distribution
in this field were reflected by urban area, coastal area,coastal cities and developing countries,
indicating that the cities in coastal areas and developing countries received significant
attention. Moreover, flood risk,flood risk management and flood risk assessment demonstrated a
significant correlation between flood vulnerability and flood risk.
From 2011 to 2015, the emergence of resilience (the most frequent term in this stage)
and urban resilience represented that the researchers had been associating urban flood vul-
nerability with the concept of urban resilience. The terms, including extreme weather event,
urban growth,rapid urbanization,road network and population density, represented the fact
that the impacts of climate change and urbanization on urban flood vulnerability received
enduring attention. Spatial distribution and spatial analysis reflected that the spatial variation
of urban flood vulnerability had become a fresh research hotspot during this stage. Mean-
while, some terms, which were not included in the top 20%, such as physical vulnerability,
socio-economic vulnerability and environmental vulnerability, also emerged, indicating that
urban flood vulnerability was started to be explored from more diversified aspects in this
stage. The terms related to research methods entered the peak emerging period in this
stage. Analytical hierarchy process was the most significant method, followed by sensitivity
analysis. In addition, other terms related to research methods and data, such as principle
Water 2023,15, 1865 14 of 23
component analysis,field survey,vulnerability curve,census data and remote sense (not shown in
Table 7), were also involved. The most important new subject term was metropolitan area,
and global south also emerged as a main research subject.
Since 2016, during the rapid development stage, community vulnerability has been the
newly emerged term with the highest occurrence frequency. The attention to the impact
of urban development was maintained, which was reflected by land use planning and land
cover. In terms of research methods, hydraulic model and storm water management model (not
shown in Table 7) reflected the fact that hydrological modeling approaches had become
one of the mainstream methods. In addition, with the recent development of big data
technology, machine learning was also involved in this field. The terms related to research
subjects were generally consistent with those in the previous period, which were mainly
focused on developing countries (e.g., Accra,Ghana and Brazil, which were not shown in
Table 7).
3.4.2. Timeline of Term Clusters
Figure 9shows the timeline of the top 10 most significant clusters in the field of urban
flood vulnerability. Among these clusters, “climate change” had the longest duration,
which existed throughout the entire study period from 1997 to the present. It is regarded
as the most significant factor influencing urban flood vulnerability. The cluster with the
largest size was “flood risk management”, which was active from 1999 to 2019. In this
paper, flood risk management was considered to be an important objective of urban flood
vulnerability studies. The main terms under this cluster included adaption opinions,impact
assessment,flood intensity,risk reduction, etc.
Water 2023, 15, x FOR PEER REVIEW 14 of 23
Since 2016, during the rapid development stage, community vulnerability has been the
newly emerged term with the highest occurrence frequency. The attention to the impact
of urban development was maintained, which was reflected by land use planning and land
cover. In terms of research methods, hydraulic model and storm water management model (not
shown in Table 7) reflected the fact that hydrological modeling approaches had become
one of the mainstream methods. In addition, with the recent development of big data tech-
nology, machine learning was also involved in this field. The terms related to research sub-
jects were generally consistent with those in the previous period, which were mainly fo-
cused on developing countries (e.g., Accra, Ghana and Brazil, which were not shown in
Table 7).
3.4.2. Timeline of Term Clusters
Figure 9 shows the timeline of the top 10 most significant clusters in the field of urban
flood vulnerability. Among these clusters, “climate change” had the longest duration,
which existed throughout the entire study period from 1997 to the present. It is regarded
as the most significant factor influencing urban flood vulnerability. The cluster with the
largest size was “flood risk management”, which was active from 1999 to 2019. In this
paper, flood risk management was considered to be an important objective of urban flood
vulnerability studies. The main terms under this cluster included adaption opinions, impact
assessment, flood intensity, risk reduction, etc.
Figure 9. Term clusters of urban flood vulnerability research.
The clusters of “urban flood”, “vulnerability assessment” and “flood hazard map”
also emerged in the early phase of the study period and maintained active until the pre-
sent. Specifically, “urban flood” and “flood hazard map” involved the key terms includ-
ing fluvial flood, flood modeling, urban flood prediction and geospatial analysis. These two clus-
ters indicated that the hydrological process of flood disasters attracted constant attention
from the academic community. In addition, “vulnerability assessment”, of which the main
terms included social vulnerability and indicator-based approach, reflected that the evaluation
of urban flood vulnerability was a core topic of urban flood vulnerability research.
Since the mid-term of the study period (around 2005), “urban areas” and “land use
change” became significant clusters, with the key terms of building construction, social en-
vironment, ecosystem service, etc. The appearance of these two clusters may be a sign that
Figure 9. Term clusters of urban flood vulnerability research.
The clusters of “urban flood”, “vulnerability assessment” and “flood hazard map”
also emerged in the early phase of the study period and maintained active until the present.
Specifically, “urban flood” and “flood hazard map” involved the key terms including
fluvial flood,flood modeling,urban flood prediction and geospatial analysis. These two clusters
indicated that the hydrological process of flood disasters attracted constant attention from
the academic community. In addition, “vulnerability assessment”, of which the main terms
included social vulnerability and indicator-based approach, reflected that the evaluation of
urban flood vulnerability was a core topic of urban flood vulnerability research.
Water 2023,15, 1865 15 of 23
Since the mid-term of the study period (around 2005), “urban areas” and “land use
change” became significant clusters, with the key terms of building construction,social
environment,ecosystem service, etc. The appearance of these two clusters may be a sign
that the attention of studies in this field started to broaden, from flood hazards to the
characteristics of the built environment of urban systems. In addition, “urban resilience”
and “flood resilience” also emerged during this period, indicating that one of the objectives
of the studies is to support the establishment and promotion of resilient cities. Furthermore,
“vulnerability mapping” was the latest cluster, appearing around 2011, emphasizing that
the spatial distribution of high-vulnerability areas has received increasing attention.
4. Discussion
4.1. Current Research Focuses of Urban Flood Vulnerability
This study reveals the research focuses and development trajectory of urban flood vul-
nerability studies by analyzing the term co-occurrence network and term cluster evolution
of this field. Based on the previous results, the major research focuses present in this field
are as follows:
“Flood risk management” is observed as the largest cluster in the CiteSpace analy-
sis. It reveals the significant correlation between urban flood vulnerability and flood risk
management, which is confirmed through the previous analysis of the top-cited literature.
Flood vulnerability is widely considered to be one of the fundamental components of
flood risk function, juxtaposed with hazard and exposure [
63
–
66
]. Flood risk is a compre-
hensive concept integrating the probability of flood hazards and the degree of negative
consequences [
67
]. Fuchs et al. [
68
] argued that the consequences of a natural hazard
are significantly connected to the vulnerability of the elements at risk, irrespective of the
magnitude and spatial extent of the hazards. In other words, flood vulnerability can be
regarded as a partial perspective of flood risk focusing on describing the inclination and
potential to suffer losses or damage due to flood hazards [
69
]. Consequently, a more precise
perception of flood risk, which is considered to be a crucial prerequisite in terms of flood
risk reduction, can be achieved by exploring a more comprehensive understanding of
vulnerability [9,70–72].
The term clusters of “urban resilience” and “flood resilience” show that current
studies commonly associate urban flood vulnerability with urban resilience. In general,
flood vulnerability and flood resilience are two overlapping and distinguishing concepts.
Flood resilience is widely accepted as a holistic conceptual framework for flood mitigation
that emphasizes the integration of the ability to tolerate flooding and to reorganize in
the face of disruption [
4
,
73
–
75
]. Meanwhile, flood vulnerability primarily focuses on the
exposure and potential damage to the social–ecological system [
22
]. Moreover, several
studies have further explored the relationship between flood vulnerability and resilience.
For instance, Sun et al. [
76
] suggest that clarifying the correlation between vulnerability
and resilience is beneficial for comprehensively quantifying flood resilience. Meanwhile,
Song et al. [
77
] indicate that the deficiency and inequality of adaption resources to flood
disasters can exacerbate the vulnerability of urban areas. In contrast, the assessment of
vulnerability may provide important implications regarding flood resilience enhancement,
particularly in relation to advising the allocation of resources. Percival and Teeuw [
78
] point
out that assessing vulnerability can contribute to more effectively targeting interventions to
enhance resilience.
The term cluster of “vulnerability assessment” appeared during the very early stage,
indicating that assessing vulnerability is a central topic throughout the entire study period.
Previous studies have endeavored to profile the fundamental characteristics underlying
flood vulnerability. For the temporal evolution of research, the research mainly concen-
trated on the perspectives of public policies, topographic conditions and the hydraulic
characteristics of floods in the first decade [
79
–
82
]. Although a few studies also glanced at
social-demographical features, these features were not emphasized in this period [
83
,
84
].
However, since 2009, terms such as social vulnerability,socio-economic vulnerability and com-
Water 2023,15, 1865 16 of 23
munity vulnerability have emerged, indicating that the diversified aspects of flood vulnera-
bility were emphasized in the theoretical research. In terms of the research methodology,
the major approaches applied for vulnerability assessment included the indicator-based
method [
18
,
55
,
85
–
87
] and vulnerability curve [
88
,
89
]. The indicator-based method was
most dominant in this field, and was applied to various study subjects and scales, and the in-
dicators were usually selected by the researchers based on their respective objectives [
90
,
91
].
During this process, various studies selected a wide range of indicators, including, but not
limited to, demographic structure, socio-economic status, employment and education situ-
ation, household composition, coping capacity, etc. [
38
,
54
,
56
,
86
,
92
]. Moreover, the weight
of each indicator was mainly identified by using the analytical hierarchy process [
72
,
93
,
94
]
or principal component analysis [86,95,96]. On the other hand, the vulnerability curve (or
function) was mainly used to assess the physical dimension of flood vulnerability based on
exploring the relationship between flood hazard and the degree of damage or loss [89,97].
Terms such as spatial pattern and spatial distribution, and the cluster “vulnerability map-
ping”, which started to emerge from the mid-term of the study period, reflect that analyzing
the spatial characteristics of urban flood vulnerability is an important research topic. Iden-
tifying the spatial variation of vulnerable areas to flood is an essential task for vulnerability
assessment as it can facilitate decision makers in establishing more effective management
policies and strategic planning to prevent and mitigate flood
impacts [18,19,42,98]
. Previ-
ous studies have attempted to map the vulnerability to flood at various scales, including the
city scale, district scale and community scale [
18
,
55
,
99
,
100
]. The main approaches involved
included modeling methods based on GIS [
19
,
94
,
101
], flood models [
102
,
103
], coupled
models [
40
,
104
,
105
], machine learning algorithms [
106
–
108
], etc. GIS-based modeling and
flood modeling were two types of tools commonly used to identify flood-prone areas.
GIS-based modeling mainly determined the potential inundation area simply through
topography analysis and only required the DEM of the study area and the peak level of
floodwater [
109
]. Flood modeling involved hydrological and hydrodynamic principles to
simulate the rainfall–runoff process, which can provide more precise outcomes, whereas
more computation time and data were required [
109
]. Furthermore, with the recent devel-
opment of artificial intelligence technologies, machine learning algorithms have proven
reliable for urban flood vulnerability analysis without the need for costly field surveys and
complicated hydrodynamic modeling [62,107].
The result of term analysis also highlights the correlation research investigating the im-
pacts of climate change and urbanization on urban flood vulnerability. Term co-occurrence
analysis shows that the influential factors affecting urban flood vulnerability can be grouped
into the factors related to climate change and those related to urbanization. The term clus-
ters of “land use change” and “climate change” also confirm the academic attention on the
correlation between climate change, the urbanization process and urban flood vulnerability.
Many scholars have investigated the role of climate change in altering flood hazards and
vulnerabilities. It is evident that climate change has a significant correlation with a series of
natural phenomena, such as aggravating sea level rise and changing precipitation patterns,
resulting in the increasing frequency and intensity of flood hazards [
110
–
114
]. In addition,
the physical vulnerability of individuals to floods can be further affected due to physical
instability and drowning caused by changes in flood hazards [
115
]. On the other hand, the
impact of the urbanization process on flood vulnerability is also discussed widely. The
sprawl of cities and the increasing impervious surfaces due to the process of urbanization
have altered the hydrological processes in urban areas, increasing surface runoff [
116
,
117
].
Moreover, the concentration of population, infrastructure and assets in urban areas can lead
to higher potential losses in terms of lives and property when flood events occur [15,118].
In terms of the research subjects, the term co-occurrence network indicates that the
cities in the coastal area and developing countries are highly concentrated. Coastal areas are
not only more likely to aggregate populations, settlements and human activities but are
also commonly located in lower-lying areas where flood hazards can be exacerbated by
subsidence and sea level rise. Therefore, case studies concerning urban flood vulnerability
Water 2023,15, 1865 17 of 23
in coastal areas were largely observed during the entire study period [
78
,
82
,
95
,
119
–
121
].
Furthermore, the cooperation network of countries shows that the practical applications
were mainly initially conducted in developed countries in North America and Europe in the
earlier stage. However, the result of term analysis indicates that developing countries have
received enduring attention recently, including Brazil [
122
], Ghana [
123
], Nigeria [
124
],
Indonesia [
125
], Malaysia [
126
], Vietnam [
127
], etc. It is believed that developing countries
are more vulnerable to flood events due to the rapidly increasing population, disorderly
urban planning and inadequate infrastructure [42,128,129].
4.2. Future Prospects
In the context of global climate change and urbanization processes, research concerning
urban flood vulnerability is expected to maintain a continuously expanding trend in the
future. The following prospects for future research are proposed with the goal of inspiring
researchers and practitioners with new insights for promoting the development progress in
this field.
Initially, the optimization of vulnerability assessment is expected to be a significant
direction for future research. With the development of research in this field, the scope
of flood vulnerability has been expanded to various dimensions, and a wide range of
indicators to assess vulnerability has been identified. However, the vulnerability is mainly
evaluated by obtaining a “total vulnerability score” without considering the interaction
between the different indicators. In addition, there is also a lack of investigation into
the situational variability of flood vulnerability indicators. For instance, the effect of the
same indicator on flood vulnerability may be diametrically opposed in different scenarios.
Consequently, urban flood vulnerability needs to be evaluated while considering the
intersection between the indicators and the temporal variations of specific indicators
throughout the progression of flood disasters.
Moreover, an in-depth study combing flood vulnerability with flood risk and flood
resilience also deserves further attention. Research related to urban flood vulnerability
is recognized as being closely related to these two concepts. Vulnerability has become
increasingly crucial in research concerning flood risk, and researchers are expected to
continually seek ways to mitigate flood risk from the perspective of reducing urban flood
vulnerability. In addition, a growing number of studies have attempted to combine flood
vulnerability with flood resilience. However, more endeavors are necessary to adequately
elaborate their intrinsic connection. Therefore, the intrinsic relationship between flood
vulnerability, flood risk and flood resilience can be further investigated in the future.
5. Conclusions
This study retrieved 1134 articles on urban flood vulnerability published between 1997
and 2022 from the WoS Core Collection database and undertook a bibliometric analysis
using CiteSpace software to depict the research status and development trends in this
field. The literature was comprehensively reviewed from multiple perspectives, including
publication volumes and trends, distribution of disciplines, cooperation networks in terms
of countries, institutions and authors, co-citation analysis of journals and literature, as well
as term analysis.
This study concludes that the development of research related to urban flood vul-
nerability has exhibited an upward trajectory, characterized by three stages in terms of
publication volumes: the sprouting stage, the stable development stage and the rapid de-
velopment stage. During the process, there has been a clear trend towards interdisciplinary
studies in this field, with water resources, environmental science and geoscience being the
major disciplines involved. In addition, the United States, China, England and Germany
provided the most publications among all of the countries involved in this field. Texas
A&M University, Asian Inst Technol, Arizona State University, Delft Univ Technol and
the Chinese Academy of Science were among the top institutions in terms of publication
number. In terms of co-citation analysis, Natural Hazards,Natural Hazards and Earth Sys-
Water 2023,15, 1865 18 of 23
tem Sciences and Global Climate Change were the top-cited journals. The most influential
literature was the article proposed by Koks et al. in 2015 [
54
]. Based on the results of
term co-occurrence analysis and term cluster analysis, vulnerability assessment and map-
ping emerge as primary research focuses. The research has evolved from a narrow focus
on physical vulnerability to integrating a multidimensional exploration of vulnerability,
including social, economic and community dimensions. Additionally, investigating the
impacts of climate change and urbanization on urban flood vulnerability has become an
enduring research topic, while integrating urban flood vulnerability with flood risk and
urban resilience has also become a significant area of interest. Furthermore, this study also
suggests potential areas of interest for future research in this field, including the further
optimization of vulnerability assessments and in-depth studies considering the intrinsic
relationships between flood vulnerability, flood risk and flood resilience.
This study fills the gap by providing a holistic panorama of the entire research status
and the development process on urban flood vulnerability, which has been lacking in
previous studies. It contributes to grasping the current mainstream research topics in this
field for researchers and practitioners, as well as obtaining insights into the prospects for
future research.
On the other hand, despite the contributions made in this study, the following lim-
itations still exist. To begin with, the literature collection in this study was based on the
data in the WoS Core Collection with the language set of English, leading to the omission
of publications from other databases and those written in languages other than English.
Non-academic documents, such as book reviews, government policies and documents
published by other authoritative organizations were also excluded from this study. Thus,
a more comprehensive consideration of multiple databases with various document types
and languages is necessary. In addition, the outcomes of the literature in the WoS Core
Collection significantly depend on the settings applied in the search strategies. With the
update of relevant research, more keywords and document types can be involved in search
strategies to collect more detailed information. Furthermore, several different bibliometric
analysis tools have been developed, such as VOSviewer, HistCite, SATI, etc. Approaches
combining various tools can be attempted to improve the performance of the literature
analysis and visualization.
Author Contributions:
Conceptualization, S.L., J.H. and J.W.; methodology, S.L; software, J.H.;
validation, S.L., J.H. and J.W.; formal analysis, S.L.; investigation, S.L.; resources, S.L.; data curation,
S.L.; writing—original draft preparation, S.L.; writing—review and editing, S.L.; visualization, J.H.;
supervision, J.H. and J.W.; project administration, J.H.; funding acquisition, J.H. All authors have
read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Data Availability Statement:
The data presented in this study are available on request from the
corresponding author.
Conflicts of Interest: The authors declare no conflict of interest.
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