Flooding and health in Australia: a scoping review and coauthorship analysis of published research

Abstract

Background

Australia is frequently affected by floods, and their severity and frequency are predicted to increase due to the effects of climate change. Over the past decade, there has been an increase in the number of publications reporting on the health impacts of flooding in Australia, but no synthesis of this research evidence has previously been published. The aim of this scoping review is to identify and map publications on the health impacts of flooding in Australia and to describe the networks of researchers contributing to this research.

Methods

In the study, we applied the scoping review methodology guided by Johanna Briggs Institute and coauthorship network analysis. Searches were conducted in MEDLINE, Embase, PsycINFO, CINHAL, Scopus and Web of Science for all publications up to 31 December 2023. Screening, full-text review and data extraction were completed by two independent reviewers. Coauthor networks were constructed using social network analysis methods.

Results

69 publications were included, spanning a 70-year period from 1951 to 2023. The top three health impacts studied were post-traumatic stress disorder (PTSD), distress and child developmental outcomes, with the predominant focus in the past 10 years of recent publications on prenatal maternal stress, child outcomes and mental health impacts. There was minimal focus on socially vulnerable groups and long-term health impacts and few qualitative research studies were reported. Coauthorship analysis showed the primarily disease-specific nature of flood-related research.

Conclusion

Our review enhances understanding of the research on the physical and mental health impacts of flooding in Australia by identifying the areas of relatively greater research activity, existing research gaps and potential future research priorities. Given the context-dependent nature of flood and other climate-related health impacts, and of mitigation and adaptation responses, we anticipate that our review findings will enhance the understanding of this topic for Australia and other higher-income countries, identifying areas of focus and current research gaps.

STRENGTHS AND LIMITATIONS OF THIS STUDY

• The study’s methodological strengths include the use of a published protocol and adherence to the JBI methodological approach for scoping reviews.

• A comprehensive search strategy focussed on primary research studies that have been published in journals that are indexed in six major bibliographic databases.

• We excluded grey literature, theses, peer-reviewed commentaries and perspectives, and we did not conduct manual searching; hence, some publications relevant to the topic are not included in this review.

• Screening and data extraction were conducted independently by two reviewers, with discussions to reach consensus at each stage.

Introduction

Globally, floods have been the most frequent type of weather-related disaster,^{1 2} and their frequency and severity are predicted to increase due to the effects of climate change.^{1 3} Parts of Australia have often been affected by floods, including in 2022 and 2023 when devasting floods swept through many communities on the east coast.⁴,⁷

Previous international systematic reviews document the various physical and mental health impacts of flooding.⁸,¹² Physical impacts include injury, infectious disease outbreaks, malnutrition, lower birth rates and an increase in the occurrence or severity of chronic diseases.⁹,¹² Mental health impacts include anxiety, post-traumatic stress disorder (PTSD), depression, distress, insomnia, nightmares and suicidal ideation.⁸,¹⁰¹²

Flooding and climate-related extreme weather events more generally have differential impacts across population groups.^{13 14} These events expose and exacerbate existing inequalities and render some population groups more vulnerable to physical and mental health impacts.^{15 16} These groups, here referred to as ‘priority populations’, include people living with socioeconomic disadvantage,¹³¹⁷,¹⁹ those in rural locations,^{20 21} people with disability and their carers,^{22 23} Aboriginal and Torres Strait Islander communities,^{19 24} those who identify as LGBTIQ+,²⁵ children and young people^{13 26 27} and older people.²⁸

In recent years, there has been increased research attention on the physical and mental health impacts caused by flooding in Australia, but until now, the published evidence on the range of impacts studied, methodological challenges (eg, defining exposure to flooding) or the collaborative research networks engaged in this field have not been systematically examined.

Mapping of coauthorship networks provides a nuanced perspective on a research area by enhancing our understanding of influential contributors’ attributes and popular spheres for collaboration, while also uncovering peripheral themes within the broader area, unique perspectives and fragmented parts of the research landscape.^{29 30} By visualising collaboration patterns, tools of network analysis can reveal the structural organisation of research interactions, highlighting authors and institutions that play a key role in connecting the field around focal topics. By visually mapping these patterns, researchers can better understand the current state of the field and pinpoint areas of low collaboration as well as identify opportunities for establishing new partnerships that could strengthen the field by bridging uncovered gaps. Ultimately, bibliometric network mapping can guide future research directions.

Therefore, the aim of this scoping review is to identify and map publications on the health impacts of flooding in Australia and to describe the networks of researchers contributing to this research. Given the context-dependent nature of flood and other climate-related impacts on health and of mitigation and adaptation responses, we anticipate that our review findings will enhance the understanding of this topic for Australia and other higher-income countries and identify areas of focus and gaps in the current research.

Methods

In the study, we applied the scoping review methodology guided by the work of JBI^{31 32} (formerly known as the Johanna Briggs Institute) and Levac and colleagues’³³ and coauthorship network analysis (as described by Fonseca et al³⁴ in their health sector analysis). The scoping review steps were conducted in accordance with a published a priori protocol.³⁵ Reporting was guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR).³⁶ Neither critical appraisal nor risk-of-bias assessment of identified publications was conducted, consistent with the JBI methodology.³²

Locating the authors of this manuscript

Our research team, affiliated with the University of Sydney, brings together diverse expertise in areas such as flooding and health, disaster risk reduction, climate change adaptation, public health and network analysis. Six authors (JB, BA, JL, RMc, GM and RB) are based at the University Centre for Rural Health (UCRH) in the Northern Rivers region of New South Wales (NSW), a region prone to flooding. Following the 2017 floods in the Northern Rivers, the UCRH team conceived the ‘After the Flood’ study³⁷ to investigate the differential mental health impacts of flooding. JB, JL, GM and RB have published findings from this study, with several of these publications being relevant to this review. As academic researchers in a rural-based centre with a focus on health inequities and priority populations, we were uniquely positioned to respond to the flooding events. While our research interests naturally aligned with these issues, the serendipitous timing of the floods heightened both the relevance and urgency of our work in the Northern Rivers region.

Research question

The research question was as follows: ‘What is the scope of research into the health impacts of flooding in Australia’.

The sub-questions for the review were as follows:

1. What are the characteristics of the research in terms of year of publication, setting, rurality of study setting, study design and period of study?

2. Which physical and mental health impacts have been examined?

3. Do the publications examine impacts for priority populations, if so, which groups?

4. How is flood exposure measured or described?

5. Which researchers are publishing in the field, and how are they connected to other researchers, as reflected by the coauthorship on publications?

Relevant literature identification

An initial search was conducted on Medline and Google Scholar to identify publications on the topic and create a list of relevant search terms. A full search strategy was developed in Medline in consultation with an academic librarian (KE) and experts on the health impacts of climate change (JB, RB, JL, GM and EJ). We searched Medline (OVID-SP), Embase (OVID-SP), CINHAL (EBSCO), Scopus (Elsevier) and Web of Science (Clarivate) for publications from the earliest date covered by each database up to 31 December 2023. Online supplemental file 1 contains the full search strategy.

Study selection

Inclusion criteria were identified and refined by the review team, according to the schema set out by JBI as follows.

Population

Populations impacted by flooding, through either direct or indirect exposure. Indirect exposure occurs when individuals’ mental or physical health is affected through mechanisms other than damage to health by personal contact with floodwaters or through damage/loss of personal property by floodwaters.²⁴ Such indirect impacts may occur through disruptions to transportation, availability of services in areas affected by the flood, perceptions of responsible agencies’ responses to the flood event or mental impacts on individuals of general community distress/disruption.

Concepts

This review considered all publications related to two concepts: (1) our focus is on all types of flooding; (2) the mental health or physical health impacts of flooding. Publications that were related only to health service and system disruption were excluded. Publications that presented aggregated results across multiple exposures (ie, not specific to flooding) were excluded.

Context

This review considered publications set in Australia. International publications that included Australia and other countries were reviewed if we could identify specific data on the health impacts of flooding on Australian populations.

Types of evidence sources

Primary research results from peer-reviewed literature, including quantitative, qualitative and mixed-method study designs were included. For this scoping review, we performed empirical research on the topic; therefore, study protocols, conference abstracts, conference proceedings, letters to the editor, discussion papers, editorials, commentaries and opinion papers were excluded. Grey literature and reviews, such as scoping and systematic reviews, were excluded. We treated separate papers that address different questions through different analyses of the same dataset or follow-up data on the same cohort as separate publications.

The search results were imported into Covidence³⁸ for duplicate removal, screening and data extraction. Two independent reviewers (JB and BA) conducted the title and abstract screening and full-text screening using the predefined inclusion and exclusion criteria. Discrepancies between the reviewers about the eligibility of a publication were resolved through discussion, and, where required, consultation with the senior author (RB) was done.

Data extraction

Data were extracted by two independent reviewers (JB and BA) using a data extraction tool created in COVIDENCE and available in online supplemental file 2. Any points of uncertainty in extraction were checked with the senior author (RB), and disagreements were resolved through discussion. This section outlines the categorisation process for data extraction.

Organisations

The affiliations of the authors (as per their citation on publications) were coded into universities/research institutes; hospitals/medical centres; government; non-government; and independent consultants. The following criteria were used to categorise publications:

• The author’s university rather than their specific department and, if named, the research institute rather than the university.

• Where authors identified a rural health department of the university—for example, University Centre for Rural Health, University of Sydney—we used this affiliation.

• Government—refers to departments in the government at local, state and national levels.

• Non-government organisation—refers to a voluntary, non-profit group formed by individuals or organisations that operate independently of government control—for example, Royal Life Saving Australia.

Region of the study setting

Five categories were developed: (1) urban; (2) rural; (3) remote; (4) rural and remote; and (5) general. The ‘general’ category relates to, for example, state-wide or national studies.

Timing of study of outcomes in relation to time of flood events

We categorised publications based on the timing and period of outcome data collection in relation to when the flood event occurred. For example, retrospective publications that investigated the number of flood-related drownings were categorised as ‘at the time of flood/retrospective analyses’; publications related to the longer-term health outcomes from the Queensland Flood Study (QF2011)³⁹ were classified according to the time period between the flood event and the final assessment of outcomes for the children affected by it.

Flood exposure

We identified four approaches to flood exposure measurement: (1) mapping/records of rainfall and/or river heights; (2) self-report to a structured questionnaire; (3) self/witness reports (eg, in police or mortality data); (4) not specified.

Health impacts

We developed six categories of health impacts to reflect the focus of the publications included in our study: (1) vector-borne disease; (2) mental health and well-being; (3) mental and physical health; (4) physical health; (5) mortality; and (6) prenatal stress and child development. We decided that a combined category of ‘mental and physical health’ was needed to cover publications that reported the impacts of both, as distinct from those that reported on either physical health or mental health and well-being. While ‘vector-borne disease’ could be included under ‘physical health’, we identified this as a separate category because of the different mechanisms by which flooding may contribute to vector-borne disease as compared with other aspects of physical health. Similarly, ‘prenatal stress and child development’ could have been included under ‘mental health and wellbeing’, or ‘physical health’ or ‘mental and physical health’ depending on the health outcome reported, but we identified this as a separate category because of the relatively specific focus of multiple publications based on data relating to the 2011 Brisbane floods.

Within the category of ‘mental health and wellbeing’, we identified four sub-categories: (1) symptoms of mental disorders or illnesses—for example, depression, anxiety, PTSD and suicidal ideation—that are often the focus of standard screening tools; (2) other symptoms of mental distress—for example, tension, distress, instability, social/emotional and behavioural mental health and attention issues—that were generally less clearly or specifically defined; (3) general assessment of mental health—for example, life satisfaction, coping style, perceived mental health, temperament, sleep quality; (4) positive traits—for example, stoicism and post-traumatic growth. Within the category of physical health, we identified seven sub-categories: (1) infectious disease; (2) physical symptoms/non-specified illness/disease; (3) general self-assessed health; (4) respiratory and cardiac conditions; (5) children’s birth and development outcomes; (6) injury; (7) metabolic/biological measures of health.

Data analysis and synthesis

Following the guidance of JBI,³² we developed a descriptive summary of the review findings using the research questions as our organising frame. This process, carried out by JB and RB, was iterative in nature and required going back to the included publications.

Deviations from the scoping review protocol

We note several deviations from the original published study protocol.³⁵ Firstly, we included papers that related to any type of flooding, as opposed to just river flooding. Secondly, we extracted further data items to those detailed, including assessment time point, data source and study population. Thirdly, a further research question was added: ‘Which research networks are emerging in the field?’ To address this question, we added the coauthorship network analysis.

Network assembly and visualisation

We first created a node list containing every individual who had published an included publication along with their attributes (unique identifier, organisation type, topic published, international author and year published) and an edge list representing all pairs of individuals listed as authors on the same publication. In the visualisation, the size of each node reflects the number of relevant publications by the author, whereas links represent coauthoring relationships between pairs of authors. The resulting network was visualised using the R package igraph.⁴⁰ We computed a spring-embedded type of network layout (‘graphopt’ layout in igraph), which iteratively positions authors with more mutual partners relatively closer to one another and highly interconnected nodes in the centre of their network components, thus intuitively communicating their prominence.⁴¹ Using these computationally determined relative positions of authors inside their components, separate network components (ie, network parts without any interconnection) were positioned in the diagram based on the predominant research themes of each.

Patient and public involvement

No patients or members of the public were involved in the design, analysis or reporting of this study.

Results

A total of 2058 publications were retrieved from database searches. After duplicate removal, title and abstract screening, and subsequent full-text review, we included 69 publications in the review. The key findings are available in the online supplemental file 3. One-third (n = 22) of all publications emanated from the QF2011 cohort, a study examining the association between prenatal maternal stress caused by the 2011 floods in Brisbane (the State capital of Queensland) and child cognitive and developmental outcomes.³⁹ 10 of the publications were set in the Northern Rivers region of NSW, of which eight emanated from a cross-sectional survey, carried out 6 months post-major flooding in 2017, exploring the mental health impacts of this flood event (After the Flood Study²⁴). The PRISMA-ScR flow diagram shown in figure 1 presents the process for the inclusion/exclusion of publications.

Figure 1. Preferred Reporting of Items for Systematic Reviews and Meta-Analysis Extension for Scoping Reviews selection of sources of the evidence flow diagram.

Publication characteristics

Timeframes

Publications included in this review were published over a 70-year period from 1951 to 2023 with more than 75% (n=52) in the last 10 years (2014–2023). Over the 60-year period from 1951 to 2011, there were only 11 publications (figure 2).

Figure 2. Number of included publications, by year published and by health impacts examined, 1951 to 2023. Note: the x axis shows the year of publication and is discontinuous to enable the display of 70+ years of publications included in the review.

Geographic distribution, rurality and setting of publications

Figure 3 and table 1 show the geographic distribution of the included publications. More than half of the publications were set in Queensland (n=39), followed by NSW (n=12) and publications based on Australia-wide data (n=9). Brisbane generated the largest number of publications (n=22), with 7 emanating from research in other urban locations and 24 from research in rural/remote locations (table 1).

Figure 3. Geographical distribution of publications related to health impacts of flooding in Australia, 1951 to 2023.

Table 1. Summary of the characteristics of the included publications, 1951 to 2023.

Characteristics of publications	N=69
Location of study
Queensland	39
New South Wales	12
Australia-wide	9
Victoria	3
Northern Territory	2
Western Australia	2
Multiple States and Territories	2
Rurality of the study setting
Urban	29
Rural	20
Remote	3
Rural and remote	1
General	16
Study design
Cohort study	22
Case series	19
Cross-sectional survey	12
Descriptive/ecological	6
Before and after study	4
Qualitative	2
Case report	1
Predictive modelling	1
Time-series	1
Mixed methods	1
Investigation timeframe post-flood event
Projection/modelling	1
At the time of the event/retrospective analysis	25
≤ 6 months post-flood	4
6 months–≤ 1 year	18
1–≤ 2 years	6
2–≤ 3 years	5
> 3 years	10
Flood exposure assessment methods
Self-report to structured questionnaire	38
Mapping/records of rainfall and/or river heights	20
Self/witnesses’ reports—qualitative	8
Not specified	3
Health impacts assessed
Prenatal maternal stress and child development	22
Mental health and well-being	14
Physical health	12
Mortality	8
Vector-borne disease	7
Combined mental and physical health	6
Analysis by priority group
Pregnant women and children	22
Aboriginal and/or Torres Strait Islander people	7
Children and/or adolescents	2
People with disability and/or carers	1
LGBTIQ+	0
Older people	1
Type of organisational affiliation of authors
University/research institute	41
Hospital or medical centre	19
Government	10
Non-government organisation	1
Independent consultant	1
International organisational affiliation of authors
University/research institute (nine Canada; two UK; one America; one China; one New Zealand; one Czech Republic; one Spain)	16
Hospital /Medical centre (one New Zealand; one Canada)	2
Government (two America)	2

Most of the 69 publications reported on the flood events in coastal areas of eastern Australia that occurred in 1974, 2011 and 2017. Two reported on the health impacts of the 1974 floods in the Northern Rivers region and in Brisbane. 33 publications explored the health impacts of the 2011 floods in Queensland (n=30), Victoria (n=2) and Central Australia (n=1).

Study methods

Most publications employed quantitative methods (n=63), with 22 of these from the QF2011 study that used a cohort design.³⁹ Other study designs included case series (n=19), cross-sectional surveys (n=12) and descriptive/ecological approaches (n=6) (table 1).

Period of study

25 publications reported retrospective analysis of routinely collected or administrative data collected during the time of flood events.⁴²,⁶⁶ Four reported on data collected less than 6 months post-flood,⁶⁷,⁷⁰ with 18 reporting between 6 months and 1 year after the flood event.^{1922 24 71},⁸⁵ A few publications reported data from 1 to 2 years post-flood⁸⁶,⁹¹ and from 2 to 3 years post-flood.⁹²,⁹⁶ Of the 10 publications that reported data collected more than 3 years post-flood, nine were related to the QF2011 study examining child developmental outcomes. The publication in this category, which had the longest timeframe post-flood in the review, was a cross-sectional survey that examined mental health outcomes 6 years after the 2011 flood event in South East Queensland.⁹⁷ There was one publication based on projections of vector-borne disease related to flooding.⁹⁸ The periods of study are illustrated in table 1 and in the online supplemental file 4.

Flood exposure assessment

The most frequently used method for assessment of flood exposure was by self-reporting to a structured survey (n=38). Of these 38 publications, 22 used a bespoke tool developed for the QF2011 study. Other frequently used methods were mapping or records of rainfall and/or river heights (n=20). Case series and studies that used official reports or routinely collected mortality data were based on the self-report in case notes, police and/or witness reports. (Online supplemental file 5 contains details regarding the flood exposure assessment measures for each publication.

Health impacts examined

Health outcomes most frequently reported were related to prenatal maternal stress and child outcomes (n=22) and were all part of the QF2011 study.³⁹ This was followed by the categories of mental health and well-being (n=14), physical health (n=12), mortality (n=8), vector-borne disease (n=7), and combined mental and physical health (n=6) (table 1).

In table 2, we identify the subcategories of health conditions examined by physical health, mental health or mortality. For publications that examined mental health and well-being impacts, symptoms of mental disorders were most frequently reported, followed by other symptoms of mental distress. For publications that examined physical health impacts, infectious diseases and children’s birth and developmental outcomes were most frequently reported. The health conditions that were reported in five or more publications include PTSD (n=13), psychological distress (n=13), child language and/or cognitive and/or motor development and/or behavioural outcomes (n=9), depression (n=7), melioidosis (n=5), leptospirosis (n=5) and Murray Valley encephalitis (n=5) (table 2).

Table 2. Sub-categories of health impacts in publications that reported on mental or physical health impacts or mortality, 1951 to 2023.

Category of health impact	Sub-category (1)	Sub-category (2)	Publications
Mental health and well-being	Symptoms of mental disorders/illness—21 publications1924 67,69 71 73 75	Post-traumatic stress disorder	13 publications1922 24 68 69 71 73 77,80 87 97
		Depression	Seven publications19 24 68 75 77 80 86
		Anxiety	Five publications19 24 68 77 80
		Childhood anxiety symptomology	Four publications103109,112
		Suicidal ideation	Three publications19 24 77
		Mental health disorders	One publication76
	Other symptoms of mental distress—18 publications1922 24 67 69 71 72 77,80 86	Psychological distress/distress/subjective distress (also called peritraumatic stress and dissociation)	13 publications1922 24 67 69 71 72 77,80 87 97
		Nervous tension	One publication86
		Depressed mood	One publication86
		Irritability	One publication86
		Child attention problems	One publication103
		Maternal mood (anxiety, depression and stress)	One publication113
		Infant social-emotional and behavioural problems	One publication88
		Psychological symptoms*	One publication90
	General assessment of mental health—seven publications68 71 72 81 83 96 103	Coping style	One publication72
		Satisfaction with life	One publication68
		Perceived mental health	One publication68
		Infant temperament	One publication83
		General mental health and well-being	One publication81
		Child’s theory of mind	One publication96
		Sleep quality	Two publications71 103
	Positive traits—two publications68 93	Post-traumatic growth	One publication93
		Stoicism	One publication68
Physical health	Infectious disease—13 publications4249 53 54 56,58 61 63 64 66 76 86	Leptospirosis†	Five publications54 57 61 63 64
		Melioidosis	Five publications49 53 56 58 66
		Infection	One publication76
		Mycobacterial infection	One publication42
		Infectious disease in general	One publication86
	Children’s birth and developmental outcomes—11 publications74 82 84 89 91 92 94 95 103 114 115	Child language and/or cognitive and/or motor development and /or behavioural	Nine publications82 84 89 91 92 95 103 114 115
		Children’s birth outcomes	One publication74
		Autism spectrum disorder traits	One publication94
	Vector-borne disease—seven publications44,4651 60 62 98	Murray Valley encephalitis	Five publications44,4651 60
		Kunjin virus	Two publications46 51
		Ross River virus	One publication62
		General vector-borne	One publication98
	General self-assessed health—four publications68 71 86 90	Subjective health assessment and overall health	Four publications68 71 86 90
	Physical symptoms/non-specified illness/disease—two publications76 86	Gastrointestinal	One publication86
		Headache	One publication86
		Weight loss	One publication86
		Pain	One publication86
		Illness	One publication76
		Disease	One publication76
	Metabolic/ biological measures of health—two publications85 116	Alterations in placental glucocorticoid system	One publication85
		Urinary metabolomes	One publication116
	Respiratory and cardiac conditions—two publications47 71	Respiratory health	One publication71
		Takotsubo cardiomyopathy	One publication47
	Injury—one publication76	Injury	One publication76
Mortality	Mortality—eight publications43 48 50 52 55 59 65 70	Flood fatalities – general	Four publications48 50 52 55
		Vehicle-related flood fatalities	One publication43
		Suicide	One publication70
		Drowning	One publication59
		All cause, cardiovascular and respiratory mortality	One publication65

^*‘irritability, nervous tension, depression of mood, worry and sleeplessness’ which was given a descriptive label by the authors—‘the psychiatric cluster’

^†For the purpose of this review, we have included leptospirosis under ‘Infectious disease’ rather than with the more ‘classic’ ‘Vector-borne disease’.

Analysis by priority populations

Of the 22 publications that examined the health outcomes of pregnant women and children, all are linked to the one QF2011 study. Seven publications examined health impacts among Aboriginal and Torres Strait Islander people,^{19 46 49 56 75 77 79} one among people with disability and their carers,²² one with older people⁶⁸ and two with children and/or adolescents^{42 59} (separate to the grouping above related to QF2011). There were no publications examining the health impacts on the LGBTQI+ community (table 1). Two publications examined differential health impacts of flooding for people with existing health problems, education levels, employment, age groups, gender and renting/home ownership status.^{69 71}

Research collaboration

As shown in figure 4, the coauthorship network is fragmented across several separate components that correspond to research interest in health conditions. There is only one distinct research group examining prenatal stress and child development, with Australian authors and more than 21 international individual authors—20 from Canada and one from China (online supplemental file 3)—but their activity appears centralised around a smaller number of authors in this core group. The University of Sydney’s University Centre for Rural Health in the Northern Rivers region emerged as a prominent research group focussed on mental health and well-being outcomes following flood events. Their publications reflect relatively wide collaborations compared with other research groups, with more than 10 coauthorships with researchers outside of the core group. There were eight clusters of researchers examining physical health, six examining mortality and five examining the combined physical and mental health impacts of flooding. There is most overlap between authors with different interests across health outcomes that involve research groups looking at mortality (two separate groups), mental health (one group of five authors), physical health (one group of five authors) and the combined category of physical and mental health (one small group of three authors only).

Figure 4. Coauthorship network analysis of individual authors of publications included in this review, by health impacts studied, 1951 to 2023. Note: numbers refer to individual authors of publications, as assigned in the data gathering/collation process.

As shown in table 1, there were 72 different organisational affiliations for authors on publications, with 41 of these being universities and research institutes. Of the 239 individual authors, 10 published more than five publications each. The authors with five or more publications were from two research groups, namely, the prenatal maternal stress and child development study (QF2011 Study) and the Northern Rivers After the Flood Study.^{24 37} More than 70% (n=199) of all authors had one publication. There were 37 individual authors who used an international affiliation, 21 of whom were from Canada, predominantly associated with the QF2011 study.

Discussion

This review assesses the scope of the literature on the health impacts of flooding in Australia, using both descriptive and coauthorship analysis of publications. In the review, we identified 69 publications published over a 70-year period (1951–2023) by 239 authors with 72 different organisational affiliations.

Key findings include the following: (1) more than two-thirds of the publications were published in the last 10 years, with over one-third of these by one research group, based on a cohort study design following a single flood event; (2) the most common health impacts published related to prenatal maternal stress and child developmental outcomes studied in the cohort design referred to above, followed by mental health and well-being; (3) few publications reported on priority populations other than the Brisbane study of pregnant women and child development; (4) publications focussed on specific health conditions rather than more comprehensive health assessments or assessments of the impact of flood events across multiple health conditions; (5) the majority of publications were based on research conducted in Queensland and NSW, consistent with the observation that these states have the most flood-prone regions⁹⁹; (6) most publications were based on data gathered at a single point in time, with few that reflect impacts on, or experiences of, people over multiple years; (7) few publications were based on qualitative research; (8) studies used a range of approaches to exposure measurement (largely unstandardised/unvalidated). Furthermore, within the constraints of this scoping review, it appears that publications were largely from isolated research groups, with little evidence of collaboration between them; and that the majority of authors (>70%) had only one publication related to the health impacts of flooding, suggesting relatively limited engagement on this research topic.

A substantial and growing number of publications worldwide have examined the mental health impacts on those affected by flood events.^{8 10} For example, in a systematic review of the long-term physical and psychological health impacts following flooding, defined as more than 6 months post-floods, Zhong et al¹⁰ found in their global review that the six most studied health outcomes were PTSD, suicide, depression, psychiatric disorders, stress and general health. This aligns with the scope of mental health conditions studied in our review of the Australian literature. Similarly, international reviews also show an increase in research on infectious and vector-borne disease.^{9 11 12} A notable difference between the Australian and the international research covered in our review¹⁹,¹¹ is the relative lack of Australian research about flood-related acute trauma and injury, poisoning and gastrointestinal infections. As these may have important impacts on other pre-existing chronic conditions, more research is needed to determine the extent to which this is the case.

International reviews by Zhong et al¹⁰ and Fernandez et al⁸ identified a lack of studies that monitor the ongoing or longer-term health outcomes of populations affected by floods, such as disability, chronic diseases and cancer, all of which are also topics that have received less attention in Australian research. We found that apart from the suite of publications examining child developmental outcomes after prenatal exposure to stress related to flood events, there was a paucity of research that followed-up populations over time, with most only reporting on data collected at a specific point within a year of the flood. Thus, there is a need for more longitudinal studies. Furthermore, there is a need for more qualitative research to understand people’s experiences and how these played out over time in relation to the impacts of flooding on mental health, chronic illness, disability and associated issues of access to and quality of services.⁸

International reviews on the health impacts of flooding^{8 10} indicate that most reported studies have lacked control groups or baseline measures, which is consistent with our review of the Australian research. Fernandez et al,⁸ while acknowledging the difficulties of linking administrative health datasets, suggest that these datasets could offer valuable insights into post-flood outcomes that can be compared with pre-event rates: for example, suicide rates, psychotropic medication use, hospital admission patterns and emergency visits. In our review, only one publication examined such data in the form of hospitalisation admission datasets from two hospitals in the Northern Rivers region of NSW in 1974.⁷⁶ The development of research with appropriate baseline measures and control groups and the use of administrative health datasets in conjunction with individual and/or community flood exposure data are areas of further study. There are studies from Australia that have linked administrative data sets to other exposures, for example, heat.¹⁰⁰ Further collaboration between researchers who work on flooding and other exposures could advance this area of work.

While there has been some development of standardised measures for assessing the health impacts of flood exposure on individuals and communities (eg, Verger et al¹⁰¹ and Lieberman-Cribbin et al¹⁰²), both Australian and international studies tend to use a variety of flood definitions and measures of exposure.¹⁰³ This may be at least partly explained by the diversity in the health impacts studied and the nature and context of flood events. However, future research would benefit from more attention to assessing the validity of exposure measures and the potential for standardisation, including the improved availability of data on the spatial extent of specific flood events and the time period and severity, details of which are often held by local governments.¹⁰⁴ Satellite data are also becoming increasingly available in defining flood extents, for example, that held by the European Space Agency,¹⁰⁵ Dartmouth Flood Observatory¹⁰⁶ and Digital Earth Australia.¹⁰⁷

Our review also found a marked lack of any research examining health outcomes for priority populations, for example, people with disability, Aboriginal and Torres Strait Islander people, the elderly and those with low socioeconomic status. Given the internationally observed disproportionate impacts of floods on these groups,¹⁴ it is vital that flood research in Australia examines the differential impacts of flood events and the implications for policymakers and practitioners in devising strategies to mitigate these impacts on priority populations.

The largely disease-specific nature of flood-related research highlights important priorities for future research. Health-related flood research has been concentrated on two main studies: the prenatal maternal stress and child development study (QF2011 Study) and the mental health and well-being outcomes study (After the Flood Study). Both studies were, in some ways, opportunistic. The QF2011 Study built on an existing randomised control trial (the M@NGO trial), which was already collecting psychosocial data from pregnant women when the 2011 Queensland floods occurred. This pre-existing cohort and data collection process enabled researchers to assess the flood’s impact on these women.³⁹ Similarly, for the After the Flood Study in the Northern Rivers, we (JB, JL, GM and RB) were based in the region affected by the 2017 flooding. Our established research interests in health inequities uniquely positioned us to respond to this disaster. Since both studies were somewhat opportunistic, it raises the question of how to develop a research network capable of providing a more comprehensive assessment of the health impacts on communities and the efficiency of healthcare services. Collaborations between established research groups, including those experienced in environmental epidemiology and exposure assessment, could offer valuable insights that would be instrumental in protecting health and supporting recovery efforts.¹⁰⁸

Strengths and limitations

The strengths of our scoping review are as follows: (1) the rigorous process of two reviewers independently conducting title and abstract screening, full-text review, data extraction and engaging in discussions to reach consensus at every stage; (2) a search strategy designed with both an experienced academic librarian (KE) and experts in the field of flooding research; (3) no start date beyond the initiation date of indexed databases to enable a full picture of published floods and health outcome research in Australia; (4) the use of a published protocol and adherence to the JBI methodological approach for scoping reviews.

Review limitations include the following: (1) exclusion of related evidence as published in grey literature, theses, and peer-reviewed commentaries and perspectives and that could only be identified through manual searching; (2) we did not specifically search for or extract data on how health services or access to care were impacted by flooding (we plan to do this as a separate review); (3) four of the authors on this publication (JB, JL, GM and RB) were also authors on nine publications included in this analysis. However, to mitigate against potential bias, the following authors, who have not published in the field of flooding and health, were involved in all stages: PM conducted the network analysis, BA was one of the independent authors who screened publications and extracted the data and KE conducted the academic literature search. We also reflected on our positionality as researchers, as described above.

This review is timely as Australia continues to grapple with increased frequency and severity of flood events. Drawing on our findings, Box 1 proposes several recommendations for further research in Australia on the health impacts of flooding.

Box 1. Implications for further research.

• Further research is to examine the health outcomes for priority populations, ideally using control or comparison groups to understand differential impacts.

• Using existing administrative datasets in Australia, potentially with a before-and-after design, to better understand the impact of flood events on health outcomes.

• More studies that examine the long-term health outcomes from flooding, potentially using cohort designs to follow-up over the longer term.

• Further research into chronic illness, injuries and longer-term mental health outcomes to align more with international research on health outcomes.

• More qualitative studies to understand the experience of people and their health outcomes.

• Further work on defining flood exposure for individuals and communities, including an assessment of their validity and their potential for standardisation.

• Building research collaborations across geographic and disease-focus areas and growing capacity in areas of priority need.

• Improved access to all levels of government data resources on flooding extents and greater sharing of exposure data between research groups to help develop consistent and robust exposure metrics from health studies.

Conclusion

Our review enhances the understanding of the nature and extent of research concerning the physical and mental health impacts of flooding in Australia by identifying areas of relatively greater research activity, existing gaps in research and potential priorities for future research. As flooding risks escalate due to climate change, addressing identified gaps and fostering diverse collaborations is imperative for developing evidence-based strategies to mitigate health impacts, particularly for priority populations. By examining the collaborations of individual authors and identifying the health outcomes they studied, our review highlighted the disparate nature of research on the health impacts of flooding in Australia. These results could assist researchers in this area to identify research strengths, which could be enhanced through strategic collaborations. It is incumbent on researchers and other stakeholders to prioritise the production of robust evidence on the range of health impacts of flooding to facilitate informed decision-making by policymakers and others.

Data availability statement

No data are available.