The bibliometric analysis analysed 84 papers in total; this resulted in the identification of common themes, which could then be compared.
What hazards are the focus?
This analysis shows that natural hazards (73%) are more commonly researched than man-made hazards (14%) (Fig. 4a), and for these man-made hazards terrorism (83%) is the concern of the majority. In general, generic natural hazards (37%) are covered more frequently than any one specific hazard type (Fig. 4a). Generic natural hazards, in this context, are those papers where a specific hazard type is not allocated and instead reference is only made to natural disasters in general. For the specific hazard types identified, the most common research hazards are hydrological (20%) and geophysical (20%), followed by meteorological (15%).
The papers in this study were limited to years between 2000 and 2017 (as previously discussed). From these papers, the peak number of papers published was during 2003 (Fig. 4b). Research on terrorism only appears in publications from 2001 onwards, the same year which saw the 9/11 USA terror attacks (Fig. 4b). Other than the link to terrorism, there seems to be no distinct pattern with the year of publication and the hazards researched in papers (Fig. 4b). For example, after the Hurricane Katrina event in 2005, there does not appear to be a significantly greater number of papers on meteorological hazards published.
From the 84 papers analysed, 48% of papers included a case study as part of their study. In agreement with the hazards covered in papers, the case studies included also primarily focus on natural hazard disasters (95%), rather than man-made hazards (Fig. 5a). Of the natural hazards covered, earthquakes (28%) and hurricanes/cyclones/typhoons (28%) are the most covered, followed by flooding (25%) (Fig. 5a). Other types of hazards, including landslides (4%), hailstorms (4%) or drought (2%), are not well covered in comparison (Fig. 5a). Generally, these are the hazards which are less prevalent worldwide and therefore the amount and availability of data for case studies are likely to be reduced. The pattern of case study hazards has not changed significantly over time, demonstrating a continual commitment to case studies on earthquakes, flooding and hurricanes/typhoons/cyclones (Fig. 5b).
What research is undertaken?
The results of this study have shown that the peak number of publications was seen in 2003 (13%), when the number of journal publications peaked, before gradually decreasing over the subsequent years until 2014 (2%) (Fig. 6a). From the papers analysed, nearly 50% use a review methodology and include little original or novel work (Fig. 6b). However, nearly 40% included some form of modelling technique in the paper, with the remaining 10% of papers consisting of case studies or introductory articles (Fig. 6b).
The exact study length of paper can be quite difficult to define, particularly in the case of review papers. Previous studies have tended to consider only case study papers and based the length upon the research period alone (Chappin and Ligtvoet 2014; Chappin and van der Lei 2014), with time periods defined as: short < 1 year, medium 1–10 years and long > 10 years. To adapt this technique for review papers, we consider the length of the paper to be based upon the references (e.g. we define the time period as the publication date of the paper itself to that of the earliest reference used). We also need to adapt the time periods used, as if the same criteria are applied we would have no short studies, 42% medium and 58% long. As such, we propose the following criteria: short < 10 years, medium 10–24 years and long > 25 years. Using this new timescale, we find that the analysed journal papers can be classified into: short (17%), medium (63%) and long (20%). Generally, papers with longer reference times tended to be review papers (Fig. 6c).
The papers were split into those that were qualitative (review or case study papers) and those that were quantitative (included modelling). Out of the 84 papers, over 50% were qualitative, which was interesting as one of the search terms was simulation, so it was anticipated there would be a larger number of quantitative papers (Fig. 6d). Out of the quantitative papers, 80% included a case study, whereas 80% of the qualitative papers do not contain a case study (Fig. 6e). Of the different methodologies used, over 80% of the review papers were qualitative and over 75% of the modelling papers were quantitative, which is as expected, for example if a paper uses review techniques it is more likely to be qualitative and vice versa (Fig. 6f).
Where is research focused?
An important aspect of disaster management is related to the location of threats. Certain locations are more vulnerable to specific hazards or more frequently experience event types. Therefore, there is a need to understand where current research is carried out and whether this correlates with the locations of the most frequent, deadly or costliest natural disasters across the globe. Locations feature in papers in numerous ways, including the author’s country, the research focus of papers and the location of case studies. By looking into these, it is possible to understand whether there is any correlation and if these locations are linked with the key disaster trends.
This study has found that corresponding authors are located across the globe, with the largest proportion in North America (59%), then Europe (18%), Oceania (12%) and Asia (11%) (Fig. 7a).The analysis also considered the focus of papers in terms of location. It was found that the focuses ranged from non-specific worldwide themes (44%) and developing countries (5%), to specifics on the USA (33%), others combined a country and a worldwide emphasis, for example USA/worldwide (10%), and some focused on specific locations (8%) (Fig. 7c). Also, a number of papers included case studies to help demonstrate their findings or for use within modelling techniques; the locations were North America (60%), Asia (18%), Europe (15%) and Oceania (7%) (Fig. 7e).
The corresponding authors can be used to give an indication of the likely area covered by a paper. It appeared that this may not be the case as over 40% of the papers had a worldwide/generic focus (e.g. they were not specific to any one country or continent). However, over 40% of the papers are specifically linked to either the USA or a combined USA/worldwide approach (Fig. 7c). This demonstrates that for some locations, the author location does influence the focus of the paper (Fig. 7b). It can be deemed that in general if an author is based in the USA, their research will focus on the USA (Fig. 7b). It is to be expected that there would be large amounts of research carried out in the USA, as they are frequently affected by natural hazards and the financial implications in absolute values are large for the country.
The obvious exception to this are the authors who choose to carry out generalised research and to not focus on a specific location. There are also some examples where author location does not affect the research location choice. For example, a UK author researches on a case study in Greece (Fig. 7b), but in contrast this is still part of the same continent.
There are a wide range of case studies included within the papers, with locations across the globe in North America, Asia, Europe and Oceania (Fig. 7e). This location spread is to be anticipated due to the corresponding author locations. Asia is not well covered with case studies (18%), and there are no case studies in Africa. Commonly, it is seen that case studies are carried out in the same locations as authors or in close proximity (Fig. 7d). This is likely to be due to the availability, accessibility or reliability of information and/or data and the local knowledge of authors. Also if there is any requirement for field trips or data collection, this is generally easier to facilitate when in close proximity. Again, the largest number of case studies is focused on North America (60%), tying into the frequency of events and the financial costs (Fig. 7d).
It is also the case that hazards reflect the common hazards seen on a continent rather than extreme or one-off events, for example North America experiences flooding, earthquake and hurricanes, whilst Asia experiences flooding, earthquakes, typhoons and landslides (Fig. 7f). This is to be expected for case studies, as a quantity of reliable data is often required.
Where to find this research?
The vast majority of research is undertaken in academic institutions and in research facilities across the globe. With large volumes of research produced on different topic areas, it is necessary to understand whether this information is located in the same journals, what impact this research has and whether citations can help to increase the prevalence and impact of the research.
The most prevalent journal in this study was Natural Hazards (10%), Natural Hazards Review (8%) and Disaster Prevention and Management: An International Journal (7%) (Fig. 8). In total, 57 different journals were recorded in the study; out of a total of 84 papers, there were only 11 instances where there were repeated articles in the same journal publication. The highest impact factors do not correspond with the mostly commonly used journals in this study (Fig. 8). It is perhaps not surprising that all of the most prevalent journals in the study contain a keyword from the search criteria, e.g. “natural hazards” or “disaster management”.
Google Scholar as part of its search results provides a record of the number of citations a paper has received. The majority of the papers in this study have been cited 0–100 times (33%), 101–200 (25%) or 201–300 (11%). This shows that as the number of citations increases, the number of papers achieving the level required decreases; however, there are examples of some journals being cited over 1000 times and one is cited over 3000 times (Fig. 9). It is also interesting to consider the number of citations given by Google Scholar and the position of the journal paper in the Google Scholar search results. This shows that Google Scholar does not identify journal papers on the number of citations alone (Fig. 10). In the search that uses simulation, there are a number of papers with higher numbers of citations in the initial results compared to the “agent based simulation” search where the number of citations is spread more evenly amongst the search position.
Of the most prevalent journals, the Google Scholar citations indicate that Natural Hazards has a range between 0 and 300 citations, Natural Hazards Review has a larger range of 0–700 citations and Disaster Prevention and Management has a range between 0 and 500 times (Fig. 11). This shows that journals with a higher number of published papers (in this study) do not correlate with a higher number of citations per paper, according to Google Scholar, nor does having a higher journal impact factor link to a larger number of citations. For example, Environmental Modelling and Software has one paper with 0–100 citations and another with 101–200 citations, whilst in Tourism Management one paper has 101–200 citations and one has 501–600 citations (Fig. 11). However, the exception to this is Global Environmental Change which has one paper cited 1001–2000 times and one cited over 3000 times (Fig. 11), which ties well with the high impact rating. This indicates that the topic and contents of the paper are the driving factors behind citations, rather than the high impact factor of the journal.
Keyword search terms
With any journal publication, authors are required to select several keywords to reflect the overall themes of the paper. This can be a good indication of the overarching themes of the work and can be influential in whether a paper appears in a search or not. The keywords from all the papers were collected together as part of this study. It is interesting to note that not all papers provided keywords with 26% not including keywords. From the keywords, the search terms of “natural hazards”, “disaster management” and “simulation” were removed. “Agent based simulation” was not removed, as although this was one of the search criteria, it was decided to determine how prevalent the term was within the keywords.
After removing the search terms, the most prevalent words were “risk” (5%), “modelling” (3%), “flood” (3%), “GIS” (3%), “evacuation” (3%) and “emergency” (3%) (Fig. 12a, c). It is interesting to note that “agent” (1%) was not in the top keywords, even though it had been one of the search criteria for the papers.
Although the keywords can be useful for determining the themes of a paper, keywords can often be limited to a selection list (set by the journal), meaning that important themes may be missing. Therefore, after analysing the 84 papers, the key themes and terms were extracted by the reader from the papers to determine whether this matched with the author’s keyword selection. The most common terms were “risk” (4%), “vulnerability” (2%), “evacuation” (2%), “emergency” (2%) and “systems” (2%) (Fig. 12b, c). Again, the term agent (0.8%) was not in the top keywords, even though it had been one of the search criteria for the papers. This shows that there is correlation between the author’s selection and those chosen after reading the papers, suggesting that the use of lists for keyword selection does not adversely affect the selection of keywords.
The search terms selected for the literature search were aimed at producing results relating to modelling and simulation techniques in a disaster management context for natural hazards. However, when the search term “simulation” was used, over 60% of the papers included no modelling, and the modelling papers did not relate to agent based modelling (Fig. 12d). Using the search term “agent based simulation”, 50% of the papers generated contained no modelling, 35% contained reference to a modelling technique and only 15% of the papers specifically used agent based modelling (Fig. 12d). There were a number of papers that appeared as results for both “simulation” and “agent based simulation”; of these papers, over 60% had no modelling included, with just under 20% having a modelling technique in and the same amount (< 20%) having a specific mention of agent based modelling (Fig. 12d). Despite the use of specific search terms to extract modelling- and simulation-based papers, the use of these search terms was not particularly successful at producing relevant results.