Introduction: landslide disasters and the significance of integrated landslide study

A landslide is a downslope movement of soil, rock, or both (Highland and Bobrowsky 2008), slightly modified from “the movement of a mass of rock, debris or earth down a slope” (Cruden and Varnes 1996). Landslide disasters are caused by the exposure of people to hazardous motions of landslides that threaten vulnerable human settlement in mountains, cities, coasts, and islands. No single landslide disaster can threaten as many people as did the 2011 Tohoku earthquake and tsunami disaster. There are, however, many more landslide disasters occurring in more places over the world. Some of them kill many people or destroy many houses, farms, and other human infrastructure. Many smaller landslide disasters are not recorded. However, large landslide disasters of the world are recorded. Table 1 is a list of major world landslide disasters (from Wikipedia http://en.wikipedia.org/wiki/List_of_landslides) to which we have added the historically largest landslide disaster, the historically largest volcanic disaster, and one of the largest tsunami disasters in Japan as no. 1 (Sassa et al. 2014). It is the 1792 Unzen–Mayuyama landslide in Nagasaki, Japan. A megaslide with a volume of 3.4 × 108 m3 was triggered on a volcano by a nearby earthquake (M = 6.4 ± 0.2), and the landslide mass entered the sea causing a huge tsunami. The landslide directly killed 10,139 people, and the landslide-induced tsunami killed 5014 people on the opposite shore and islands.

Table 1 List of major landslide disasters (source: Wikipedia http://en.wikipedia.org/wiki/List_of_landslides)
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In recent years, there have been a few landslide disasters in Japan. Small and shallow long-runout landslides were triggered by a localized heavy rainfall, and 74 people were killed in an urban area of Hiroshima city in 2014. The number of deaths was not as large as those reported in Table 1, but this disaster had a large impact on the society of Japan, one of the most advanced countries for landslide risk mitigation. Therefore, we have added this landslide as no. 24 of Table 1.

Figure 1 shows the disastrous large landslide that occurred in Afghanistan on 2 May 2014 (no. 23 of Table 1). This rapid and long-runout landslide killed 2700 people including many people who sought to rescue others caught in an earlier landslide.

Fig. 1
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Badakhshan mudslide of 2 May 2014, Afghanistan. Death toll: 2700. Photos from http://www.dailymail.co.uk

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Figure 2 shows the Hiroshima landslide disaster on 20 August 2014 (no. 24). Initial landslides were very small with depths of a few meters, and they changed to debris flows before reaching the area of human settlement. Initial landslide and debris-flow masses were not great, but 52 people were killed by this landslide (Fig. 2). This disaster illustrates one of the dangers associated with urbanization near mountains. To mitigate such risk requires an integrated landslide study, which includes the physical, social, and institutional vulnerability of the people as well as scientific research and technological development of mitigation measures appropriate for the cultural psyche of the local people. It requires reliable hazard and risk assessments, and reliable risk mitigation involving a mix of effective engineering works, enforcement of land-use regulation, reliable landslide prediction, early warning, and evacuation.

Fig. 2
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Overall view of the debris slides–debris flows of 20 August 2014 in an urban area (Yagi), Hiroshima, Japan

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Impact of the journal Landslides

One of the indices pertinent to the impact of a publication to society is impact factor, which is annually reported by Thomson Reuters (Institute for Scientific Information (ISI)). It is calculated by dividing the number of current year citations to the source items published in that journal during the previous 2 years.

The impact factors for Landslides over the 5 years from 2009 to 2013 are listed in Table 2. The value has gradually increased from 1.703 in 2009 to 2.814 in 2013 although it has not been a monotonic increase. This increase shows that the influence on the community of authors to Landslides is steadily increasing. In 2014, Thomson Reuters presented the 2013 impact factors of 33 international journals in the category of “Engineering, Geological.” Twenty of these journals had an impact factor greater than 1.0 as listed in Table 3. Within this table, ten journals including Landslides are bimonthly journals, six are monthly journals, and four are quarterly journals. Landslides has maintained an impact factor greater than 2.0 over these 3 years (2011–2013). Only two journals in this category have had impact factors of more than 2.0, which demonstrates that Landslides has a high impact in academic society in this field.

Table 2 Impact factor, total articles, and total cites of Landslides in the recent 5 years (2009–2013)
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Table 3 Twenty journals with more than 1.0 impact factor in the category of “Engineering, Geological” (Thomson Reuters)
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Citation of each paper and downloading

Impact factors are calculated based on the time of citation of each paper. Google Scholar also presents the number of times each paper is cited. The number of times cited was investigated both from the ISI (Institute for Scientific Information) and Google Scholar, and the results are presented in Table 4. We list 26 papers for Landslides which have been cited more than 30 times and the order of times cited noted in Google Scholar, since both trends are similar. The number of times cited in Google Scholar is around two times greater than that in ISI; this is because Google Scholar counts citations from a greater number of publications, while ISI counts citations from a small number of selected journals. Six papers including the most cited paper dealt with earthquake-induced landslides. Six papers studied time prediction and early warning of landslides. Five papers were related to susceptibility mapping and analysis. Other papers dealt with satellite technology, climate change, landslide dams, vulnerability, and inventory. The table shows the interest of authors of Landslides.

Table 4 Times cited per paper in Landslides counted by Google Scholar (http://scholar.google.com/) and ISI
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Table 5 presents the number of downloading of papers published in Landslides from January to November in 2013. Some papers were published in 2014 but were already cited in 2013. Those papers were downloaded as online publications. Comparing the number of times cited (Table 4) to the number of downloads (Table 5) shows that trends in the two tables are quite different. For example, the paper by Francesca Cigna “How to assess landslide activity and intensity with Persistent Scatterer Interferometry (PSI): the PSI-based matrix approach” is listed as no. 4 in Table 5 but as no. 24 in Table 4. However, other papers exhibited a different trend. The number of downloads is an index of the numbers of end-users of the information provided by the paper, while the number of citations is an index of the number of researchers who found the paper useful in their research.

Table 5 Number of downloads of each paper published in Landslides (downloaded from January to November 2013)
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The impact on readers/users of Landslides and the impact on authors of papers published in various journals and publications will be different. Therefore, the impact factor calculated from the frequency of research citation does not always present the true significance of a journal to its readers who include practitioners and decision makers.

The period of online publication

Table 5 shows that many papers are downloaded soon after they become available as an online publication, before the digital and printed versions of the issue appear. Here, we explain the delay between the first appearance of the online publication (DOI number) to the issue as a digital and printed publication (with volume and issue numbers and page numbers) in Landslides. The period of online publication was around 8 months in 2012. Landslides moved from a quarterly to a bimonthly journal in 2013; this, however, failed to reduce the backlog of accepted papers waiting for publication. To reduce the accumulating backlog, two options were examined, (1) reduce the rate of acceptance by utilizing tougher reviews (technically not easy) and (2) reduce the maximum page length for each paper from 12 pages to 8–10 pages. However, the range of backgrounds of landslide studies is much greater than for other well-established science and technology fields. It takes more pages to present research content with color photos (common information sources), maps, and drawings of landslides so that it can be easily understood by readers with different backgrounds. Instead, we decided to gradually increase the total number of pages per issue from 100 pages to 200 pages in Vol. 11, No. 4 in 2014. With this effort, the backlog of accumulated papers has been reduced significantly. Currently, the waiting time is around 4 months, a half of the peak waiting time in 2012.

Categories of articles

Landslides has four major categories of articles from its establishment period.

  1. 1.

    Original Papers (6–12 pages): original research and investigation results

  2. 2.

    Recent Landslides (generally less than 6 pages): reports of recent landslides including location (latitude/longitude), plan, section, geology, volume, movement, mechanism, and disasters within available extent

  3. 3.

    Technical Note (less than 6 pages): research notes, review notes, case studies, progress of technology, and best practices in monitoring, testing, investigation, and mitigation measures.

  4. 4.

    International Consortium on Landslides (ICL)/International Programme on Landslides (IPL) Activities (length depending on the content): progress of IPL projects and ICL Committee activities.

The concept of “Original Papers” is the same as in other journals.

The category of “Recent Landslides” is unique to Landslides that carries on the tradition begun by Landslide News 1987–2003. The Japan Landslide Society published an international newsletter, Landslide News, annually from 1987 to 2003. It was printed in three colors (red, blue, and black), with some issues in full color. Of the 5000 copies printed, 2000 copies were distributed to worldwide landslide researchers and organizations free of charge (copies are currently accessible at the website of the Japan Landslide Society, http://www.landslide-soc.org/publications/l-news/index.html) (Sassa et al 2009).

The category of Technical Notes is the same as in other technical journals. But there is an emphasis on case studies from developing countries from where very few papers/reports are published in other journals. Recent Landslides also gives priority to landslides in developing countries from where very few papers and reports are published in other journals.

The ICL aims to contribute to the United Nations International Strategy for Disaster Reduction through developing landslide sciences, technology, and capacity building, and strengthening global cooperation for landslide risk reduction within developed and developing countries. The ICL established the International Programme on Landslides (IPL) together with ICL supporting organizations (UNESCO, UNISDR, WMO, FAO, UNU, ICSU, WFEO, and IUGS). These activities are reported in ICL/IPL Activities. Table 6 presents the number of times articles in each category were cited based on the information available from Google Scholar and ISI.

Table 6 Times cited in each category of Landslides
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Published number of articles and average times cited by Google Scholar and ISI for each category have a similar trend. After removal of the not-yet-cited articles (right side of the table), the trend appears to be similar. Specifically, original papers are the most frequently cited followed by Recent Landslides, Technical Notes, and ICL/IPL Activities. Citations and downloading of Recent Landslides are relatively high. Technical Notes are less cited and downloaded than Recent Landslides. ICL/IPL Activities include Announcements and Reports of World Landslide Forum and other meetings as well as reports of IPL projects. It is natural that these are not cited in scientific papers; consequently, the number of times cited for this category is not high. Although this category does not contribute to the impact factor of Landslides, publication of such news and reports is important to further the aim and the expected role of Landslides.

Classification of articles in Landslides

When articles are submitted to the WEB editorial system of the Editorial Manager (EM) of Landslides, authors are asked to classify their article by selecting from a list of classifications. Around 100 editors and 400 reviewers of Landslides register to the EM, identifying classifications pertinent to their research area. Editors and reviewers are searched by classification matching. Hence, the classification of articles is an important aid to finding suitable editors and reviewers for each submitted article.

Starting from Vol. 6, No. 3 in 2008, the current classification (Table 7) has four major classes: Background Science (Geology, Geomorphology, Geotechnology, Geophysics, Hydrology & Meteorology); Methodology (Field investigation and ground exploration, Monitoring, Material testing, Physical modeling, Numerical simulation, GIS, Remote sensing, Planning and design); Application (Hazard and Risk mapping, Early Warning, Risk Assessment, Remedial measures & prevention works, Risk reduction strategy, Database, Capacity development); and Types of landslides (Debris flows, Rock falls, Earthquake-induced landslides, Rain-induced landslides, Landslides in cultural/natural heritage sites, Anthropogenic landslides, Landslides in urban areas). This classification has functioned well so far. The classifications of Methodology and Types of Landslides were used to decide sessions and books for the Third World Landslide Forum.

Table 7 Classification of articles in Landslides
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Figure 3a shows the classification of background sciences from Vol. 6, No. 3 to Vol. 10, No. 6. The proportion of published papers based on Geotechnology and Geomorphology are 34 and 33 %, respectively. These two sciences account for two thirds of the total. Published papers on Geophysics and Geology are 15 and 14 % of the total, respectively. Hydrology & Meteorology are important as triggering factors, but constitute as little as 4 % of the background science.

Fig. 3
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Articles classified by Background Sciences (a) and Methodology (b)

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Figure 3b shows the classification of Methodology. Papers on Field investigation and Ground exploration have the greatest portion of 33 %; papers on Monitoring and Numerical Simulation have the same portion of 16 %. Then, GIS and Remote sensing papers occupy 11 and 10 %, respectively. Papers on Material testing and Physical modeling are the same, at 6 %. Planning and design is the least at 2 %. The total of Field Investigation and Ground exploration and Monitoring account for half of all papers. This analysis reveals that the most important methods of landslide studies to understand landslide phenomena are “Field investigation” and “Field monitoring.”

Figure 4a shows the application area. Forty percent of published papers are on landslide risk assessment. Twenty-five percent of papers are applied to Hazard mapping, and Early Warning (19 %) will follow them. These three applications are 84 % of the total contributed papers. On the other hand, papers on high-cost Remedial measures & prevention works are only 4 %. Most studies focus on non-structural and economical measures for landslide disaster risk reduction, namely risk assessment, hazard/risk mapping, and early warning. Structural measures for landslide risk reduction have not much been included in published papers but are still important to protect cultural heritage sites, densely populated areas, and other sites of high societal value.

Fig. 4
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Articles classified by Application (a) and Types of Landslides (b)

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Figure 4b presents the type of landslides published in Landslides. Papers on “Rain-induced landslides” are dominant at 62 %. Debris flow and earthquake-induced landslides follow with 16 and 15 %, respectively. Rock-fall-related papers are at 6 %. Landslide threats to cultural and natural heritage sites such as Machu Picchu are socially very important, but the number of papers in this category is only 1 % in these 5 years.

Figure 5 shows the ratio of published articles in different categories; 60 % are original papers.

Fig. 5
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Published articles in Landslides under four different categories

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Most authors wish to publish their papers as original papers. The editorial board or editors often suggest that some papers are more suitable as Technical Notes including Case Studies or Recent Landslides. The sum of the papers for the “Recent landslides” and “Technical Notes” categories is 30 %. The ICL/IPL Activities cover a total of 10 %. Catastrophic landslide disasters are reported from various parts of the world. Those reports provide very important information for landslide risk reduction. The editorial board would like to see the proportion of articles in “Recent Landslides” increase over the next 5 years.

Finally, the number of authors of published papers from each country is presented in Fig. 6. Some authors have published multiple papers in these 5 years, but they are only counted once in this figure. Each coauthor other than the first author or the corresponding author is counted as one. The largest number of authors is from Italy, followed by China, Japan, the USA, Canada, India, Spain, and Czech Republic. Others (21 first authors) include those from developing countries of Nigeria, South Africa, Saudi Arabia, Iran, Mali, Chile, and Vietnam.

Fig. 6
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Country-wise distribution of the number of individual authors. Each author is counted only once, even if they published multiple papers

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Acknowledgement and call for cooperation for landslides

The editorial committee of Landslides of ICL deeply appreciate all editors and reviewers for their voluntary contributions to editing and reviewing. In the last 5 years, the number of papers published in Landslides has increased by three times from 100 pages/issue and 4 issues/year to 200 pages/issue and 6 issues/year. This has increased the working load on editors and reviewers of Landslides. To reduce the working load for each editor and reviewer, ICL has invited more editors and reviewers in these years. Furthermore, ICL introduced “Rejection without in-depth review” by adopting a rapid screening process by a small group of executive editors to avoid assigning editors with papers very unlikely to be accepted. It has been effective in reducing the load on the majority of editors/reviewers and to the authors as well due to the quick review result.

Thematic issues

Landslides has created a new editorial system for thematic issues. The proposal for thematic issues is invited. The concept of thematic issues is different from special issues.

Special issues are decided to publish in the stage of planning. The priority is its publication.

Thematic issues in Landslides keep exactly the same editorial flow and the review level as with the regular issues. It is not predetermined how many papers will pass the review process and go to publication, namely publication in a thematic issue is not guaranteed. However, anyone can propose it. The process is as follows:

  1. 1.

    Anyone can propose a thematic issue with its aim and the list of potential authors and papers.

  2. 2.

    If the proposal is accepted, the thematic issue title will appear in the Editorial Manager. Authors will contribute their papers by selecting an intended thematic issue.

  3. 3.

    Each paper will be reviewed through the usual editorial flow.

  4. 4.

    Accepted papers will be published online one by one with DOI number.

  5. 5.

    If the number of online published papers under the planned theme reaches around 200 pages, they will be compiled as a full thematic issue. If they only reach half of one issue (around 100 pages), they will be compiled as a partial thematic issue. In cases where the number of accepted papers is much fewer than 100 pages, those papers will be published in a regular issue.

The quality of papers published in thematic issues in Landslides will be the same as in the regular issues and will pass through the same review process. Thematic issues will be useful to promote research in a theme of research and provide a good tool for landslide risk reduction efforts.

Landslides invites competent researchers to cooperate as editors and reviewers, and propose thematic issues. Please contact the editorial office of Landslides, which is the following:

Editorial office of Landslides

UNITWIN Headquarters Building

Kyoto University, Uji Campus, Uji,

Kyoto, 611-0011, Japan

e-mail: journal@iclhq.org. URL: http://www.iplhq.org/