the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 19 Jun 2026
An extended hazard interaction matrix for exploring multi-hazard complexity in data-scarce regions: An application to Kerala, India
Abstract. This paper extends the analysis of multi-hazard interrelationships beyond the primary focus on cascading and amplifying mechanisms, through the development of an evidence-based database in a data-scarce context. The methodology is applied to Kerala, India. To support interpretation, an adapted hazard interaction matrix was developed that extends existing frameworks by (i) incorporating a broader range of interaction mechanisms beyond traditional cascading and amplifying effects, and (ii) enabling representation of three-way hazard interactions, advancing beyond conventional pairwise depictions. The matrix was further enhanced to capture seasonal variation in interaction potential throughout the year. Drawing on academic literature, grey literature, and media sources, the database captures evidence for both well-documented and underreported hazards and their interactions, whether historically observed or theoretically possible. The final database contains evidence of 22 distinct hazard types across six hazard groups and 137 potential hazard interrelationships. Results indicate that, while cascading and disposition-alteration mechanisms dominate the interrelationships observed in Kerala, accounting for additional interaction mechanisms increases the number of identified interrelationships by 36 %. This suggests that restricting analyses to a limited subset of interaction types may not fully capture the region's multi-hazard complexity. The matrix was further enhanced to capture seasonal variation in interaction potential throughout the year. Incorporating seasonality reveals distinct temporal windows of elevated interaction potential shaped by monsoon rainfall and temperature variability. When applying seasonal filters, the number of potential interrelationships identified was reduced by approximately 6%. This study demonstrates that interaction-focused, seasonally informed frameworks can reveal multi-hazard dynamics that may otherwise be overlooked when analysing only a subset of hazard types and interaction mechanisms
Competing interests: At least one of the (co-)authors is a member of the editorial board of Natural Hazards and Earth System Sciences.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2026-2999', Anonymous Referee #1, 06 Jul 2026
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RC2: 'Comment on egusphere-2026-2999', Anonymous Referee #2, 20 Jul 2026
This is a very nice piece of work, with an extensive and well-documented evidence base that has clearly been developed with great care. I think the framework has considerable potential for application not only in data-scarce regions but also in areas where more extensive data are available, providing a useful tool to assess the multi-hazard profile of a region. I also appreciate the quality of the figures, which greatly support the reader in navigating the complex methodology.
My main suggestions concern the clarity and presentation of the manuscript. The study adapts and combines a large number of existing frameworks, definitions, and methodologies, which at times makes it difficult for the reader to follow the narrative, especially early in the paper. I believe these revisions would improve the readability and accessibility of an otherwise strong and valuable contribution.
1. Introduction
- Some references do not seem to fully support the statements they accompany. For example, de Ruiter and Van Loon (2022), cited right at the start of the paper, focuses primarily on dynamic vulnerability and how vulnerability changes in multi-hazard contexts, rather than providing evidence for the frequency or increasing occurrence of multi-hazard events experienced by societies. Moreover, Gill et al. (2022) provides a handbook of definitions and does not support the statement that multi-hazard events produce impacts that exceed the sum of their individual effects. I would therefore recommend critically reviewing the use of references throughout the manuscript.
- In line 32, the manuscript states that several frameworks were proposed in response to the Sendai Framework (2023), whereas most of the cited frameworks actually predate 2023.
- I also think it would help the reader if the overall purpose of the paper were introduced before Section 1.1. After reading the introduction, the objective of the study still is somewhat unclear.
1.1 Gaps in multi-hazard research
- The statement that there are "no standardized definitions adopted" is a bit strong. Consider only leaving the following statement that multiple definitions have developed in parallel across different research communities, which is more nuanced.
- The second paragraph of Section 1.1.2 focuses primarily on reporting bias and the representation of multi-hazards in disaster databases, which seems conceptually distinct from geographical imbalance. It may therefore be worth considering this as a separate subsection. More generally, the subsection headings could perhaps be revised to reflect the specific research gap discussed in each section, although the current headings are also adequate.
1.2 Aims of the paper
- The transition from Section 1.1 is somewhat abrupt. Consider moving up the introduction of the overall aim and making the link between the aims and the discussed research gaps more explicit.
- As someone not familiar with the region, I would find it helpful to know immediately that Kerala is located in India when the case study region is first introduced.
- The aims themselves are quite specific and rely heavily on references to existing methodologies and frameworks, making them difficult to follow without prior familiarity with the cited studies. I believe it might be clearer to focus the aims more strongly on the intended outcomes of the study, while introducing the specific frameworks later in the methodology. Alternatively, a brief line explaining what the frameworks entail would be already more helpful than only naming them. For example, the wording in lines 201–202 ("Building on the identification of single hazards...") provide the reader with more information than referring only to the “use of the methodology of Gill et al.” (aim 1).
2. Kerala
- For completeness, consider adding a legend explaining the green shading in Figure 1.
- In line 155, I would consider explicitly referring to disasters (e.g., "most disaster-affected countries" or "recording over 400 disaster events...") for clarity.
- In line 175, it was not entirely clear to me what is meant by "conventional datasets," "supplementary evidence," or "structure inference." A brief clarification would be helpful.
- The sentence in line 176 appears to be incomplete.
3. Methodology
- It is somewhat difficult to link the more general terminology used at the start of this section to the specific frameworks as they are currently introduced in the aims, so the relationship between the aims and the methodological approach is not immediately apparent. The methodology would be a more natural place than the aims to explicitly introduce these frameworks.
- Similarly to my comments on the introduction, it may be worth reconsidering the subsection headings so that they more closely reflect the structure introduced at the beginning of Section 3. This could help guide the reader through the different methodological steps.
- Because the manuscript draws on several existing frameworks, I think it would help the reader if each framework would be introduced more comprehensively at first mention and referred to more consistently throughout the manuscript. For example, in line 191 the "Gill and Malamud (2014) hazard classification framework" is introduced, whereas later (lines 265–266) the manuscript refers to the "hazard interaction matrix of Gill and Malamud (2014)."
4. Results
- Overall, I think the results section is clearly presented and the figures are generally of a high quality
- In Figure 7 I found the "theoretical" gridded fill somewhat difficult to distinguish from the other categories. Increasing the contrast between these may improve readability. I would also consider rotating any labels that are completely upside down.
- Similarly, for Figure 11, rotating the headers that are fully upside down would make the figure easier to read.
5. Discussion
- Lines 377–378: The cited reference (de Ruiter and van Loon, 2022) does not support the statement that disasters evolve through interactions among hazards, as it focuses on dynamic vulnerability and exposure.
Citation: https://doi.org/10.5194/egusphere-2026-2999-RC2
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I would like to thank the authors for a very interesting manuscript; I very much enjoyed reading it. I agree with the authors that detailed local case studies such as this one are novel and very valuable, and that they help address the global imbalance in multi-hazard research towards data-rich regions. I also really like the visualizations; in particular Figures 2, 7 and 10 are a very nice way of conveying a lot of information, and I can see the seasonal matrix being a useful communication tool. I do have some general comments that I would like to exchange thoughts on with the authors, mostly around positioning the extended matrix within recent classification work and the interpretation of some of the headline numbers.
General comments
Minor comments
Suggested literature