While the topic and methodology of the paper present some interesting and novel ideas, i feel the manuscript needs a significant amount of work and restructuring before it can be published in NHESS, which i why i am suggesting major revisions to the manuscript. The main challenge is that this paper tried to do too much. It is hard to follow the narrative/ red thread, and i found myself getting lost in the many steps of the methodology, which is rather eclectic in nature. I feel the paper could benefit from a reduction in steps and aims, which would then link the methods to the results more clearly.

Major comments 

Introduction

The introduction needs significant restructuring and rewriting to draw out the main research gap and aims that the paper is trying to close. The use of non-technical language makes it hard to follow. Review the use of sentences such as the following.

- The third decade of the 21st century debuted with a pivotal epidemiological hazardous event that taught human communities

worldwide formative and often cruel lessons. 

- In the new multi-hazard-prone era

The main sentence and aim of the paper is hidden "This study delves deeper into the changes in vulnerability under hazard-generated impacts, taking as a case study two co-occurrent, independent hazards (i.e., floods and the COVID-19 pandemic) that severely affected a European

country." and the current text does not speak so much to this. The introduction should be restructured to present the challenge, gap and how your work supports closing it.

Methodology

The number of different steps in the methodology make it very hard to follow. While interesting, it is a somewhat eclectic approach in certain areas. I do not agree with the comment "Elevating the Impact Chain from its above mentioned original purposes to a diagnosis and prediction tool represents a pioneering research endeavor, standing out as an element of methodological novelty". Rather, i feel that the entire paper should step away from the statement that you are predicting vulnerability dynamics, as it does not account for the myriad other factors that influence vulnerability (e.g. governance, development, systemic risks) etc etc. 

The ranking of vulnerabilities based on their augmentation is a step that you could consider removing from the publication, given its length and that it is trying to cover a lot for one paper.

Results

4.1 reads like a literature review. I do not see how it links to the methodology presented in the previous section. Are the impacts and events you are describing findings from the synthesis of literature and enhancing the impact chain? If so, state this. The main focus of the paper is how multi-hazard interaction and responses have augmented vulnerability. I suggest to focus of this and reduce the other findings to keep the narrative more easy to follow. 

Discussion

The discussion would benefit much more from reflecting on the methodology and its limitations. currently the limitations are mostly focused on data limitations, and not the limitations of the approach that you took, of which there are some significant ones. A discussion that looks at the novelty of the methods, and how they can be improved would significantly strengthen the paper.

Conclusions

Could be much sharper. The seven key take aways should be reduced to 2/3, that speak to the method you developed and the context specific findings form your case study.

The statement that "Vulnerability is expected to increase due to inaction" is simply not true and is simplification of realty. interaction does not equal intensitication. 

Minor comments

Abstract

Review the use of non-scientific language, which will make it more direct and easy to pull out the main messaging

Setting the scene 

While the content is all relevant, i feel it can be shortened to get the message across more quickly.

The work presented in this manuscript delves into the challenging and forward-looking realm of assessing vulnerability dynamics arising from multi-hazard risks. It does so by introducing a novel application of Impact Chains within a multi-hazard framework. For these reasons, this work holds significance and potential for publication following substantial restructuring.

I report hereafter the major issues that I strongly encourage the authors to fix before publication:

• The final aim of this work is not well explained in the introduction. Is the analysis of multi-hazard pandemic-floods vulnerability dynamics in Romania the main goal, or is it the development of an “enhanced” multi-hazard Impact Chain approach? The authors should pay more attention in framing their research question.
• Lines 93-94: It is not explained which specific transformation has been performed to the original Impact Chains approach. Clarifying this from the outset of the paper would be advantageous, as it would better underscore the novelty of the approach and its advancement beyond the current state-of-the-art. Additionally, it would be beneficial to provide a brief explanation of what are Impact Chains in the introduction, outlining their typical development purpose and traditional field of application.

• The paper is very long and sometimes difficult to follow. I invite the authors to consider shortening some sessions. More specifically, I suggest shortening Sections 2 and 4.
• Lines 152-154: warnings do not always result in actual floods. It's unclear how you linked warnings to real flood events. Did you incorporate data from other sources, as indicated in line 158? This aspect lacks clear elucidation. If mentioned, it should be elaborated upon, including details of the validation procedure.
• The methodology, as explained in Section 3 and illustrated in Figure 4, is very complex and difficult to understand and follow. More specifically, I do not understand the rationale behind presenting two distinct impact chains —the one from the PARATUS project and the one incorporating vulnerability dynamics, and to make a comparison among them (e.g., in Fig.7). In my view, this unnecessarily complicates the methodology and results presentation, potentially confusing the reader. Instead, it would be advantageous to emphasize the modifications made from the original Impact Chains approach to the one delineated in this paper. This should encompass alterations introduced to accommodate multiple hazards as well as those aimed at identifying patterns of dynamic vulnerability. I suggest restructuring the overall methodology to simplify it and also change the presentation of the results in Chapter 4 accordingly.
• Line 224: The Impact Chains approach is a standardized and codified procedure, well-developed and documented in a substantial body of literature. Given that this work builds upon the "original" Impact Chains approach, it is essential to provide additional background references on this methodology and introduce its founding principles in more detail. Regarding the references, please consider citing the following:
  • Menk, L., Terzi, S., Zebisch, M., Rome, E., Lückerath, D., Milde, K., & Kienberger, S. (2022). Climate change impact chains: a review of applications, challenges, and opportunities for climate risk and vulnerability assessments. Weather, Climate, and Society, 14(2), 619-636.
  • Zebisch, M., Schneiderbauer, S., Fritzsche, K., Bubeck, P., Kienberger, S., Kahlenborn, W., ... & Below, T. (2021). The vulnerability sourcebook and climate impact chains–a standardised framework for a climate vulnerability and risk assessment. International Journal of Climate Change Strategies and Management, 13(1), 35-59.
  • Schneiderbauer, S., Baunach, D., Pedoth, L., Renner, K., Fritzsche, K., Bollin, C., ... & Ruzima, S. (2020). Spatial-explicit climate change vulnerability assessments based on impact chains. Findings from a case study in Burundi. Sustainability, 12(16), 6354.
• The “enhanced” Impact Chains approach introduced in this manuscript is presented in several sentences along throughout the text as a predictive tool. However, it appears that Impact Chains are primarily utilized as an analytical tool to deepen the understanding of multi-hazard vulnerability dynamics. I encourage the authors to reconsider this aspect and revise this concept throughout the manuscript.
• Section 3.2 – “Exploring multi-hazard impacts” presents several unclear points.
  1. How the “relevance” and “confidence” parameters are related to the identification of multi-hazard impacts?
  2. The “relevance” and “confidence” parameters are determined by applying the logical data model provided in Figure 5. However, interpreting this scheme may prove challenging for the reader without a more detailed explanation in the main body of the text. Please, explain more in detail.
  3. Please consider explaining the significance of the two metrics presented in Table 2 for identifying multi-hazard impacts. This could also be achieved by incorporating a dedicated column directly into the table.
• The presentation of the Results in Section 4 does not follow the same structure of the methodology, as it is presented in Section 3, and this is not facilitating the understanding of the overall work. I suggest the authors simplify the methodology illustrated in Section 3 and then present the results accordingly.
• Lines 400-401: It is still not clear to me how the Kumu metrics and the relevance parameters are combined to practically identify multi-hazard impacts. This aspect lacks clarity in Section 3 and remains somewhat ambiguous even when transitioning from the methodology to the results. The authors should provide a clearer and replicable explanation of their methodology, particularly concerning the novel aspects they have introduced.
• Following from the previous point, I strongly recommend that the authors incorporate into the Appendix an integration of the original Impact Chains guidelines by Pittore et al. (2023). This would require presenting the new elements they have introduced to the methodology in a standardized and replicable manner.
• Section 5.2: I invite the authors to discuss also some methodological limitations or assumptions they made, which are currently not mentioned, e.g. the limited participation of stakeholders in the construction of the Impact Chains. Indeed, Impact Chains are well suited for use in a transdisciplinary perspective for the co-production of knowledge.
• The entire manuscript would benefit from a systematic review of the language, including enhancements to the vocabulary and terminology.

Other medium to minor issues:

• Lines 30-31: The authors affirm that the co-occurrence of COVID-19 and other natural hazards has “caused a paradigm shift” from multi-ayer single hazard approaches to interacting hazards. Indeed, the shift has been started before the occurrence of COVID-19. The co-occurrence of COVID-19 and other natural hazards has instead increased the attention to potential synergies and asynergies between pandemics and other hazards from the Disaster Risk Management and Emergency Management perspectives (see Terzi et al, 2022). Please, consider rephrasing this sentence.
• Lines 34-35: please add references for the Sendai Framework and the Paris Agreement.
• Lines 42-43: “a European country”. I think it would be more beneficial to indicate directly which country.
• Lines 61-62: Here there is a sudden shift of topic. The authors previously discussed vulnerability dynamics up to line 61, but then abruptly shifted focus to operational hazard management procedures during the COVID-19 pandemic. It seems there's a gap here, lacking a sentence that introduces why and how COVID-19 has posed challenges from a multi-hazard perspective.
• Table 1. This table, as it is presented, is not very informative and useful. It would be more beneficial to add a column to specify which kind of management issue has been encountered in each of the presented real-world cases.
• Section 4.1, lines 378-381: several hazards are mentioned, but only pandemics and floods are selected. The authors should support this choice by providing some evidence. Moreover, I suggest moving this discussion to the beginning of Section 2, when the case study of floods and COVID-19 is discussed for the first time.
• Section 4.1: it would be beneficial to include a table summarizing the main multi-hazard impacts discussed in the text.
• Figure 8 does not seem to be so relevant to be included in the paper, since a specific analysis and discussion of spatial distribution of flood impacts is not performed in the study.