Conundrum of Hydrologic Research: Insights from the Evolution of Flood Frequency Analysis
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsGeneral comments
Good review paper that needs more detail before publication. Please, see the specific comments to fix the current issues. I am available to review the manuscript a second time under request of the editors.
Specific comments
Lines 37-39. “Furthermore, it appears that scientists and engineers are increasingly pursuing separate paths as hydrology has become a part of geosciences”. Please, insert hydrological reviews that incorporates surface / groundwater interaction from schools of geoscience.
- Agbotui, P. Y., Firouzbehi, F., Medici, G. 2025. Review of effective porosity in sandstone aquifers: insights for representation of contaminant transport. Sustainability, 17(14), 6469.
- Sophocleous, M. (2002). Interactions between groundwater and surface water: the state of the science. Hydrogeology journal, 10(1), 52-67.
Line 63. Introduce the word “aim” or “goal” of your research here.
Line 63. Describe the specific objectives of your research by using numbers (e.g., i, ii, and iii).
Line 88. “geologic dating”. Please, be more specific. Do you mean providing the age of alluvial sediments by fossiliferous content or other techniques?
Line 557. You don’t treat much the revolution which might be at the door with AI. Is it worth to comment on that?
Line 446. “a”, “b”, “c”, and “d”. Are the specific objectives four (see comment above)?
Line 559. Integrate the relevant hydrological literature suggested above.
Figures and tables
Table 1. The table does not mention all the key elements. Please, expand description.
Table 2. Same here. The table does not mention all the key elements. Please, expand description.
Figures. Figures are absent. I would add 2 or 3 conceptual schemes. Review papers are typically characterized by such figures.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments and Suggestions for AuthorsThe manuscript is both timely and relevant, offering a thoughtful reflection on the persistent epistemological divide between hydrologic science and engineering practice. To further enhance its clarity and practical impact, the authors could consider adding a concise visual summary, such as a table or diagram, illustrating the five historical eras and their dominant paradigms. The conclusion would also benefit from a clearer articulation of how the historical insights presented translate into actionable guidance for contemporary engineering practice, for example, in relation to flood design standards or resilience-based approaches. Finally, the discussion on “synthesis” among scientists, engineers, and stakeholders could be expanded to suggest tangible pathways or frameworks through which such interdisciplinary collaboration might be achieved.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
Comments and Suggestions for AuthorsIn this work, the Authors discusses the scientific progress and research obstacles in the field of Hydrology in the 19th and 20th centuries, with focus in the flood-frequency analysis; I much enjoyed reading this paper, and I only have some (mainly) minor suggestions to further highlight it:
1) I find difficult to understand the connection analogy between "quantum and Newtonian physics" for the hydrological research; do the Authors mean that the field of Hydrology needs also a strong leap forward? If yes, please consider enhancing this comparison by mentioning some specific examples between Physics and Hydrology (e.g., ancient Greek Mythology vs. Newtonian physics and Hydrology; see examples for flood explanations for floods in Angelakis et al., 2023; doi.org/10.3390/land12061211).
2) There is an interesting review paper, which could be added in the discussion of the Authors regarding their literature review, about the history and criticism of hydrological models, with focus on the uncertainty in frequency analysis and continuous simulation models by Beven (2021; doi.org/10.1002/hyp.14203).
3) The Authors mention that there is a "lack of a unified best practice for modeling univariate extremes, along with the challenges of fitting and interpreting complex models with intricate structures" by also mentioning the L, LH moment etc.; please see the latest research by Koutsoyiannis (2024; doi:10.57713/kallipos-1), where they try to accomplish exactly this (i.e., review and new mathematical achievements, such as the K-moments, in the risk analysis of the hydrological extremes).
4) Regarding the statistical analyses and the selection of a unique probability distribution, which has several benefits over the most commonly used in rainfall-runoff processes (such as the 4-parameter generalized gamma and the Burr distributions), please see a recent global-scale analysis on the key hydrological-cycle processes, where the truncated mixed Pareto-Burr-Feller distribution is found to be theoretically and practically quite acceptable in thousands of rainfall and runoff processes around the globe by applying certain methods to tackle the different lengths and seasonality of each station.
5) Regarding the GEV distribution, please note that it is indeed (as the Authors mention) "the unique limiting distribution for the normalized maxima of a sequence of independent and identically distributed random variables"; however, there are evidence that maxima are not always independent and therefore, a different mathematical technique should be applied to deal with the hidden persistence in extremes (see discussion and suggestions in Iliopoulou and Koutsoyiannis, 2019; doi:10.1080/02626667.2019.1657578).
6) The Authors mention several ML models; please consider adding to the review one of the latest applied ML models in rainfall-runoff processes (see Tepetidis et al., 2024; doi:10.3390/w16202882), which is the Informer initially applied to temperature.
7) As a final remark, I would suggest adding to the breakthroughs in Hydrology frequency analysis, the Stochastic analysis (which is not the same as the mentioned statistical analysis); I think this is one of the major accomplishments in the last centuries, where through the field of Stochastics, hydrologists managed to link strong mathematical theories and fields (such as fractals, chaos, etc.) to the practical need in Hydrology in order to tackle the issue of uncertainty (regarding rainfall-runoff processes, there is a recent study that links the streamflow process in 9-orders of magnitude, and thus, highlighting that although there may be different climatic regimes or various hydrological conditions, there are certain stochastic similarities in hydrological processes permitting hydrologists to observe the hidden model of the target process; see Pizarro et al., 2022; doi:10.3390/hydrology9070126).
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors have made the necessary changes
Author Response
Comment 1: The authors have made the necessary changes.
Response 1: Thank you so much for reviewing this paper.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors have carried out a major revision of the text. The structure is now more coherent, and several comments from the reviewers have been addressed. The authors have added references and corrected linguistic issues. Some minor improvements are required concerning the clarity of some sections and the quality of the images.
Author Response
Comment 1: The authors have carried out a major revision of the text. The structure is now more coherent, and several comments from the reviewers have been addressed. The authors have added references and corrected linguistic issues.
Response 1: Thank you so much for reviewing the paper.
Comment 2: Some minor improvements are required concerning the clarity of some sections and the quality of the images.
Response 2: The comment was addressed. The authors thoroughly proofread the manuscript to improve clarity. All figures were reinserted without distortion or stretching, and high-resolution PNG/JPG file for each figure was uploaded separately.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe Authors have addressed all comments and provided details and justifications to their replies and revisions; please see only a couple minor ones:
1) Figure 3 seems to be unevenly stretched; please check the quality resolution.
2) A good practice in such works is to illustrate Graphs from the Google Scholar Ngrams (https://books.google.com/ngrams/info), as for example, have the words "Hydrology" and "Flood Frequency" increased or decreased throughout the last decades, etc.
Author Response
Comment 1: The Authors have addressed all comments and provided details and justifications to their replies and revisions.
Response 1: Thank you so much for reviewing the paper.
Comment 2: please see only a couple minor ones:
1) Figure 3 seems to be unevenly stretched; please check the quality resolution.
Response 2: The comment was addressed. All figures were reinserted without distortion or stretching, and high-resolution PNG/JPG file for each figure was provided separately.
Comment 3: 2) A good practice in such works is to illustrate Graphs from the Google Scholar Ngrams (https://books.google.com/ngrams/info), as for example, have the words "Hydrology" and "Flood Frequency" increased or decreased throughout the last decades, etc.
Response 3: Canva was used to prepare Figure 3. It is important to note that recent studies report contradictory findings regarding whether flood frequency is increasing or decreasing (e.g., https://doi.org/10.5194/hess-24-1805-2020). A thorough investigation of this topic would require more in-depth analysis or a dedicated review, which is beyond the scope of the present study. The authors also emphasize that the purpose of Figure 3 is to illustrate the divergent evolution of hydrologic research, rather than to imply any specific trend.
