Review of “Development of A Land-River-Ocean Coupled Model for Compound Floods Jointly Caused by Heavy Rainfalls and Storm Surges in Large River Delta Regions” by Zhang and Yu

This work develops a Land-River-Ocean coupled model and evaluates its performance in simulating flood inundation through its application in the Pearl River Estuary. The results indicate that the model's simulation matches well with observations, demonstrating the potential practical application value of the developed model. Overall, this work leans more toward technical model development and evaluation, with relatively weaker scientific novelty. However, considering its practical application value, I recommend publication after revisions. Specific comments are as follows:

Major comments:

1. Incomplete model configuration information. In Section 3, the authors chose the Pearl River Estuary as the study area and examined several typhoon-related flood inundation events to evaluate the model's simulation capability. However, the authors seem to omit some critical information. For example, the source of depth and elevation data is not shown, which is crucial as they largely determine the simulation results. Did the authors use publicly available topographical data, or did they extract it from nautical charts? What is the resolution? How accurate is it? These details should be explained thoroughly in the text. The source of the boundary conditions and tidal forcing data for the ocean model. What is the resolution of these data? The authors also seem to have omitted this information entirely.
2. The model's advantage. The authors frequently mention the advantage of this coupled model in the text. For instance, in Lines 59-69, the authors state that previous models have simplified the coupling to some extent, whereas the model developed here has made no such simplifications. Similarly, in Lines 252-257, the authors claim that the accuracy of their model is higher than that of previous studies. They further suggest that one possible reason for the improved accuracy is the more comprehensive coupling in their model. I believe the highlight of this work is indeed the more comprehensive coupling. However, the authors do not provide any direct evidence to demonstrate that the improved simulation results are due to this comprehensive coupling. Simply comparing the results to previous studies is insufficient. The differences in simulation results could arise from many factors, such as differences in topographical data or atmospheric forcing data. The authors have not excluded these factors before concluding that the improvements are due to the coupling, which is not convincing.

Minor comments:

1. Line 16-18: This statement is obvious. The authors conducted quantitative analyses in the text and should provide their quantitative contributions here.
2. Line 128: When calculating wind stress here, the eAWBLM model considers the influence of waves. Does it also account for ocean currents? Figure 2 seems to suggest that ocean currents are not considered in this model.
3. Line 137-138: remove the extra parentheses.
4. Line 230: In this section, the authors analyze the results for runoff, storm surges, and flood inundation, showing that the model performs well. However, as mentioned in Major Comment 2, the authors should conduct a more in-depth study of what aspects the model performs well in and what aspects it does not. For example, they could conduct sensitivity experiments to demonstrate which aspects are due to the coupling and which are due to accurate wind field data.
5. Figure 6: The upper subplot should also have the label. The comparison of flood inundation here seems overly qualitative. Could the authors provide some quantitative results to clarify the issue? For instance, what is the observed inundation area? What is the simulated inundation area? Are there significant differences between the two?
6. Figure 8: The quantitative results here should be reflected in the abstract.
7. Line 355: The conclusion is overly simplistic, with most of the section describing the simulation results in the Pearl River Estuary. It does not highlight the key points of this study, such as the effects of more comprehensive coupling and the improvements in simulation performance.

The manuscript develops a land-river-ocean coupled model to simulate compound floods caused by the combined effects of storm surges, astronomical tides, storm waves, precipitation, and river flow. The model’s effectiveness is validated through hindcasting of five typhoon events (including Hagupit 2008, Koppu 2009, Vicente 2012, Hato 2017, and Mangkhut 2018) in the Pearl River Delta region. The manuscript explores the contributions of ocean processes, river base flow, and precipitation to compound floods, and compares the results of one-way and two-way coupling models, revealing the impact of different coupling approaches on flood simulation outcomes.

The study is well-structured, and the methodology is sound. Nevertheless, it is expected that the manuscript will undergo further refinement before publication to address the identified issues.

Major comments:

1. Although the manuscript highlights the advantages of the two-way coupling model, it does not address the computational cost comparison with one-way coupling. A discussion on the computational complexity, including whether two-way coupling significantly increases computation time and if optimization can reduce costs, would be valuable.
2. The manuscript mainly focuses on the Pearl River Delta region. Although it mentions the model's general applicability, it would be helpful to include a discussion in the conclusion on the model's applicability to other regions, such as large river deltas or low-lying areas, and assess whether the model needs to be adjusted based on the characteristics of different regions.
3. The manuscript demonstrates the advantages of two-way coupling by comparing it with one-way coupling. It would be beneficial to further compare this model with existing coupled models, particularly the most advanced ones, and discuss its strengths and limitations, especially in terms of accuracy and efficiency.

Minor comments:

1. LN 152-155: " In this study, we perform … simulate compound floods." - The original sentence is too long and contains too much information. It should be split into two clearer and simpler parts to improve readability. - "This study hindcasts five tropical cyclone (TC) events [Hagupit (2008); Koppu (2009); Vicente (2012); Hato (2017); Mangkhut (2018)] that caused destructive floods in the Pearl River Delta over the past two decades, to validate the model developed for simulating compound floods."
2. LN 358-359:“ …induced by five Typhoon events occurred…” - "Occurred" is in the past tense, but since "induced" is in the past participle form, they should be consistent. Therefore, "occurred" needs to be changed to the past participle "that occurred" to maintain tense consistency in the sentence.
3. The image quality is insufficient. It is recommended to replace the image with a vector format.