We are pleased to respond to the helpful and constructive comments of the anonymous referee, which were posted on the NHESS Discussion page on July 31, 2023 , respectively. The referee’s comments and our responses are presented below. 

 Reviewer 1 

 1. Novelty uncertain - In the review, different modeling approaches are described (e.g., physical, physically-based, and empirical), but there is no review on the current state of physically-based modeling which is the modeling method used. A review on physically-based approaches and their applications is needed to demonstrate the need for and novelty of this work. Similar datasets exist from First Street Foundation and Fathom. Comparing this dataset to existing ones can provide further context of this work. 

 RESPONSE: We will discuss the state of physically-based modeling in the literature review to contribute to the context of this paper. We will then reflect on this state in the discussion and conclusion sections to make the novelty of the presented method more apparent. 

 2. Modeling details - The description of the modeling methods was very general. More details are needed to understand how the dataset used was produced, especially for pluvial modeling since pluvial was the driving mechanism in the results. 

 RESPONSE: In the revised manuscript, we will provide more information on the methodology as suggested.  

 3. Include more return periods in analysis - There were several return periods listed that the data was available for, but results were only reported for the 100-year event. Consider comparing the driving flood mechanism across multiple return periods as this could yield interesting and innovative results. 

 RESPONSE: We will consider comparing and presenting the driving flood mechanism across multiple return periods. 

 4. Line-specific comments. 

 Pg. 2, line 35 - The IPCC citation is not included in the reference list and not in alphabetical order 

RESPONSE: The IPCC citation will be added to the reference list and the in-text citation will be presented in alphabetical order. 

 Pg. 2, line 40 - change anticipating to anticipate 

RESPONSE: “Anticipating” will be changed to “anticipate”. 

 Pg. 4, line 106 - Section is not numbered 

RESPONSE: Section number will be added. 

 Pg. 4, line 142 - Is citation reference to the 2022a or 2022b reference? 

RESPONSE: The citation is in reference to Natural Resources Canada, 2022a. We will update the citation. 

 Pg. 5, line 154 - The review of Canadian flow mapping throughput history and different initiatives provides nice context. 

RESPONSE: Thank you. 

 Figure 1 - Consider condensing Figures 1 and 2. Could add a fourth panel to Figure 2 that shows the inundation including all flood mechanisms for the 100-yr event and eliminating Figure 1. 

RESPONSE: Figure 1 will be eliminated, and a fourth panel will be added to Figure 2 that includes all flood mechanisms for the 100-yr event. 

 Pg. 6, line 176 - use of the ‘coverage observed’ - this could be confusing for readers since this isn’t referring to a historical, observed event. Consider changing the language to ‘coverage modeled’ or ‘observed from modeling.’ 

RESPONSE: The language will be changed to “observed from modeling”. 

 Pg. 6, line 177 - The use of low to high scale. Figure 2 includes depth ranges instead of qualitative scale. Could the flood depths scale be used for Figure 1? 

RESPONSE: We will explore whether using the flood depths for Figure 2 is viable. 

 Pg. 6, line 184 - Figure 2 captions says its mapping the 100-yr event not the 1,500-year RP. 

RESPONSE: The reference to Figure 2 will be amended to reflect the 100-yr event. 

 Pg. 8, line 198 - “infiltration coefficient” - I would like to see more details on how this was calculated and applied. Was it assumed to be the same across the study site, or did it vary based on land use or % imperviousness or some other method? 

RESPONSE: We will add some clarity around how the infiltration coefficient is determined and applied. We do use different coefficients in our modelling to represent different land-use (rural, semi-urban, urban and so on). However, for this study, the same consistent infiltration coefficient was used across the whole urban area. We recognize that this is a limitation because the true infiltration capacity at any given location will vary, but very detailed information on drainage isn't always available, or more importantly, is not always reliable. Hence a general assumption was applied.  

 Pg. 8, line 210 - Include more detail on these “change factors” - how are they developed and applied. 

RESPONSE: We will expand this section to provide more clarity. 

 Pg. 8, line 216 - Again, more detail on “change factors.” Were the change factors for the hydrographs calculated differently than the change factors for the rainfall? 

RESPONSE: We will add some clarity. 

 Page 12, line 283 - make “elevation” plural 

RESPONSE: We will make elevation plural. 

 Page 12, line 285 - Was there consideration of making additional thresholds for measuring the severity of building exposure? Could include an additional threshold equivalent to the height of a first floor since the flood depths exceed 6 meters in some scenarios. 

RESPONSE: We will assess the feasibility of additional thresholds for measuring severity of building exposure. 

 Page 12, line 292 - “combination of flood types” - Does this mean a building was flooded by both or all three flood types? Add a brief clarification as to how this was determined. 

RESPONSE: A clarification will be added. 

 Page 12, line 292 - Change “combination” to “multiple” because the modeling considered the flood mechanism separately, and did not implement compound modeling where the mechanisms are included simultaneously in the model. Combination might imply flood mechanisms occurring at the same time and be misleading. 

RESPONSE: We will change “combination” to “multiple”. 

 Page 13, line 300 - Results show pluvial is the driving mechanism of flood exposure. Why do you suppose that is? Consider adding this to the discussion. 

RESPONSE: It is indeed very common for pluvial flooding to be the dominant flood type - partly as it is not limited to areas close to rivers or the coast, but also in urban environments where the drainage capacity is insufficient to handle the volumes of rain experienced. We shall add some thoughts into the discussion, including more specific thoughts on the situation in Vancouver.  

 Page 13, line 306 - Mention the role of “infrastructures and waterways.” Does the model consider stormwater infrastructure? 

RESPONSE: We apply only drainage capacity assumptions, rather than adding any specific details on stormwater infrastructure. We will add a sentence into the text to clarify. 

 Figure 4 - Is the middle map of a different location? Why not use the same location for the pluvial flood mechanism as well? 

RESPONSE: We will clarify and/or replace the middle map as suggested. 

 Pg. 19, line 32 - Word choice of the word “greater.” Consider changing the first instance to “larger amounts of water” and the second instance to “further exposure” to add clarity. 

RESPONSE: We will adjust the language in accordance with the suggested wording. 

 Figure 5 - Consider splitting the classification of “continued exposure” into two groups: “continued exposure” and “worsened exposure” based on a building going from moderate to severe exposure. This could add more information to the figure to show not only where new exposure occurred but also where it was made worse by climate change. 

RESPONSE: We will explore the feasibility of stratifying the climate change results into "continued exposure" and "worsened exposure". 

 Page 20, line 41 - What model assumptions are being referred to? Be specific. 

RESPONSE: We will add greater specificity around the model assumptions that were referenced. 

 Page 20, line 43 - “two of the three assets.” The sentence before mentions 14 buildings, so not sure where three assets are coming from. 

RESPONSE: The “two of the three assets” are illustrated in Figure 6 as a subset of the 14 buildings determined to be exposed in a non-climate change state, but not exposed under RCP 8.5 for 2080 at the 100-year return period. We will clarify this in the revised paper. 

 Page 20, line 46 - the small pockets of disjointed water causing changes. Perhaps this is an opportune place to discuss the role of model uncertainty on the output since the only input that was changed was increasing rainfalls based on climate change. 

RESPONSE: We will add some discussion on the role of model uncertainty on the output here. These very small artifacts in map output (e.g. where we are seeing flooding in the future map that wasn't present in the non-climate change state) do reflect the complexity in the modelling process, and for example, the way rounding of parameters can propagate through to the end map slightly differently.  

 Page 21, lines 54-56 - can add that pluvial flooding was the driving mechanism, so excluding this in flood mapping could result in harmful consequences 

RESPONSE: We will add a sentence explaining the consequences that excluding pluvial flooding could have on flood mapping. 

 Page 21, line 61 - Provide more detail on the approaches' scalability. 

RESPONSE: We will expand on the scalability of the modeling approach.  

 Page 21, line 62 - Why is there greater uncertainty in the pluvial flood estimation? 

RESPONSE: We will clarify why there is greater uncertainty in the pluvial flood estimation. 

 Page 22, line 83 - make ‘building’ plural 

RESPONSE: We will make “building” plural. 

 Page 22, line 84 - Add clarity to wording. Buildings are not a source of exposure, but an increase in development leads to a greater density and number of buildings that can be exposed to flooding. 

RESPONSE: We will revise the sentence to clarify that future development will lead to higher risks under future climate conditions because of the anticipated added density and number of buildings that will be exposed. 

 Page 22, line 85 - Again, buildings are not a source of flooding, but they increase the number of assets that can be exposed. 

RESPONSE: Noted. We will make corrections to the sentence. 

 Page 22, lines 95-96 - Sentence is unclear. 

RESPONSE: We will clarify that while the model helps produce high resolution maps, further physical modelling could help to improve the precision to a 1- to 2-metre resolution. 

 Page 22, line 98: Validation is discussed, but what about the roles of uncertainty of and sensitivity analysis on the dataset and the results? 

RESPONSE: We will revise the paper to include a discussion on the roles of uncertainty and sensitivity analysis on the dataset and the results. 

 Page 24, line 161 - Reference is in the reference list but not cited in the manuscript 

RESPONSE: This reference will be removed. 

 Page 27, line 236 - Reference is in the reference list but not cited in the manuscript 

RESPONSE: The Pörtner et al. (2019) reference listed refers to the IPCC 2019 in-text citation that was listed on page 2. We will adjust the IPCC 2019 reference to Pörtner et al. (2019). 

1. I agree with the first reviewer that the level of novelty in this paper is uncertain. 

RESPONSE: We will present the state of physically based modeling in the literature review and reflect on that state in the discussion and conclusions sections to make the novelty of the paper clearer. 

 2. The authors claim that their primary focus is on a general flood exposure approach, but upon examination, it becomes evident that 90% of the content is around the flood hazard model. The introduction and literature review sections primarily delve into flood hazard modeling techniques and approaches. While a flood exposure method is presented in the methodology section, it appears to be quite limited. 

 RESPONSE: We will expand on the flood exposure method description in the methodology section. 

3. The flood exposure methodology introduced in this paper is notably simple, and the level of uncertainty associated with it is high. In line 264, it is explained that when any part of a building is implicated by flood hazard data, the maximum flood depth value is assigned. Given the localized nature of the analysis, I would recommend that the authors explore alternative approaches to reduce this uncertainty.  

 RESPONSE: For the revised manuscript, we will explore alternative approaches to reduce the uncertainty, or we will explain why this is inappropriate or impossible. 

4. Furthermore, the authors make certain assumptions, such as those presented in line 279 where they introduce subclasses of exposure. While they argue that these assumptions are reasonable for Canada, they neither provide a comprehensive explanation nor support them with relevant literature. 

RESPONSE: For the revised manuscript, we will explain why the assumptions made to achieve the subclasses of exposure are appropriate for Canada. 

5. In light of these concerns, I would recommend major revisions to the paper. The primary objective of the paper should be clearly defined, and appropriate methodologies and approaches should be employed accordingly. There is a substantial body of literature available on flood exposure and local-level methods, which the authors should draw upon to enhance their work. 

RESPONSE: The primary objective of the paper will be clearly defined, and the description of the methods will be expanded where possible. Moreover, the literature review will include more information on flood exposure and local-level methods, which will then be reflected on in the discussion section of this paper.