the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Exploring the driving factors of compound flood severity in coastal cities: a comprehensive analytical approach
Abstract. Coastal cities frequently face various types of flooding triggered by heavy rainfall and storm surges, such as fluvial flooding and pluvial flooding. Currently, Currently, there is a lack of comprehensive methods to analyse the sources of severe compound flooding. This study, using the Shahe River Basin in Guangzhou, China as an example, establishes and validates a coupled 1D and 2D hydrodynamic model. Based on historical data, it constructs joint probability distributions of rainfall and tidal levels with different return periods and durations. Using the results from the coupled model under various design scenarios, it proposes an impact index to quantify the contributions of rainfall and tides to flooding. Furthermore, it quantifies the interactions between fluvial flooding and pluvial flooding. Flood-prone areas are delineated, and the causes of flooding are analyzed. The results show that when the return periods of rainfall and tide level are both 10 years, the Kendall return period for the combined event of rainfall and tide level is 36.35 years, greater than the “Or” return period (5.40 years) and less than the “And” return period (66.88 years). The impact degree index of rainfall on flooding varies between 0.5 and 1, with the minimum at 24-hour duration, indicating that the study area is primarily affected by rainfall and the influence of tide level is most significant at 24-hour duration. The pluvial flooding caused by the influence of river water level on the drainage outlet accounts for 19.08 % of the total volume at most. This shows that fluvial flooding affects the seriousness of pluvial flooding by influencing the water levels of outlets. The flood-prone area is divided into different regions based on the main natural factors (rainfall and tidal level) and social factors (pipeline network, drainage outlets, and riverbank defenses) to help decision-makers identify the causes of flooding in each drainage unit and better formulate targeted disaster reduction strategies to improve flood control capabilities.
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Status: open (until 20 Jul 2024)
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RC1: 'Comment on hess-2024-100', Anonymous Referee #1, 06 May 2024
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In this study, the authors conducted a comprehensive investigation of the driving factors behind compound flooding in coastal cities using a combination of hydrodynamic modeling and mathematical statistics. Their research yielded insights into the impact of rainfall and tidal levels on compound flooding, as well as the contributions of different types of floods to compound flooding. The conclusions of this study are novel and have positive implications for risk management. The chosen topic also aligns with the scope of the journal "Hydrology and Earth System Sciences." , I have several suggestions and recommendations that would help enhance the manuscript.
Specific comments
- It is necessary to indicate whether there are tide prevention facilities in the study area and how this factor is considered in the model.
- In the "Model construction and validation" section, a one-dimensional and two-dimensional hydrodynamic coupling model was constructed, but the analysis of flood severity primarily relied on flood volume, with limited analysis on indicators such as flood area and flood depth. This aspect needs to be supplemented.
- The paper only mentioned the length of the original data but did not elaborate on the sample data situation for constructing the Copula function.
- The paper is lengthy, and to be concise, compressing the research methods section would be helpful. For example, common formulas in Correlation and Copula.
- In the section "Spatial interaction of drainage units," the analysis of the interaction forces between different drainage units is not highly relevant to the main theme of this paper.
- In section 4.4 "Causes and prevention measures of floods in drainage units," flood prevention measures should not be discussed in the research results. It is suggested to elaborate on them in the discussion section.
- The conclusion needs further refinement.
Technical comments
L11: The word "Currently" is repeated.
L31: Change "in this year" to a specific year.
Figure 1: Mark all drainage outlets in the figure.
Table 1: Explain why the RMSE of the edge distribution function corresponding to the optimal tidal level for 3h is not the best.
L430-431: What is the specific relationship? It needs to be clarified.
L457-459: Drainage unit 14 appears in both cases simultaneously, please verify.
L460-461: Same as above.
L508-509: This is an observation, not a conclusion.
Figure 14: The discussion of the causes of sudden changes is crucial.
L520-522: This should be in the Methods section.
Citation: https://doi.org/10.5194/hess-2024-100-RC1 -
AC1: 'Reply on RC1', Ting Zhang, 04 Jun 2024
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请随函附上对 Reviwer 1 评论的回应 pdf。
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AC2: 'Reply on RC1', Ting Zhang, 04 Jun 2024
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Dear Reviewer,
Thank you again for your comments. I am writing to apologize for the inadvertent inclusion of Chinese text in our last response to your review comments. Due to a browser error, our intended English text was partially replaced by Chinese characters, which might have caused confusion.
The correct expression is: “Please find attached a PDF responding to the comments of Reviewer 1.” The attachment file in the last reply is correct.
Thank you for your patience and support.
Best regards,
Ting Zhang
Citation: https://doi.org/10.5194/hess-2024-100-AC2
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