Technical Note: Operational calibration and performance improvement for hydrodynamic models in data-scarce coastal areas

Rodrigues do Amaral, Francisco; Camenen, Benoît; Nguyen Trung, Tin; Anh Tu, Tran; Pellarin, Thierry; Gratiot, Nicolas

doi:https://doi.org/10.5194/egusphere-2024-1563

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https://doi.org/10.5194/egusphere-2024-1563

Preprints

08 Jul 2024

| 08 Jul 2024

Technical Note: Operational calibration and performance improvement for hydrodynamic models in data-scarce coastal areas

Francisco Rodrigues do Amaral, Benoît Camenen, Tin Nguyen Trung, Tran Anh Tu, Thierry Pellarin, and Nicolas Gratiot

Abstract. In this study, we address the challenges posed by data scarcity in hydrodynamic modeling within one of the most vulnerable coastal zones in the world—the Saigon-Dongnai tidal river system in South Vietnam. We investigate calibration strategies for a 1D hydrodynamic model using minimal in-situ data obtained from an existing local monitoring program, which provides 48 hours of measurements per month. To further improve discharge estimation from the 1D model, the coupling of a modified Manning-Strickler (MS) equation is explored. Calibration efforts reveal distinct trends in friction coefficients along the river. The introduction of indirectly measured discharge data significantly improves model performance, particularly for the Saigon River branch. Validation against independent measurements demonstrates promising results, with the coupling of the modified MS equation providing improved discharge estimates. The study underscores the complexities of calibrating hydrodynamic models in data-scarce regions, with recommendations for future modeling endeavors including incorporating more accurate upstream boundary conditions. The long time-series of estimated water level and discharge provided by this study have practical implications for water resource management and decision-making in data-scarce estuarine systems and are provided in open-access for operational use.

Received: 24 May 2024 – Discussion started: 08 Jul 2024

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Journal article(s) based on this preprint

12 Sep 2025

Technical note: Operational calibration and performance improvement for a 1D hydrodynamic model in a data-scarce coastal area

Francisco Rodrigues do Amaral, Benoît Camenen, Tin Nguyen Trung, Tran Anh Tu, Thierry Pellarin, and Nicolas Gratiot

Hydrol. Earth Syst. Sci., 29, 4327–4340, https://doi.org/10.5194/hess-29-4327-2025,https://doi.org/10.5194/hess-29-4327-2025, 2025

Short summary

Francisco Rodrigues do Amaral, Benoît Camenen, Tin Nguyen Trung, Tran Anh Tu, Thierry Pellarin, and Nicolas Gratiot

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2024-1563', Anonymous Referee #1, 15 Oct 2024
The study involves the development of a coupled 1D and Manning-Strickler (MS) equation. This framework facilitates computationally efficient and accurate estimation of discharges in the data-scarce tidal river system in South Vietnam. The study also discusses the implications of calibrating the framework using discharge and water-level measurements. Though the concept and the calibration approaches are interesting, the paper could benefit from a detailed revision in terms of content, organization, and clarity. The following points need to be addressed.
Given that there are several cost-efficient and more accurate modelling approaches, such as the quasi-2D local inertial (Bates et al., 2010; Sridharan et al., 2020) and sub-grid approaches (Neal et al., 2012; Nithila Devi et al., 2024), it is not clear how the proposed method is more computationally efficient and accurate. It would be nice to see a comparison of the proposed approach with a local inertial formulation in terms of accuracy and computational cost.

For a longer reach, as used in the study, there may be lateral inflows, and it would be ideal to set up a coupled hydrological and hydraulic modelling system. If the authors are not attempting it, then a valid reason can be provided for the same, or this should be mentioned as a limitation. It is also unclear what the intended use of this modelling framework is – real-time forecasting or long-term continuous simulation. Again, for a longer-duration simulation, it is necessary to couple hydrological and hydraulic models.

The methodology is not clear and difficult to understand. A concise description of the overall framework or the coupling can be provided at the beginning of the methodology section. Is it only the energy slope that has been calculated by the 1D code at the point of interest by the MS equation? If other hydraulic variables are also calculated from the 1D code, it should be mentioned in the methodology flow chart.

The paper should explicitly state the calibration and validation periods used in the proposed method. This is important as the calibration and validation periods have to be distinct (For example, Bhargav et al., 2024). It is unclear from the text which events from 2016, 2017 and 2022 have been used for calibration and validation.

With the advent of technologies, getting a high-resolution elevation data set would be possible. Whether the surveyed cross-section has been used to construct the 1D model or a high-resolution dataset has been used to represent the bathymetry is not clearly mentioned in the paper.

Importantly, if the point of this exercise is to have a good simulation of flooding in urban areas, as mentioned in the article, then the ideal choice would be to use a simplified 2D model that can effectively represent the flood inundation dynamics on the complex urban flood plains. The presence of urban infrastructure, such as buildings, roads, streets, etc., governs flood conveyance and distribution. Also, such a claim requires validation using post-flood depth surveys. A coupled 1D and 2D modelling approach can be preferred in this case. Therefore, the authors need to acknowledge the proposed approach's limitations, constraints and advantages. In the introduction, it is also worthwhile to mention whether the focus is only on discharge estimation.

Specific comments
The usage of the term indirectly measured discharge in the abstract is misleading.

The introduction can include a concise literature review of the existing accurate and computationally efficient hydraulic modelling approaches (not just the ones specific to the region). And briefly discuss how the proposed framework stands out from the existing.

Line 27. How is drought modelling relevant here? Are we looking at continuous simulation across all the seasons?

Line 34. Please mention the advantage of the proposed method over Camenen et al. (2021) clearly and why it requires continuous water-level data for calibration.

Line 39. What do you mean by “calibration was not precise?”

Line 56. What is Mage code? It is suddenly introduced in the text here.

Lines 60 – 70. These lines look like the conclusion of the study.

Line 162. Please explain Brent’s algorithm in a sentence or two.

The results and discussion sections are too wordy. They can be shortened to convey things clearly and concisely.

References
Bates, P. D., Horritt, M. S., & Fewtrell, T. J. (2010). A simple inertial formulation of the shallow water equations for efficient two-dimensional flood inundation modelling. Journal of hydrology, 387(1-2), 33-45.
Bhargav, A. M., Suresh, R., Tiwari, M. K., Trambadia, N. K., Chandra, R., & Nirala, S. K. (2024). Optimization of Manning’s roughness coefficient using 1-dimensional hydrodynamic modelling in the perennial river system: A case of lower Narmada Basin, India. Environmental Monitoring and Assessment, 196(8), 743.
Neal, J., Schumann, G., & Bates, P. (2012). A subgrid channel model for simulating river hydraulics and floodplain inundation over large and data sparse areas. Water Resources Research, 48(11).
Nithila Devi, N., & Kuiry, S. N. (2024). A novel local‐inertial formulation representing subgrid scale topographic effects for urban flood simulation. Water Resources Research, 60(5), e2023WR035334.
Sridharan, B., Gurivindapalli, D., Kuiry, S. N., Mali, V. K., Nithila Devi, N., Bates, P. D., & Sen, D. (2020). Explicit expression of weighting factor for improved estimation of numerical flux in Local Inertial models. Water Resources Research, 56(7), e2020WR027357.
Citation: https://doi.org/10.5194/egusphere-2024-1563-RC1
- AC1: 'Reply on RC1', Francisco Rodrigues do Amaral, 07 Mar 2025
  
  Dear Reviewer 1,
  
  We sincerely appreciate the thorough evaluation of our manuscript and would like to thank you for your comments.
  We address reviewers' suggestions in the attached document.
  With kind regards,
  The Authors
  
  Citation: https://doi.org/10.5194/egusphere-2024-1563-AC1
RC2:
'Comment on egusphere-2024-1563', Anonymous Referee #2, 24 Jan 2025
The study presents coupling of a 1D hydrodynamic model with a MS equation for modelling tidally impacted river systems in a data-scarce scenarios. The content of the paper is interesting and novel. However, the paper structure needs to be revised to make the paper more readable and to effectively pass the message to the reader. As such, some of the following points might help improve the paper.
The paper title does not correspond to the content of the paper. For example, ‘hydrodynamic models’ cover a range of different types of modelling approaches. Please be more specific to reflect what this paper is about.

Aims and goals of the study are poorly defined and unclear. Please be more explicit in what this study is trying to achieve and what is out side of the scope of this study. Once this is defined it will help to formulate a more specific tittle for the paper.

Methodology needs to be improved. More details are needed about the model, input data, model structure and outputs, etc. so that the reader could have more understanding about the model itself. Additionally, more details need to be supplied about how the model was applied to the system. Which characteristics of the system were included and which were disregarded and reasons why.

More details about the calibration/validation of the model – especially about the data used, as pointed by the other reviewer.

The results and discussion sections need to be more concise and to the point. At the moment there is too much text, which can be more concise.
Citation: https://doi.org/10.5194/egusphere-2024-1563-RC2
- AC2: 'Reply on RC2', Francisco Rodrigues do Amaral, 07 Mar 2025
  
  Dear Reviewer 2,
  
  We sincerely appreciate the thorough evaluation of our manuscript and would like to thank you for your comments.
  We address reviewers' suggestions in the attached document.
  With kind regards,
  The Authors
  
  Citation: https://doi.org/10.5194/egusphere-2024-1563-AC2

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2024-1563', Anonymous Referee #1, 15 Oct 2024
The study involves the development of a coupled 1D and Manning-Strickler (MS) equation. This framework facilitates computationally efficient and accurate estimation of discharges in the data-scarce tidal river system in South Vietnam. The study also discusses the implications of calibrating the framework using discharge and water-level measurements. Though the concept and the calibration approaches are interesting, the paper could benefit from a detailed revision in terms of content, organization, and clarity. The following points need to be addressed.
Given that there are several cost-efficient and more accurate modelling approaches, such as the quasi-2D local inertial (Bates et al., 2010; Sridharan et al., 2020) and sub-grid approaches (Neal et al., 2012; Nithila Devi et al., 2024), it is not clear how the proposed method is more computationally efficient and accurate. It would be nice to see a comparison of the proposed approach with a local inertial formulation in terms of accuracy and computational cost.

For a longer reach, as used in the study, there may be lateral inflows, and it would be ideal to set up a coupled hydrological and hydraulic modelling system. If the authors are not attempting it, then a valid reason can be provided for the same, or this should be mentioned as a limitation. It is also unclear what the intended use of this modelling framework is – real-time forecasting or long-term continuous simulation. Again, for a longer-duration simulation, it is necessary to couple hydrological and hydraulic models.

The methodology is not clear and difficult to understand. A concise description of the overall framework or the coupling can be provided at the beginning of the methodology section. Is it only the energy slope that has been calculated by the 1D code at the point of interest by the MS equation? If other hydraulic variables are also calculated from the 1D code, it should be mentioned in the methodology flow chart.

The paper should explicitly state the calibration and validation periods used in the proposed method. This is important as the calibration and validation periods have to be distinct (For example, Bhargav et al., 2024). It is unclear from the text which events from 2016, 2017 and 2022 have been used for calibration and validation.

With the advent of technologies, getting a high-resolution elevation data set would be possible. Whether the surveyed cross-section has been used to construct the 1D model or a high-resolution dataset has been used to represent the bathymetry is not clearly mentioned in the paper.

Importantly, if the point of this exercise is to have a good simulation of flooding in urban areas, as mentioned in the article, then the ideal choice would be to use a simplified 2D model that can effectively represent the flood inundation dynamics on the complex urban flood plains. The presence of urban infrastructure, such as buildings, roads, streets, etc., governs flood conveyance and distribution. Also, such a claim requires validation using post-flood depth surveys. A coupled 1D and 2D modelling approach can be preferred in this case. Therefore, the authors need to acknowledge the proposed approach's limitations, constraints and advantages. In the introduction, it is also worthwhile to mention whether the focus is only on discharge estimation.

Specific comments
The usage of the term indirectly measured discharge in the abstract is misleading.

The introduction can include a concise literature review of the existing accurate and computationally efficient hydraulic modelling approaches (not just the ones specific to the region). And briefly discuss how the proposed framework stands out from the existing.

Line 27. How is drought modelling relevant here? Are we looking at continuous simulation across all the seasons?

Line 34. Please mention the advantage of the proposed method over Camenen et al. (2021) clearly and why it requires continuous water-level data for calibration.

Line 39. What do you mean by “calibration was not precise?”

Line 56. What is Mage code? It is suddenly introduced in the text here.

Lines 60 – 70. These lines look like the conclusion of the study.

Line 162. Please explain Brent’s algorithm in a sentence or two.

The results and discussion sections are too wordy. They can be shortened to convey things clearly and concisely.

References
Bates, P. D., Horritt, M. S., & Fewtrell, T. J. (2010). A simple inertial formulation of the shallow water equations for efficient two-dimensional flood inundation modelling. Journal of hydrology, 387(1-2), 33-45.
Bhargav, A. M., Suresh, R., Tiwari, M. K., Trambadia, N. K., Chandra, R., & Nirala, S. K. (2024). Optimization of Manning’s roughness coefficient using 1-dimensional hydrodynamic modelling in the perennial river system: A case of lower Narmada Basin, India. Environmental Monitoring and Assessment, 196(8), 743.
Neal, J., Schumann, G., & Bates, P. (2012). A subgrid channel model for simulating river hydraulics and floodplain inundation over large and data sparse areas. Water Resources Research, 48(11).
Nithila Devi, N., & Kuiry, S. N. (2024). A novel local‐inertial formulation representing subgrid scale topographic effects for urban flood simulation. Water Resources Research, 60(5), e2023WR035334.
Sridharan, B., Gurivindapalli, D., Kuiry, S. N., Mali, V. K., Nithila Devi, N., Bates, P. D., & Sen, D. (2020). Explicit expression of weighting factor for improved estimation of numerical flux in Local Inertial models. Water Resources Research, 56(7), e2020WR027357.
Citation: https://doi.org/10.5194/egusphere-2024-1563-RC1
- AC1: 'Reply on RC1', Francisco Rodrigues do Amaral, 07 Mar 2025
  
  Dear Reviewer 1,
  
  We sincerely appreciate the thorough evaluation of our manuscript and would like to thank you for your comments.
  We address reviewers' suggestions in the attached document.
  With kind regards,
  The Authors
  
  Citation: https://doi.org/10.5194/egusphere-2024-1563-AC1
RC2:
'Comment on egusphere-2024-1563', Anonymous Referee #2, 24 Jan 2025
The study presents coupling of a 1D hydrodynamic model with a MS equation for modelling tidally impacted river systems in a data-scarce scenarios. The content of the paper is interesting and novel. However, the paper structure needs to be revised to make the paper more readable and to effectively pass the message to the reader. As such, some of the following points might help improve the paper.
The paper title does not correspond to the content of the paper. For example, ‘hydrodynamic models’ cover a range of different types of modelling approaches. Please be more specific to reflect what this paper is about.

Aims and goals of the study are poorly defined and unclear. Please be more explicit in what this study is trying to achieve and what is out side of the scope of this study. Once this is defined it will help to formulate a more specific tittle for the paper.

Methodology needs to be improved. More details are needed about the model, input data, model structure and outputs, etc. so that the reader could have more understanding about the model itself. Additionally, more details need to be supplied about how the model was applied to the system. Which characteristics of the system were included and which were disregarded and reasons why.

More details about the calibration/validation of the model – especially about the data used, as pointed by the other reviewer.

The results and discussion sections need to be more concise and to the point. At the moment there is too much text, which can be more concise.
Citation: https://doi.org/10.5194/egusphere-2024-1563-RC2
- AC2: 'Reply on RC2', Francisco Rodrigues do Amaral, 07 Mar 2025
  
  Dear Reviewer 2,
  
  We sincerely appreciate the thorough evaluation of our manuscript and would like to thank you for your comments.
  We address reviewers' suggestions in the attached document.
  With kind regards,
  The Authors
  
  Citation: https://doi.org/10.5194/egusphere-2024-1563-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

ED: Reconsider after major revisions (further review by editor and referees) (14 Mar 2025) by Matthew Hipsey

Thank you for your submission and replies to the reviewers during the discussion period.

As hydrologists we are always trying to balance simplicity vs complexity so a study that advocates for a simple approach is attractive, particularly where it offers advantages to help practitioners in developing areas of the world where data is limited but decisions still need to be made. For this reason, the paper is in scope and of potential interest to the HESS community. On the other hand, the challenge with a simple model approach is meeting the threshold for conceptual or methodological innovation, which is a focus when we are selecting papers for publication.

The key issue for this paper is what is the key findings that take it beyond a site specific case study. Whilst the work is a very nice application, based on their comments, the reviewers seem to yet be fully convinced that this study meets this threshold for publication. In short, the reviewers require a more solid rationale and justification for the approach and improved more precise description of the methods.

The comments made by the authors in reply seem are in some cases not fully addressing the concerns raised by the reviewers. Particular the first comments of reviewer 1, need to be solidly addressed – why would I use this approach compared to a simple 2D approach? The reply is “... the primary objective of our study is not to model urban flooding or floodplain inundation but rather to obtain accurate water level and discharge estimates in a complex, tide-dominated river network with minimal in-situ data. Given this focus, a 1D hydrodynamic model is a priori a more computationally efficient choice”. Yet, this really is an assertion that 1D is easier and quicker, and the focus of a 2D modeller is also to accurately resolve water level and discharge through a network, so I don't really buy this argument when worded like this. Whilst I understand the point behind your comment, it simply needs to be more thoroughly argued in framing the paper - why would I use this approach and when would it no longer be the right approach to use? The replies also argue that the 1D approach is quick and therefore good for MCMC and uncertainty analysis – and this is a strong argument, but then when I went back and read the paper again I realise this wasn’t done – so the justification for the approach is still not really proven. Adding MCMC would greatly strengthen the argument in this paper, as in a data limited setting quantifying the posterior likelihood of the river is the most responsible thing to do - ie the modeller acknowledges the data is limited and makes effort to explain the uncertainty bands.

The writing in the paper also needs to be more precise. For example, the abstract is not yet convincing with sentences like “Validation against independent measurements demonstrates promising results…”. This is not a scientific statement and certainly not precise enough for an abstract of an international journal – what do you mean “promising”? Based on what? Readers need to know more specifics – do you mean the results are comparable to other tidal/delta models that are more complex (in terms of routine error metrics like RMSE, NSE?). Similarly, the aim (i) in introduction is “demonstrate the challenges of operating a 1D model….”. Certainly most people already fully accept 1D in a complex network like your field site is challenging, and therefore they would go 2D. So this needs reframing – the aim should be to show how you overcame these challenges, and how 1D is still useful despite the network complexity, right?!

I hope you can therefore consider these points in your revised manuscript and aim to thoroughly address in your re-submission how the revision addresses the reviewers concerns.

Kind regards
Matt

Hide

AR by Francisco Rodrigues do Amaral on behalf of the Authors (29 Mar 2025) Author's response Author's tracked changes Manuscript

ED: Publish as is (03 Jun 2025) by Matthew Hipsey

Thank you for the substantial revision to the paper, and apologies there were some delays in re-issuing for further review.
In assessing the revision I acknowledge the authors’ thoughtful and comprehensive revisions. The authors have clarified that the principal contribution of the study is a novel calibration approach using a modified Manning-Strickler equation, with broader applicability to tide-dominated and data-scarce systems. This has helped shift the focus from a site-specific application to a methodological advancement of general relevance.

The revision also now better addresses the justification for using a 1D model over 2D alternatives. The authors have expanded the introduction and methods sections to articulate the computational advantages of 1D modeling, especially for rapid simulations and uncertainty analyses in data-limited contexts. They provide support from relevant literature and emphasize that their aim is accurate river discharge estimation rather than the nuance of floodplain dynamics.

In response to suggestions about incorporating uncertainty quantification techniques which could be enabled by a simpler approach, the authors comment that this is out of scope but they acknowledge the relevance of such techniques and position them as priorities for future research

Finally, improvements in writing clarity are noted throughout. The abstract now includes specific performance metrics, and revisions to the introduction and methods sections improve transparency regarding model calibration and validation.

Given this updates, we are therefore pleased to accept the paper for publication in HESS and wish the researchers continued success in their work.

Hide

AR by Francisco Rodrigues do Amaral on behalf of the Authors (09 Jun 2025) Manuscript

Journal article(s) based on this preprint

12 Sep 2025

Technical note: Operational calibration and performance improvement for a 1D hydrodynamic model in a data-scarce coastal area

Francisco Rodrigues do Amaral, Benoît Camenen, Tin Nguyen Trung, Tran Anh Tu, Thierry Pellarin, and Nicolas Gratiot

Hydrol. Earth Syst. Sci., 29, 4327–4340, https://doi.org/10.5194/hess-29-4327-2025,https://doi.org/10.5194/hess-29-4327-2025, 2025

Short summary

Francisco Rodrigues do Amaral, Benoît Camenen, Tin Nguyen Trung, Tran Anh Tu, Thierry Pellarin, and Nicolas Gratiot

Data sets

Water discharge and water level output from the MAGE 1D hydrodynamic model for the Saigon and Dongnai rivers, Vietnam, 2016-2022 Francisco Rodrigues Do Amaral et al. https://doi.org/10.23708/KLQMSR

Model code and software

Mage Jean-Baptiste Faure and Theophile Terraz https://gitlab.irstea.fr/jean-baptiste.faure/mage

Francisco Rodrigues do Amaral, Benoît Camenen, Tin Nguyen Trung, Tran Anh Tu, Thierry Pellarin, and Nicolas Gratiot

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This study explores how to improve models predicting water flow in South Vietnam's Saigon and Dongnai rivers, where data is scarce. By testing three different methods to adjust the river model using river water level and river discharge measurements, we found ways to better predict river behavior. These findings can help manage water resources more effectively and aid decision-making for flood protection and environmental conservation.


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