Flooding in the Mekong Delta: the impact of dyke  systems on downstream hydrodynamics

Thanh, Vo Quoc; Roelvink, Dano; van der Wegen, Mick; Reyns, Johan; Kernkamp, Herman; Van Vinh, Giap; Linh, Vo Thi Phuong

doi:https://doi.org/10.5194/hess-24-189-2020

Articles | Volume 24, issue 1

https://doi.org/10.5194/hess-24-189-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/hess-24-189-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 24, issue 1

Research article

|

16 Jan 2020

Research article |

| 16 Jan 2020

Flooding in the Mekong Delta: the impact of dyke systems on downstream hydrodynamics

Vo Quoc Thanh, Dano Roelvink, Mick van der Wegen, Johan Reyns, Herman Kernkamp, Giap Van Vinh, and Vo Thi Phuong Linh

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Final revised paper (published on 16 Jan 2020)
Preprint (discussion started on 19 Feb 2019)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Comments on "Flooding in the Mekong Delta: Impact of dyke systems on downstream hydrodynamics"', Anonymous Referee #1, 28 Mar 2019
- RC2: 'Track changes', Anonymous Referee #1, 04 Apr 2019
  - AC4: 'Response to Reviewer1's comments track changes', Vo Quoc Thanh, 18 Jun 2019
- AC1: 'Response to Reviewer1's comments', Vo Quoc Thanh, 24 Apr 2019
RC3: 'Review of manuscript: “Flooding in the Mekong Delta: Impact of dyke systems on downstream hydrodynamics”.', Anonymous Referee #2, 12 Apr 2019
- AC2: 'Response to Reviewer2's comments', Vo Quoc Thanh, 24 Apr 2019
RC4: 'Review', Anonymous Referee #3, 14 Apr 2019
- AC3: 'Response to Reviewer3's comments', Vo Quoc Thanh, 24 Apr 2019
- AC5: 'Response to Reviewer's comments', Vo Quoc Thanh, 18 Jun 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Publish subject to revisions (further review by editor and referees) (25 Jun 2019) by Giuliano Di Baldassarre

AR by Vo Quoc Thanh on behalf of the Authors (27 Jun 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (10 Jul 2019) by Giuliano Di Baldassarre

RR by Anonymous Referee #2 (07 Aug 2019)

RR by Anonymous Referee #3 (07 Aug 2019)

Suggestions for revision or reasons for rejection

The Authors have improved the manuscript, which I believe is now almost ready for publication. However, they have partially faced some of my previous comments. I believe some clarifications are needed:
- Accuracy of the model: I think the Authors have misunderstood my previous comment (at least looking at their reply), which is reported below:
“Differences in terms of water elevation are in most of cases very minimal and of the same magnitude of the error of the model. What is the representativeness of such results? How can you exclude that those limited variations obtained among different configurations do not depend on the model itself, or on the way it reproduces the interaction between river and dyke rings?”

Errors of the model after calibration are comparable to the variability of water levels founded among different scenarios, if not even larger at some locations. Let’s say, if your model is on average precise with an error of +- 15 cm, what is the reliability of differences of 0.0x cm (see Table 2). I know it is difficult to establish the accuracy of your model but, at least, this point must be clearly pointed out. Your model can be used in relative terms, while you should be careful when providing specific water levels and discharges.

This comment is also related to another one risen by a different Reviewer, who highlight the uncertainty of topographic data (SRTM) adopted for the model. Although SRTM is used only for the floodplains, the errors on this data are not negligible and they can significantly affect the simulation results. This limitation should also be highlighted, emphasizing the fact that the model enables to better understand the dynamics of the system and might serve as a tool for comparative studies.

Finally, I haven’t understood the reply to my following comment; can you please further elaborate the concept?
- Comment: “Figure 2 and 3: why the number of dykes is significant? Probably reporting their overall length is more relevant”
- Authors’ response: In my opinion, the high dykes are separated by the canal system. Thus the mean areas of floodplain protected by high dykes can reflex flood water conveyance. For example, in the same area of floodplain protected by high dykes, the smaller mean area has higher water conveyed capacity.

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ED: Publish subject to revisions (further review by editor and referees) (08 Aug 2019) by Giuliano Di Baldassarre

AR by Vo Quoc Thanh on behalf of the Authors (18 Sep 2019) Manuscript

ED: Referee Nomination & Report Request started (26 Sep 2019) by Giuliano Di Baldassarre

ED: Publish subject to minor revisions (review by editor) (11 Nov 2019) by Giuliano Di Baldassarre

AR by Vo Quoc Thanh on behalf of the Authors (20 Nov 2019) Author's response

ED: Publish as is (03 Dec 2019) by Giuliano Di Baldassarre

AR by Vo Quoc Thanh on behalf of the Authors (05 Dec 2019) Manuscript

Short summary

The Vietnamese Mekong Delta (VMD) is a rice bowl of not only Vietnam, but also the world; agriculture is the main source of livelihood in the delta. The VMD is facing threats related to water management and hydraulic structures. Dykes are built to protect agricultural crops in the floodplains and may influence water regimes downstream in the VMD. If the VMD floodplains are completely protected by dykes, yearly mean water levels could increase by 3 cm (at Can Tho) and 1.5 cm (at My Thuan).