Preprint Article Version 1 This version is not peer-reviewed

Hydrodynamic and Hydrographic Modeling of Istanbul Strait

Version 1 : Received: 27 August 2019 / Approved: 28 August 2019 / Online: 28 August 2019 (15:23:55 CEST)

A peer-reviewed article of this Preprint also exists.

Koşucu, M.M.; Demirel, M.C.; Kirca, V.O.; Özger, M. Hydrodynamic and Hydrographic Modeling of Istanbul Strait. Processes 2019, 7, 710. Koşucu, M.M.; Demirel, M.C.; Kirca, V.O.; Özger, M. Hydrodynamic and Hydrographic Modeling of Istanbul Strait. Processes 2019, 7, 710.

Journal reference: Processes 2019, 7, 710
DOI: 10.3390/pr7100710

Abstract

The aim of this study is to model hydrodynamic processes of the Istanbul Strait with its stratified flow characteristic and calibrate the most important parameters using local and global search algorithms. For that two open boundary conditions are defined, which are in the North and South part of the Strait. Observed bathymetric, hydrographic, meteorological and water level data are used to set up the Delft3D-FLOW model. First, the sensitivities of model parameters on the numerical model outputs are assessed using PEST toolbox. Then, the model is calibrated based on the objective functions focusing on the flowrates of upper and lower layers. The salinity and temperature profiles of the Strait are only used for model validation. The results show that the calibrated model outputs of Istanbul Strait are reliable and consistent with the in-situ measurements. The sensitivity analysis reveals that the Spatial Low-Pass Filter Coefficient, Horizontal Eddy Viscosity, Prandtl-Schmidt Number, Slope in log-log Spectrum and Manning Roughness Coefficient are most sensitive parameters affecting flowrate performance of the model. The agreement between observed salinity profiles and simulated model outputs is promising whereas the match between observed and simulated temperature profiles is weak showing that the model can be improved particularly for simulating the mixing layer.

Subject Areas

Istanbul Strait; stratified flow; gravity driven flow; numerical modelling

Comments (11)

Comment 1
Received: 9 September 2019
The commenter has declared there is no conflict of interests.
Comment: This study mainly suffers from the straightforward application of the numerical model, DELFT3D, without any insight into the basic oceanographic principles of the Bosphorus Strait. Complete dependence on Delft 3D might lead only to erroneous scientific conclusions, as is the case in this study. Herein, the logical thinking is completely overlooked. The following points may shed light for the improvement of the paper.
1-It has surprisingly seen in the paper that the authors applied water level BC at stations Anadolu Kavagı and Pendik in Fig. 1 of their original manuscripts. Water level measurements should be placed offshore, close to the open boundary. However, it is seen that Pendik station is almost on the land. This station might reflect long term variations (like tides). What about the short term effects? Besides, islands just in front of this station might influence the water level fluctuations, which can lead to erroneous predictions. Pendik station should not be applied as boundary condition.
2-No information is given about the sampling rate of the stations. The quality of the measured data is neither checked nor discussed.
3-It is quite obvious that authors did not perform the literature review in detail. The most comprehensive and accurate environmental monitoring system is installed in the Bosphorus between September 2004 and January 2006, in relation to the design and construction requirements of the Bosphorus Tube Crossing Project. (Guler et al., 2006; Yuksel et al., 2008; Aydogan et al., 2010). Yuksel et al., (2008), Ozturk et al., (2012), Erdik et al., (2019) employed this monitoring system, at the northern and southern of Bosphorus, respectively, with 10-min sampling rate. This monitoring system is the most reliable and accurate data system in Bosphorus. Besides, stations are exactly at the northen and southern boundaries of the Bosphorus.
4-The proposed model has some deficiencies. The authors claim that “the calibrated model outputs of Istanbul Strait are reliable and consistent with the in-situ measurements”. My first question is where is the calibration? Do authors really think that the prediction of monthly upper and lower layer discharges satisfy the calibration purposes? Hydrodynamic conditions in Bosphorus vary on a daily basis, driven by meteorological, oceanographic conditions, and hydrologic conditions. Monthly discharge prediction might be applicable to main rivers in the globe but not to the chaotic straits, as is the case with Bosphorus. Please check with Jarosz et. al., (2011) to obtain daily discharges.
5- The prediction capacity of the best model is achieved with R=0.447. I have not seen nor heard any model, which claims to accurately predict discharges with R2=0.20.

References

Aydogan, B.; Ayat, B.; OztUrk, M.N.; Ozkan Cevik, E.; Yuksel, Y. Current velocity forecasting in straits 415 with artificial neural networks, a case study: Strait of Istanbul. Ocean Eng. 2010, 37, 443–453.
Erdik, T., Sen, O., Ozturk, I. 3D Numerical Modeling of Exchange Flows in Golden Horn Estuary. J. Waterway Port Coastal Ocean Eng., 2019, 145(5).
Guler, I.; Yuksel, Y.; Yalciner, A.C.; Cevik, E.; Ingerslev, C. Measurement and evaluation of the 410 hydrodynamics and secondary currents in and near a strait connecting large water bodies-A field study. 411 Ocean Eng. 2006, 33, 1718–1748. 412
Jarosz, E.W., Teague, J., Book, J.W., Besiktepe, S. Observed volume fluxes in the Bosphorus Strait. Geophysical Res Letters, 2011, 38, L21608.
Ozturk, M., Ayat, B., Aydogan, B., Yuksel, Y. 3D Numerical modeling of stratified flows: case study of the Bosphorus Strait." Journal of Waterway, Port, Coastal, and Ocean Engineering, 2012, 138(5), 406-419.
Yuksel, Y.; Ayat, B.; Nuri Ozturk, M.; Aydogan, B.; Guler, I.; Cevik, E.O.; Yalciner, A.C. Responses of the 413 stratified flows to their driving conditions-A field study. Ocean Eng. 2008, 35, 1304–1321.
+ Respond to this comment
Response 1 to Comment 1
Received: 18 September 2019
Commenter: Mehmet Cüneyd Demirel (Click to see Publons profile: )
The commenter has declared there is no conflict of interests.
Comment: “We kindly invite you to submit a discussion paper to the published paper in Processes-MDPI (soon online available) and reveal your identity so that we can clearly assess if there is any potential conflict of interest. We openly shared our manuscript and we expect our readers not to hide themselves when writing a public comment. Finally please use a proper/professional language in your informal comment. For that please follow the 11 steps described in Copernicus: https://www.hydrology-and-earth-system-sciences.net/for_reviewers/obligations_for_referees.html.
Response 2 to Comment 1
Received: 21 September 2019
The commenter has declared there is no conflict of interests.
Comment: My discussion above presented scientific comments and/or questions about the paper by authors. I strongly suggest authors make themselves aware of fatal errors in their paper and prepare a response to my comments. In addition, I would like to remind the authors that criticism of your paper addresses problems within your study in order to improve science and make your paper better.
Response 3 to Comment 1
Received: 21 September 2019
The commenter has declared there is no conflict of interests.
Comment: There are two options to send scientific comments:

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Why did you choose the first one and hide yourself?

Please refer to the following link for a serious comment and check the final decision of this article:

https://www.hydrol-earth-syst-sci-discuss.net/hess-2018-342/hess-2018-342-SC1.pdf
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Response 4 to Comment 1
Received: 7 October 2019
The commenter has declared there is no conflict of interests.
Comment: "Is writing directly to the journal without waiting for the DOI ethical?"

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Comment 2
Received: 10 September 2019
The commenter has declared there is no conflict of interests.
Comment: The present paper has some mistakes in the basic application of the error statistics. By using the data depicted in Fig. 7a, the basic error statistics are calculated as Mean absolute error 3968 m3/s, R2 0.24 and finally BIAS -8.58. These findings suggest that the proposed model is poorly calibrated, yielding inaccurate output. In addition, the model seems to be biased.
+ Respond to this comment
Response 1 to Comment 2
Received: 18 September 2019
Commenter: Mehmet Cüneyd Demirel (Click to see Publons profile: )
The commenter has declared there is no conflict of interests.
Comment: “We kindly invite you to submit a discussion paper to the published paper in Processes-MDPI (soon online available) and reveal your identity so that we can clearly assess if there is any potential conflict of interest. We openly shared our manuscript and we expect our readers not to hide themselves when writing a public comment. Finally please use a proper/professional language in your informal comment. For that please follow the 11 steps described in Copernicus: https://www.hydrology-and-earth-system-sciences.net/for_reviewers/obligations_for_referees.html.
Response 2 to Comment 2
Received: 7 October 2019
The commenter has declared there is no conflict of interests.
Comment: "Is writing directly to the journal without waiting for the DOI ethical?"

Now our revised paper is waiting for your harshest comments via susy system.

Submit your discussion/comment paper with your real identity which will increase your scientific visibility.

Thank you
Comment 3
Received: 14 September 2019
The commenter has declared there is no conflict of interests.
Comment: Some misuses and flaws are encountered in this study. For the improvement, the following points are suggested:

1-Authors mention in lines 129 and 130 of their manuscript “While the upper layer flow is towards North from the Black Sea to the Marmara Sea, the lower layer flow is towards South from the Marmara Sea to the Black Sea”. Authors really consider upper layer flow towards North and lower layer flow towards South? In Fig. 1 of your original manuscript, Marmara Sea is in the South while Black Sea is at the North.

2-Why did authors employ arc-shaped boundaries? This issue is not discussed.

3-How could station measurements be interpolated at arch-shaped boundaries? Station Anadolu is located inside the Bosphorus.

4-Authors did not divide the data into the training and testing parts.

5-Why did the authors apply PEST for calibration purposes? OpenDA of Delft3D pinpoints sensitive parameters automatically. What is the purpose of using PEST? In some cases in the paper, manual calibration seems to be better.

6- The authors applied only the correlation coefficient (CC) in the study. However, CC only considers linear relationships between X and Y and for any relationship to exist, any change in X has to have a constant proportional change in Y. If the relationship is not linear then the result is inaccurate. At first sight, no lineer relationship exists.

7-Authors did not pay attention to temperature and salinity vertical profiles in the Bosphorus. This is one of the main flaws in the study.

8- The authors mention northern sill in Fig. 2 of their manuscript. However, it is not included in the developed mesh in Fig. 6. Please pay attention to the Oguz et al., (1990) to discover how northern sill influences flow patterns in the strait.


9-The authors did not consider some basic conceptions underlying the Bosphorus principle in the model. They assumed that upper and lower layer flow rates at the southern end are almost the same as 9150 and -9720 m3/s. This issue is the biggest pitfall in this study. As seen in Table 3 of the original manuscript, upper and lower flow rates are almost the same only in January. What about the other months? Authors inevitably contradict themselves.
+ Respond to this comment
Response 1 to Comment 3
Received: 18 September 2019
Commenter: Mehmet Cüneyd Demirel (Click to see Publons profile: )
The commenter has declared there is no conflict of interests.
Comment: “We kindly invite you to submit a discussion paper to the published paper in Processes-MDPI (soon online available) and reveal your identity so that we can clearly assess if there is any potential conflict of interest. We openly shared our manuscript and we expect our readers not to hide themselves when writing a public comment. Finally please use a proper/professional language in your informal comment. For that please follow the 11 steps described in Copernicus: https://www.hydrology-and-earth-system-sciences.net/for_reviewers/obligations_for_referees.html.
Response 2 to Comment 3
Received: 7 October 2019
The commenter has declared there is no conflict of interests.
Comment: "Is writing directly to the journal without waiting for the DOI ethical?"

Now our revised paper is waiting for your harshest comments via susy system.

Submit your discussion/comment paper with your real identity which will increase your scientific visibility.

Thank you

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