the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 24 May 2022
A translation wave model: Güneycedere case study
Abstract. This study proposed a flood routing model which was derived from Saint-Venant (SV) equations. It can be called translation wave model (TWM). In this model, bed slope term and friction slope term were ignored in the momentum equation of SV equations. This means, the difference between bed slope and friction slope are relatively small compared to other terms in the SV equations. This approach is similiar to the one in kinematic wave model (KWM), but in KWM inertia and pressure terms are neglected. In this study, governing equations for the proposed model were derived and solved numerically by using an explicit scheme. Then, validation of the proposed model was obtained through real flood data that belong to an actual creek reach in Isparta Province, Turkiye. The creek reach was between two stream gauging stations and the inflow and outflow hydrographs of a real flood event were available. Also, KWM was implemented for this creek reach using this real flood event. Thus two simulated outflow hydrographs; one that belongs to KWM and another that belongs to TWM were created. Then the two simulated outflow hydrographs were compared by differences in peak discharge, time to peak flow and hydrograph volume. Since KWM fails to predict attenuation and dispersion in outflow hydrographs, relative error of peak flow in KWM is calculated bigger than in TWM (2,19 % > -0,27 %). Relative error of time to peak flow in TWM is calculated as 0,00 % while it is calculated -2,50 % in KWM and the two models failed to provide volume conservation. Also, TWM and KWM were evaluated by the statistical parameters; Root Mean Square Error (RMSE), Mean Absolute Error (MAE) and Nash-Sutcliffe Efficiency (NSE). The results were in acceptable range but KWM gave better results since the creek reach had a steeper slope than average (S0 ≥ 0.005). Finally, for comparison, an inflow hydrograph from literature was routed with KWM and TWM in a rectangular channel.
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Interactive discussion
Status: closed
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RC1: 'Comment on hess-2022-192', Anonymous Referee #1, 21 Jun 2022
The authors suggest an alternative model to the Saint-Venant equation to simulate flood routing. This model, called Translation Wave Model (TWM) consists in neglecting two terms in the Saint-Venant momentum balance equation: the gravity term linked to the river bed slope and the term due to friction forces.
From a physical point of view, it means that the river bed is close to horizontal and that the energy loss due to friction can be neglected. Therefore, the parameters involved in TWM are related to the geometry of the cross sections only through equation 8.
These simplifications limit the use of TWM especially under field conditions. Moreover, it contradicts the statement ‘TWM can be suitable for mild slopes’ (L199), statement which is not demonstrated in the paper.
The authors compared TWM with a more common simplification of the Saint-Venant equation, the kinematic wave model (KWM). Applied to a real test case, both models provide same simulated outflow (Fig. 8). For the synthetic test case, TWM show some instabilities in the results (Fig. 9 around time 1400 s and 1900 s, KWM does not. Therefore, the authors do not demonstrate the interest of TWM
Due to its limited interest in field case modelling, the paper is not suitable for HESS.
Citation: https://doi.org/10.5194/hess-2022-192-RC1 -
RC2: 'Comment on hess-2022-192', Anonymous Referee #2, 22 Jun 2022
The presented paper proposes a new flood routing model ‘TWM’ in which slope variables are neglected in the momentum equation of SV equation. The TWM is compared with kinematic wave model KWM for only one flood event occurred in actual creek reach. Furthermore, another flood event for hypothetical reach was simulated using both TWM and KWM flood routing models.
The paper is unacceptable to be published in its current form in this reputable journal. The research idea is original, which is the only thing good in the paper. The manuscript is written poorly. Presentation of the results is poor and there is no discussion of the results. Paper does not provide scientific soundness. Paper needs to be re-written again.
The most important thing is that the number of studied flood events are very less (only 2) which does not justify the capability of TWM. Number of flood events needs to be increased significantly along with number of cross-sections of channel. Also, TWM needs to be tested in various gradients of slope. The author keeps saying that TWM is good for mild slope but two flood events on mild slope tells nothing. Methodology needs to be clear. The results should be presented in detail with discussion focussing on what factors/reasons are making TWM better and why, also discuss the situations where TWM are underperforming and why.
The paper title should include 1-D.
Introduction part need major revision, What are the previous works done using KVM and why KVM was better for steep slope and is does not simulate correctly the attenuation and dispersion in outflow hydrographs. Why dynamic model according to previous works was not good for varying cross sections and very small slopes. How it can be concluded in introduction that TVM can be suitable for mild slopes, its a new approach, never been tested. Although it is written it neglects slope variables but neglecting of them is not discussed in introduction. Furthermore, assumption of TVM better performance by ignoring slope without any testing done yet is not justifiable in introduction section.
Line 86-92: slope of the studied area needs to be given as the slope is neglected in the modified SV equation.
Line 109: what is slope gradient of the study and what is the slope gradient of the creeks with which author is comparing from to say that the understudied slope is mild. It is confusing to say relatively mild. Does is make steep is some areas but in most in mild?
Line123: what is meant by good hydrograph shapes?
Please put Fig 1, 2 and 3 together. Make another fig showing the observed inflow and outflow hydrographs that are discussed in section 2.2.
Please give the units of the variables given in the equations.
Section 3.1 please state clearly that author is using 1-D SV equation and derivating it.
Line 177: author should write that term 1-3 in eq 2 representing inertia and pressure terms are neglected for KVM.
Line 199-200: it is not proved yet TWM is suitable for the mild slope, not tested it yet.
Line 261: upstream boundary condition should be from tp to tb ,it can not start from zero.
What is the downstream boundary condition? Is it free flow? If so, please give the numerical scheme also for that.
Line 287-289: did the author divide the reach into segments, if so, does the cross section area variables (bottom width and inverse of side slope) of channel is changing, is it not uniform. Why converting the reach length in segments, please discuss.
Line 305: please tell which version of HEC-HMS was used.
Line 356 Qj+2 is Q3 and so on.
Line 332 to line 361 author discuss the functionality of scheme after the results which is irrelevant and basic as it is obvious by seeing the numerical scheme given in section 3.2 numerical solution. This numerical scheme has been used for decades to solve KWM. The author did not create a new numerical scheme, why discuss it. Author did not discuss the rising or recession limb of hydrographs, please discuss.
Line 363-366 why making the cross-sections from digital topographic map. Did the author divide the reach length in segments and than give bottom width and inverse of side slope for each segment.
The author need to make the figure showing the division of segments in the reach and state clearly what actually he/she did. And, do not discuss division of segments or discussion of scheme in results it should be done before showing the results fig 5.
Line 370-378 Author did not discuss the rising or recession limb of hydrographs, please discuss.
Figure 8 is not discussed-comparison between TWM and KWM.
Section 3.3.2 why the KWM hydrograph is delayed with respect to TWW. Also hydrographs characteristics (peak, rising and recession limb shapes) are different. There is no discussion why it is happening.
Conclusion 4- line 487-491: Inflow peak is closer to KWM peak, KWM is simulated outflow. how it tells the capability of KWM, observed outdlow not compared with KWM. How it is concluded that TWM has acceptable value range and had good shape.
Line 493-496: TWM needs one boundary condition? If downstream boundary condition is open, it is still downstream condition. If it is closed, than does author mean this TWM scheme will not work? Superficial flows does not need downstream boundary condition? What is the relevance of superficial flow, boundary condition and TWM? Every numerical scheme simulating flows needs boundary conditions.
Citation: https://doi.org/10.5194/hess-2022-192-RC2
Interactive discussion
Status: closed
-
RC1: 'Comment on hess-2022-192', Anonymous Referee #1, 21 Jun 2022
The authors suggest an alternative model to the Saint-Venant equation to simulate flood routing. This model, called Translation Wave Model (TWM) consists in neglecting two terms in the Saint-Venant momentum balance equation: the gravity term linked to the river bed slope and the term due to friction forces.
From a physical point of view, it means that the river bed is close to horizontal and that the energy loss due to friction can be neglected. Therefore, the parameters involved in TWM are related to the geometry of the cross sections only through equation 8.
These simplifications limit the use of TWM especially under field conditions. Moreover, it contradicts the statement ‘TWM can be suitable for mild slopes’ (L199), statement which is not demonstrated in the paper.
The authors compared TWM with a more common simplification of the Saint-Venant equation, the kinematic wave model (KWM). Applied to a real test case, both models provide same simulated outflow (Fig. 8). For the synthetic test case, TWM show some instabilities in the results (Fig. 9 around time 1400 s and 1900 s, KWM does not. Therefore, the authors do not demonstrate the interest of TWM
Due to its limited interest in field case modelling, the paper is not suitable for HESS.
Citation: https://doi.org/10.5194/hess-2022-192-RC1 -
RC2: 'Comment on hess-2022-192', Anonymous Referee #2, 22 Jun 2022
The presented paper proposes a new flood routing model ‘TWM’ in which slope variables are neglected in the momentum equation of SV equation. The TWM is compared with kinematic wave model KWM for only one flood event occurred in actual creek reach. Furthermore, another flood event for hypothetical reach was simulated using both TWM and KWM flood routing models.
The paper is unacceptable to be published in its current form in this reputable journal. The research idea is original, which is the only thing good in the paper. The manuscript is written poorly. Presentation of the results is poor and there is no discussion of the results. Paper does not provide scientific soundness. Paper needs to be re-written again.
The most important thing is that the number of studied flood events are very less (only 2) which does not justify the capability of TWM. Number of flood events needs to be increased significantly along with number of cross-sections of channel. Also, TWM needs to be tested in various gradients of slope. The author keeps saying that TWM is good for mild slope but two flood events on mild slope tells nothing. Methodology needs to be clear. The results should be presented in detail with discussion focussing on what factors/reasons are making TWM better and why, also discuss the situations where TWM are underperforming and why.
The paper title should include 1-D.
Introduction part need major revision, What are the previous works done using KVM and why KVM was better for steep slope and is does not simulate correctly the attenuation and dispersion in outflow hydrographs. Why dynamic model according to previous works was not good for varying cross sections and very small slopes. How it can be concluded in introduction that TVM can be suitable for mild slopes, its a new approach, never been tested. Although it is written it neglects slope variables but neglecting of them is not discussed in introduction. Furthermore, assumption of TVM better performance by ignoring slope without any testing done yet is not justifiable in introduction section.
Line 86-92: slope of the studied area needs to be given as the slope is neglected in the modified SV equation.
Line 109: what is slope gradient of the study and what is the slope gradient of the creeks with which author is comparing from to say that the understudied slope is mild. It is confusing to say relatively mild. Does is make steep is some areas but in most in mild?
Line123: what is meant by good hydrograph shapes?
Please put Fig 1, 2 and 3 together. Make another fig showing the observed inflow and outflow hydrographs that are discussed in section 2.2.
Please give the units of the variables given in the equations.
Section 3.1 please state clearly that author is using 1-D SV equation and derivating it.
Line 177: author should write that term 1-3 in eq 2 representing inertia and pressure terms are neglected for KVM.
Line 199-200: it is not proved yet TWM is suitable for the mild slope, not tested it yet.
Line 261: upstream boundary condition should be from tp to tb ,it can not start from zero.
What is the downstream boundary condition? Is it free flow? If so, please give the numerical scheme also for that.
Line 287-289: did the author divide the reach into segments, if so, does the cross section area variables (bottom width and inverse of side slope) of channel is changing, is it not uniform. Why converting the reach length in segments, please discuss.
Line 305: please tell which version of HEC-HMS was used.
Line 356 Qj+2 is Q3 and so on.
Line 332 to line 361 author discuss the functionality of scheme after the results which is irrelevant and basic as it is obvious by seeing the numerical scheme given in section 3.2 numerical solution. This numerical scheme has been used for decades to solve KWM. The author did not create a new numerical scheme, why discuss it. Author did not discuss the rising or recession limb of hydrographs, please discuss.
Line 363-366 why making the cross-sections from digital topographic map. Did the author divide the reach length in segments and than give bottom width and inverse of side slope for each segment.
The author need to make the figure showing the division of segments in the reach and state clearly what actually he/she did. And, do not discuss division of segments or discussion of scheme in results it should be done before showing the results fig 5.
Line 370-378 Author did not discuss the rising or recession limb of hydrographs, please discuss.
Figure 8 is not discussed-comparison between TWM and KWM.
Section 3.3.2 why the KWM hydrograph is delayed with respect to TWW. Also hydrographs characteristics (peak, rising and recession limb shapes) are different. There is no discussion why it is happening.
Conclusion 4- line 487-491: Inflow peak is closer to KWM peak, KWM is simulated outflow. how it tells the capability of KWM, observed outdlow not compared with KWM. How it is concluded that TWM has acceptable value range and had good shape.
Line 493-496: TWM needs one boundary condition? If downstream boundary condition is open, it is still downstream condition. If it is closed, than does author mean this TWM scheme will not work? Superficial flows does not need downstream boundary condition? What is the relevance of superficial flow, boundary condition and TWM? Every numerical scheme simulating flows needs boundary conditions.
Citation: https://doi.org/10.5194/hess-2022-192-RC2
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