Fluctuations of Winter Floods in Small Austrian and Ukrainian Catchments
, Juraj Parajka 2,3, Liudmyla Gorbachova 1, Borbála Széles 2,3, Günter Blöschl 2,3, Oleksandr Aksiuk 1, Rui Tong 2,3,4 and Jürgen Komma 3Round 1
Reviewer 1 Report
Article Fluctuations of winter floods in small Austrian and Ukrainian catchments describes the evaluation of winter floods on selected floodplains in Austria and Ukraine. The paper has clearly described hypotheses and solution methods that are standard in the field of hydrology.
I recommend the authors of the study/article especially in the presentation of the results, so that they are more understandable:
- Figure 1: the bottom image is not clear, I suggest adding streamflow arrows
- Figure 5: consider whether it is not possible to present the variability in a different way (e.g. a barplot with points - the range for each year)
- Figure 6: the bottom panels: change colour of grey lines, the whole spectrum of red colours is not represented in the legend
- Figure 9: the bottom panels: change colour of grey lines
Comments:
- 99 mention that there are a ski resorts
Table 3 it should be interesting add also month, 2015/01...
Table 3 missing description, coefficient of variation?
Why time series finish 2015, especially last years were reduced flows
Caption 3.2. add a brief comment on why these climatic variables were chosen,
After editing, I recommend to publish the article
Author Response
We want to thank the reviewer for her/his positive, helpful and insightful comments on the manuscript. Please find below our responses to the comments (in italics).
Article Fluctuations of winter floods in small Austrian and Ukrainian catchments describes the evaluation of winter floods on selected floodplains in Austria and Ukraine. The paper has clearly described hypotheses and solution methods that are standard in the field of hydrology.
Response: Thanks for a positive evaluation.
I recommend the authors of the study/article especially in the presentation of the results, so that they are more understandable:
Figure 1: the bottom image is not clear, I suggest adding streamflow arrows
Response: In order to improve the clarity of the bottom images, we have modified the figure and added a symbol legend representing the streamflow gauges. We are not sure about the meaning of streamflow arrows, but we will be happy to revise the figure further if more details and explanations are given.
Figure 5: consider whether it is not possible to present the variability in a different way (e.g. a barplot with points - the range for each year)
Response: In response to this comment, we revised the figure as suggested. We have plotted the variability as a floating barplot.
Figure 6: the bottom panels: change colour of grey lines, the whole spectrum of red colours is not represented in the legend
Response: In response to this comment, we have changed the colour of grey lines as suggested and corrected the typo in the legend.
Figure 9: the bottom panels: change colour of grey lines
Response: We changed the colour as suggested (in a similar way as in Fig. 6)
Comments:
99 mention that there are a ski resorts
Response: In response to this comment, we have revised the paragraphs as follows: “All analyzed catchments represent a natural regime and are not affected by a significant human impact in terms of winter flood seasonality or flood magnitude. The flood data in Austria has been quality checked within the recent national flood risk zoning project (https://www.hora.gv.at) and existing small ski resorts do not have any impact on the occurrence or magnitude of flood peaks.”
Table 3 it should be interesting add also month, 2015/01...
Response: We have revised Table 3 as suggested by the reviewer.
Table 3 missing description, coefficient of variation?
Response: We have revised Table 3 caption as follows: “The length of flood records, coefficient of variation Cv (November-April) and the largest and smallest winter (November-April) and annual (No-vember-October) flood discharges.”
Why time series finish 2015, especially last years were reduced flows
Response: The processing and quality check of flood and climate data by the National Hydrographic services typically shifts data availability. We plan to extend the dataset used in this paper in the future but will be beyond the scope if this analysis.
Caption 3.2. add a brief comment on why these climatic variables were chosen,
Response: In response to this comment, we have added the following sentence: “These characteristics have been found as one of the most relevant for flood seasonality assessment in Europe [3[.”
After editing, I recommend to publish the article
Response: Thanks for your very useful and constructive comments.
Reviewer 2 Report
The authors studied the fluctuations and seasonal timing of winter floods, in a large number of medium to small size basins in Austria and Ukraine. The characteristics of terrain between both basin datasets is hetereogenous. For the analysis, authors used a long term dataset, starting in 1950's until late 2010's. Authors explored the linkage between winter flood fluctuations, and explaining drivers, including max 7-day cumulative precipitation, snowpack total and air temperature.
I really enjoyed reading this manuscript and recommend it for publication in its current state. The paper is very well written and concise. The methods are simple and well explained, and the corresponding analysis is clear and straight to the point. I do not detect any flaw in the methodology. Looking forward to see the results in an extended region.
I am sure the paper will be of the interest to readers of Hydrology.
Author Response
The authors studied the fluctuations and seasonal timing of winter floods, in a large number of medium to small size basins in Austria and Ukraine. The characteristics of terrain between both basin datasets is hetereogenous. For the analysis, authors used a long term dataset, starting in 1950's until late 2010's. Authors explored the linkage between winter flood fluctuations, and explaining drivers, including max 7-day cumulative precipitation, snowpack total and air temperature.
I really enjoyed reading this manuscript and recommend it for publication in its current state. The paper is very well written and concise. The methods are simple and well explained, and the corresponding analysis is clear and straight to the point. I do not detect any flaw in the methodology. Looking forward to see the results in an extended region.
I am sure the paper will be of the interest to readers of Hydrology.
Response: We want to thank the reviewer for her/his very positive evaluation of the analysis.
Reviewer 3 Report
Firstly I would like to thank the Authors for their hard work and interesting article. I have read the manuscript very carefully. In my opinion, refers very important topic which is floods seasonality. The manuscript is prepared very well. It can be interesting for all researcher who deals with the similar study. Nevertheless, I had some comments:
- Keywords: ‘small mountain rivers’ should be replaced with ‘small mountain catchment’. The ‘Danube River’ is not necessary as a keyword.
- The introduction is the weakest part of the manuscript. It must be re-written. In Introduction the Authors must focus on information regarding the analyzed topic. The literature review must be done. Currently, in Introduction the Authors described analyzed catchment. This part must be moved to chapter “Study area”. Also, the references style does not meet the requirements of MDPI.
- In the study area, I would like to see information about basically meteorological factors in the analyzed catchments (as mean yearly precipitation and mean temperature). Also, the Authors should provide information about land use, which is a very important factor in the point of flooding view.
- Table 3 and Figure 2: in my opinion, it should be moved to Results. What could be factors which affect high values of coefficient of variation?
- Results: The trend analysis was carried out using the graphical method. But it is not described in the methodology. Why the Authors decide to use them and not the Mann-Kendall test, which is most common in such analysis.
- Discussion and conclusion should be separated chapters. In the Discussion, the Authors should discuss additional results regarding trend analysis. Also, the factors controlling winter flood fluctuations must be clearly highlighted. In the conclusion, I would like to see what are the future plans of the Authors for the study to continue.
Author Response
We want to thank the reviewer for her/his positive, helpful and constructive comments on the manuscript. Please find below our response to the comments (in italics).
Firstly I would like to thank the Authors for their hard work and interesting article. I have read the manuscript very carefully. In my opinion, refers very important topic which is floods seasonality. The manuscript is prepared very well. It can be interesting for all researcher who deals with the similar study. Nevertheless, I had some comments:
- Keywords: ‘small mountain rivers’ should be replaced with ‘small mountain catchment’. The ‘Danube River’ is not necessary as a keyword.
Response: We have revised the keywords as suggested by the reviewer
- The introduction is the weakest part of the manuscript. It must be re-written. In Introduction the Authors must focus on information regarding the analyzed topic. The literature review must be done. Currently, in Introduction the Authors described analyzed catchment. This part must be moved to chapter “Study area”. Also, the references style does not meet the requirements of MDPI.
Response: Our main idea is to keep the Introduction part compact. We aim to provide context and importance of evaluating floods and their changes, particularly in the trans international Danube region. We show that previous research in this area indicates the change in floods, but the factors controlling the change are still not completely understood. We believe that citing more than 30 references covers the essential studies relevant to our main objectives. In response to the reviews, we have added additional suggested references and prefer not to extend the Introduction section further. We believe that the reference style in the Introduction is in line with the MDPI guidelines (i.e. reference citation numbers are placed in square brackets), but we will be happy to revise it if more details are requested..
- In the study area, I would like to see information about basically meteorological factors in the analyzed catchments (as mean yearly precipitation and mean temperature). Also, the Authors should provide information about land use, which is a very important factor in the point of flooding view.
Response: In response to this comment, we have added information about the mean annual precipitation, air temperature and forest coverage as suggested by the reviewer.
- Table 3 and Figure 2: in my opinion, it should be moved to Results. What could be factors which affect high values of coefficient of variation?
Response: Our main aim of the study is to analyse winter flood fluctuations and seasonality. Table 3 and Figure 2 provide some overview and synthesis of the flood magnitude dataset, so we prefer to leave it in the Data section. The larger CV is consistent with the results of pan-European patterns of flood moments (Lun et al., 2021, https://doi.org/10.5194/hess-25-5535-2021) and is likely related to the climate controls, i.e. increased effects of continentality and synchronicity in snowmelt timing.
- Results: The trend analysis was carried out using the graphical method. But it is not described in the methodology. Why the Authors decide to use them and not the Mann-Kendall test, which is most common in such analysis.
Response: We are not sure whether we understand this comment correctly. We did not aim to analyse the trends nor use a graphical method. The results refer to quantifying the fluctuation and seasonality indices, which are already described in the Methods.
- Discussion and conclusion should be separated chapters. In the Discussion, the Authors should discuss additional results regarding trend analysis. Also, the factors controlling winter flood fluctuations must be clearly highlighted. In the conclusion, I would like to see what are the future plans of the Authors for the study to continue.
Response: We prefer not to split the discussion and conclusions section. The trend analysis is out of the scope of our analysis, so we prefer not to further extend the discussion with respect to previous trend assessments. We note that we already discussed our findings with the results of the European flood change assessment (Bloschl et al., 2017 and 2019). In the future, we plan to further evaluate the effects of elevation and to explore its interplay with the runoff generation processes. As it is already indicated, we plan to focus our next efforts on evaluating the combination of hydro-genetic method and seasonality assessment in the entire Alps-Carpathian region. The main aim will be to examine the spatio-temporal patterns of flood fluctuations along selected transects in Europe and to identify regions with similar fluctuation characteristics. In response to this comment, we have formulated the part related to the future plans more precisely.
Reviewer 4 Report
The article is about fluctuations of floods magnitude and timing during the cold period in the Danube basin. The study examines winter and spring floods in the Rika River Basin (Ukraine) and in the Steyr River Basin (Austria). Hydrological regime of the chosen rivers differs significantly, especially in winter and spring floods formation. Winter and spring floods in the Rika River Basin mostly result in maximum annual discharges while in the Steyr River Basin the winter floods are usually lower in comparison to floods of the warm season. Comprehensive approaches are used for the combined hydrometeorological analysis of winter floods and their factors. The study shows interesting results but the presentation may be improved.
The term “winter floods” seems to be inappropriate considering floods from November to April. In the Introduction it is noted that in the Ukrainian part “the most significant floods frequently occur in spring and are generated by snowmelt and rain-on-snow events [7, 8, 9]”. “Spring snowmelt floods” is often used to describe snowmelt floods after long snow accumulation [Blöschl et al., 2017] which sometimes occurs in the Carpathians catchments. It may have been better to call those floods “cold season floods”.
The conclusion “in the last decades, the increasing phase in melt temperatures has resulted in decreasing winter floods in Ukrainian catchments, which corresponds well with changes in flood magnitude identified by [2] in Eastern Europe” should be extended. It is important to note that several studies indicate a simultaneous increase in number of winter floods as a result of thawing and a general increase in winter flow volumes in Eastern European rivers [Volchek, Shelest, 2012; Kireeva et al., 2020]. Probably, authors should add some more review on winter floods in Europe in the introduction section.
In general, Discussion and conclusions look weaker than other sections and could be deepened.
Some smaller notes:
There may be some inconsistency the sentences. Abstract: “The most significant winter floods tend to occur in November and December”. Study area: “The mountain rivers of the Carpathians are characterized by an unstable thermal regime and frequent transitions from negative to positive air temperatures in December-February, which leads to numerous snow melt events. … In such a case, floods with very high runoff peaks tend to occur.” To which region does the sentence in the abstract refer?
- What coordinates are mentioned in the Tables 1 and 2?
- Line 106: Daily maximum discharge. What is meant here: instantaneous maximum discharge (it is usually published in hydrological yearbooks as monthly maximum discharge) or mean daily maximum discharge? Is it compared to maximum (instantaneous) annual discharge?
- Is it snow depth (cm) that is analyzed in the paper? Snow water equivalent would be more meaningful for hydrological purposes. At least lack of the long and regular SWE time series should be mentioned. Maximum snow accumulation term may be a little confusing because it generally more refers to SWE, not snow depth.
References:
Blöschl, G.; Hall, J.; Parajka, J.; Perdigão, R.A.P.; Merz, B.; Arheimer, B.; Aronica, G.T.; Bilibashi, A.; Bonacci, O.; Borga, M.; 384 Čanjevac, I.; Castellarin, A.; Chirico, G.B.; Claps, P.; Fiala, K.; Frolova, N.; Gorbachova, L.; Gül, A.; Hannaford, J.; Harrigan, S.; 385 Kireeva, M.; Kiss, A.; Kjeldsen, T.R.; Kohnová, S.; Koskela, J.J.; Ledvinka, O.; Macdonald, N.; Mavrova-Guirguinova, M.; 386 Mediero, L.; Merz, R.; Molnar, P.; Montanari, A.; Murphy, C.; Osuch, M.; Ovcharuk, V.; Radevski, I.; Rogger, M.; Salinas, J.L.; 387 Sauquet, E.; Šraj, M.; Szolgay, J.; Viglione, A.; Volpi, E.; Wilson, D.; Zaimi, K.; Živković, N. Changing climate shifts timing of 388 European floods. Science. 2017, 357(6351), 588-590. doi: 10.1126/science.aan2506
Kireeva, M.B.; Rets E.P., Frolova, N.L.; Samsonov, T.E.; Povalishnikova, E.S.; Entin, A.L.; Durmanov, I.N.; Ivanov, A.M. Occasional Floods On The Rivers Of Russian Plain In The 20Th–21St Centuries. Geography, Environment, Sustainability. 2020, 13(2), 84-95. doi: 10.24057/2071-9388-2020-29
Volchek, A.A.; Shelest T.A. Formation of winter floods on the rivers of Belarus, Scientific notes of the Russian State Hydrometeorological University, Rubric: Hydrology, 2012. 25, 5-19 (in Russian).
Comments for author File: 
Comments.docx
Author Response
We want to thank the reviewer for her/his positive, helpful and constructive comments on the manuscript. Please find below our response to the comments (in italics).
The article is about fluctuations of floods magnitude and timing during the cold period in the Danube basin. The study examines winter and spring floods in the Rika River Basin (Ukraine) and in the Steyr River Basin (Austria). Hydrological regime of the chosen rivers differs significantly, especially in winter and spring floods formation. Winter and spring floods in the Rika River Basin mostly result in maximum annual discharges while in the Steyr River Basin the winter floods are usually lower in comparison to floods of the warm season. Comprehensive approaches are used for the combined hydrometeorological analysis of winter floods and their factors. The study shows interesting results but the presentation may be improved.
Response: Thanks for your positive and constructive assessment.
The term “winter floods” seems to be inappropriate considering floods from November to April. In the Introduction it is noted that in the Ukrainian part “the most significant floods frequently occur in spring and are generated by snowmelt and rain-on-snow events [7, 8, 9]”. “Spring snowmelt floods” is often used to describe snowmelt floods after long snow accumulation [Blöschl et al., 2017] which sometimes occurs in the Carpathians catchments. It may have been better to call those floods “cold season floods”.
Response: Yes, we agree that finding a clear formulation for the floods occurring during a cold season is not straightforward. On the one hand, there is some variability in the definition of winter floods in the literature (please see, e.g. Mudelsee et al., 2006, : https://doi.org/10.1623/hysj.51.5.818, or Jeneiova et al., 2016, DOI:10.1515/johh-2016-0037), but we agree that the term winter flood can be confusing with the meteorological definition of the winter (December-February). Still, using the cold season floods term in the entire document can make reading somewhat difficult. So in response to this comment, we have decided to add an explanation to the Introduction section referring to what we mean under winter floods: “The term winter flood used in this study refers to floods occurring in the cold season of the year (i.e. November to April).”.
We believe this can compromise the clarity of the presentation and the precise wording.
The conclusion “in the last decades, the increasing phase in melt temperatures has resulted in decreasing winter floods in Ukrainian catchments, which corresponds well with changes in flood magnitude identified by [2] in Eastern Europe” should be extended. It is important to note that several studies indicate a simultaneous increase in number of winter floods as a result of thawing and a general increase in winter flow volumes in Eastern European rivers [Volchek, Shelest, 2012; Kireeva et al., 2020]. Probably, authors should add some more review on winter floods in Europe in the introduction section.
Response: Thanks for references to interesting recent papers from Eastern Europe. We have added the suggested references into the Introduction section.
In general, Discussion and conclusions look weaker than other sections and could be deepened.
Response: In response to this comment, we have added suggested references also into the Discussion section.
Some smaller notes:
There may be some inconsistency the sentences. Abstract: “The most significant winter floods tend to occur in November and December”. Study area: “The mountain rivers of the Carpathians are characterized by an unstable thermal regime and frequent transitions from negative to positive air temperatures in December-February, which leads to numerous snow melt events. … In such a case, floods with very high runoff peaks tend to occur.” To which region does the sentence in the abstract refer?
Response: In response to reviewer 1 and this comment, we have extended Table 3, which indicates the month of the occurrence of flood maxima. Table 3 supports the finding that the largest winter floods occur in November and December (as indicated in the Abstract). To avoid confusion, we have revised the sentence in the Study area section as follows: “The mountain rivers of the Carpathians are characterized by an unstable thermal regime and frequent transitions from negative to positive air temperatures during winter, which leads to numerous snow melt events.”
- What coordinates are mentioned in the Tables 1 and 2?
Response: These are geographical coordinates. In order to clarify it (and in response to this comment), we have revised the Table captions as follows: “Characteristics of catchments and geographical coordinates of the catchment outlets in the …”
- Line 106: Daily maximum discharge. What is meant here: instantaneous maximum discharge (it is usually published in hydrological yearbooks as monthly maximum discharge) or mean daily maximum discharge? Is it compared to maximum (instantaneous) annual discharge?
Response: The analysis is based on the mean daily maximum discharges. We have added this information into section 2.2.
- Is it snow depth (cm) that is analyzed in the paper? Snow water equivalent would be more meaningful for hydrological purposes. At least lack of the long and regular SWE time series should be mentioned. Maximum snow accumulation term may be a little confusing because it generally more refers to SWE, not snow depth.
Response: As indicated in sections 2.2 and 3.2, we have analysed the snow depth data. We agree that analysis of snow water equivalent data would be interesting. Unfortunately, long-term snow water equivalent data are unavailable for the study regions.
References:
Blöschl, G.; Hall, J.; Parajka, J.; Perdigão, R.A.P.; Merz, B.; Arheimer, B.; Aronica, G.T.; Bilibashi, A.; Bonacci, O.; Borga, M.; 384 Čanjevac, I.; Castellarin, A.; Chirico, G.B.; Claps, P.; Fiala, K.; Frolova, N.; Gorbachova, L.; Gül, A.; Hannaford, J.; Harrigan, S.; 385 Kireeva, M.; Kiss, A.; Kjeldsen, T.R.; Kohnová, S.; Koskela, J.J.; Ledvinka, O.; Macdonald, N.; Mavrova-Guirguinova, M.; 386 Mediero, L.; Merz, R.; Molnar, P.; Montanari, A.; Murphy, C.; Osuch, M.; Ovcharuk, V.; Radevski, I.; Rogger, M.; Salinas, J.L.; 387 Sauquet, E.; Šraj, M.; Szolgay, J.; Viglione, A.; Volpi, E.; Wilson, D.; Zaimi, K.; Živković, N. Changing climate shifts timing of 388 European floods. Science. 2017, 357(6351), 588-590. doi: 10.1126/science.aan2506
Kireeva, M.B.; Rets E.P., Frolova, N.L.; Samsonov, T.E.; Povalishnikova, E.S.; Entin, A.L.; Durmanov, I.N.; Ivanov, A.M. Occasional Floods On The Rivers Of Russian Plain In The 20Th–21St Centuries. Geography, Environment, Sustainability. 2020, 13(2), 84-95. doi: 10.24057/2071-9388-2020-29
Volchek, A.A.; Shelest T.A. Formation of winter floods on the rivers of Belarus, Scientific notes of the Russian State Hydrometeorological University, Rubric: Hydrology, 2012. 25, 5-19 (in Russian).
Round 2
Reviewer 3 Report
All my concerns were solved. In my opinion the work can be publish in Hydrology.
