Channel Changes and Controlling Factors over the Past 150 Years in the Basento River (Southern Italy)

Round 1

Reviewer 1 Report

This study provides a solid analysis of maps and images to investigate the evolution of the Basento River. Although the methodology itself is not innovative, the study is a good application effort that offers better understanding of the study area. That said, the analysis of images is not well corroborated by physical interpretations, and thus a revision is recommended.

 

General comments:

Please go though a typo check and have a professional editor polish up the flow of the narratives. Since the main body of the study is telling the story of how the river changed, the quality of story telling directly affects the perceived quality of your work. The current manuscript is understandable but does not make a compelling and enlightening story.

The explanations of Figures 5 through 8 takes up a significant portion of section 4. However, most of the explanations seem to be redundant if Figures 5 through 8 could be improved for better visualization (e.g., breaking up into subplots or other ways of visualization). What would be more informative is the physical interpretation of the trends and numbers shown in the Figures, such as the plausible physical process causing the changes. The same suggestion applies to section 4.3 as well. If Figure 8 could have a bar chart of pie chart indicating the percentages of land use on the side, much of the section 4.3 could be replaced by more insightful explanations, e.g., the reasons of changes in land use (urban planning, economy reform, land reclamation, etc.).

 

Specific comments:

Line 54: What does lower resonance mean? Are all South Italy rivers small? Please clarify in the manuscript.

Line 59: If phase III is concurrent with the other two, why would it be a phase and not a "background effect"?

Section 2.3: Given the abundance of extreme event, the average annual rainfall and flow may not be informative and may not even be meaningful. Please elaborate on the statistics by providing the period of which the statistics are calculated, and by providing a more detailed overview of the variable (e.g., inter-annual variability, intra-annual variability, distributions, etc.).

Line 135-137: It's interesting to see that intense floods are observed during summer in Mediterranean stream. In some other examples, such as California in the U.S., summer is often super dry. What would cause the intense floods in summer in the Basento River?

Line 183: What about the first and the second segments?

Line 204: Define "Ra".

Line 207: Define Braiding Index (BI).

Figures 5 through 8: Also, it is not clear how many "data points" are available for each reach. The number of points shown here for each should be equal to the number of images analyzed for each reach. Does that mean no image was analyzed for the period between 1870 and 1940s?

Line 269-279: There's no 1st and 2nd segments in Figure 8.

Line 283-284: It's interesting that the pattern did not change while the width changes significantly. Please elaborate in the manuscript (e.g., what would be the physically plausible explanation).

Line 313-314: Please elaborate on these banks and levees, e.g., what are the features of their designs and how are they expected to affect the flow and/or sedimentation of the river.

Line 330-331: Is this maybe from a report or any form of document? If so, it should be properly cited.

Line 343: Define SPI and elaborate on its physical meaning.

Line 392-393: The argument that the widening of Basento FP could not be correlated to human interventions seems to contradict the previous argument that the stop of mining at the end of 1990s inverted the trend in Basento FP. Is mining not considered a sort of human interventions? Please justify the argument.

Author Response

Dear editor,

We appreciate your helpful comments and those of the reviewers. The manuscript has been deeply revised and we feel that the manuscript is now improved.

We have made revisions based on the comments/suggestions of reviewers I, II and III.  The comments are numbered below, with our response (clarifications and changes) following.

We have also improved some other parts of the paper to make them clearer, as well as updated the English language and grammar thank to language experts (see certificate).

 

Response to Reviewer 1 Comments

 

Point 1 Please go though a typo check and have a professional editor polish up the flow of the narratives. Since the main body of the study is telling the story of how the river changed, the quality of story telling directly affects the perceived quality of your work. The current manuscript is understandable but does not make a compelling and enlightening story.

We had a language review by English experts. See certificate.

The explanations of Figures 5 through 8 takes up a significant portion of section 4. However, most of the explanations seem to be redundant if Figures 5 through 8 could be improved for better visualization (e.g., breaking up into subplots or other ways of visualization). What would be more informative is the physical interpretation of the trends and numbers shown in the Figures, such as the plausible physical process causing the changes. The same suggestion applies to section 4.3 as well. If Figure /9 could have a bar chart of pie chart indicating the percentages of land use on the side, much of the section 4.3 could be replaced by more insightful explanations, e.g., the reasons of changes in land use (urban planning, economy reform, land reclamation, etc.).

All the images were enlarged, fonts have been enlarged too and have been changed in “Palatino Linotype”, which is the same of the text. Figure 5 has been modified to facilitate the view of river reaches trend. In particular, this figure is now composed by two graphs (a & b), which represent the trend respectively from reach 3.1 to 4.1 and reaches from 4.2 to 5.3. This subdivision was the same used in section 5 (discussion), in which the same subdivision would to facilitate discussion of the main trend. Figure 8 (section 4.3) was modified as requested.

Specific comments:

Line 54: What does lower resonance mean? Are all South Italy rivers small? Please clarify in the manuscript.

We clarified in the text at line 60.

Line 59: If phase III is concurrent with the other two, why would it be a phase and not a "background effect"?

To be more precise, the time intervals of the three phases are as follows: the first phase goes from the mid-1800s to the mid-1900s, the next phase (II) from the second half of the 1900s to the end of the 1990s, and the third and last phase from the late nineties to today. The last phase isn’t concurrent to the second one.

Now this aspect has been better specified in the text (lines 66 -73).

Section 2.3: Given the abundance of extreme event, the average annual rainfall and flow may not be informative and may not even be meaningful. Please elaborate on the statistics by providing the period of which the statistics are calculated, and by providing a more detailed overview of the variable (e.g., inter-annual variability, intra-annual variability, distributions, etc.).

We thank the referee for this comment. We improved this aspect in section 4.4. “Flood events and precipitation patterns”. All information reported in this section is pointing to specific literature.

Line 135-137: It's interesting to see that intense floods are observed during summer in Mediterranean stream. In some other examples, such as California in the U.S., summer is often super dry. What would cause the intense floods in summer in the Basento River?

This aspect has been clarified in the text. To be more precise, the pluviometric regime of the Basento hydrographic basin maritime type, was characterized by a maximum, that occurs between November and January (autumn/winter), and a minimum, typical in July or secondarily of August (summer) [63]. Considering recent review about intense flood events occurred in Basilicata from 1921 to 2014 [82], 48 flood events were identified, of which 13 were most intense. These events occurred most frequently in the period between October and March.

In previous version of the manuscript this aspect was not well developed which instead turns out to be very important. The manuscript was updated.

Line 183: What about the first and the second segments?

This aspect has been corrected and improved better explaining the segmentation steps (lines 229-236).

Line 204: Define "Ra".

Done (lines 255-261).

Line 207: Define Braiding Index (BI).

It has been defined at lines 271-275.

Figures 5 through 8: Also, it is not clear how many "data points" are available for each reach. The number of points shown here for each should be equal to the number of images analyzed for each reach.

In section 3.1 a table was added showing the main data used to evaluate River changes over the past 150 years.

Does that mean no image was analysed for the period between 1870 and 1940s?

It’s right, unfortunately no other historical data were available between 1873 and 1943.

Line 269-279: There’s no 1^st and 2^nd segments in Figure 8.

The error has been correct. Unfortunately, in one of the manuscript versions reach numbering was reported in reverse way, instead of the correct one.

Line 283-284: It’s interesting that the pattern did not change while the width changes significantly. Please elaborate in the manuscript (e.g., what would be the physically plausible explanation).

Thanks for pointing out this. We made some changes to better illustrate data (“Results” section) and to interpret the overall moderate changes in channel pattern (“Discussion” section).

Line 313-314: Please elaborate on these banks and levees, e.g., what are the features of their designs and

how are they expected to affect the flow and/or sedimentation of the river.

We have explained how meander cut-off and levees likely affected channel processes (e.g. sedimentation and bank erosion).

Line 330-331: Is this maybe from a report or any form of document? If so, it should be properly cited.

The reference is added.

Line 343: Define SPI and elaborate on its physical meaning.

SPI stand for Standardized precipitation index and is computed in order to define the drought period of a given area. SPI quantify drought taking rainfall into account, or rather SPI quantifies precipitation deficits on multiple time scales (1, 3, 6, 12, 24, 48 months).

The SPI is computed by fitting a gamma probability density function to a given frequency distribution of precipitation data at a location for a specified time period. Then, the cumulative distribution of precipitation is determined, and, for each value of precipitation, it is transformed into the standard normal random variable Z with a mean of zero and a variance of one, which is the value of the SPI. An SPI value of ≤ 0 indicates dry period (drought period), while SPI value of ≥ 0 indicates wet period (with more frequent precipitation).

This explanation has been added in the manuscript at line 503.

Line 392-393: The argument that the widening of Basento FP could not be correlated to human interventions seems to contradict the previous argument that the stop of mining at the end of 1990s inverted the trend in Basento FP. Is mining not considered a sort of human interventions? Please justify the argument.

It is clear what the reviewer has pointed out, but actually what we want to stress is that there have been no “new” and significant human interventions, able to cause a new river trend. Instead  a suspension of river mining (which is a human intervention) and the new climate tendency may have caused, together the new trend shown by the river. At the beginning of the 2000s the effects of the absence or strong breaking of the mining activity could have influenced the river widening, but it is also true that in the same period flood events begin to be more frequent more intense, contributing to sharpen river widening trend.

This aspect has been better explained in the manuscript.

Reviewer 2 Report

A copy of the manuscript is attached that contains the locations where changes should be considered.  There are 2 major concerns among numerous smaller ones.

1)  Overall, there seems to be a lack of support for the primary thesis that was stated on lines 441-413 that says climate is a major driving factor yet is barely discussed.

2) The trends on figure 5 clearly indicate significant widening in 1953 but is not addressed in the text.  This is erroneously supported on line 421 that says 'later widening' after 1990, but the data do not agree with this assessment.  The widening in 1953 is more significant than the narrowing.

Most of the text on the figures and tables are of a different font than the manuscript and is too small to see and read.

Consistency for tense and word usage requires attention.

If the apparent inconsistencies in 'widening' vs. 'narrowing' in the 4 phases is defined more clearly and in terms of climate (if climate is in fact a major driver), it would be in publishable form.

 

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 2 Comments

Comments and Suggestions for Authors

A copy of the manuscript is attached that contains the locations where changes should be considered.  There are 2 major concerns among numerous smaller ones.

1)  Overall, there seems to be a lack of support for the primary thesis that was stated on lines 441-413 that says climate is a major driving factor yet is barely discussed.

This aspect has been improved in the discussion section in the manuscript. We have focussed the new version more on the discussion of the climatic aspect.

2) The trends on figure 5 clearly indicate significant widening in 1953 but is not addressed in the text.  This is erroneously supported on line 421 that says 'later widening' after 1990, but the data do not agree with this assessment.  The widening in 1953 is more significant than the narrowing.

Erroneously in section 4.1, were reported only the main phases characteristics and trends, leaving out, instead, an aspect that, as far as it concerns only some reaches, is still important to know the morphological Basento River evolution. Although it was not dealt with in the points highlighted, the widening trend shown by some reaches between 1943 and 1953, however, was highlighted and explained in the "discussion”. The arguments highlighted by the reviewer in the lines (section “Results” and “Conclusion”) has been improved.

Most of the text on the figures and tables are of a different font than the manuscript and is too small to see and read.

The text on the figure and tables (font and dimension) has been changed.

Consistency for tense and word usage requires attention.

Done.

If the apparent inconsistencies in 'widening' vs. 'narrowing' in the 4 phases is defined more clearly and in terms of climate (if climate is in fact a major driver), it would be in publishable form.

We hope that we clarified this aspect in the new version of the manuscript.

peer-review-5697201.v1.pdf

All the corrections reported in the .pdf file have been integrated.

About the main corrections and comment pinned at first page:

Paragraph indent has been corrected. Figures and figures text have been enlarged. The overuse of the word “show” has been corrected as requested. We would show, thanks to this study, that latest (from the end of 1990s to now) morphological Basento River changes (widening channel width trend) could be attempted by more intense and frequent flood events and also boosted by mining activity suspension.

This latest aspect has been improved in the manuscript.

However I would to point out that this aspect is not the only and most important purpose of this work, which also wants to show Basento River channel dynamics when the river has been heavily affected by human activities, and possible peculiarities and differences with respect to what has been observed up to now in other Italian rivers.

Reviewer 3 Report

Dear authors,

overall, I am not sure what is new from different similar studies across Italy. By starting with the abstract (l.12-14) - the using of the quantitative approach seems promising, but you only pointed to cause-effect connections by quantitative changes in the channel (yet limited on the channel width and sinusoity parameters, what is quite typical for this kind of studies). I expected to see quantitative information about interventions at the catchment scale (e.g., % of land use changes affecting % of annual sediment supply, lenght of constructed channel embankments preventing from lateral erosion, maybe some rainfall-runoff and river morphodynamic modelling etc.)
I am also at doubts that you did not analyzed the entire contributing catchment area - this needs to be justified. E.g., changes in land use in mountainous parts will strongly affect sediment production (and rainfall-runoff processes) as well as some direct interventions (e.g., presence of check-dams in torrents).

Introduction
l. 35 - this is very general statement - you should add that it depends on the scale (reach, basin, size of the river in general)
l. 52-60 - this is also valid for southern Italy? Or do you see some differences between the northern (e.g. pre-Alpine rivers) and southern rivers in Mediterranean climate?
l. 64-66 - this statement should be placed into wider context (thinking that there are many rivers which were not analyzed so far)

Study area
2.4 chapter - this should be better connected with your results (chapter 4.3)

Data and methods
3.2 - I am not sure whether it is really necessary to divide the studied river into so many reaches, which can later make your results somehow confused. E.g., why you separated 4.4-4.7 river reaches although all were characterised as meandering in unconfined valley settings? Later in the discussion (Fig. 11) it is clear that there are some similar tendencies even by dividing entire studied part of the river into two sections (and many renundant trends are evident also on Fig. 5, 6 and 8). In addition, results chapter 4.2 and 4.3 do not tell much about interventions assigned to individual reaches, which increases confusion. I would recommend to use longer reaches, which make your results clear.
l. 195 - so how you identified channel margins for your further analysis?
- you should add into methods how you acquired information about human interventions in the channel, if you want to have 4.3 chapter in results (and not in study area) - e.g., did you study some archives?

Results
l. 230-237, l. 291-293 - this should go to methods
Fig. 9 - I am not sure, but do you have the same hydrologic network on the maps? I think that e.g. meander bends should change according to changes in sinusoity between the studied years.
4.3.2 and 4.3.3 - I think that you should localise all the described changes - by assigment to individual reaches or by showing on the map. This will bring some new quantitative data into your analysis (e.g. nr. of affected reaches or length of banks with some interventions).
4.4 - there should be stated in methodology which parameters (and why) did you analysed. The river is not gauged? Because information about important floods (and droughts) may also explain potential (rapid) changes in river geometry.

Discussion
- I would like to see the discussion more focused on some wider (e.g. European) context; now there are too many comparisons with situation in Italy only. Also, you can discuss some future trends.

Best wishes

 

 

 

 

Author Response

Response to Reviewer 3 Comments

Dear authors,

overall, I am not sure what is new from different similar studies across Italy.

We improved this aspect in the new version of the manuscript.

Actually, we studied morphological variation in last 150 years for the last portion of Basento river, that nobody has studied up to now, excepted [63], in which were reported an analysis of morpho-evolutive characteristics of the Basento River along the lower valley (from Pisticci to the mouth) from 1812 to 1989. Reference reported [63] shown variation in pattern morphology but not about river width variation, moreover it discussed about the only connection between morphology pattern variation and anthropic interventions.

In our study, even if interest only a part of the Basento River, due to lack data, we shown variations and quantify the amount, in term of river width (for each reach of each datum) and morphology pattern (sinuosity Index) in each photo/map and datum available, covering (with some necessary and unsolvable gaps due to data missing) the last 150 years from 1873 to 2013.

The approach used in our study is similar to  other studies across Italy, because in this kind of study the approach is the same as the scope itself. In addition, we wanted to compare Basento river variation trend (width and morphology pattern + causes) with some of italian river variations (references 44-62), synthetically reported to understand possible common trend (and causes) and local differences.

By starting with the abstract (l.12-14) – the using of the quantitative approach seems promising, but you only pointed to cause-effect connections by quantitative changes in the channel (yet limited on the channel width and inuosity parameters, what is quite typical for this kind of studies). I expected to see quantitative information about interventions at the catchment scale (e.g., % of land use changes affecting % of annual sediment supply, length of constructed channel embankments preventing from lateral erosion, maybe some rainfall-runoff and river morphodynamic modelling etc.).

The new version of the manuscript was improved in this sense. More information about human interventions were added in section 4.3.

I am also at doubts that you did not analyzed the entire contributing catchment area - this needs to be justified. E.g., changes in land use in mountainous parts will strongly affect sediment production (and rainfall-runoff processes) as well as some direct interventions (e.g., presence of check-dams in torrents).

This was undoubtedly our first thought (the study of entire contributing catchment), however we encountered severe limitations in the available data, which led us to focus only on one part of the river. We know very well how important are changes in land use in mountainous parts that will strongly affect sediment production (and rainfall-runoff processes) as well as some direct interventions of check-dams in torrents. But unfortunately, it did not depend on our choice.

Introduction

line 35 - this is very general statement - you should add that it depends on the scale (reach, basin, size of the river in general)

Done.

lines 52-60 - this is also valid for southern Italy? Or do you see some differences between the northern (e.g. pre-Alpine rivers) and southern rivers in Mediterranean climate?

Synthesis about the three main phases of morphological “adjustment” reported at lines 57-73 has been made studying references reported at lines 44-59. In some phases has been well noticed exceptions, related to the start and duration of the morphological “adjustment” phases. In particular has been noticed that rivers located from central Italy to southern Italy (e.g. Trigno, Biferno, Volturo, Crati and Sinni) started the narrowing II phase with up to 20 years later (not in 1950 but up to 1970), while the northern rivers (e.g. Tagliamento, Piave, Panaro, Vara) whose second phase begun in 1950s. Another difference has been noticed for the beginning of the third phase. This last phase on average goes from the end of 1990s, in some cases with a delay or an advance of 10 years, up to the -present. It was characterised by less intense channel adjustments and, in some cases, by some morphological recovery. For this phase has been noticed many local differences in terms of the beginning and duration and not a clear temporal trend followed distinctly by northern rivers and those of central and southern Italy.

It was not possible to notice if there are differences relating to the first phase, because in some cases the analysis does not cover the entire time interval (end of the 19th century to the middle of the 20th century).

All aspects above explain have been improved in the text (lines 57-73).

lines 64-66 - this statement should be placed into wider context (thinking that there are many rivers which were not analyzed so far)

Done

Study area

2.4 chapter - this should be better connected with your results (chapter 4.3)

This part has been improved introducing, in a synthetic way, some human interventions better explained in chapter 4.3.

Data and methods

3.2 - I am not sure whether it is really necessary to divide the studied river into so many reaches, which can later make your results somehow confused. E.g., why you separated 4.4-4.7 river reaches although all were characterised as meandering in unconfined valley settings?

We agree that dividing the study area in several reaches gives results with more scattering and more difficult to interpret. On the other hand, we think that it is useful to have data at reach scale since they better represent “real” changes and the range of variations, and in some cases of different trends, within the study area. We preferred to use a wider scale (i.e. dividing the study area into two long sectors) only in the “Discussion”, and this was possible because we could group reaches with similar evolutionary trends.

Later in the discussion (Fig. 12) it is clear that there are some similar tendencies even by dividing entire studied part of the river into two sections (and many redundant trends are evident also on Fig. 5, 6 and 8).

As specified above, procedure followed [2] to divide segments, provides the consideration of many aspects in addition to confinement and morphology pattern (e.g. hydrological discontinuities, variations of morphological units and variations in the size of the plain and/or of the confinement index). We could not consider these aspects because they could have influenced differently morphological dynamics evolution over the last 150 years.

In addition, results chapter 4.2 and 4.3 do not tell much about interventions assigned to individual reaches, which increases confusion. I would recommend to use longer reaches, which make your results clear.

See comment above

line 195 - so how you identified channel margins for your further analysis?

We clarified in the manuscript the meaning of “channel area” (line 255).

Channel margins were digitized considering the bankfull river [89]. More details were improved at lines 255-261.

you should add into methods how you acquired information about human interventions in the channel, if you want to have 4.3 chapter in results (and not in study area) – e.g., did you study some archives?

We agree and it was done.

Results

lines 230-237, l. 291-293 - this should go to methods

Lines 318-338 (old 297-317) have been deleted because these complicate the explanation more than it could clarify it.

What has been explained at lines 399-417 (old 291-293) of results section, has been previously introduced in method at lines 275-278.

Fig. 9 - I am not sure, but do you have the same hydrologic network on the maps? I think that e.g. meander bends should change according to changes in sinusoity between the studied years.

This aspect has been changed.

4.3.2 and 4.3.3 - I think that you should localise all the described changes - by assigment to individual reaches or by showing on the map. This will bring some new quantitative data into your analysis (e.g. nr. of affected reaches or length of banks with some interventions).

About section 4.3.2, a new image has been added, showing Basento River different kind of leeves (beaten and/or entrenched levees or caged banks levees) and their localization.

4.4 - there should be stated in methodology which parameters (and why) did you analysed. The river is not gauged? Because information about important floods (and droughts) may also explain potential (rapid) changes in river geometry.

This aspect has been improved

Discussion

I would like to see the discussion more focused on some wider (e.g. European) context; now there are too many comparisons with situation in Italy only. Also, you can discuss some future trends.

We added some sentences at the end of the “Discussion” to put this work in a wider context.

Round 2

Reviewer 1 Report

My comments have been addressed and I think the manuscript is almost ready.

Please proofread the manuscript again to correct some remaining errors, such as the numbering of Figures, and the unit of a trend (line 422, a trend of -133 mm over what), etc.

 

Author Response

Response to Reviewer 1 Comments

My comments have been addressed and I think the manuscript is almost ready.

Please proofread the manuscript again to correct some remaining errors, such as the numbering of Figures, and the unit of a trend (line 422, a trend of -133 mm over what), etc.

The text has been proofread, correcting figure numbering and some typing errors, but also erasing some sentences or part of these, in which were reported some redundant and unnecessary information (e.g. what has been reported and then cancelled at line 155).

 

Submission Date

18 November 2019

Date of this review

05 Jan 2020 04:47:26

Reviewer 3 Report

Dear Authors,

thank you for the revision of you paper, especially for explaining your motivation and added information about the studied river. I still have some minor remarks:

there are quite frequent typo errors in the added/modified text (e.g., l. 11 "approaches haves", l. 283 "tcalled") - please check these issues l. 230 - it is not clear for me what is the difference between full banks and bankfull l. 394-397 - why in bold? Figure b - x-axis - I guess there shoud be "downstream distance" Table 1 - why not use "bw" for black and white photo?

Best wishes

 

 

Author Response

Response to Reviewer 1 Comments

Dear Authors,

thank you for the revision of you paper, especially for explaining your motivation and added information about the studied river. I still have some minor remarks:

there are quite frequent typo errors in the added/modified text (e.g., l. 11 "approaches haves", l. 283 "tcalled") - please check these issues l. 230 - it is not clear for me what is the difference between full banks and bankfull

394-397 - why in bold? Figure b - x-axis - I guess there shoud be "downstream distance"  Table 1 - why not use "bw" for black and white photo?

The text has been revised, correcting typing errors, some bold periods and what has been suggested for the table 1.

About what is explained at line 255, as specified, channel area limits coincides with the so-called full riverbed (also called full banks or bankfull in scientific literature - among them synonyms), associated with the maximum flow rate that could be contained within the riverbed without flood occurrence.

We changed the X axis caption in “downstream distance” in fig 2 (b)

 

Best wishes

 

Submission Date

18 November 2019

Date of this review

04 Jan 2020 10:53:00