Medium-term dynamics of a middle Adriatic barred beach

Postacchini, Matteo; Soldini, Luciano; Lorenzoni, Carlo; Mancinelli, Alessandro

doi:https://doi.org/10.5194/os-13-719-2017

Articles | Volume 13, issue 5

https://doi.org/10.5194/os-13-719-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/os-13-719-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 13, issue 5

Research article

|

18 Sep 2017

Research article |

| 18 Sep 2017

Medium-term dynamics of a middle Adriatic barred beach

Matteo Postacchini, Luciano Soldini, Carlo Lorenzoni, and Alessandro Mancinelli

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Final revised paper (published on 18 Sep 2017)
Preprint (discussion started on 09 Jan 2017)

Interactive discussion

Status: closed

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

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RC1: 'Medium-term dynamics of a Middle Adriatic barred beach - os-2016-106', Anonymous Referee #1, 07 Feb 2017
- RC3: 'review of paper OS-2016-106', Anonymous Referee #3, 09 Feb 2017
  - AC2: 'Reply to Reviewer #3', Matteo Postacchini, 01 Mar 2017
- AC1: 'Reply to Reviewer #1', Matteo Postacchini, 01 Mar 2017
RC2: 'Medium-term dynamics of a Middle Adriatic barred beach- Anonymous Referee comments', Anonymous Referee #2, 07 Feb 2017
- AC3: 'Reply to Reviewer #2', Matteo Postacchini, 01 Mar 2017

Peer-review completion

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

AR by Matteo Postacchini on behalf of the Authors (05 Apr 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (08 May 2017) by Eric J.M. Delhez

RR by Anonymous Referee #4 (20 May 2017)

RR by Anonymous Referee #2 (23 May 2017)

Suggestions for revision or reasons for rejection

Summary
This referee acknowledges significant changes to the manuscript and commends the authors for their diligent revisions. The responses below are specific to previous comments from “Anonymous Referee #2”. With minor technical changes and minor suggestions for revision, this referee recommends this research paper for publication.

General & Specific Comments
The extended explanation of medium-term dynamics, with careful distinction of factors that can be teased apart and those that remain indistinguishable is appreciated. It is now my understanding, thanks to the authors’ revision, that even though the change in bathymetry between annual surveys could be/sometimes is influenced by a dramatic storm just before the survey, this storm is incorporated into the medium-term dynamics analysis, and that the changes in the annual bathymetry are of a different magnitude than what has been observed from a single storm. Therefore, the conclusions drawn from the differencing of bathymetric maps between years represents the cumulative effect of calm and stormy conditions (varied directional forcing is also accounted for) without being biased by short-term changes. Is my understanding correct? If so, I think one additional comment on the relative magnitude of observed short-term changes to a bar system with respect to medium-term changes would be appropriate. It does not need to come from this field site- observations from a similarly sandy, barred beach would suffice.

The explanation of the Dean-type equilibrium beach profile is presented early and in the context of this field site. The authors’ changes clarify that the study beach has been found to match the Dean-type equilibrium profile (shape parameter A is relatively constant in time) and that the profile varies as expected with the changing d_50.

Thank you for specifying your wave time series and spectral processing. These details substantiate the decisions you made to analyze specific bands in wave height and wave period.

The addition of the outer bar change parameters to Table 3 and the discussion of those parameters in the adjacent text clarify your message about the link between wave and wind climate and the bar morphodynamics.

In section 4.2 Bathymetric surveys, on p. 14, the paragraph beginning with “The influence of the Rotonda”: In this section, the authors describe bathymetric variation local to the engineered structures and ascribe these changes in specific years to the presence of the structures. I am assuming this influence was expected due to the predictable effects of engineered structures on sediment migration under given wave conditions, but this link is not explicitly made by the authors. Perhaps it is more appropriate to limit the results section to describing the changes and stating that they were observed local to the structures, and then discuss why this was expected and how the data confirms this prediction in the Discussion section.

Technical Comments
p. 1, line 3: “area in the Region” does not need a capital “R”.

p. 14, line 26: typo- doubled dash between 25 and 40%.

p. 20, line 8: “seward” change to “seaward”

p. 20, line 9-11: “rather than by” suggests that the 2012-2013 ESE climate does not produce significant changes, but it does. Perhaps you are trying to say that the bimodal wave climate in 2010-2011 does not produce large changes, but the NNE and ESE climates do produce large magnitude changes in opposite directions. If so, try rewording “rather than by” to “or by”.

p. 22, line 32: “suggested us to” is not quite correct; use “suggested we” or “led us to”.

p. 23, line 11: “Lagrangian dirfters, able at measuring” change to “capable of measuring”.

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RR by Anonymous Referee #5 (23 May 2017)

Suggestions for revision or reasons for rejection

Overview:
The paper under review couples the movement of subtidal bars along a stretch of the Adriatic to wind wave forcing with respect to medium-term time scales. The area of study is significant because 1) it is located along the coast of a semi-enclosed basin, 2) has a small tidal range, and 3) a range of wave forcing that deviates greatly from the average. The effects of short- and long-term dynamics appear relatively frequently in literature. In the present study, the authors consider the cumulative effects of middle-term timescales (on the order of years). Using data from an offshore, waverider buoy and bathymetric surveys collected in consecutive years, the author’s link the bar movement between surveys to the breaking of wind waves.
Approach:
1) I understand the authors’ argument of cumulative effects when referring to medium-term dynamics and responses. However, I cannot completely convince myself that any given survey is not skewed toward the most recent wave event or lack thereof. In the first sentence of the conclusion, the authors suggest that medium-term evolution falls between decadal and event timescales. As presented, the analyses focus on the periods between available surveys. It would be convincing to see that surveys from 2011 or 2012 can be “predicted” given the other available surveys and the wave data.
2) While the steps of the wave statistical analysis given on page 9 are useful, I would like to know more about how the wave data were processed. It is not clear if the authors used bulk wave parameters or processed spectral data from the buoy.
3) The statistical analyses of the wave data provide estimated values of wave parameters for the directional bins of interest to the authors. Given the statistical procedure, it is not accurate to refer to the values as “mean” values (page 10, lines 13 and 22). It appears that the “mean” values reported were determined by assigning the middle value of the bin chosen by the authors (table 2). Actual mean values can be reported by taking the average of all the values that fall into the bins. If this is how the mean was determined, it should be made clearer in the text. Furthermore, mean values should be denoted in the text using a subscript, overbar, or some other marking to distinguish it from the bulk wave parameters that are derived from the full wave spectra.
Discussion:
1) On page 14, line7, the authors state, “…the yellow pattern…indicating bed erosion…”. It was previously stated that red patterns indicate accretion, and in figure 4, yellow falls on the positive side of the color bar with red. This seems to be contradictory.
2) It is unclear what “local” refers to in the discussion of the bar dynamics (page 19, beginning with line 31). Are the local wave parameters reported for a certain point along a chosen profile? If so, which profile and what is the location of the reported local parameters?
Presentation:
1) The use of phrases “the former”, “the latter”, etc. are confusing and cumbersome to comprehension. Please replace these phrases with the intended nouns for a more clear presentation of the work.
2) Page 2, line 11: I think the authors intended to use the word “experiments” in place of “experiences”.
3) Page 6, line 9: The authors do not define DTM.
4) Referring to the wave directional sectors by either the abbreviation or the range in degrees would make the text easier to read.
5) It would be useful to refer to fig 5 when the green and purple lines are discussed on page 15, line 15.
6) Correct the run-on sentence on page 16, line3 – page 17, line 2.
Figures:
1) It would be useful to show the location of the waverider in the subpanel of Figure 1(a).
2) It would be useful to note the profile number of the profiles shown in fig 2.
3) It would be useful to have the line markers in fig 4 match the markers used of the inner, interm, and outer bars as shown in figure 5.

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ED: Reconsider after major revisions (26 May 2017) by Eric J.M. Delhez

AR by Matteo Postacchini on behalf of the Authors (08 Jul 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (10 Jul 2017) by Eric J.M. Delhez

RR by Anonymous Referee #5 (28 Jul 2017)

ED: Publish subject to technical corrections (10 Aug 2017) by Eric J.M. Delhez

AR by Matteo Postacchini on behalf of the Authors (11 Aug 2017) Manuscript

Short summary

Sandy beaches are a common landscape feature of the Italian Adriatic coast. From an economic and touristic point of view, the unprotected beach of Senigallia is an important area, frequently monitored in the last decades. The annual evolution of the submerged bars can be related to the climate: waves from the NNE/ESE, characterized by larger/smaller steepness and relative height, induce seaward/shoreward bar migration and bar smoothing/steepening.