Global Distribution and Morphodynamic Patterns of Paired Spits Developed at the Mouths of Interdistributary Bays of Deltas and within Coastal Channels

Round 1

Reviewer 1 Report

The manuscript entitled “Global distribution and morphodynamic patterns of paired spits developed at the mouth of interdistributary bays of deltas and within coastal channels” is of a very interesting topic. The authors attempt to determine the global distribution, geomorphic characteristics and morphodynamic evolution of paired spits located at both interdistributary bays of deltas and within coastal channels by analyzing 27 spits. The topic is within the scope of the journal “Remote Sensing”.

The paper is well written and well structured. Here are some comments and suggestions that could improve the final version of the paper:

It is not clear to me what were the criteria for the selection of the spits included in the study. How did the authors select the paired spits? These are the only paired spits in the whole world? Was there a “Google earth” searching for the identification of any paired spits around the globe? This needs to be clarified more clearly in the “Materials and Methods” section.

At the “Materials and Methods” section, an illustration (maybe of the most representative spit) showing (explaining) what the authors measured on satellite images and/or charts/maps would be very helpful to the reader of the article.

A world map showing the location of all the spits included in the analysis is required.

One of the main issues is that at the “Discussion” section a lot of details regarding the studied spits are provided (many names of locations, places and toponyms) without any maps showing all these locations. This makes it difficult for the readers (who probably are not familiar with so many different places around the world) to follow the discussion.

line 18: please replace They…. by The…..

line 84: what do you mean with ….beach cups? maybe …….beach cusps?

line442: …it suggests…… instead of …..it suggest…..

line 449: …… by analysis of satellite images…… add an “of”

line 649: …... at the mouth of the Volta River delta….. add a “the”

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

The article by Alcantara-Carrio et al., is an interesting global study about the distribution and characterization of paired spits systems. The topic and approaches are appropriate for the audience of Remote sensing Ocean. Several remarks including to shortened and more focus discussion parts can be addressed to the authors to help them to improve the manuscript

Introduction

L39 : You can also mention the temporal decrease of sediment supply (Robin et al., 2020 ESPL) L48: You can also mention the refraction of waves on ebb delta or the welding of swash bars (FitzGerald et al., 2000 USACE)

Methods

L80-103 : It would be useful to provide a graphical illustration (conceptual or based on a field site) detailing the identification of each indicator would be appreciated.

L118: Authors do not specify the analysis of wave pattern for each sectors (Hs (offshore buoy, direction about coastline orientation). This data seems necessary to classify field sites and to deduce morphological classes from it.

Results

A representation on a world map would be interesting to better visualize their lat/long distribution

L141: I may have a problem defining the types of system studied. But there are many examples in macrotidal. For example, all of the inlets of the west coast in Normandy (megatidal, Robin et al., 2020 ESPL) or the French atlantic coast (e.g Arçay spit) have a paired spits...

Discussion

It would be useful in this section 1, to have the wave characteristics on a figure or table and possibly the littoral drift rates (possible to be calculated by empirical formulas). This will make it easier to support the discussion on hydrodynamic control. Local data including refraction and data close to both spits is illusory, I am aware, but average data would be useful. In general, this paragraph gives examples of the influence of certain hydrodynamic parameters on the morphology or dynamics of sites but the description remains very general and it is difficult to get a global idea of how hydrodynamic parameters can act and detail the conceptual figure 5. A figure with quantitative data is perhaps missing to illustrate the impact on morphology /dynamics of each site, to make this section more universal.

L320-323 : see my comments previously about french megatidal coast. Beyond the tidal context, it is the available sediment and the irregularity of the shoreline that is important for the formation of spits. A high tidal range in open coast can also induce a strong littoral drift.

This section 2 could be reduced significantly by switching the description of the dynamics of the sites in a result part in order to focus more easily on the role of sediment availability. Discussion about different sources that can develop the spits is an interesting approach that could be further developed and related to Figure 5.

The figure 5 provides a graphical illustration of several paired spits system nicely. May be add t1, t2, t3. Is it possible to add the correspondence with the sites on each category and to illustrate the three morphodynamic patterns of figure 4.

In the same way, the discussion of the section 4 would gain if it did not refer again to the characterization of each site. This information can be summarized in a table in the result section. This would allow the authors to further conceptualize and discuss the anthropogenic influence on these systems.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The authors responded to the various comments allowing the quality of the document to be significantly improved.