Seasonal and Intra-Annual Patterns of Sedimentary Evolution in Tidal Flats Impacted by Laver Cultivation along the Central Jiangsu Coast, China

Round 1

Reviewer 1 Report

The authors succeeded collecting numerous images and processing DEM by water line method of a tidal flat in China. The reviewer basically enjoyed the work, however, there are some points that need clarification before appearing in the journal.

(Comments)

1.         Images used in the study: The authors state that they collected 662 images, however, it is not clearly described how many are used actually in the analyses. At Line 121, it is described that 160 images are used, but the relation with the images listed in Table 1 is not explained.

2.         Please discuss the details of physical effects of laver aquaculture on erosion / accretion of tidal flat. Also please discuss possible sediment sources in this area.

3.         Please consider to display variations of tide level, wave height, river discharge (or water level) during the period of the study, which are important to understand morphological variation.

4.         Line 81: “numerical simulations technologies”: There is no numerical technique used in this study.

5.         Table 1: Is the unit of “Height” wrong? Also, “Height” should be better “Tide level”?

6.         Figure 1 and Table 1: Many of the description of the panels (e) – (l) are inconsistent with Table 1. (Acquisition date, tide level)

7.         Figure 3: Please explain the validity of the processed result of DEM.

8.         Figure 3: Please show evidence that the morphology during the processing period can be regarded (almost) unchanged.

9.         Figure 5: The display is not suitable to understand the temporal variations of volume of different places in the tidal flat. Please consider to display the temporal variations of total volume, total volume of lower portion and total volume of upper portion of each place.

10.     Figure 6: Since legends for panels (a) – (f) are missing, the reviewer couldn’t understand the meaning of the figure.

Author Response

For details of the revisions, please see the annex document.

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper “Seasonal and intra-annual patterns of sedimentary evolution in tidal flats impacted by laver cultivation along the central Jiangsu coast, China” is an intresting paper that could be of interest for the jorunal.

I have two major concerns.

The first one is more related to the break trought results that the paper is trying to demonstrate considering the first methodology part that is already published (Liu, Yongxue, et al. "Topographic mapping of offshore sandbank tidal flats using the waterline detection method: A case study on the Dongsha Sandbank of Jiangsu Radial Tidal Sand Ridges, China." Marine Geodesy 35.4 (2012): 362-378.). The first part of the method do not add much more innnovation to the new submission. I also have been reading the previous paper and the fact that is considering the mixed approach of the model delft 3D togheter with the medium resolution images reconstraction for the DEM is not giving enough evidence that the resolution of the generated DEM is suitable for a robust study for sediment erosion. There is a bunch of recent and very new reference in tidal flat sediment detection detection using earth Observation that the authors must consider before starting the method discussion:

-       Adolph, Winny, et al. "Remote Sensing Intertidal Flats with TerraSAR-X. A SAR Perspective of the Structural Elements of a Tidal Basin for Monitoring the Wadden Sea." Remote Sensing 10.7 (2018): 1085.

-       Manzo C., et al., (2015), Spectral characterization of coastal sediments using Field Spectral Libraries, Airborne Hyperspectral Images and Topographic LiDAR Data (FHyL), International Journal of Applied Earth Observation and Geoinformation 36, 54–68

-       Wang, W.; Yang, X.; Liu, G.; Zhou, H.; Ma, W.; Yu, Y.; Li, Z. (2016): Random Forest Classification of Sediments on Exposed Intertidal Flats Using ALOS-2 Quad-Polarimetric SAR Data. Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci. 2016, 8, 1191–1194, DOI 10.5194/isprsarchives-XLI-B8-1191-2016.

-       Valentini, E.; et al., (2015), An effective procedure for EUNIS and Natura 2000 habitat mapping in estuarine ecosystems integrating ecological knowledge and remote sensing analysis, Ocean and Coastal Management, 108: 52-64, http://dx.doi.org/10.1016/ j.ocecoaman.2014.07.015.

-       Jung, R.; Adolph, W.; Ehlers, M.; Farke, H.: A multi-sensor approach for detecting the different land covers of tidal flats in the German Wadden Sea — A case study at Norderney. Remote Sens. Environ. 2015, 170, 188– 202, DOI 10.1016/j.rse.2015.09.018.

-       Adolph, W.; Jung, R.; Schmidt, A.; Ehlers, M.; Heipke, C.; Bartholomä, A.; Farke, H. Integration of TerraSAR-X, RapidEye and airborne lidar for remote sensing of intertidal bedforms on the upper flats of Norderney (German Wadden Sea). Geo-Mar. Lett. 2017, 37 (2), 193–205, DOI 10.1007/s00367-016-0485-z. Geng, X.-M.; Li, X.-M.; Velotto, D.; Chen, K.-S. Study of the polarimetric characteristics of mud flats in an intertidal zone using C- and X-band spaceborne SAR data. Remote Sens. Environ. 2016, 176, 56–68, DOI 10.1016/j.rse.2016.01.009.

-       Wang, W.; Gade, M. A new SAR classification scheme for sediments on intertidal flats based on multi- frequency polarimetric SAR imagery. Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci. 2017, XLII-3/W2, 223–228, DOI 10.5194/isprs-archives-XLII-3-W2-223-2017.

Thus the introduction is not a reflection of the context of the subject considering the different reference that are missing.

Based on the above here the major problems that I see: to investigate the question of model sensitivity to sediment functions for scaling or aggregation of wetland attribute and thus its evolution, it is necessary to work within the context of a given model’s data requirements and sensitivity. Model sensitivity to input data error propagation can be evaluated to specify the form and acceptable limits of accuracy of input data sets describing sediment surface attributes. For certain processes like sediment patterns that are strongly dependent on different parameters, much of the process variations at sufficiently large spatial and temporal scales can be explained with complex modelling that has to be introduced by the authors. Where are these? I would like to have seen a diagrams with statistics and accuracy data.. Trough the manuscript the are several generic statement dealing with this quantitative analysis:

“Hydrodynamics plays a significant role in affecting sediment transport and appears seasonal variations [35]. Impacted by the monsoon climate, rough sea conditions in the sea north of Jianggang port caused by cold waves in autumn and winter play a leading role in the partial sediment transition [42], while typhoon wave in summer affect southern part of radial sandbanks”…

For a Seasonal patterns of tidal flats in aquaculture and non-aquaculture regions I urge a validation quantitative approach that can really make the paper in the context. Thus also missing is references to sediment relationships modelling that from the abstract is one of the goal fo the paper, which is an important and influential body of work of different authors, and essentially tackles related kinds of problems addressed in this paper if the paper do really want to deal with the seasonal and-intrannual sediment pattern analysis:

-       Taramelli, A, et al. "Indications of dynamic effects on scaling relationships between channel sinuosity and vegetation patch size across a salt marsh platform." Journal of Geophysical Research: Earth Surface (2018).

-       Bouma, T. J., van Belzen, J., Balke, T., van Dalen, J., Klaassen, P., Hartog, A. M., et al. (2016). Short-term mudflat dynamics drive long-term cyclic salt marsh dynamics. Limnology and Oceanography: Methods, 61(6), 2261–2200, 2275. https://doi.org/10.1002/lno.10374

-       Taramelli, A et al. 2017. A hybrid power law approach for spatial and temporal pattern analysis of salt marsh evolution. Journal of Coastal Research, 77, 62-72.

-       Choi, J.-K.; Eom, J.A.; Ryu, J.-H. Spatial relationships between surface sedimentary facies distribution and topography using remotely sensed data: Example from the Ganghwa tidal flat, Korea. Mar. Geol. 2011, 280 (1-4), 205–211, DOI 10.1016/j.margeo.2010.10.022.

-       Taramelli, A.; et al. (2014), Modelling uncertainty in estuarine system by means of combined approach of optical and radar remote sensing, Coastal Engineering. 10.1016/j.coastaleng.2013.11.001

There is no comparison with physical based approaches. The message that some new data processing and analysis can help define boundaries better is no doubt true, but not very enlightening--the same would apply to additional effort paid to other different approach already present in literature. So please make an effort in that direction.

Thus I'm a bit disappointed by the manuscript overall. I think the authors have not much of the clarity that a basic quantitative sediment estimation approach is deserving much more details in sediment budgt estimation. My sense here is that the authors made a host of effort to communicate the differenet detection thay can face, but did not actually integrate those into a really discussion of such a complex mudflat value added reasoning within the manuscript. Mainly instead of having been melted down and discuss what a reader of these system could increase in her/his knowledge using the innovative remote sensing approach, the text seems to have lots of parts bolted on.

At this point, the manuscript needs an aggressive edit – tangential departures need to be culled; related ideas need to be grouped; and the authors' main argument needs to be emphasised and streamlined. What is the main goil of tha paper? Just to demostrate how good is the already published methodology for sediment budget detection in a tidal falt area? The scale of the different morpholgic detection into intra and inter annual variability could really can be casted in a better way.

Plus, considering also the SAR image processing the authors are stating, the backscatter characteristics depend on the orientation of the morphology relative to the radar. In general, backscatter is very low over flat area fields, except for facets directly facing the radar, which are extremely “bright,” resulting from the angle of repose of different material, and the incidence angle of the data take. Unfavorably oriented slopes cause specular reflection away from the radar and thus little backscatter energy. Different-band, because of longer or short wavelength can penetrates more than X-band into these materials (especially if they are wet), and backscatter comes from “targets” buried within these materials. The result (in general) can be enhanced if the backscatter relative to X-band from the loose, and not unconsolidated materials.

A comparison of the processed SAR images could be evisable with some optical data like Sentinel-2 or Landsat for areas with a relatively wet condition could show what the radar penetrates through thin sheets of sand or the other material and backscatter could occurs from the underlying bedrock surface. This is important for estimating the actual dry or wet materials that could be observed in the optical data and used in the acquaculture detection.

Finally results and discussion are often overlapping without showing real spatial discusion at least with some detailed figures without informing the readers in the study area of what they are talking about. Are we discussing about the innovative methodology of remote sensing or we are discussing about the sediment budget estimation? Looks like the different authors contribution were not really discussed in front a map or even better in the filed. This is something that has to be carfully accomplished from the authors otherwise is not well demonstrated that the already published method is good for sediment budget estimation.

For this reason the paper need really a strong revision first in the main scope of tha paper and then on giving a way much more detailed and quantitative discussion on the obtained results.

I wish the Authors a good luck in the resubmission.

Kind Regards

Comments for author File: Comments.pdf

Author Response

For details of the revisions, please see the annex document.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear authors,

After a careful reading of your paper "Seasonal and intra-annual patterns of sedimentary evolution in tidal flats impacted by laver cultivation along the central Jiangsu coast, China", I have found a really and detailed nice work on the digital imagery and a fine data extraction from them. The references are updated.

The work is quite well written and a minor spelling is needed. For example:

Line 27: use superscript for the squares

Line 89: Figure 1a instead of Figure 1

Line 170: Extraction instead of Extranction

Lines 220 and 221: Use superscripts for the squares. Change km2/a for km2/y

In other hand, in line 143, a marine hydrodynamic simulation model is invoked, which model?

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However, the abstract and in the introduction is clearly stated that the evolution of the tidal flats will be investigated in response to the laver cultivation using a time series strategy. I did not find at all such a strategy nor results, but a qualitative analysis (with very simple reasoning and results) from a visual inspection.

In my opinion, it is hardly needed a quantitative conclusive result between the time series of the area of the laver aquaculture and the sand volumen of the tidal flats. I agree with you that the behaviour of the tidal flats can be different because of the different hydrodynamic. However, you must consider a simple statistical procedure as:

Take the time series of sand volumen and carry a Principal Component Analysis (Hotelling's transform) on to simplify the complexity of the problem. 

Depending on the weight of the modes, reconstruct a time series to catch the main features of the sand volumen time series.

Cross the resulting time series of (2) with the time series of the area (or with its derivative). This can be regression analysis.

Now you can state a conclusive quantitative relationship following what you proposed.

Because of this, I have considered that you work is not finished.

Author Response

For details of the revisions, please see the annex document.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I regard the work is now good for publication.

Author Response

Many thanks for your approval of the manuscript. 

Reviewer 2 Report

The review of the paper improved the manuscript but still one of the main point of the first review is still there:

Results and discussion are often overlapping without showing real spatial discusion at least with some detailed figures without informing the readers in the study area of what they are talking about. Are we discussing about the innovative methodology of remote sensing or we are discussing about the sediment budget estimation? Looks like the different authors contribution were not really discussed in front a map or even better in the filed. This is something that has to be carfully accomplished from the authors otherwise is not well demonstrated that the already published method is good for sediment budget estimation.

I urge the authors to solve the matter.

Author Response

For details of the revisions, please see the annex document.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear authors,

I like very much all your answers and the work you have carried out for them is valuable.

Congratulations for a fine work.

Author Response

Many thanks for your approval of the manuscript. 

Round 3

Reviewer 2 Report