Correlation of Environmental Parameters and the Water Saturation Induced Deterioration of Earthen Archaeological Sites: The Case of World Heritage Liangzhu City, China

Round 1

Reviewer 1 Report

This paper assesses the correlations between environmental parameters and deterioration patterns at the earthen heritage site of Liangzhu City in south-eastern China. The research focuses on the Laohuling dam section of the site which exhibits a range of deterioration features. The authors develop an image algorithm to detect the location of the phreatic line at the base of the earthen section. The pixel area of the saturation region was used in the correlation and factor analyses with environmental data taken from round the site. They use these results to identify temperature and humidity as being significant factors in driving deterioration at the site.

There is need for research that assesses the role of multiple environmental parameters in driving deterioration at earthen heritage sites and the application of image recognition algorithms could help this. However, this paper in its current form is not suitable for publication. To be considered, it needs substantial revisions with particular focus re-adjusting the scope of the paper to make it more focused on the role of water saturation as function of environmental conditions. Conclusions relating to environmental conditions as driver of earthen heritage deterioration should be suggestions at most – ensuring that a distinction between correlation and causation is maintained.

General comments

The authors identify the phreatic line on images taken from around the site to determine zones of saturation which are then correlated with environmental parameters to determine the primary drivers of deterioration. To focus on a feature caused by the presence/absence of water as a proxy for deterioration across the site fails to capture the range of interactions between the environment and the earthen heritage which causes deterioration features to form. The authors also corroborate correlation for causation. As such, the authors need to narrow the scope of this paper, focusing on the role of water saturation as function of environmental conditions, without making broader conclusions.   

There also needs to be much greater discussion/explanation around the mechanisms by which zones of saturation cause deterioration to form, how these mechanisms are likely to vary around the site/at other sites and what other mechanisms need to be considered to form other deterioration features present at the site.

Specific comments

Title:

1. Unsure what “sitesL” is. I assume this is a typo.

Abstract:

1. This would be stronger if it started with the broad scale question this research is trying to answer before introducing the site.
2. Key results and their impact on our current understanding of earthen heritage deterioration need to be reported.
3. Additional information on the monitoring system needs to be provided
4. Need to be more specific about the eleven indexes used

Introduction:

The authors cover key points. However, this section should be shortened and I suggest substantially restructuring it so all site information is included within the site description. Please also ensure that the Introduction does not jump around topics and instead clearly develops the authors argument. End the introduction with the research aim and/or research questions.

1. Instead of starting with the importance of the site, I suggest starting with the importance of earthen heritage more generally and then focusing in on why you have decided to focus your research on one specific site.
2. Can you explain how earthen heritage “protects national unity”?
3. Ekert should be Elert. Please check your other references are spelt correctly.
4. You provide a list of studies after the sentence “Contemporary studies involving cultural relic protection are mainly focused on the selection of monitoring system, reinforcement materials and technologies.”. These could be put in a table and highlight which have been successful or not.
5. Figure 1. This needs to be enlarged and could you refer to where around the site these photos are taken
6. “For a long period, researchers were focused on the wind erosion of earthen sites in the arid and semi-arid areas along the Silk Road and in northwest China, thus producing a large number of research results.” Please include references to these studies. Again, the subsequent list of studies could also be tabularised and discussed in the text.
7. Additional discussion of the potential drivers of deterioration in humid environments is needed. Why are they different to semi arid environments?
8. “there is a limited number of studies on the deterioration and loss of earthen sites under humid environments”. The authors should re-phrase this acknowledging the work undertaken in humid environments around the world e.g. France.
9. Move all sections of site description into the Site Description section
10. The importance of the phreatic line and saturation zone needs to be introduced in the introduction. Please include references to other studies that have shown that this zone is important for earthen heritage deterioration.

Materials and methods:

Justification for the choice of methods is lacking through out this section.  

Site description

1. Please add the historic purpose and function of the site.
2. Add an explanation regarding the importance of the Laohuling dam
3. Please add a map showing the site’s location in China and the key areas of the site.
4. Figure 2. This needs enlarging. Why has the glass shed been removed? Without the roof, this doesn’t provide the reader with a representative idea of the site. Please label figures c and d within whether they are taken post rainfall.
5. Explain how the deterioration that has already occurred at the site will influence further deterioration.
6. Figure 3. This figure needs improving. Please enlarge all panels so the annotations can be read. Please also indicate where these photos were taken round the site. Please put panels b and d next to each other if they are linked.
7. More information is needed on the monitoring components. Where are these devices located, what are their precision/accuracy? You also need to comment on how the location of these individual devices are suitable. Please comment on how the data could be limited by microclimates around the site – especially given the glass shed.
8. More detail is required on how the images where collected: how where the sites chosen? How many sites were assessed? Who took the photos? What camera did you use? How often where photos taken? Etc.
9. Figure 4 might be clearer if it was presented as a map.
10. Is figure 6 required? Please explain why it matters if the distribution is bimodal?
11. Explain the benefits of developing this image recognition algorithm when the phreatic line could have been manually determined. Explain also why some errors occur with the bounding regions and how these might impact results.

Correlation analysis

1. Please cite other studies who have also used correlation analysis in determining factors of earthen heritage deterioration.
2. Introduce the environmental parameters in this section. Explain why they were chosen and why they are relevant to the study. Also comment on how the correlations will be impacted by your decision to map the phreatic line rather than a different form of deterioration.

Results:

1. Please move the first paragraph into the appropriate part of the methods section. Why was the largest saturation area chosen? This seems to not correspond with Figure 8 where at least 3 different areas are shown.
2. Figure 8. The relevance of why these 36 images have been chosen for display needs to be explained
3. Please put the data relating the number of days and pixel area in a table. Please also express this as a percentage of the total number of pixels present. Also, please add in the impact of using pixel area rather than actual area has on the results.
4. Table 2. This should be in the methods section and justifications for each parameter should be included. Remove “_” from the table.
5. The correlation and data-driven model section needs more explanation. I am unsure how the wet pixel equation was established and why it is important.
6. Please make the factor analysis section more concise and justify all methods used.

Discussion:

This section to have additional sections added that address the following areas:

1. The impact of variations in environmental/climatic conditions around the site on the results
2. The impact of the glass shed on the processes occurring at the site
3. The limitations with correlations in determining drivers of deterioration
4. Discussion over why temperature and humidity were strongly correlated. How would this have been different is a different feature at the site (e.g. cracks) had been the focus of the study.
5. The applicability of these results to other sites

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper is interesting and also suitable for the journal. The theme of correlating monitoring data with each other is as always important to reiterate and the case presented here is appropriate.

Just few amendments are suggested to improve the paper.

There should be an error in the title “earthen archaeological sitesL”: probably the last L is a mistake.

In the abstract “In this study is proposed the methodology for the..” it is better to write “we propose..” or “..a methodology for...is proposed”.

Do not use so much the term “relic” alone, but add an adjective such as “archaeological relics” in order to clearly understand that you are not talking about body relics found in the ground.

In page 3, explain what is a PVA composite soil for not expert in parentheses.

It is unclear to me when the glass cover was put in and if it resulted in any benefits. This needs to be said, because there are cases where a cover dries out and creates more damage.

In page 7 you wrote “To improve algorithm efficiency, a 9 * 9 window was selected” 9 what?

I appreciated the synthesis of the data elaboration but maybe it is necessary to be clearer, also adding the aim of the Kaiser-Meyer-Olkin (KMO) measure and Bartley sphere tests, for those who are not expert.

A conclusions paragraph is missing, so your last paragraph could be renamed in Discussion and Conclusions.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

The article is very interesting even if it is based on a fairly common concept about the degradation of an archaeological site affected by humidity and temperature changes. However, it is interesting to underline the methodological approach adopted for defining the decay without particular measurements in situ except of periodic observation and processing of the images. Practically, the article is the description of the method applied and the results obtained, but it does not allow the reader to follow the scientific interpretation because the single determined values and the PCA plots are not reported. It would be better for the understanding of the text to insert these graphs to support the accepted conclusions, perhaps in a Supplementary Information article

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

General comments

This paper has been notably improved. However, further improvements are needed throughout to improve its clarity. Please find my comments below with regard to each section.

Abstract

• “Liangzhu City which” should be “Liangzhu City that”
• What is “simple total radiation of the air”? Please provide additional information

Introduction

• “However, most of the earthen sites have been damaged due to centuries of environmental erosion and varying influences of wind and blowing sand, rainfall, groundwater and humanmade factors.”

Please include references to the large body of literature behind this statement.

• It would be more concise to put the examples of conservation methods (Para 1 of intro: Elert et al 2015… ) as a table, rather than listing them in the text. I provided this suggestion in my initial review and still think that it would benefit the clarity of this paper. I note that the authors have said that they cannot make a table as they cannot list all the publications. However, this could be acknowledged in the table caption saying “a selection of…” or some such phrase.
• “In the arid and semi-arid environment, the site always suffered from wind erosion, rain erosion and salt damage. In a humid environment, the site can always be weakened by high water content and suffers from dry– and wet cycles.”

Please include references for both sentences

• Again, please put the list of scientific research examples in a table (Para 2 of intro: Kong et al 2019…). This will help shorten this very long paragraph. Please also consider breaking this paragraph into smaller sections to help the reader.

Site Description

• Para 1 – in multiple places there are issues with referencing and cross referencing figures that makes it difficult to review this paragraph effectively. This is particularly the case at the bottom of page 3. Other examples include: “s [De Reu et al.”; “Internet of Things []”; “archaeological sites [According”; and “hydrophobicity of ].”. Please check reference formatting.
• Please be more specific on how the following paragraph directly relates to the site description: “Lv et al. 2017 investigated the suitability of a new type of grout material composed of gypsum, quicklime, soil, and admixtures for cracks reparation in earthen sites [De Reu et al. ] proposed the utilization of laser scanning technologies for the conservation of the archaeological heritage. Xiao et al. 2013 proposed the health monitoring and risk evaluation of earthen sites with the application of Internet of Things []. Fujji et al. 2009 proposed the application of the digital photogrammetry technology for the documentation of structural damage in earthen archaeological sites [“
• Page 4; paragraph 2 – “The four relics are continuously damaged”

Is damage genuinely continuous? Or isn’t is more likely to occur in given finite periods of time?

• Figure 2. Please increase the size of the scale bar so the units are readable
• Figure 3. Please highlight the specific locations of the deterioration you mention in the text and label the deterioration type. This could be with arrows.
• Table 2. How can monitoring devices installed vertically be a set distance from the ground surface (e.g. 300 cm vertical). Please clarify

Identification of the saturation area

• The opening sentence “The saturation area is one of the performance which” does not make sense. Please clarify.
• Please remove Figure 4 as this photo is repeated in Figure 5. Please make this photo in figure 5 larger.
• In the step by step explanation for identifying the saturation area, please remove “3)” and “4)” etc. which are repeats of “3.” And “4.”. etc.
• Page 9 para 2. How are you defining “precise”. Has this been judged using visual assessment.
• Page 9 para 3. “However, only 191 images can visualize the deterioration area clearly”. Why is this?

Correlation analysis

I recommend that the authors read the following papers refer to them in this section:

1. Du, Y. et al. A Model Characterizing Deterioration at Earthen Sites of the Ming Great Wall in Qinghai Province, China. Soil Mech. Found. Eng. 53, 426–434 (2017).
2. Cui, K., Du, Y., Zhang, Y., Wu, G. & Yu, L. An evaluation system for the development of scaling off at earthen sites in arid areas in NW China. Sci. 7, 14 (2019).

Results

1. Page 10 para 5. “However, only 191 images can visualize the deterioration area clearly.” This has already been stated in the methods. Please remove.
2. Page 10 bottom. Please remove this repeated section of Table 2.
3. As you have mentioned in your reviewer comments, please include a full set of results as supplementary material.
4. The method for the Factor analysis should be included in the methods section rather than the results.

Discussion and Conclusion

1. “Through control of the eleven indicators, the saturation of the slope foot of the Laohuling dam site.” This sentence does not make sense. Please clarify.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf