Rate of Fen-Peat Soil Subsidence Near Drainage Ditches (Central Poland)
Round 1
Reviewer 1 Report
The paper is well written and the results are clearly stated.
The authors should expand the comparison of their results as shown by the two equations with previously published equations by more explicitly stating that the subsidence predictions in the new equations are for locations at drainage ditches while previous studies were for general subsidence over larger areas not just for near-ditch locations..
Author Response
Reply to Reviewer 1:
As suggested by the Reviewer, we clarified in the Materials and methods section that the empirical equations in Table 1 apply to the subsidence of larger areas of peatlands, not just the locations near the ditches.
We very appreciate your suggestions and comments.
Ryszard Oleszczuk
Ewelina Zając
Janusz Urbański
Jan Jadczyszyn
Reviewer 2 Report
The article is a case study confirming the phenomenon of bog subsidence during drainage. The performed tests allowed to determine the characteristics of depressions along the drainage ditches and their bottom. The presented empirical equations show the behavior of peat soil near the ditches in this particular area. Therefore, one cannot generalize in the conclusions that the determined formulas can be used to determine the general characteristics of the phenomenon. The authors themselves noted that this is a much more complex problem. The measurement experiment described in the article is only a fragment of possible analyzes describing the geometry of the phenomenon in this area. Narrowing them down to the studies performed, it would also be worth showing graphs with cross-sections of the depressions along with an indication of a potential depression cone (s) along the ditches, as also mentioned by the authors. Cross-sections in several places along the presented kilometer will be able to confirm the behavior of the phenomenon of shallowing the ditches and the magnitude of subsidence. Figs 3.a and 3b are basically the same and differ only in the scale used. In fact, if you divide by the new scale range of 50 (90 / 1.80), you get practically the same regression equation as in Figure 3b. It is understandable that the relationship between settlement and the rate of settlement per year is linear, because there is no analysis of intermediate values in previous years. Then, Figure 5b would have its justification and significantly change the relations of settlement in relation to the adopted comparative periods. I believe that the article is worth publishing as an interesting case study showing increased subsidence and shallowing near drainage ditches for this particular case. However, it may be a comparative element for studies carried out on other peat bogs. Were analyzes of the water depth in the ditches performed? Its depth may also have a significant impact on the degree of trench bottom subsidence.
However, I suggest you take into account my suggestions for: 1) cross-sectional analysis, 2) limitations / changes to the conclusions, generalizing the conclusions to other areas (point 4).
Author Response
Reply to the Reviewer 2:
1. Cross-sections of an example R-29 ditch are included in the paper (Figure 3). The numbering of the figures has changed accordingly.
2. The empirical equation (11) makes it possible to estimate the total amount of subsidence of the peat deposit surface (Figure 4a), while the time-scale subsidence, i.e. the rate of subsidence, can be estimated from Equation 12 (4b) The use of Equation 12 describing the average annual rate of subsidence makes it possible to compare results at sites in different countries, as they are usually in this form. Similarly, for subsidence of peat soils in the Notec River valley (Table 1), the same measured data were used to develop empirical equations describing the magnitude (2, 3, 4) as well as the rate (8, 9, 10) of subsidence.
3. The location of the groundwater level in a drained peat deposit may be one of the elements affecting the magnitude of subsidence. This can be evidenced by the empirical patterns of Schothorst (1977) Jurczuk 2000, Querner (2012) and Evans (2019) ect. No archival measurements of groundwater table location were available at the analyzed section of the Solec site. No water management has been conducted at the site for approximately 30 years. The Mała River running through the center of the site is draining water in the range of about 100 m on each side. In the growing season the ditches are usually dry and after short-term intensive rainfall the depth of water in the ditches is about 15-20 cm.
4. Conclusion 4 has been rephrased as suggested by the Reviewer.
We very appreciate all your suggestions and comments.
Ryszard Oleszczuk
Ewelina Zając
Janusz Urbański
Jan Jadczyszyn
