Monitoring the Coastal Changes of the Po River Delta (Northern Italy) since 1911 Using Archival Cartography, Multi-Temporal Aerial Photogrammetry and LiDAR Data: Implications for Coastline Changes in 2100 A.D.
Round 1
Reviewer 1 Report
Dear Author,
Thank you for the revision.
I am satisfied with it.
Yours,
Reviewer 2 Report
Dear Massimo:
You have made the indicated modifications, therefore the article is accepted.
Best regards.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
The ms shows interesting results for the PRD through a very detailed analysis of the multitemporal coastaline changes.
I have not particular comments on this study which is well organized and with consistent results.
I just suggest to change the title in "Monitoring the coastal changes of the Po river delta (northern Italy) since 1911 using archival cartography, multi temporal aerial photogrammetry and LiDAR data: implications for coastaline changes in 2100 A.D."
Please, explain all the acronyms you have used in the ms.
Text needs to be revised by a native English (sentences are too long, etc.)
Reviewer 2 Report
This work describes development of Po River Delta by assembling different data. Methods and results are basically well described. The reviewer would like to ask followings to improve the manuscript.
(1) L457 - 466
a) Why can you conclude definitely that the accuracy of the surveys is the cause of stabilization? If coastal works were done actively in this period, this can be also the cause of stabilization. Also, if you regard the accuracy is an important factor, how would you evaluate the estimation for the former periods, which shows huge change.
b) Please elaborate what are 'anthropogenic activities'.
c) Please elaborate what are 'seasonal vegetation effect'. Do they trap and release sediments?
(2) Please try to discuss the contribution (percentage) of RSLR in loss of land. The area can lose sand by RSLR (sinking underwater) and sediment motion by river flow and waves. The former can be estimated considering amount of RSLR and slopes of the foreshore.
(3) Please consider to show temporal variation of amounts of land subsidence. They are documented in the manuscript, however, a graphical display would be more informative.
Reviewer 3 Report
Monitoring of coastal changes in the Po River Delta (Northern Italy) since 1911 using archival cartography, multi-temporal aerial photogrammetry, LiDAR data and scenarios prevision for 2100
Very interesting article about the application of geomatic techniques (cartography, photogrammetry, GNSS, LiDAR) at the mouth of the Po River delta. Congratulate the author for the work done, where different geomatic techniques are mixed for a large number of years. A great job has been done.
My recommendation is to accept the article with minor revisions.
Abstract:
It is correct.
Keywords:
Delete the keyword: "Relative Sea Level Rise forecasts for 2100". It should be summarized in a one, two, three or four (this is too much) word term, for example: Relative Sea Level Rise 2100.
- Introduction
It is correct.
An analysis is made of the current situation of the deltas in the world, where many people live in them and are affected by floods. Next, it is indicated how the study will be developed with the use of geomatic techniques in the delta of the Po river (Italy). Some more reference could be made to this type of techniques applied in the coastal retreat.
- Study area and instability process
Indicate the coordinate system of figure 1. Are they UTM or Gauss-Boaga coordinates? Should the Y coordinate axis be N (m)?
- Materials and Methods
3.1. Available datasets
3.1.1. Archival cartographies
What is the local reference system?.
3.1.2. Aerial photogrammetric surveys
Given the quality of the flights for the years 1933, 1944, 1949 and 1955, for which no calibration certificate is available, you cannot get the idea that it is better to eliminate these flights from the study. Although later it is verified that the results (adjustments) are not so bad. I understand the author that it is better to include them, since the errors are not very big and provide information from the past.
3.1.3. LiDAR data
This table indicates an important value, which is the tide. In the Mediterranean the variations of the tides should not be very considerable, between high and low tide (less than 1 meter). Therefore, the influence in this study will not be the same as if it were analyzed on the Atlantic coast (for example, with differences greater than 5 meters).
In table 2, in 2018, where Average covered area (km x km) is indicated, it would not be: 0.2x57?, it is better to put 0.2 than 1/5, to homogenize data.
3.2. Methods for the coastline changes evaluation 169
3.2.1. Aerial photogrammetric images orientation and coastline restitution
The photogrammetric restitutions have been made by measuring the elevation, that is, the coastline has not been digitized in planimetry, it has therefore been done in 3D. Is there really a difference between making it 3D and planimetry ?, since the determination of the heights of the ground points for the absolute orientation of the photogrammetric process is obtained in a predictive way in old flights.
Line 184: "restitution of the coastline performed by 5 different operators": This means that the coastline has been drawn 5 times by 5 different people? How was the final line selected?
3.2.2. Co-registration between archival cartographic and photogrammetric data
How many photogrammetric control points from 1955 have been used in the 1911 and 1924 cartographies? And of these, some points that have not been used in the adjustment have been set aside to see the precision of the coordinate adjustment. The numerical value of the adjustment should be indicated in the article, as has been done with the flights (Table 3). The coordinate system used in the comparison of the different coastlines should also be indicated. Is it the Gauss-Boaga system?.
3.2.3. Emerged surfaces computation from LiDAR data
With the LiDAR DTM, has the level curve 0 been obtained? But this curve may not coincide with the one obtained by photogrammetry, due to the tide of the moment of the photographs for photogrammetric flights and LiDAR can also be done at a time where curve 0 is submerged ?.
3.2.4. Scenario of emerged surfaces by 2100
Point out what the acronym means: IPCC: Intergovernmental Panel on Climate Change (IPCC)
- Results
4.1. Data processing and 3-D models extraction
Figure 2 does not clearly show the limits of the 1911 coastline, which is an important value of this study. Is it interesting to evaluate the outer coastline or also those inside the delta of the Po River?
Line 245: The residual of the mapping adjustment is not indicated, while if the photogrammetry is indicated: (80-100 cm). Do these values indicate planimetry? And the altimetric adjustment?
Line 258: It has been used: "automatic correlation", therefore I do not understand what is indicated in line 184, where it indicates that "restitution of the coastline performed by 5 different operators".
4.2. Co-registration accuracy
Table 3 and 4. To analyze the precision of the adjustment, wouldn't it be more convenient to take a flight or the most recent LiDAR (2014 or 2018, respectively) and compare it with the rest of the observations? The most recent data is understood to be more accurate. For example, the 1933 and 1944 flights do not have the resolution (photographic quality) of current flights and therefore the errors are greater.
Table 2: The vertical has not been analyzed. Has the coastline been digitized? Since if stereoscopy had been performed, altimetry could be obtained.
The values of the average of the LiDAR flights are the results that are normally obtained. I think it's correct.
4.3. Coastline restitutions and changes detection
Figure 9: There is too much information and it is not possible to distinguish the changes. I would recommend making a selection of the years with the most significant changes. For example, I think that between 1944 and 1949 is not a long period of time and therefore there cannot be great differences. It is a shame to delete information (years) but if it shows no change from its previous or later year, it is better to delete it. Just indicate the years that there are considerable changes.
If we limit ourselves to the outer coastline, the inner refunds are left over. Too much information is indicated that cannot be appreciated. You could even enlarge areas with backtracking indications as is done with figure 9.b.
4.4. Sub-aerial surface changes
As indicated in the article, what happened in the Bacino Bonelli Levante area in November 1957 also occurred in other areas of the Po delta, such as areas 2 and 4 and to a lesser extent in other areas. Does this storm have a greater impact on the delta than many other events (possibly the human influence has not been greater than that produced by this storm)? There is a direct relationship between the storms and the coastal retreat, I am not going to tell the author to make an analysis of the storms since 1911, but to make a greater incidence (pointing to it in the article) in the storm of November 10, 1957. Until now, it had not indicated anything about this event, but the graphs in figure 11 indicate that in all areas a lot of surface was lost with this storm and after the years it has not been recovered.
By pointing out that a great storm can be more devastating than human influence, I am not indicating that as this can happen, then we must continue to degrade the environment. This is the concept of climate change deniers. We must protect the environment as much as possible.
What is the reason why the surface has not been recovered in the delta, since it is an agricultural area like other deltas and fillings could have been carried out or as a result of this storm, they gave up on gaining ground in the areas flooded by fear of another event similar to 1957 ?.
- Discussion
Line 472: The loss of submerged area is due to the subsidence of the land, but there is no table that indicates the subsidence of each of the years analyzed. The same that has been done with the loss of surface, a figure like figure 10 or figure 11 could be made, where the years are related to the sinking. Even relate the subsidence with the loss of surface. There must be a direct relationship between subsidence and surface loss, as indicated on line 472.
Line 502: Could it be that Albarella Island does not lose surface until 2100 because it is completely urbanized: golf course and buildings and the owners of the buildings will not allow the sea to gain ground by moving back the coastal line?.
The forecast for 2100 is based on current data and past events, but there are too many factors that will play a role in the future that cannot be foreseen (human interventions: channeling of the river mouth canals, farms for agriculture, fish farms, …), As well as other natural events that may occur: rise in sea level, large storms, large floods of material contributed by the fluvial erosion of the Po river. With climate change, episodes of strong storms (increasingly aggressive and frequent),… can cause marine erosion but deposition of river material.
- Conclusions
The conclusions are a summary of the article. These are correct.
Regarding the bibliography, in general it is very localized (Italian articles), where some reference could be made to similar articles that have been made in recent years where these geomatic techniques applied to the coastal study have been applied: photogrammetry, TLS, UAV, ...
Since 2014 there are only 9 articles, of the 42 references that the article has. When in recent years great contributions have been made in this type of study.
