the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 07 Jun 2022
Assessing riverbank erosion in Bangladesh using time series of Sentinel-1 radar imagery in the Google Earth Engine
Jan Freihardt
Othmar Frey
Abstract. Riverbank erosion occurs along many of the Earth’s river systems, affecting riverine populations by destroying agricultural land and housing. In this study, we detected past events of riverbank erosion along the Jamuna River in Bangladesh using time series of Sentinel-1 satellite radar imagery, ground range detected (GRD) data with a 12-day revisit cycle, available in the Google Earth Engine (GEE). Eroded land is detected by performing a land cover classification and by detecting land cover changes from vegetated areas before the monsoon to sand or water after the monsoon. Further, settlements are detected as persistent scatterers, and classified as eroded if they are located on eroded land. We found that with Sentinel-1 data, erosion locations can be determined already one month after the end of the monsoon, and hence potentially earlier than using optical satellite images which depend on cloud-free daylight conditions. Further, we developed an interactive GEE-based online tool allowing the user to explore where riverbank erosion has destroyed land and settlements along the Jamuna in five monsoon seasons (2015–2019). The source code of our implementation is publicly available, providing the opportunity to reproduce the results, to adapt the algorithm and to transfer our results to assess riverbank erosion in other geographical settings.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(2318 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(2318 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Jan Freihardt and Othmar Frey
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2022-319', A. H. Kanan, 19 Jul 2022
Assessing riverbank erosion in Bangladesh using time series of Sentinel-1 radar imagery in the Google Earth Engine Recommendation: Minor revision
Recommendation: Minor revision
General Comments:
This paper presents a well-designed, effectively executed, and clearly communicated project that assessed the Jamuna riverbank erosion in Bangladesh using the time series of Sentinel-1. The paper tried to contribute to the methodological aspect. The methodology is clear with the supporting documents. However, the background information in the introduction is not sufficient. So, need to address why you considered the Jamuna river? (e.g., the status/dynamics and impact of Jamuna river bank erosion). Some links to the relevant study area are given below:
-https://doi.org/10.1080/15715124.2022.2068561
-https://doi.org/10.4236/gep.2017.59006
-Assessing the long-term planform dynamics of Ganges–Jamuna confluence with the aid of remote sensing and GIS (10.1007/s11069-022-05416-6)
-Prediction of fluvial erosion rate in Jamuna River, Bangladesh (10.1080/15715124.2022.2068561)
-Jamuna River Erosional Hazards, Accretion & Annual Water Discharge – A Remote Sensing & GIS Approach (doi:10.5194/isprsarchives-XL-7-W3-831-2015)
--How are the present study/methodology/findings superior (e.g., degree of accuracy, etc.) compared to the results of other studies already completed on the Jamuna river? Because, recently, there are several studies already have done on the Jamuna river! The discussion part should enlarge……..
--A number of the concluding statements included the abstract, introduction, discussion, and conclusions concerning the applicability of the work. These repetitions should be either removed or modified significantly.
--The appendices might be fixed in the main body of the paper (optional)
These and other specific points to be addressed are listed in the table below.
Actual Page number in the document (Line number) Comments 1
(22-23)
Need references for the following statements:
- In Bangladesh, located in one of the world's largest river deltas (….)
1
(28-30)-Jamuna River is one of the largest braided river systems in the world, forming various channels at a total width of around 12 km (….)
-Since the 1970s, its bank line has shifted by around 20 km (…..)
- AC1: 'Reply on RC1', Jan Freihardt, 05 Sep 2022
-
RC2: 'Comment on egusphere-2022-319', Anonymous Referee #2, 26 Jul 2022
The paper has presented a crucial topic of land use change and high-intensity natural hazards in the case study Jamuna. It has used open source data and tools for overcoming high-quality and up-to-date data access for river erosion-related disaster events and even river management in comparison to the optical RS approach. It has also tried to address the need of the stakeholder and practitioners rather than only theoretical contributions. The study satisfied open science practice in the publication of results. The source code has been made available which can promote reproducibility and transparency. However, there are still scopes for revision for enhancing readability before taking a publication decision. Here are some thoughts and observations:
• Title: an observation– highlighting “google earth engine” in the title is not necessary; but the author can think to highlight their important study finding …. “We found that with Sentinel-1 data, erosion locations can be determined already one month after the end of the monsoon, and hence potentially earlier than using optical satellite images” for example.
• Introduction: The orientation of the Case study Bangladesh can come a bit later, so far this paper does not have any dedicated section for theoretical discussion or literature review, it this is thinkable to address here. It will help to understand the state of the art and detect the research gap and that even can relate to the motivation of the case study section and the formulation of the objective.
• Section 2 “Method and data”: some of the sub-section headings are identical to section 3 “Results” e.g. 2.3 same as 3.1, 2.4 same as 3.2. This is completely confusing and contributes to poor readability. It is recommended to revise the sub-section headings in the “Results” section. They should be more declarative rather than general about the particular highlights or findings of the section.
• Some terminology can be more clarified – e.g. “land” - does it refer to open space / agricultural land/ forest?
• The URL link for code and tool needs to be presented in a standard format and with Meta-description (repository like platform Zenodo with DOI may be an option) and push the access link URL, DOI in them in the annexe of the paper only refer them in the original text.
• After opening the given link - in the current state – it makes to rethink the author’s statement “the code and tool developed in this study might be of interest to both policymakers and practitioners working in the fields of disaster risk management and communication” (SECTION 430)
• The paper focused only on the physical aspect by quantification changes and intensity of erosion; however, it will be necessary to shed light on some discussion and policy implications – how these results can be fed to the other research direction for example socio-economic dimensions.
• So far, the data processing task allows for to production of indicators in time series and spatial scale; the reader may also expect - what is the scope to do some predictive analytics in the future research scope.Citation: https://doi.org/10.5194/egusphere-2022-319-RC2 - AC2: 'Reply on RC2', Jan Freihardt, 05 Sep 2022
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2022-319', A. H. Kanan, 19 Jul 2022
Assessing riverbank erosion in Bangladesh using time series of Sentinel-1 radar imagery in the Google Earth Engine Recommendation: Minor revision
Recommendation: Minor revision
General Comments:
This paper presents a well-designed, effectively executed, and clearly communicated project that assessed the Jamuna riverbank erosion in Bangladesh using the time series of Sentinel-1. The paper tried to contribute to the methodological aspect. The methodology is clear with the supporting documents. However, the background information in the introduction is not sufficient. So, need to address why you considered the Jamuna river? (e.g., the status/dynamics and impact of Jamuna river bank erosion). Some links to the relevant study area are given below:
-https://doi.org/10.1080/15715124.2022.2068561
-https://doi.org/10.4236/gep.2017.59006
-Assessing the long-term planform dynamics of Ganges–Jamuna confluence with the aid of remote sensing and GIS (10.1007/s11069-022-05416-6)
-Prediction of fluvial erosion rate in Jamuna River, Bangladesh (10.1080/15715124.2022.2068561)
-Jamuna River Erosional Hazards, Accretion & Annual Water Discharge – A Remote Sensing & GIS Approach (doi:10.5194/isprsarchives-XL-7-W3-831-2015)
--How are the present study/methodology/findings superior (e.g., degree of accuracy, etc.) compared to the results of other studies already completed on the Jamuna river? Because, recently, there are several studies already have done on the Jamuna river! The discussion part should enlarge……..
--A number of the concluding statements included the abstract, introduction, discussion, and conclusions concerning the applicability of the work. These repetitions should be either removed or modified significantly.
--The appendices might be fixed in the main body of the paper (optional)
These and other specific points to be addressed are listed in the table below.
Actual Page number in the document (Line number) Comments 1
(22-23)
Need references for the following statements:
- In Bangladesh, located in one of the world's largest river deltas (….)
1
(28-30)-Jamuna River is one of the largest braided river systems in the world, forming various channels at a total width of around 12 km (….)
-Since the 1970s, its bank line has shifted by around 20 km (…..)
- AC1: 'Reply on RC1', Jan Freihardt, 05 Sep 2022
-
RC2: 'Comment on egusphere-2022-319', Anonymous Referee #2, 26 Jul 2022
The paper has presented a crucial topic of land use change and high-intensity natural hazards in the case study Jamuna. It has used open source data and tools for overcoming high-quality and up-to-date data access for river erosion-related disaster events and even river management in comparison to the optical RS approach. It has also tried to address the need of the stakeholder and practitioners rather than only theoretical contributions. The study satisfied open science practice in the publication of results. The source code has been made available which can promote reproducibility and transparency. However, there are still scopes for revision for enhancing readability before taking a publication decision. Here are some thoughts and observations:
• Title: an observation– highlighting “google earth engine” in the title is not necessary; but the author can think to highlight their important study finding …. “We found that with Sentinel-1 data, erosion locations can be determined already one month after the end of the monsoon, and hence potentially earlier than using optical satellite images” for example.
• Introduction: The orientation of the Case study Bangladesh can come a bit later, so far this paper does not have any dedicated section for theoretical discussion or literature review, it this is thinkable to address here. It will help to understand the state of the art and detect the research gap and that even can relate to the motivation of the case study section and the formulation of the objective.
• Section 2 “Method and data”: some of the sub-section headings are identical to section 3 “Results” e.g. 2.3 same as 3.1, 2.4 same as 3.2. This is completely confusing and contributes to poor readability. It is recommended to revise the sub-section headings in the “Results” section. They should be more declarative rather than general about the particular highlights or findings of the section.
• Some terminology can be more clarified – e.g. “land” - does it refer to open space / agricultural land/ forest?
• The URL link for code and tool needs to be presented in a standard format and with Meta-description (repository like platform Zenodo with DOI may be an option) and push the access link URL, DOI in them in the annexe of the paper only refer them in the original text.
• After opening the given link - in the current state – it makes to rethink the author’s statement “the code and tool developed in this study might be of interest to both policymakers and practitioners working in the fields of disaster risk management and communication” (SECTION 430)
• The paper focused only on the physical aspect by quantification changes and intensity of erosion; however, it will be necessary to shed light on some discussion and policy implications – how these results can be fed to the other research direction for example socio-economic dimensions.
• So far, the data processing task allows for to production of indicators in time series and spatial scale; the reader may also expect - what is the scope to do some predictive analytics in the future research scope.Citation: https://doi.org/10.5194/egusphere-2022-319-RC2 - AC2: 'Reply on RC2', Jan Freihardt, 05 Sep 2022
Peer review completion
Journal article(s) based on this preprint
Jan Freihardt and Othmar Frey
Jan Freihardt and Othmar Frey
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(2318 KB) - Metadata XML