07 Jun 2022
07 Jun 2022
Status: this preprint is open for discussion.

Assessing riverbank erosion in Bangladesh using time series of Sentinel-1 radar imagery in the Google Earth Engine

Jan Freihardt1 and Othmar Frey2,3 Jan Freihardt and Othmar Frey
  • 1Centre for Comparative and International Studies (CIS), ETH Zurich, 8092 Zurich, Switzerland
  • 2Institute of Environmental Engineering, ETH Zurich, 8093 Zurich, Switzerland
  • 3Gamma Remote Sensing, 3073 Gümligen, Switzerland

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.

Jan Freihardt and Othmar Frey

Status: open (until 19 Jul 2022)

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Jan Freihardt and Othmar Frey

Jan Freihardt and Othmar Frey


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Short summary
In Bangladesh, riverbank erosion occurs every year during the monsoon and affects thousands of households. Information on locations and extent of past erosion can help anticipate where erosion might occur in the upcoming monsoon season and to take preventive measures. In our study, we show how time series of radar satellite imagery can be used to retrieve information on past erosion events shortly after the monsoon season using a novel interactive online tool based on the Google Earth Engine.