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

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 d revisit cycle, available inthe Google Earth Engine (GEE). Eroded land is detected by performing a landcover classification and by detecting land cover changes from vegetatedareas before the monsoon to sand or water after the monsoon. Further,settlements are detected as persistent scatterers and classified as erodedif they are located on eroded land. We found that with Sentinel-1 data,erosion locations can be determined already 1 month after the end of themonsoon and hence potentially earlier than using optical satellite imageswhich depend on cloud-free daylight conditions. Further, we developed aninteractive GEE-based online tool allowing the user to explore whereriverbank erosion has destroyed land and settlements along the Jamuna infive monsoon seasons (2015-2019). The source code of our implementation ispublicly available, providing the opportunity to reproduce the results, toadapt the algorithm and to transfer our results to assess riverbank erosionin other geographical settings.