Map of the VMD and study area with bathymetry and locations of investigated mining sites, dune fields and measurement sites. (a) Map of the study area. Areas with bank erosion were extracted from historical Landsat-7 and 8 imagery using the \(MNDWI\)59. Sentinel-2 satellite data from October 28, 2018, shortly after the completion of the second survey, was used as background image. (b) Map of the VMD based on Landsat-8 imagery from October 31, 2018. (c) Detailed view of the bifurcation spot between the Tien River and Co Chien River. (d) Water level at station My Thuan (Vietnam) for the year 2018. (e) Instantaneous discharge at station My Thuan for the year 2018. Grey dashed line indicates the mean hydrograph for the years 2009–201648. Raw data for water level and discharge was provided by the SRHMC. Landsat-7, Landsat-8 and Sentinel-2 (ESA) images courtesy of the U.S. Geological Survey (USGS), downloaded from the USGS Earth Resources Observation and Science (EROS) Center (https://earthexplorer.usgs.gov/). Copernicus Sentinel data 2018, processed by ESA. Illustrations (a–e) were generated using Matlab 2018a (http://mathworks.com).