Dynamics of very-large dunes were investigated over sandbanks subdued to marine aggregate extraction in the Belgian continental shelf. In the Flemish Banks, six areas were regularly monitored with a multibeam echosounder (MBES) providing high resolution bathymetric data. An optimization procedure was set up to estimate the dune migration distance and direction between successive campaigns. These dune migration data were compared to simulated hydrodynamic forces and indicated that dune migration was mostly driven by tidal currents, with the direction and magnitude of migration being dependent on the relative position of the dunes on the sandbanks. Closer investigation in a heavily extracted area suggested a local reorganization of sediments in the area: an accretional trend in the extraction pit is observed at the expense of the surrounding very-large dunes which presented an erosive and flattening pattern.