To gain insight into the sediment transport onto a mid-channel bar in an estuary, we measured current velocities on and along the tidal flat during six months. Our analysis shows that intertidal currents have a more pronounced three-dimensional pattern than those on shore-connected tidal flats. This has consequences for sediment transport and morphodynamics. Existing models for tidal flats underestimate flow velocities and sediment dynamics on mid-channel bars.