This paper presents an example of a two-steps equifinality reduction approach during a calibration process of a hydrodynamic 1D model, using satellite radar images as ancillary data. The study area concerns 25 km of the Mosel river between Thionville and Berg-sur-Moselle (France) for the flood event from 02/25 to 03/05/1997. Remote sensing datum is a RADARSAT satellite image acquired on 02/28/1997.