The utility of the images supplied by synthetic aperture radar (SAR) systems for flood mapping was demonstrated by several literature studies and the use of SAR data is presently well-established in operational services for inundation management. However, because of the limited SAR image swath and the need of programming SAR acquisitions in advance, some events might be missed. Nowadays a number of satellite SAR instruments are operative and this allows for a combined use of different sensors in order to cover wide river basins and, when different instruments observe the same area, to potentially improve the accuracy of flood extent maps. To fully exploit these possibilities, the flood mapping algorithm should be able to process data provided by radars working at different frequencies and observing the Earth with different incidence angles, i.e., should be robust and transferable. In order to analyze the possible synergies between X-band and C-band sensors, in this work we present some results obtained through a joint use of an X-band instrument as COSMO-SkyMed and a C-band one as Sentinel-1 for flood monitoring performed during the Po River (Italy) flood occurred in November 2014. We focus on the modifications made to an automatic algorithm originally developed for a quick classification of COSMO-SkyMed in order to increase its reliability, as well as it robustness and transferability.