Lessons learned from using COSMO-SkyMed imagery for flood mapping: Some case studies

Synthetic Aperture Radar (SAR) systems represent the most powerful tool to monitor flood events because of their all-weather capability that allows them to collect suitable images even in cloudy conditions. The quality of flood monitoring using SAR is increasing thanks to the improved spatial resolution of the new generation of instruments and to the short revisit time of the present and future satellite constellations. In particular, the COSMO-SkyMed mission offers a unique opportunity to obtain all weather radar images characterized by short revisit time. To fully exploit these technological advances, the methods to interpret images and produce flood maps must be upgraded, so that an accurate interpretation of the multitemporal radar signature, accounting for system parameters (frequency, polarization, incidence angle) and land cover, becomes very important. The COSMO-SkyMed system has been activated several times in the last few years in consequence of the occurrence of flood events all over the world in order to provide very high resolution X-band SAR images useful for flood detection purposes. This paper discusses the major outcomes of the experiences gained from using COSMO-SkyMed data for the purpose of near real time generation of flood maps. A review of the mechanisms which determine the imprints of the inundation on the radar images is provided and the approach designed to process the data and to generate the flood maps is also summarized. Then, the paper illustrates a number of significant case studies in which flood events have been monitored through COSMO-SkyMed images. These examples demonstrate the potential of the COSMO-SkyMed system and the suitability of the approach developed for generating the final products, but they also highlight some critical aspects that require further investigations to improve the reliability of the flood maps