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Dealing with flood mapping using SAR data in the presence of wind or heavy precipitation

The latest generation synthetic aperture radar (SAR) systems allows providing emergency managers with near real time flood maps characterized by a very high spatial resolution. Near real time flood detection algorithms generally search for regions of low backscatter, thus assuming that floodwater appears dark in a SAR image. It is well known that this assumption is not always valid. For instance, vegetation emerging from floodwater may produce high radar returns because of the double bounce effect involving water surface and vertical stems. However, even mapping bare or scarcely vegetated inundated terrains, or crops totally submerged by water can turn out to be a difficult task. In the presence of wind that roughens the water surface, floodwater can appear bright in SAR images. Moreover, if X-band radars as TerraSAR-X or COSMO-SkyMed are used to map inundation, not only missed detection, but also false alarms may occur because of artifacts caused by heavy precipitating clouds that attenuate the radar signal. This paper proposes possible strategies to cope with flood mapping using SAR data in the presence of wind or heavy precipitation.