Polarimetric SAR data for improving flood mapping: An investigation over rice flooded fields

In this paper, we investigate the role of polarimetric features to improve flood mapping in agricultural areas. Considering that the double bounce enhancement due to standing water can increase the backscatter from flooded agricultural fields, polarimetry can potentially detect this mechanism and mitigate the misdetection of algorithms based on the identification of dark areas in the image. The investigation was carried out by analysing a polarimetric and multifrequency SAR dataset (COSMO-SkyMed, Alos-2, Radarsat-2) collected over the Vercelli district in North Italy, characterized by a widespread and intense cultivation of rice crop, were the fields were routinely artificially flooded and dried according to the agricultural practice. The investigation demonstrated that the polarimetric data are able to recognize the double bounce return in areas with high backscattering. They overcome the need of a pre-flood image, otherwise required to identify a sudden increase of backscatter to be ascribed to the standing water.