Ers-2, Radarsat Sar Backscattering Characteristics of the Parana River Delta Wetland, Argentina

The Lower Delta Islands of the Paraná River in Argentina constitute a major coastal tidal freshwater wetland located at the De La Plata River estuary, very close to Buenos Aires City. It is a complex region where the landscape pattern is characterized by mosaics of natural and man made ecosystems. Since the last few years an increased number of SAR images have been available for monitoring coastal areas, offering the possibility of analyzing the microwavevegetation-water-interaction mechanisms that are taking place. This study was conducted to assess the potential of combined imagery from RADARSAT (C-band, HH polarization) and ERS 2 (C-band, VV polarization) SAR systems for monitoring wetland ecosystems and assess flood condition. The SAR response from RADARSAT, and ERS 2 systems, for three distinct vegetation types (forest, marshes, and rushes) under different flood conditions is analyzed. For this task, SAR images were first carefully calibrated and geolocated. To establish hypothesis about the links between land cover structure, flood condition, sensor characteristics (C HH, C VV) and resulting scattering process the information extraction procedure consisted of the multitemporal analysis of the backscattering characteristics of well identified samples. The results show that C VV response is capable of detecting changes due to flood conditions within marshes, and rushes, but not within forest areas. On the other hand, C HH backscatter in forest changes strongly from normal to flooded conditions, but marshes have a similar response. A flood map for the event of el Niño 1998 based on change detection procedures is presented. The strong differences in SAR response between both satellite systems give a clear indication of the potentialities of future ASAR Envisat data for ecosystems mapping and monitoring.