Multi-Sensor Remote Sensing of Coastal Discharge Plumes: A Mediterranean Test Site

Various spaceborne sensors have been used to assess environment features in the north-western Mediterranean Sea, at a test site along the Catalan coast, between the Ebro river delta and the greater Barcelona area. The aim was to demonstrate that the combination of different kinds of data allows for an improved monitoring potential, in particular for applications to coastal zone management. The sample imagery considered for this task was acquired by the ERS-2 Synthetic Aperture Radar (SAR), the Along- Track Scanning Radiometer (ATSR) and the Sea-viewing Wide Field-ofview Sensor (SeaWiFS). By combining different data, it proved possible to overcome the specific drawbacks of each sensor, like insufficient temporal coverage, or dependence on weather and daylight conditions. Within the target area, three main features, visible on many of the analyzed images, were selected as test cases. The Ebro river plume, as seen by SeaWiFS, presents a high load of water constituents, changing seasonally and interacting with offshore dynamics. The plume system in the Barcelona area, mostly due to the Llobregat river, exhibits similar traits and high surfaceactive compounds, so that it is detected by both the SeaWiFs and the SAR, as well as low surface temperature, detected by the ATSR. A smaller plume of cooling water, released from a nuclear power plant, cannot be detected in the optical or thermal images, but causes surface turbulence in the coastal zone, giving rise to signatures detected by the SAR.