Nearshore Bathymetry of Figueira da Foz, Portugal, Derived from Sentinel-1 SAR Satellites

Remote sensing imagery enables large coastal areas to be mapped effectively. In particular, in low-lying sandy coasts exposed to high energetic wave conditions, where rapid and significant morphological changes can occur, the development of satellite-derived bathymetry methodologies represent a cost-efficient technique to estimate water depths. This work presents a satellite-derived bathymetry map of Figueira da Foz coastal stretch in Portugal, using Sentinel-1 synthetic aperture radar (SAR) data. The results are obtained with the application of a wavelet methodology where the nearshore bathymetry is inferred from the observed swell wave patterns captured by the satellite imagery. The results are compared with data extracted from Coastal Nautical Charts and from the Portuguese COaStal Monitoring Program (COSMO). The results indicate a good agreement to map water depths up to 30 m. However, errors increase close to the shore and are practically of the same order of the morphologic feature elevations such as longshore bars or rip channels. Improved results require higher imagery resolution to provide more accurate estimates.