Multi-Decadal Evolution of Continental Portuguese Beaches Using Landsat Satellite Imagery.

Supervisors: Ricardo Trigo, Rui Taborda (Univ. Lisbon).
Sandy beaches form an essential part of coastal zones as they have a key-role in the ecosystem, while providing socio-economic goods and services at the same time. Despite the ecological and social importance of these ecosystems, sandy beaches are increasingly under anthropogenic pressure. In mainland Portugal the coastal zones are one of the most populated and developed zones of the country, where, in order to adequately manage these vulnerable coastal zones, understanding of beach dynamics on various time- and spatial scales is crucial. In this MSc thesis project we used long records of freely available Landsat satellite imagery to study the evolution of beaches along the continental Portuguese coast during the last 35 years. The main objectives was to automate the process of continental Portuguese beach classi_cation in Landsat imagery, using a machine learning random forest classi_er-algorithm; and to track morphological changes of these beaches over the last decades. In total we used 8734 Landsat images to study sandy beach extent, beach, shore and coastline evolution, over seven time periods, each composed of _ve-year Landsat imagery. In line with previous studies we found an overall trend of decrease in beach area, from about 90 km2 in 1984-89 to 65 km2 in 2014-19. Furthermore we present maps showing the dynamics and change of continental Portuguese beaches, while providing qualitative information on shore and coastline evolution at the same time.