Historical and recent changes of the Sele River coastal plain (Southern Italy): natural variations and human pressures

As in other alluvial coastal plains in Italy, the Holocene evolution of the Sele River coastal plain was strongly controlled by the events occurring after the Last Glacial Maximum (ca. 19 ky) when, because of progressive sea-level rise, marine transgression affected the outer portion of the present plain. From the Middle Holocene (ca 5.0-6.0 ky BP), the decrease in the sea-level rise led to coastal progradation testified by the building and the seaward migration of a barrier-lagoon system formed by the composite Sterpina-Laura beach-dune ridge system and the back-ridge flat area behind it, characterised by lagoonal to marsh environments. The present paper deals with the reconstruction of the coastal evolution focusing on the last 3,000 years. Geomorphological and geoarchaeological data were used to constrain the evolution of the area in remote times, while the analysis and comparison of historical and recent topographic maps, orthophotographs and aerial photographs allowed to highlight the shoreline trends in recent centuries. The coastline changes that occurred along the Sele River coastal plain during the last 3,000 years highlight two main evolutionary trends in time: firstly a coastal progradation and then a coastal retreatment which has recently been followed by a phase of substantial coastline stability. The coastal progradation (up to 500 m ca.) was favoured by the increased amounts of fluvial sediments delivered to the Sele coast because of the increase in agricultural activity and of periods of climate deterioration (the last being the Little Ice Age). During the last 150 years the Sele coast has been affected by prevailing erosion. From 1870 to 1984 the shoreline progressively retreated, reaching the highest erosion rates around the main river mouths. This shoreline retreatment can mainly be related to human activities (land reclamation, dam building, urbanisation) that reduced the quantity of sediment delivered to the coast. Due to this recent shoreline retreatment, even the historical dune system was locally affected by erosion too. Since 1984 the shoreline has been fairly stable while the Sele mouth zone has experienced erosion.