Gli effetti antropici nell'evoluzione storica della costa "Picena.

The historical evolution of the southern Marche shoreline (between the Conero promontory and the Tronto river mouth) has been investigated and evaluated with regards to natural and anthropic changes. All the available historical maps and observations deriving from archeological and documental findings have been researched, geo-referenced and digitized in a GIS environment, in order to reconstruct the position of the shoreline at different times, especially at fluvial mouths. This allowed us to highlight that for the last two millennia anthropic interventions influenced coastal dynamics more than climate variations. For all investigated sites a close relation between shoreline fluctuations and forestation/deforestation processes was clearly identified. In addition, it emerged that river mouth progradation continued until 1930, well after the end of the "Little Ice Age" (around 1850). The above relation is particularly evident for the past two centuries, as we have accurate maps and census of forested areas for this period. During the XIX century, in spite of the warm climate having favored slope protection, widespread deforestation resulted in regular shoreline accretion (average rate of circa 4.95 m/y for the first half of the century and 1.08 m/y for the second half ). In the XX century coastal behaviour was more irregular, with substantial retreat after the 1930s: this derives almost exclusively from anthropic interventions in river basins (construction of dams, riverbed quarrying, river reshaping, abandonment of crops etc.) leading to a severe decrease in solid load. For the past few decades and at present, the most important factors driving the behavior of coastlines resulted to be the various interventions carried out along and in front of beaches to reduce erosion.