Recent variations of italian central Adriatic coastline.

A wide portion of the Italian Central Adriatic shorelines were studied in order to add some original and relevant information to the defmition of its recent transformations. Recent Holocene evolution has been investigated mostly basing upon analysis and comparison of historical documentation, maps at various scales, photographs and drawings of different ages, as well of detailed field surveys. The above studies demonstrated that during the recent Holocene successive phases of progradation and erosion alternated in the area and that the present situation is strongly influenced by anthropic interventions, both along the coast and in the river basins. The pre-Roman age is characterized by a slow progression of river mouths. This trend has been interpreted as a consequence of the moderate but progressive deforestation (produced by Italic people during the Bronze and Iron ages) of valley slopes, which induced slope degradation and, subsequently, increase of river solid load. During the Roman period this progradation was interrupted as the sediments accumulated only in the coastal swamps, but took place again during the Middle age and the Renaissance. In the century ranging from ca. 1870 and 1970 the shoreline was affected by a severe erosion (up to some hundreds metres at the mouth of the Tronto River) as a consequence of massive anthropic intervention along the valleys (reforestation, agricultural countermeasures to soil erosion, river damming etc.) that dramatically reduced solid load of rivers. This regression was particularly intense during the second half of the '30s, when many artefacts (mainly small dams) were placed along river and creek courses, thus stopping sediment transportation and inducing thalweg downcutting. A second enhancement of shoreline retreat happened during the '60s and the first portion of the '70s, as a consequence of intensive river bed quarrying to obtain material for road construction and artefacts. At the River Tronto mouth the regression rate during this period was ca. 5 m per year. The effects of this quarrying were not completely inhibited by the introduction of specific laws against river quarrying, since along many reaches the river undercutting already reached the pelitic bedrock underlying the alluvial mattress, whose contribution to solid load is completely ineffective for the conservation of beaches. During the last decades, to prevent this strong retreat of shorelines several protection works (mostly breakwaters and surface and submerged reefs, with only sporadic beach replenishments) were made, thus strongly altering both profile and sedimentologic features of many portions of the shoreline. What is worse is that these countermeasures often demonstrated their inadequacy to protect the beaches during the most intense storms: as a consequence, most of the investigated area still is affected by coast regression that threatens many buildings and infrastructures, including the railway connecting the whole south-eastem portion of Italy with northern Italy and the rest of Europe.