Retreat of the Shoreline in the Gulf of Castellammare di Stabia (Gulf of Napoli, Southern Italy)

The results of this study have allowed to verify that longshore sediments transport along the coast of Napoli Gulf (southern Italy) takes place from Northwest to Southeast. The current analysis describes the results of an integrated sedimentological and geomorphological study of the neapolitan coastal area.

A sedimentological and morphosedimentary study was carried out by bathymetric survey and sampling of bottom sediments. The analysis of modal isodensity curves shows that all the sediments are moved by longshore currents parallel to the coastline from NW to SE.

The morphological evolution of Castellammare di Stabia Gulf coastal area, based on historical coastline changes, starts from 1865, when the sandy littoral was wide and in its natural state. Since the construction of the Torre Annunziata harbour in 1871, sediments carried by a NW-SE longshore drift have become trapped, inducing the genesis of a new wide triangular-shaped beach on the updrift side (NW) of the harbour breakwall.

This process induced a significant shoreline retreat of the littoral to SE, in the whole coastal physiographic unit of Castellammare di Stabia Gulf (delimited by two ports), slightly marked in the southern portion. We can note a slight rotation of the shoreline towards East and a general trend for regression, with typical overall accentuation of shoreline concavity, and significant widening of the triangular shaped-beaches at the end of the falcate. This reduced sediment input removed from the sedimentary budget a significant sediment share - hardly restorable due to the scarce solid contribution by the Sarno river and its tributaries.

In addition to this new and important derived morphologic feature, other recent human interventions have contributed to further modifications of morphologic characteristics of emerged and submerged beach. The intense use of the territory caused modifications on the fluvial course and on the river mouth, with direct and indirect effects on the shoreline and the hydrographical reticulum of Sarno River.