The beach of Calambrone is located on the Tuscany coast between the harbour of Livorno, to the south, and the Arno River mouth, to the north. Longshore transport is north to south and the beach is fed by sediments carried to the coast by the Arno and, more recently, sediments derived from erosion of its delta. The beach lies adjacent to the rocky headland where Livorno is located and is protected by the Secche della Meloria, a shoal comprised of beach-rock extending 2.5 miles from the coast. The regional position of this beach was favourable for progradation. Since Roman times coastal plain expansion was approximately 6 kilometers. From 1851 to 1938 the shoreline advanced by approximately 500 m, and 50-60 m from 1938 to 1997. The harbour of Livorno, built in the 16th century without any external structures, was protected by a circular dyke in 1852 and then progressively expanded to the north, occupying the coastal plain and adding long breakwaters. In 2000 a new harbour expansion was carried out, with the construction of a breakwater enclosing an area to be filled with sediment dredged inside the harbour which was determined to be too polluted to be dumped offshore. Immediately after the construction of this structure, beach evolution at Calambrone was changed and severe erosion consequently led to the damage of several bathing facilities. This study, based on morphlogical and sedimentological analyses as well as nu-merical models using MIKE21, demonstrates that the recent breakwater, although located downdrift of the beach, is responsible for its erosion. The structure forms an angle of 45° with the coast and, through wave reflection, induces a reversal in the natural longshore transport, which results in the erosion at Calambrone and in the accretion at Tirrenia, a few hundred meters to the north. Analysing the historical coastal evolution in this area, it was discovered that such a process accompanied other similar harbour expansions that used breakwater constructions with similar geometries and orientations. In all cases the location of the depositional lobe was shifted northward maintaining the same distance from the various harbour breakwaters.
A case of up-drift erosion induced by an harbour breakwater / L.Cappietti; C.Cammelli; E.Farrel; S.Ferri; P.L.Aminti; E.Pranzini. - STAMPA. - (2003), pp. 1707-1718. (Intervento presentato al convegno Medcoast 03 International Conference tenutosi a Ravenna - Italy nel 2003).
A case of up-drift erosion induced by an harbour breakwater
CAPPIETTI, LORENZO;AMINTI, PIER LUIGI;PRANZINI, ENZO
2003
Abstract
The beach of Calambrone is located on the Tuscany coast between the harbour of Livorno, to the south, and the Arno River mouth, to the north. Longshore transport is north to south and the beach is fed by sediments carried to the coast by the Arno and, more recently, sediments derived from erosion of its delta. The beach lies adjacent to the rocky headland where Livorno is located and is protected by the Secche della Meloria, a shoal comprised of beach-rock extending 2.5 miles from the coast. The regional position of this beach was favourable for progradation. Since Roman times coastal plain expansion was approximately 6 kilometers. From 1851 to 1938 the shoreline advanced by approximately 500 m, and 50-60 m from 1938 to 1997. The harbour of Livorno, built in the 16th century without any external structures, was protected by a circular dyke in 1852 and then progressively expanded to the north, occupying the coastal plain and adding long breakwaters. In 2000 a new harbour expansion was carried out, with the construction of a breakwater enclosing an area to be filled with sediment dredged inside the harbour which was determined to be too polluted to be dumped offshore. Immediately after the construction of this structure, beach evolution at Calambrone was changed and severe erosion consequently led to the damage of several bathing facilities. This study, based on morphlogical and sedimentological analyses as well as nu-merical models using MIKE21, demonstrates that the recent breakwater, although located downdrift of the beach, is responsible for its erosion. The structure forms an angle of 45° with the coast and, through wave reflection, induces a reversal in the natural longshore transport, which results in the erosion at Calambrone and in the accretion at Tirrenia, a few hundred meters to the north. Analysing the historical coastal evolution in this area, it was discovered that such a process accompanied other similar harbour expansions that used breakwater constructions with similar geometries and orientations. In all cases the location of the depositional lobe was shifted northward maintaining the same distance from the various harbour breakwaters.
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