Giuliano Fierro

The port of Genoa-Voltri (Liguria, Italy): A case of updrift erosion

The effects of port structures on ‘downdrift’ shoreline areas have been extensively studied and are widely known today. Their effects on ‘updrift’ areas are less well known. However, these morphosedi-mentological variations, although not comparable in intensity to the previous variations, can produce relatively important phenomena on the shoreline, especially in the case of a significant drift. In fact, they can modify the coastal exposure to the wave–wind climate and produce a variation in the drift and sedimentary budget in different areas; consequently, they can produce erosive and accumulation phenomena. This paper presents a study of the shoreline to the west of the port structures of Genoa-Voltri that have altered the local sedimentary dynamics, causing disequilibrium to the nearby beach with an evident progradation in the eastern area of the shoreline and a significant regression in the central area.

Artificial nourishment of the Vesima beach (Genoa): Sedimentological and morphological results

In Italy artificial nourishment has been considered as a suitable tool for dealing with the problem of coastal erosion for some years, following successful experimental programmes. In this article, we present some of the results of a case study of a nourishment programme on the beach of Vesima (Genoa). This programme was undertaken to limit the coastal erosion and increase the use of the beach and the littoral near very urbanized areas where there are extensive recreational activities such as sun bathing, swimming, fishing and vacationing. In particular, we studied the evolution of the morphological profiles of the surficial beach and the variations in the sedimentological and morphometric characteristics before and after the nourishment. These profiles represent two different seasonal settings of the beach, during calm (summer) and stormy (winter) weather. The grain size and morphometry of the sediments and the morphological profile of the beach were studied in four seasonal surveys. The elaboration of the data allowed us to correlate the nourishment and the seasonal accumulation of sediments. These studies have been extremely important for our understanding of the movement of sediments and changes in the morphology of the beach due to dynamic nearshore processes and variations to the budget of the littoral sediments. After the nourishment work in March 2000, the width of the dry beach was stable; the estimate of nourishment material (20,000 m3) and of the material left on the dry beach after 2 years (4800 m3) indicates that a remarkable quantity of sediment was taken from the shoreface to form the nearshore zone.

Evaluation of the efficacy of coastal defence structures in relation to coastline variations

A process of evaluating the efficacy or inadequacy of coastal defence structures has been proposed through a study of littoral evolution inferred by analysis of coastline variations. This study was undertaken in two parallel phases which have set the incorporation of cartographical and field measurement data in a geographical information system (GIS) package. The GIS package provided for the establishment of the distinct layers based on the chronological order of events (layer of coastal relief and layer of the construction of the defence structure). This GIS application has made it possible to construct a dynamic archive of morphological–sedimentological information useful for determining the evolution of the littoral in the period following any defensive intervention and to evaluate its efficiency. In addition, other than the usual query, it is possible to automatically calculate the areal variations of the littoral inferred from the coastlines and to consequently make a semiquantitative estimate of the sediment moved.