Artificial nourishment of the sesima beach (genoa):sedimentological and morphological results

摘要

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 (20,000m~3) and of the material left on the dry beach after 2 years (4800m~3) indicates that a remarkable quantity of sediment was taken from the shoreface to form the nearshore zone.