Evaluation of the effectiveness of a seasonal nourishment programme of the pocket beaches of the city of Genoa

Abstract

The aim of the study was to monitor several beaches of the city of Genoa following artificial nourishment programmes carried out in 2003. The programmes, which involved depositing fluvial material from the Bisagno Torrent in the swash zone, were carried out as part of the seasonal nourishment of the beaches of Boccadasse, Bagnara and Caprafico to the east of Genoa, which are subject to intense erosion. The study provided for a preliminary survey in April 2003, before the nourishment, and three other surveys were subsequently carried out to evaluate the effectiveness of the intervention through the evolution of the beach. The morphological and sedimentological surveys were carried out in July and November 2003 and April 2004 to evaluate the development of the beach in both high and low energy situations. The suitability of the material was evaluated using the method proposed by Hobson. From the data obtained from the field studies it was possible to demonstrate that the interventions had only partially counteracted the annual sedimentary losses of the beaches. The quantities of material deposited were inadequate to enable the beaches to re-equilibrate their compromised morphodynamic profiles and adapt to the wind-wave conditions. Therefore, we consider it essential to undertake the reconstruction of the beaches and not simply try to maintain them in this way. The use of greater quantities of material would permit not only the widening of the backshore but also the creation of more stable morphodynamic profiles that would last longer.

Keywords:

• pocket beach
• nourishment
• monitoring
• cross-shore profile variation
• Liguria