Performance of a Beach Dewatering System—Chiaiolella Beach, Procida Island, Italy

Abstract

Chiaiolella Beach is a 1.5-km-long pocket beach located on Procida Island (Italy). The beach is formed by medium sand generated by erosion of vulcanoclastic rocks that form cliffs around the island and at the backshore of the study site. A beach dewatering system was installed in April 2002 to provide a wider beach for users and to prevent cliff undercutting during storms. It has not been operative since December 2004, as local authorities decided to undertake cliff stabilization measures. Surveys carried out immediately before (October 2001) and 1 year after installation (October 2002) showed negligible volumetric change on the drained beach in Ciraccio (−0.52 m3/m), the NNE sector of Chiaiolella Beach, whereas on the undrained control section there was an accumulation of 1.41 m3/m. Since no long-term monitoring of beach profiles was available at the site previous to installation, to obtain an indication of the nearshore hydrodynamics and morphodynamics in absence of the drain, historical shoreline from high-resolution georeferenced aerial photography and numerical model were used. Overall, no evident positive effects of the dewatering system were confirmed, at least for mild wave energy levels. For higher wave energies, e.g., during a storm that occurred in December 2002, part of the beach (SSW sector, Ciracciello) had consistent volume losses and the dewatering system was not able to compensate them, as at some stage it was even damaged. This study points out the inadequacy of the dewatering system as coastal protection under high wave conditions.