A multidisciplinary study of sandy beaches along the Apulian coast (Southern Italy).

The Apulian coasts are leader in the seaside tourism sector, by offering a great variability of coastal landscapes with a widely acclaimed concentration of tourism on sandy beaches. The Apulia Region contains about 900 km of coastal sectors, which corresponds to 12% of the Italian littorals. During the last fifty years, a significant economic development of many maritime localities is seriously threaten by pervasive coastline retreats, which are one of the most current issues of the region. This study focuses on the processes influencing the mechanisms of erosion, transport and sedimentation in coastal areas characterized by sandy beaches in order to analyse the sedimentary dynamic with a multidisciplinary approach. To achieve this objective, two beaches have been chosen as representative examples of Ionian (Porto Cesareo, Lecce) and Adriatic (Torre Guaceto, Brindisi) sandy coastal sectors of the Apulia region. Both areas are part of Protected Marine Reserves with stunning emerged and submerged landscapes. In terms of sand compositional features, these beaches represent also end-members of the Apulian beaches: Porto Cesareo sands are mainly bioclastic, while Torre Guaceto sands have a predominant siliciclastic (lithoclastic) content. The application of a multidisciplinary approach consists of gathering and testing different techniques. Firstly, the use of the Terrestrial Laser Scanner (LST) will allow analysing the emerged beach environment in superficial and geomorphological terms by constructing three-dimensional terrain models and evaluating beach slopes. The thickness of the emerged beach will be quantified with georadar investigations, whereas a Multibeam procedure will determine different relief forms and the bathymetry of the sea floor. Lastly, the Sub Bottom Profiler technique will be applied to measure the thickness and the sediment volumes that are involved in the coastal dynamic. By a sedimentological point of view, the beaches have been monitored by measuring all possible physical data, using classical and modern techniques. Seasonal sedimentological sampling procedures were carried out through diving techniques from foreshore to lower shoreface environments (local wave base is about 6 m). The grain-size analysis allowed us to calculate the statistical parameters of sands with unimodal distribution. The variation of these parameters along the emerged and submerged subenvironments have been analysed across the entire beach profile. In addition, the relationship between the main statistical parameters (mean versus kurtosis, kurtosis versus sorting, kurtosis versus skewness and mean versus skewness) will be used to investigate the erosive or stable-prograding tendency of the beaches. The most frequent size class of the statistical distribution was investigated with a binocular optical microscope to evaluate the sands composition in quantitative terms. Therefore, the classification of sands included quarts, feldspar, carbonate grains and other components (pyroxene, amphibole and opaque minerals). Within the carbonates class, the percentage of bioclasts was also evaluated. In the end, the sedimentological study of current beach sands with those relicts of platform will allow their reliable use in sandy coast nourishments for future technical interventions.