Shoreline evolution near river mouth: Case study of Petrace River (Calabria, Italy)

An analysis and understanding of coastline variability and coastal erosion–accretion trends is important to enable scientists and local decision-makers to make appropriate decisions concerning regulatory and coastal planning. The paper describes the shoreline changes which have occurred near the mouth of the Petrace River over the last 60 years, using end point rate (EPR)and net shoreline movement (NSM)statistics. The area extends for about 5 km from the groin near the port of Gioia Tauro on the North side to the port of Palmi on the South side, and which for this study has been divided into 14 transepts orthogonal to the coast with an average spacing of 350 m. The diachronic analysis of the shoreline was carried out through the comparison of cartography data, which consists of aerophotogrammetry (by CASMEZ of 1954 and IGM of 1985, provided by the Calabria Basin Authority and previously georeferenced), orthophotos of 1996, 2006 and 2012 taken from the Open Data section of the National Geoportal and satellite imagery of 2017 provided by Google Earth Pro. The paper also analyzed the main factors influencing the coastal dynamics, in particular the deep-water wave climate, the longshore sediment transport, and the river sediment contribution, produced by variations of hydraulic structures, rainfall regime, land cover and soil erosion by water (WSE). Cross-analysis of these factors in the case study showed that the rainfall regime had a considerable influence on these changes. This result is consistent with the hydrological characteristics of most of the Calabrian rivers and in general of many Mediterranean rivers in which WSE plays an important role. The methodology for analyzing shoreline changes and related correlations with the factors involved described in the paper is therefore applicable to many geographical and hydrological contexts which are similar to the Petrace River mouth