CRITICAL ANALYSIS OF SHORELINE LOCALIZATION METHODS BY MEANS OF AERIAL OR SATELLITE IMAGERY ON MEDITERRANEAN SANDY BEACHES

Shoreline localization is fundamental for designing and planning shore protection works as well as for managing and monitoring various anthropic activities along the coast. The sea-land boundary, however, changes continually with time because of waves and tides, which makes the shoreline detection complex and dubious and the boundary line finally assumed can only be conventional. In the last few decades the use of several geomorphologic indicators has been proposed, such as the berm above sea level, the groundwater exit point, historic high tide levels, etc., but the aim has not been achieved yet. Among the methods used, analysis of aerial and satellite imagery is common, in particular when historic evolution of the coast has to be reconstructed. However, the land-sea boundary obtained by images is just one of the countless instantaneous boundaries, which is determined by the particular position of the sea surface and beach geomorphology at the time when images are taken. In this paper a multidisciplinary method is used to estimate the uncertainties caused by wave motion and tides on the shoreline position assessed by aerial or satellite imagery. The method is applied to a beach of the Mediterranean Sea in geomorphologic equilibrium, on the west coast of Sicily. The method explicitly takes into account various physical aspects of the coastal stretch studied and can be adopted for other analogous beaches.