Application of the parabolic bay shape equation to sand and gravel beaches on Mediterranean coasts

The equation most commonly used to describe the bay planform was proposed by Hsu and Evans (1989) and it was obtained through empirical analysis of sand beach planforms.In the last decade interest in gravel sediments increased owing to their greater stability on beaches, compared with sand sediments. Due to the differences between the morphodynamics of sand and gravel beaches, which is strictly influenced by their different hydraulic characteristics, it was necessary to create a predictive instrument for this beach type as well.Therefore, in this study the standard Hsu and Evans equation (1989) was modified in order to make it applicable not only to sand beaches but also to gravel beaches. The shoreline was computed according to a parabolic model in polar coordinates whose coefficients are considered linearly dependent on the wave direction and related to the beach type. The estimation of the free parameters of the model was performed according to a statistical analysis of a shorelines data set of Mediterranean sand and gravel embayed beaches.

► Sand/gravel embayed beach planforms are studied using the Parabolic Bay Shape equation. ► Planform geometries of sand and gravel beaches differ due to hydrodynamic differences between the sediments. ► On a set of sand/gravel embayed beach shorelines a statistical analysis is performed, ► The statistical analysis allows to achieve a new Parabolic Bay Shape equation coefficients. ► The coefficients allow the use of Parabolic Bay Shape equation as a predictive instrument for any type of embayed beach.