Sea defences design in the vicinity of a river mouth: the case study of Lignano Riviera and Pineta

Abstract

Abstract To guarantee the proper functioning of sea defences over a medium-long period, the knowledge of the complex interaction between tidal currents and nearshore wave field is fundamental in order to estimate the longshore sediment transport. In particular, the morphological evolution of coastal environments close to river mouths is deeply affected also by the riverine sediment transport, which can contribute to the overall coastal balance of erosion and deposition processes. Groynes are commonly used to intercept the longshore sediment transport and to stabilize the littorals, as the case of Lignano beach near the Tagliamento river mouth. In particular, the groyne closest to the river has been shortened in the recent years, influencing in this manner the coastline balance. In this study, a numerical model coupling a morphodynamic model and a wave generation spectral model has been used to study the effects of the variation of the groyne length on the beach. Results are presented and discussed, showing that the numerical modelling can be used for the sea defences design to improve the integrated coastal zone planning and management.