Modelling the morphodynamics in the vicinity of a submerged detached breakwater

Abstract

The importance that coastal zones assume in Portugal implies a necessity for adequate responses to erosion-associated risks. One example is the coastal stretch located between the Mondego and Lis rivers' inlets, which has been a frequent target of coastal protection measures, such as the construction of groins and seawalls. A possible alternative measure is a submerged detached breakwater, which can provide beach protection and enhance local surfing conditions. Thus, in this study the morphodynamics as a result of the wave - breakwater - bottom interaction in the active zone located in the vicinity of the structure was analyzed using two numerical models: a two dimensional, depth-averaged (2DH), Delft3D, and a one-line (coastline), LITLINE. The models were applied considering typical hydrodynamic forcing conditions (mean and most frequent waves) and morpho-sedimentologic conditions of the site. The sensitivity of the breakwater's parameters to the beach morphological response was analysed using Delft3D. The coastline evolution was compared with LITLINE's prediction. Delft3D is able to reproduce the circulation patterns in the structure's vicinity, and between the structure and the coastline, which influence its evolution. On the contrary, the LITLINE's model simplifications do not enable a representation of the physical phenomena which dominate the breakwater's vicinity.