Costa, S. and Coelho, C., 2013. Northwest coast of Portugal Past – behavior and future coastal defense options

Portugal's northwest coast, between Ovar and Marinha Grande presents an important sediment deficit, mainly due to rivers sediments supply reduction and harbors' constrains. The sediment transport capacity resulting from the wave's action (mainly from the northwest) is nourished with the sand of the up drift beaches, leading to the shoreline's erosion and retreat. The shoreline retreat represents conflicts with the land use and human occupation, and the protection of people and properties becomes essential. Thus, coastal interventions (seawalls and groins), try to constrain the shoreline evolution, conducting to an artificial coast and site aesthetical deterioration. This work's objective is to present an analysis of the shoreline evolution, in order to select a suitable model of coastal intervention. Thus, the current paper aimed a diagnostic based in the shoreline evolution indicators in the period between 1994–2011: a) average rate of shoreline retreat; b) number of coastal defense structures implemented; c) number of coastal emergency works and interventions; and d) number of registered events related to shoreline retreat (overtopping, dune system and coastal structures partial destruction). This analysis highlights the location of the most vulnerable areas. Furthermore, different scenarios of coastal defense interventions are discussed, having as variable the associated investment costs, which represents different strategies and impacts, namely: a) maintain the existent coastal defense structures; b) adapt the existent coastal defense structures; c) perform artificial nourishments; and d) propose new coastal defense solutions.