Coastal erosion risk assessment to discuss mitigation strategies: Barra-Vagueira, Portugal

Abstract

Worldwide coastal zones present serious erosion problems that cause loss of territory. This phenomenon exposes people and goods to the threat, being necessary to carry out a well-founded management of these areas. Coastal erosion risk assessment methodologies are an important tool for coastal management. The main goal of the present study was to evaluate and discuss coastal management strategies based on the application of a methodology of coastal erosion risk classification, allowing easy comparison of scenarios. The study was developed for the Portuguese coastal stretch Barra-Vagueira. CERA methodology and its plugin for QGIS software were applied in order to assess the erosion risk of Barra-Vagueira stretch for different coastal erosion mitigation scenarios. First, an analysis of the coastal erosion risk was carried out based on bibliographic elements and present situation characterization. Subsequently, the erosion risk was assessed considering defence, relocation and nourishment strategies scenarios and climate change scenarios. The study based on bibliographic elements shows that the coastal region between Barra and Vagueira has a high risk of coastal erosion. Generally, the different scenarios tested represent variations on coastal erosion risk classification, allowing a simple first approach to evaluate coastal erosion mitigation scenarios, helping planning and decision-makers. Performing measures that allow to constrain the shoreline retreat, as artificial nourishments, leads to greater benefits in reducing the area of the territory classified with higher risk. New coastal defence structures allow to mainly decrease the stretch's susceptibility to coastal erosion. The relocation of population leads to a decrease in the area of the territory classified as very high-risk. Climate change increases the erosion risk.