Hazards, Vulnerability, and Risk Analysis on Wave Overtopping and Coastal Flooding in Low-Lying Coastal Areas: The Case of Costa da Caparica, Portugal

Abstract

Coastal areas are densely populated areas, and they have been experiencing increasing pressures as a consequence of population growth, but also because of climate change aggravation. For this reason, hazard, vulnerability, and risk indexes have been becoming more recurrent, especially to study and analyze low-lying coastal areas. This study presents an analysis on wave overtopping and coastal flooding, using an Analytic Hierarchy Process (AHP) multicriteria methodology, in Costa da Caparica (Portugal). The definition of the different criteria, as well as their respective weighting for the overall problem and index calculation, was carried out with the help of experts in the subject. By following this methodology, and by using Geographic Information Systems (GIS), hazard, vulnerability, and risk indexes were obtained. The most hazardous areas are located closest to the sea, where the elevation is the lowest, whereas the most vulnerable areas are in neighborhoods with specific socioeconomic characteristics (high urban and economic density). Overall, around 30% of the study area displays moderate to very high risk regarding the occurrence of overtopping and flooding events. The results of this study will be helpful in decision-making processes in matters of coastal zone management and monitoring.

Approach and Permanent Human Occupation of Mainland Portugal Coastal Zone (1096–2021)

“…A large part of the buildings was built in areas at risk and the Portuguese state budget has spent millions of euros defending coastlines that are in a process of erosion that is practically irreversible [11,14,15]. It should be added that scientific reports have warned of the danger of permanent occupation of some sections of the Portuguese coastline, especially given the impact of climate change on the coastal zone [15].…”

“…This is specifically evident in low-lying coastal areas, since they are exposed to several impacts which are frequently taking place in mainland Portugal. It becomes particularly evident when it comes to events such as coastal erosion, land flooding or submergence, soil salinization, earthquakes, and windstorms, amongst others, which lead to social and environmental losses [7][8][9][10][11][12][13][14][15].…”

Is the Sea the Enemy? Occupation and Anthropogenic Impacts at Costa da Caparica (Portugal)

“…It is a sandy and low coastal plain that is part of the Caparica-Espichel coastal section, which is located on the south bank of the Tagus estuary in the Setúbal Peninsula. In geomorphological terms, Costa da Caparica coastal plain is characterized by beach, beach-dune, and fossil cliff systems [18,19]. These fossil cliff systems are parallel to the coastline and are located between Costa da Caparica and the Albufeira lagoon.…”

“…At least since the second half of the 19th century and with more intensity in the 20th and 21st centuries, this area has suffered intense erosive processes, beach profile retraction, overtopping, and flood events on the urban front. This has resulted in damage to ecological and urban systems, and also to coastal protection infrastructures [14][15][16][17][18][19]. In order to protect such social and ecological systems or to delineate interventions that could reverse their vulnerable situation, scientifically informed decisions concerning governance for the future must be made [6].…”

Evaluation of Coastal Protection Strategies at Costa da Caparica (Portugal): Nourishments and Structural Interventions

“…At Costa da Caparica town (near Lisbon, Portugal, see location in Figure 1), human encroachment is responsible for degradation and loss of coastal ecosystems over recent decades [8]. The beach suffers from chronic erosion [9,10] and has been subject to several coastal protection measures since the early 1970s, involving both hard and soft protection measures.…”