Coastal Erosion in Portugal: Capturing Data and Understanding Community Perspectives
My name is Mafalda Moura, a Portuguese Geographer pursuing a master’s degree in Hazards, Cities and Spatial Planning. I am eager to develop research and knowledge in the area of Earth Sciences. This blog post is about measuring coastal erosion and understanding community perspectives.
Nowadays we live in two ways, focusing on coastal planning and its value. One is the over-exploration and construction of land used for buildings, railways, residences, and hotels. Another is the rising of the sea, climate change and disproportional management and the problem tha,t comes with it, losing communities and natural ecosystems. Living in the coastal villas was once known to be luxurious, however in contemporary times, it is like watching the sea coming after you (almost a scary movie of seeing your house swallowed by the surroundings).
The problem with this? Commonly we focus on a national scale or even continental! But what about the local scale towards the problems and adaptations? We tend to focus on the total coast lost but not on the community approach that goes with it.
Myself and a colleague did local research about the evolution of coastal erosion in a county in Portugal with Google Earth timelapse tool and ArcGIS, including citizen's perception of it. We found a lack of recognising the concept or metrics of losses. We have already shared in the scientific community with two posters and gladly the study & presentation were distinguished, that´s the one I am about to share with you:
The Portuguese coast, defined as the strip of land along the sea, faces significant erosion challenges, resulting in the retreat of the coastline and the loss of territory (REA, n.d.). Over the last few decades, coastal erosion in Portugal has been significant, with severe erosion rates in several areas, especially in the northwestern sector of the country (Pinto et al., 2020). Erosion is affecting the Portuguese coastline from North to South: between 1958 and 2021, the Portuguese Environment Agency (APA) estimates that 1320 hectares of land have disappeared. Only 45% of the shallow sandy beaches in Portugal are under erosion? Only in recent years, the Monitoring Program for the Coastal Strip of Continental Portugal (COSMO), coordinated by the Portuguese Environment Agency (APA), has made it possible to verify maximum retreats of up to 30 meters in some sections of the low, sandy coastline in the north and centre from the country.
Coastline Changes based on satellite data (2019), in the Iberian Peninsula, by European Atlas of the Seas
Sections of coastline under erosion (period 1958-2021); Source: Portuguese Environment Agency (APA) 2022
Let´s go to the study area. Inside an Estuary and near a fishing villa and aquarium, it is supposed to be an elite beach, however, an emerging local to coastal erosion as said before in the north of Portugal and shown on the maps.
Evolution made with Google Earth Pro
Besides the appearance of the sea going to the lands, how could we measure it? By the Digital Shoreline Analysis System (DSAS) with ArcGIS system to overlay (Oyedotun & Timothy, 2014) the software that tends to analyse the data science of polylines (in this thematic shoreline), including the average, maximum and minimum, shown in the graphs.
 NSM |  EPR |  SCE
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The sharing point of the article is the importance and showing that with Remote Sensing (Google Earth Pro) delining the changes in the coast, and overpassing to ArcMap or other ArcApps we can analyse and study EarthScience Trends and Evolutions.
Research Findings
The main results? In which, the coastline movement index shows (NSM) a negative advance towards land, with a maximum of 1,8 meters and a minimum of -33 meters, with an average of -17,90 meters. In average rate of change per year (EPR) is -1,13 meters, with a maximum of 0.18 meters and a minimum of -2,1 meters. On the coastline distance (SCE) the average was 18,72 meters, minimum of 4,3 meters and maximum of 36. The data presented beforehand reveals startling findings given the scale of sixteen years. Shocking data!
What about the perception of the residents who have been with this disaster most of their lives? The most exciting part of the investigation is conducting the fieldwork and connecting with the local residents and their perceptions and liveable experiences.
On the community side, we did a local survey with the following questions:
- Knowledge of the term ‘Coastal Erosion’ (yes/no)
- Knowledge of the impacts of ‘Coastal Erosion’ (yes/no)
- Difference in beach size (yes/no)
- Sea advance (metres)
- Beach preservation and conservation strategies (yes/no)
The survey showed that the population inquired has been living in the parish for more than 20 years. There is also notable knowledge of the term “coastal erosion” and its impact on the beach. Concerning knowledge of the beach and its preservation, all the respondents said they were aware of the changes in the size of the beach and that, for the most part, there was no significant advance of up to 1 meter, which resulted in a negative hypothesis on their behalf. However, a substantial proportion of respondents reported an advance of between 1 and 10 meters, but in any case, never the correct measure (18 to 36 meters). In addition, half of the respondents were uninformed about beach conservation and preservation strategies.
 Concept and Impact of Coastal Erosion |  Advance of Coastal Erosion (Community Perception)
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What can we say about this matter? More sensitisation and communication leaders into these problems, the need for public and local participation and acknowledgement of the scenarios and training towards the nature-based mitigation and adaptation.
References:
Oyedotun, Temitope D. Timothy. (2014). Shoreline geometry: DSAS as a tool for Historical Trend Analysis.. Geomorphological Techniques (Online Edition).
Pinto, C., Silveira, T. & Teixeira, S.B. 2020. Beach nourishment practice in mainland Portugal (1950–2017): Overview and retrospective. Ocean & Coastal Management, Volume 192, 105211, ISSN 0964-5691, https://doi.org/10.1016/j.ocecoaman.2020.105211.
REA. (n.d.). Eroded coastline | State of the Environment Report. State of the Environment Report. https://rea.apambiente.pt/content/linha-de-costa-em-situação-de-erosão
Please leave comments or questions below, connect with me on LinkedIn or by email at mafaldamourageo@outlook.com
Thanks for reading!
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