Abstract
Sedimentary coastal areas change rapidly and are economically and environmentally important. This research focuses on determining the extent to which natural dynamics and human activity have contributed to visible changes on Rodas, Cíes Islands in southwestern Galicia (NW Spain). The number of visitors to the islands has increased in recent years, and the port infrastructure has therefore been expanded. Previously, this zone experimented with important sand extraction phases. These changes have influenced the ecosystem directly by modifying the sedimentary behavior and indirectly by promoting even greater numbers of visitors to the area. Aerial images and orthophotographs of the study zone were examined to identify changes that have taken place over the last sixty-one years (1956–2017). Changes in the position of the shoreline, defined as the boundary of the dune vegetation, were mapped at different times between 1956 and 2017. Changes in the shoreline were quantified using GIS (Geographic Information System) technology and Digital Shoreline Analysis System (DSAS) software. The findings revealed that the system regressed by more than 30 m between 1956 and 1981, in part as a result of sand extraction. We also identified different erosion/accretion phases that occurred before the reformation of the Rodas dock in 2010. The system is currently undergoing important changes, especially in the northern area, with a regression of 14.14 m in the last seven years. In this context, LiDAR analysis from 2010 and 2015 using Geomorphic Change Detection (GCD) tools allowed variations in the dune system to be verified. The elevation in the study zone increased in 83% of the area, mainly in the frontal dune and close to the winter inlet (north sector). However, the variations were very small.
Highlights
The coastal zone is a very vulnerable area
Tidal and storm-induced flooding and changes in coastal dynamics have huge influences on this environment by transforming it and possibly causing important material damage in the areas most strongly impacted by anthropogenic activity [1]
Aerial orthophotographs are very useful for this type of study because of the high level of detail that they provide, which improves the traditional estimates of changes in the littoral zone
Summary
The coastal zone is a very vulnerable area. Tidal and storm-induced flooding and changes in coastal dynamics have huge influences on this environment by transforming it and possibly causing important material damage in the areas most strongly impacted by anthropogenic activity [1].Coastal dynamics are affected by multiple factors such as changes in the sea level [2], the frequency and intensity of storms [3,4,5], geomorphological dynamics close to the littoral zone, and the availability of sediments [6]. The coastal zone comprises diverse types of land [9], which can be categorized as sedimentary or rocky. The former exhibits greater dynamism than the latter over a short space of time and its greater fragility has led many researchers to focus their studies on sedimentary coastline areas. The study of these systems has been driven by the strong impact of tourism in many of these areas, as coastal planning requires knowledge of such impacts and the changes that occur [10]
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