Anthropic Action on Historical Shoreline Changes and Future Estimates Using GIS: Guadarmar Del Segura (Spain)

Abstract

A good understanding of historical change rates is a key requirement for effective coastal zone management and reliable predictions of shoreline evolution. Historical shoreline erosion for the coast of Guardamar del Segura (Alicante, Spain) is analyzed based on aerial photographs dating from 1930 to 2022 using the Digital Shoreline Analysis System (DSAS). This area is of special interest because the construction of a breakwater in the 1990s, which channels the mouth of the Segura River, has caused a change in coastal behavior. The prediction of future shorelines is conducted up to the year 2040 using two models based on data analysis techniques: the extrapolation of historical data (including the uncertainty of the historical measurements) and the Bruun-type model (considering the effect of sea level rises). The extrapolation of the natural erosion of the area up to 1989 is also compared with the reality, already affected by anthropic actions, in the years 2005 and 2022. The construction of the breakwater has accelerated the erosion along the coast downstream of this infrastructure by about 260%, endangering several houses that are located on the beach itself. The estimation models predict transects with erosions ranging from centimeters (±70 cm) to tens of meters (±30 m). However, both models are often overlapping, which gives a band where the shoreline may be thought to be in the future. The extrapolation of erosion up to 1989, and its subsequent comparison, shows that in most of the study areas, anthropic actions have increased erosion, reaching values of more than 35 m of shoreline loss. The effect of anthropic actions on the coast is also analyzed on the housing on the beach of Babilonia, which has lost around 17% of its built-up area in 40 years. This work demonstrates the importance of historical analysis and predictions before making any significant changes in coastal areas to develop sustainable plans for coastal area management.

Coastal Retreat on the Spanish Mediterranean Coast in a Climate Change Context: Effects of the Regulation of the Segura River at Its Mouth and the Coastal Sand Dune in Guardamar del Segura (Alicante, Spain)

“…This enabled us to observe the historical evolution of the area's coastal retreat and relate it to the anthropogenic actions in the basin and coastal areas. The methodology applied to conduct the mapping was based on the study by Fernández-Hernández et al [49]; it entailed drawing a line between dry sand and the sand that had been wet by waves [48] (Figure 2).…”

“…The Guardamar del Segura coast has a long history of anthropogenic actions dating back to the eighteenth century [49]. As indicated by Fernández-Hernández et al [49], the dune system of this area did not consolidate due to the mass felling of trees for the fishing industry during the eighteenth century. For a long time, the village of Guardamar was "threatened" by the movements of the dunes.…”

“…With respect to the ordinary average flows of the Segura River in the headwater reservoirs, the average for the period of 1959-1980 was 541 hm 3 , while for the period of 1981-1989, it was 343 hm 3 and for the period of 1990-1994, it was 263 hm 3 [49]. The reduction in average flows was due to the regulation of the river basin and drought periods that lasted for years, such as during the last period.…”

“…The Municipal District of Guardamar del Segura has a population of 16,138 inhabitants, according to the municipal population register of the INE (2022). The principal economic activity of the region is summer tourism [49], commonly known as sun and beach or mass tourism, which places greater anthropogenic pressure on the dune system.…”

“…On the contrary, these houses were built before 1930. Over the years, the number of houses constructed on the beach increased until the end of the 1970s and remained constant until the 2000s [49].…”