J.I. Pagán

The impacts of Segura River (Spain) channelization on the coastal seabed.

Human actions over rivers and coasts have generated great changes along seaboard. In order to know future development of those changes, it is necessary to understand the development of the coast during the past. When there is a complex morphologic system as a result of the combination of natural elements with human construction elements, the study of the abovementioned changes requires a wider perspective than the one provided by traditional two-dimensional methods. Thus, the Geographic Information Systems (GIS) become a suitable tool for that kind of studies. In this work, GIS are used to understand changes in bathymetry, sediments properties and transport, as well as surface variations of plant species occurred in the Segura River mouth (Spain) within a period of 17 years due to the channelization of the river low course. The methodology followed here implies the integration of data coming from different sources and with different formats in a GIS, what allows for a spatial analysis. Results obtained show the grain-size spatial distribution for every period of time studied, as well as bathymetry changes and seabed morphology. It can be concluded that the construction works carried out in the riverbed have affected sediment grain-size in the area. Clays have nearly disappeared and consequently there is a descent of seabed level that affects plant species, such as Posidonia oceanica.

The influence of anthropic actions on the evolution of an urban beach: Case study of Marineta Cassiana beach, Spain.

Coastal areas have been historically characterized as being a source of wealth. Nowadays, beaches have become more relevant as a place for rest and leisure. This had led to a very high population pressure due to rapid urbanisation processes. The impacts associated with coastal tourism, demand the development of anthropic actions to protect the shoreline. This paper has studied the impacts of these actions on the Marineta Cassiana beach, in Denia, Spain. This particular Mediterranean beach has traditionally suffered a major shoreline regression, and the beach nourishments carried out in the 1980s would not have achieved the reliability desired. This research has analysed the historic evolution of the beach and its environment for a period of 65years (1950-2015). A Geographic Information System (GIS) has been used to integrate and perform a spatial analysis of urban development, soil erosion, stream flow, swell, longshore transport, submerged vegetation species and shoreline evolution. The results show how the anthropic actions have affected the shoreline. After the excessive urban development of the catchments, there is no natural sediment supply to the beach. The change in the typology of the sediment, from pebbles to sand, during the beach nourishments has led to a crucial imbalance in the studied area. Moreover, the beach area gained has disappeared, affecting the Posidonia oceanica meadow, and incrementing the erosion rates. The findings obtained are relevant, not only in the management and maintenance of the beaches, but also, in the decision-making for future nourishments.

The effects of the anthropic actions on the sandy beaches of Guardamar del Segura, Spain

There are many activities and uses in the coastal environment, which has historically attracted the humans. This attraction has led to many anthropic actions that have generated imbalances, more important as the human pressure increases. This research focuses on the effects of these pressures along of 11km of the coastline of Guardamar del Segura, a high-value environmental area where is the Segura River mouth and one of the last dune systems of the southeast of Spain. The historic evolution of the shoreline position has been analysed using 60years of aerial images from 1950s to 2014, the seabed depth changes, the maritime climate, the distribution of the sediment grain size and the anthropic actions such as urban development or the channelling of the river. All data were integrated and processed using a Geographic Information System (GIS). The results show that the lack of sediment supply by Segura River and the cut-off in the longshore transport due to the breakwaters and others anthropic actions has led into an increase in the beaches erosion rates, with a loss of >3.2millionm3 of sand in the last 58years (≈55,200m3/year). The conclusions of this research could be useful to the coastal managers at the moment of making the decisions of action and/or conservation on a coastal system to achieve positive results in the medium and long term.

Study of the evolution of gravel beaches nourished with sand

Coastal erosion is a worldwide problem, so accurate knowledge of the factors involved in the shoreline evolution is of great importance. This study analysed three gravel beaches that were nourished with sand from the same source. However, the evolution of their shoreline was different in each case. For its analysis, different factors were studied such as the shoreline and cross-shore profile evolution, the maritime climate, sedimentology and mineralogy. From the results, it should be noted that Centro beach is the most stable with a loss of surface after the first regeneration of 12.8%, while Carrer de mar is the most instable with a loss of 20.9%. The Posidonia oceanica meadow is one of the factors that make Centro beach the most stable despite being the one that receives the most wave energy. Another factor is its mineralogy and more specifically the composition of the particles that form the sample. Thus, it is observed how the cracking or the formation of particles by different minerals with a fragile union, are factors that make the beaches behave differently against erosion. For this reason, it is concluded that in order for the shoreline to be as stable as possible over time, a previous study of the sediment to be used for nourishment is necessary, as well as its possible effect on the ecosystem, since the future shoreline evolution will depend on it.

The effects of sediment used in beach nourishment: Study case El Portet de Moraira beach

Actions taken to prevent or reduce coastal erosion often do not have the desired effect, leading to major problems instead of solving the original one. This research focuses on why a nourished beach- with borrowed sand and 0.05% of particles <0.063 mm- causes the presence of suspended particles that are observed by beach users as turbidity. This means that the colour of the water was not its characteristic blue, even with calm wave conditions. This research involved a shoreline evolution analysis and a sedimentological study of the sand from 1977 to 2017. The results show that the turbidity episodes that occurred after the beach fill of May 2017 do not coincide with major storms that affected the beach. Furthermore, prior to this beach nourishment, even after the most important storms turbidity was not so pronounced. However, when the pre-nourishment and post-nourishment sediment are compared and analysed in detail, by studying the microstructure and morphology of the sand particles, their composition and morphology were observed to be completely different. These differences are also reflected in the accelerated particle weathering test, with the post-nourishment particles showing greater dissolution of carbonates. From its mineralogy, the post-nourishment material presents a smaller proportion of quartz in its composition and a significant amount of particles (9.6%) formed by clusters of Calcium and Silicon. The separation of this mineralogical composition produced by waves explains the formation of particles measuring <0.063 mm, a fact that has also been confirmed by the accelerated particle weathering test. This is, therefore, the cause of turbidity in the swash zone of the beach.

Causes of the different behaviour of the shoreline on beaches with similar characteristics. Study case of the San Juan and Guardamar del Segura beaches, Spain

Storms can alter the beach shape, relocating large volumes of sediments and generating drastic changes in the coastline. In the last 60years, beaches shoreline behaviour has been different even though the energy of the waves was similar. Therefore, it is necessary to understand the factors that affect the sandy coasts for better future management. In this research, two beaches, with different erosion rate, located in the southeast of Spain (separated by only 40km of distance) have been studied. The beaches: i) have similar orientations, ii) are open to waves with similar sand lengths of 9.8km and 6.6km, and iii) have similar median sediment size (D50). For its study, shoreline evolution has been analysed from 1956 to 2017. From the results obtained, it can be seen that: i) Between 1992 and 2017, San Juan just lost 3% of its surface, while in the previous period (1956-1990) it was 50%, and ii) Guardamar surface lost in 1992-2017 was 18%, and in the previous period it was 14%. For the analysis of the agents involved in both beaches, cross-shore profiles (volume), marine climate, biocenosis and sedimentology studies were carried out. The results showed that the energy on both beaches was very similar. The biocenosis had not changed and, however, the morphology of Guardamar seabed had increased to 1m deep in some places, which had caused part of the beach berm erosion. Furthermore, important differences were found from the sedimentological study, concluding that the content of calcites and the degree of homogeneity of the particles are the real factors that caused these two beaches to behave differently against erosion.

Sustainable Development City-Beach in Alicante

Tourism development in recent decades has involved a large urban development in coastal areas, with different anthropogenic structural interventions on the coast such as the construction of commercial buildings and marinas, which has led to intense erosion and large imbalances in the last century. This situation also affects the city of Alicante, with the area between the port of Alicante and the Huertas Cape, one of the most depressed areas of the city, due to various actions carried out since the 70s, for anthropic example fillers for building marinas, jetties and broken in poor condition because they are made of sandstone, and a bad connection between the two parts of the city. In this work the creation of a new promenade that communicates both zones is proposed, creating new beaches eliminating anthropogenic fillings and the remains of breakwaters along the coast, the union of diverse marine area in one marina, and the insertion of an artificial reef multipurpose. With all this it is to improve the attraction of the area, and increase the mobility of the city on the coast.

ALICANTE BEACH- CITY SUSTAINABLE DEVELOPMENT

Our research is focused on the city of Alicante (Spain). In concrete, the sunken area studied is placed at the south of Alicante Port, being the point of entry from the airport to the city. There are two important reasons that have generated that depressed area. Firstly, the development of the city has led to a change in the use of the soil, and secondly, the extension of Alicante Port. This area used to be a metallurgical industrial zone, but during the last 40 years, it has overcome an urban growth. The European Office for Harmonization in the Internal Market (OHIM), the most modern Film Studio in Europe ‘Ciudad de la luz’, a desalination plant and residential complexes and offices have settled down there. Unfortu nately, all this development has occurred without taking into account the coastal needs. Regarding to that, several elements that contribute to the deterioration of the area can be found along the coast, that is the mouth of a rift called ‘Barranco de las Ovejas’ at north, the ‘Agua Amarga’ rift at south and the desalination sewage pipe. Besides, there is a merchandise train line adjoining the Maritime-Terrestrial Public Domain that provides service to the port, but hinders the way for pedestrians going to the beach.