The erosion on the east coast of Spain: Wear of particles, mineral composition, carbonates and Posidonia oceanica

Coastal Monitoring Using Unmanned Aerial Vehicles (UAVs) for the Management of the Spanish Mediterranean Coast: The Case of Almenara-Sagunto

The concentration of the world’s population in coastal areas means an increase in pressure on the environment and coastal ecosystems. The impacts of climate change affect natural biophysical and ecological systems and human health. Research has been developed to create coastal monitoring with Unmanned Aerial Vehicles (UAVs) that allow data to be obtained and methodologies that integrate computer vision algorithms for 3D and image processing techniques for analysis, combined with maritime information. The Valencian oval is located on the Spanish Mediterranean coast and registers significant coastal erosion. It is a densely populated area, with high economic relevance and tourist activity. The main goals of the developed research in this coastal area include creating a methodology of data collection that identifies environmental indicators significant to community health and uses in the coastal areas, to test progression of interventions and to assess coastal erosion detection and monitoring. The final objective is to aid in decision-making and coastal management. Sediment characterization was obtained, and continuous maritime information was collected. The dynamic evolution of coastal areas was researched by using UAVs on the Spanish Mediterranean coast. This technique is suitable for measuring medium to small coastal changes. Flight planning was carried out using the grid mode and adapted to areas in order to obtain a homogeneous pixel size and precision. This monitoring program takes advantage of technological development with very low economic costs and is a good tool for making decisions that must be based on scientific information. With the monitoring work, an annual erosion between 12 and 6 m was detected. The monitoring program has evidenced the shoreline trend as a result of the impact of rigid structures, mainly ports and groins, in promoting down-drift erosion processes in the area.

Vulnerability of Coastal Areas Due to Infrastructure: The Case of Valencia Port (Spain)

The vulnerability of coastal areas is related to the existence and functionality of infrastructure. Ports have had increased activity in the last few decades due to growing needs of the market. At the same time, there have been huge changes in maritime traffic, and some ports are specialized in container traffic. The port in Valencia developed notably in the last expansions, in the 1980s and in the recent northern expansion. Valencia’s port specializes in container traffic, and has become a Mediterranean leader and the metropolitan area is an important logistics center. Ports can create coastal erosion by altering wave patterns. The environmental effects of the port of Valencia were analyzed. The Spanish Mediterranean coastline as well as morpho-dynamic units were monitored. The solid transport capacity to the north and south of the Valencia port was estimated, and the effects of other infrastructure on sedimentary sources of beaches were also studied. The port of Valencia’s barrier effect is responsible for the situation at the beaches to the north and south. This effect is total and impedes net sediment transport, predominantly to the south along the stretch of coastline. However, the port is not the only factor responsible for this situation, and the lack of continental sediments must also be considered. In addition, climate change has an influence on the behavior of the coastline. The vulnerability of the coast has increased due to changes in coastal morphology, variations in littoral transport rates, and coastal erosion. To promote sustainable port management, some correction measures, such as sand bypassing, dune rehabilitation, and dune vegetation, are proposed.

Factors influencing the rate of beach sand wear: Activation layer thickness and sediment durability

The construction of harbours on the coast and/or dams in river courses prevents the contribution of sediments from rivers and ravines to the coastline and interferes with natural coastal dynamics. In the present study, the main objective is to provide information to the coastal engineer to predict and quantify the wear and tear of sand for artificial beach nourishment, as well as the durability of the intervention. For this purpose: (i) the amount of sample used in laboratory tests is related to the actual activation layer due to waves, and (ii) the material durability (aging) is demonstrated. Sands belonging to 9 beaches in the province of Alicante (Spain) were tested and studied, with different sample quantities (60, 75, 100, 120 and 150 g), the granulometry, calcimetry and wear (using the accelerated particle wear test, APW). The results showed that (generally) the greater the amount of sample used (activation layer), the greater the mass loss (reduction to size <0.063 mm) during the first cycle of the wear test. This may be due to the fact that the greater the amount of material in suspension (as a consequence of greater energy for the same volume of water), the greater the possibility of collision between particles, and therefore, greater particle wear and greater erosion on the beach. In addition, when the same material was subjected to new wear test cycles, that is, without the addition of new material (as is currently happening on the coasts), the durability of the same was compromised up to its wear limit. Particle wear reduces the median sediment size, which encourages movement towards the off-shore zone. Therefore, the wave energy, the material durability and the median sand diameter are elements to be taken into account in a beach nourishment.

Mineralogy and morphology of sand: Key parameters in the durability for its use in artificial beach nourishment

Sand is the third most consumed material in the world, although it is a very scarce material. An exhaustive knowledge of sand and its behaviour against the waves is important for selecting the most suitable material to avoid shoreline erosion. To this end, a pattern of behaviour against accelerated wear test has been sought for 26 sand samples with different characteristics and origins (natural, dredged and quarried), with a focus on their mineralogy as well as a comparison of beach evolution carried out by other authors. Several techniques have been applied for characterization: granulometry, calcimetry, XRD and SEM. The results show that the different degrees of sand grain wear are not only due to their size and mineralogy, but also to the morphology of the particles.

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.

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.

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.