L. Aragonés

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.

The erosion of the beaches on the coast of Alicante: Study of the mechanisms of weathering by accelerated laboratory tests.

One of the main problems that coasts around the world present, is the regression and erosion of beaches. However, the factors involved in these processes are unclear. In this study, the influence of sediment erosion on beach regression has been analysed. In order to do that, a three-step investigation has been carried out. Firstly, coastline variations of four Spanish beaches have been analysed. Secondly, a study on sediment position along the beach profile has been developed. Finally, the process that beach sediments undergo along the surf zone when they are hit by the incident waves has been simulated by an accelerated particle weathering test. Samples of sand and shells were subjected to this accelerated particle weathering test. Results were supplemented with those from carbonate content test, XRD, SEM and granulometric analysis. Results shows a cross-shore classification of sediments along the beach profile in which finer particles move beyond offshore limit. Besides, it was observed that sediment erosion process is divided into three sages: i) particles wear due to crashes ii) dissolution of the carbonate fraction, and iii) breakage and separation of mineral and carbonate parts of particles. All these processes lead to a reduction of particle size. The mechanism responsible of beach erosion would consist of multiples and continuous particle location exchanges along the beach profile as a consequence of grain-size decrease due to erosion.

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

Erosion on sand beaches is a problem worldwide, which together with the shortage of sand justifies the great importance of understanding the processes involved in the regression of the shoreline in order to know and adopt solutions. This study analysed the influence of sediment wear on beaches regression. For this, nine morphological units on Castellón-Valencia and nine on Alicante were analysed. The results of the granulometric and mineralogical analysis and carbonate content, showed that sediments due to different mechanisms of erosion, were worn along the shoreline. This erosion was corroborated by wear obtained in the study of white and blue quartz, where the level of rolling and the particle size were observed. Given the presence of Posidonia oceanica in much of the study area, the mineralogical composition was analysed according to the presence of this seagrass, and it was observed that the closer it gets to the coast the higher the carbonate content. This is an important fact because the increase of CO2 in the atmosphere has increased the capacity of dilution of carbonates by the seawater. All this leads to the conclusion that different wear mechanisms have caused a decrease in the size of sediments, favouring both longitudinal and transverse transport with the consequent movement of the shoreline. The transverse movement increases as the particles size decrease, and when the particles exceed the depth of closure, they do not return to the shoreline, which faces the direct consequence of the backward movement of the coastline.

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.

Using the Presence of Seagrass Posidonia oceanica to Model the Equilibrium Profile Parameter A of Sandy Beaches in Spain

ABSTRACT Aragonés, L.; López, I.; Villacampa, Y., and Navarro-González, F.J., 2017. Using the presence of seagrass Posidonia oceanica to model the equilibrium profile parameter A of sandy beaches in Spain. The study of equilibrium profile is a fundamental concept in beach morphodynamics and necessary in the design of nourishment. For this reason, it is important to introduce new modelling methodologies that are capable of analysing its behaviour. The aim of the research was to generate mathematical models for obtaining parameter A of the potential function, which describes the equilibrium beach profile on the coast of Valencia and Alicante, using only those variables that are easy to obtain. The presence of Posidonia oceanica in the study area was also taken into account, and on the basis of that, the energy reduction coefficient (Kv) was included as an independent variable in the models. To select the optimal model, the volume error, root mean-square error, mean error, and relative error percentage have been used. Finally, the sensitivity of the models against small perturbations in the independent variables was studied and the models were validated with experimental data obtained from a set of beaches with similar characteristics located outside the study area.

Evaluation of coastal management: Study case in the province of Alicante, Spain

The beaches are complex systems that can be studied from different points of view and meet more than a mission to protect the coast. Their management consists of assigning solutions to problems and for this to be correct all factors involved have to be taken into account. In order to understand how management is done on the coast of the province of Alicante, surveys have been conducted among the managers of the 19 coastal municipalities of Alicante coast, covering the 91 beaches. The aim of the surveys is to try to know the problems and situations relating to the management, depending on different factors such as the level of urbanization and type of sediment. In addition, it has been investigated whether this management is aimed to protect the coastline, maintain the flora and fauna or is just a recreational management since the main economic activity is tourism. The beaches are conceived of as products offered to the user, which is what most concerns its economic importance in an area where the sun and beach tourism has a special share of the GDP. The ignorance as to the major problems regarding their physical functioning and the inability to solve them is due to a complex administrative system with which the coastal system is regulated inefficiently. The integral approach is essential for a complete and effective management of the coastal environment.

The multifunctional artificial reef and its role in the defence of the Mediterranean coast.

Multifunctional artificial reefs (MFAR) are being implemented around the world, due to their ability to provide an environment where a sports-economic-recreational use and environmental improvement is implemented, and are also elements of coastal defence. However, a lot of failures have been recorded, possibly due to disregarded local factors in the formulations used, and there is no method that has encompassed all these factors, in order to take them into account in its design. The aim of this paper was to provide the coastal engineer with a method that would be used for the design of such reefs. To do this, the Babilonia beach of Guardamar del Segura, Alicante (Spain), was chosen because it is a fully anthropised area (with houses in the Maritime-Terrestrial Public Domain, marina, channelling and river mouth) with continuous regression, in which all the elements considered in this study, were treated. Based on the performance obtained in studies and projects worldwide, the climatic characteristics, biocenosis, sediment transport, settlements and liquefaction and the evolution of the coastline, were analysed. The multidisciplinary study carried out showed that with the implementation of a MFAR, the problem was reversed. Furthermore, the area was provided with a playful-economic use, and could be used 60% of the time, by surfers whose skill level were low to intermediate, without forgetting that the diversity of the marine ecosystem in the area was increased.

Gravel beaches nourishment: Modelling the equilibrium beach profile

The erosion of the worlds coasts and the shortage of sand to mitigate beach erosion are leading to the increasingly common use of gravel for coastal protection and beach nourishment. Therefore, in order to determine the amount of gravel required for such actions, it is important to know perfectly the equilibrium profile of gravel beaches. However, at present, this profile is obtained from formulas obtained mainly after channel tests, and therefore most of them do not adapt to the real profiles formed by gravel beaches in nature. In this article, 31 variables related to sedimentology, waves, morphology and marine vegetation present on the beaches are studied to determine which are the most influential in the profile. From the study carried out, it is obtained that these variables are the steepness and probability of occurrence of the wave perpendicular to the coast, the profile starting slope (between MWL and -2m), the energy reduction coefficient due to Posidonia oceanica as well as the width of the meadow. Using these variables, different numerical models were generated to predict accurately the gravel beach profile, which will lead to a saving in the volume of material used in the order of 1300m3/ml of beach with respect to current formulations, and a greater certainty that the beach nourishment carried out will have the desired effect.