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 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.

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.