estudio de la morfología litoral en Santa Pola, con análisis de la configuración litoral del
municipio, midiendo la anchura de las playas con GPS y estudiando su perfil batimétrico
con sonar de barrido lateral.
The GESTARR project analyses the role of Posidonia oceanica in the adaptation of coasts to climate change.
Beach management must be carried out with the problems arising from coastal erosion and adaptation to climate change among its objectives. A very important problem in beach management from a social, environmental and social point of view is the landslides of plant material that accumulate on the beaches, mainly from the marine phanerogams Posidonia oceanica and Cymodocea nodosa.
The project focuses on solving the problems of municipal management of plant material arrivals, mainly from the marine phanerogam Posidonia oceanica, which accumulates on the beaches in localities economically and socially dependent on tourism. To this end, two pilot municipalities were selected: Santa Pola and El Campello, in Alicante, in which coastal processes and their effects due to natural events or human actions were studied.
It also develops a methodology for beach monitoring that responds to managers' information demands regarding their dynamism and evolution. This will help design a policy for the long-term conservation of ecosystem services in line with the needs of the tourism sector.
Rising sea levels and maritime storms caused by extreme weather events are the effects of climate change that have the greatest impact on beaches. Both factors contribute to coastal erosion. This coastal erosion is a phenomenon consisting of the permanent retreat of the shore, which can be seen over time, causing the disappearance of some beaches. In this sense, it is estimated that climate change will produce a retreat of at least 1.8 m on the beaches of the Mediterranean coast.
The presence of landslides on the coastline cushions the impact of waves on the shore, controlling erosion and sand loss. The protection of the landings is especially effective during the autumn storms typical of the Mediterranean climate.
Although arribazones have a recognized role in protecting the coast against erosion, they are generally removed from beaches and coves, mainly for aesthetic reasons, in order to favor the exploitation of tourist activities. This extraction involves:
The loss of sand, since the extraction is carried out with heavy machinery, removing large volumes of sand collaterally. It is estimated that there is 93 kg of sand/m3 of landfall, which often ends up in landfills.
The increase in erosion, since, as mentioned above, the presence of landings on the coastline cushions the impact of the waves on the shore.
The loss of nutrients that the landings themselves represent as a supply of organic matter and nutritional elements for the dune systems associated with the beaches.
The ecosystem loss of a natural substrate on which many organisms and microorganisms develop that serve as food, among others, for crustaceans, molluscs and seabirds.
The main objective of the project is to obtain results that improve the condition of the beaches through sustainable management of these, seeking a balance between recreational use and environmental conservation, which in this case involves among other issues the proper management of the arrivals of Posidonia oceanica.
However, this main objective is also intended to:
Incorporate specific scientific-technical knowledge into beach management
Raising awareness among municipal beach managers of climate change
Raise awareness of the impacts of climate change on beaches and the role of marine phanerogams in mitigating it
The pilot project has been developed in two coastal municipalities: Santa Pola and El Campello, in the province of Alicante.
In Santa Pola, the project has monitored 8 urban beaches: Levante, Calas de Santiago Bernabéu (I, II and III), Varadero and Calas del Este (I, II and III).
In El Campello, work was carried out on the beach of Carrer de la Mar, with three study coves between the mouth of the port and the mouth of the Seco River.
In these pilot areas, coastal processes and their effects due to natural events or human actions have been studied. Likewise, a methodology for beach monitoring has been developed that seeks to respond to managers' demands for information on dynamism and evolution. The results of the monitoring show a generally positive evolution over the last year, although it is necessary to continue collecting data to obtain a historical series that provides accurate information.
Awareness-raising activities have also been included, in the form of the publication of a general awareness-raising guide entitled "Posidonia and Climate Change" and another aimed at professionals "The role of Posidonia oceanica in adaptation to climate change. Guide for beach managers". All these actions have been completed with an outreach activity, a travelling exhibition entitled "Posidonia and Climate Change".
One of the expected impacts on our coasts is the disappearance of beaches due to coastal erosion.
Given that the meadows of Posidonia oceanica and the arribazones, produced by the arrival of their own plant remains on the coast, naturally slow down the erosive effects on it, protecting the meadows and carrying out correct management of the arribazones is a measure of adaptation to climate change.
Posidonia oceanica meadows naturally prevent erosion of the coast, especially of beaches. This protection function is performed at several levels:
Its roots and rhizomes promote the retention and fixation of sediments.
Its blades reduce the current's speed and decrease the waves' energy and, therefore, the force with which they reach the shore
Its remains, deposited on the beach as landslides, attenuate the force of the waves and protect it from coastal erosion, preventing the loss of sand due to the effect of the waves.
Keeping the landings in place is the best solution from an ecological point of view and should be done when there is no conflict with bathing requirements and the beaches are subject to erosion processes.
The coastal zone should be considered as a natural and living environment, not just as an "asset" of the local recreational offer, which must be kept clean. For this reason, the management of algae and other plant remains on the beach must be carried out in a sensitive way, both to the needs of the visitor and to the maintenance of biodiversity.
To make tourist uses and conservation compatible, the arrivals can be removed during the summer season, from May to October, although it is recommended that this be shortened from June to September in the case of the Spanish Mediterranean. Therefore, elimination should be avoided during winter and spring, when storms are more likely to occur and the presence of arrivals is more necessary to cushion the effect of the waves on the beach.
A whole series of activities have been carried out in both locations:
Technical: The technical activities carried out can be summarised in three areas:
Study of coastal morphology.Analysis of the coastal configuration in both municipalities, measuring the width of the beaches with GPS with differential correction and studying their bathymetric profile with side-scan sonar.
Modelling of coastal dynamics. A coastal modelling system has been developed, implementing an approved model of coastal dynamics adapted to the local conditions of the pilot municipalities.
Coastal management of Posidonia oceanica landings. Monitoring and control of landings deposited on the beaches, as well as the cleaning operations carried out by the operating companies and analysis of the effects of beach maintenance work.
Informative and/or awareness-raising:
Guide for the awareness of beach managers. Preparation of a guide of good practices to raise awareness among municipal managers about the role of Posidonia oceanica in the balance of the coastal dynamics of their municipalities and its importance in adapting to climate change.
Environmental education campaign. Design of a travelling exhibition on the effects of climate change on Posidonia oceanica meadows and their role in the adaptation of coastal areas.
Dissemination of results. The results obtained have been published on the website of the Institute of Coastal Ecology (IEL) and have been widely disseminated in the press. They were also disseminated through the traveling exhibition, developed with a reach of more than 600 people in municipalities with problems of management of arrivals and through distributed brochures and published papers and scientific works.
Protecting the coastal meadows of Posidonia oceanica and carrying out a correct management of its landings on the beaches are an important measure of adaptation to climate change.
The maintenance of the landings is a substantial element for the protection of the beaches, which can also be used according to their seasonality. In addition, the underwater meadows of Posidonia oceanica themselves reduce turbulence, the force of the wave when it reaches the coast.
Fortunately, the high season of massive use of the beaches by users coincides with a period where there are usually no storms; however, during the autumn-winter low season, no systematic removal of arrivals should be carried out.
In this sense, coastal protection increases during the low season, with a greater loss of sediments estimated otherwise, that is, if they had been removed during the period with greater hydrodynamic activity. However, its removal only during the high season, together with the occasional contribution of sand during the year and beach cleaning operations, do not seem to have a counterproductive effect on the dynamics of the beaches.
The seasonal use of the arribazones in this sense would constitute a technique for the sustainable protection of the beaches, consisting of carrying out their selective extraction on certain beaches and periods of the year. They would be left to act as a plant biological barrier for as long as possible, acting as sand retainers and elements of protection against waves, as well as as a biological substrate that favours biodiversity.
During the period in which the cleaning operations are carried out, the fraction of landings located in the area of contact with the sea are removed last, extending their protective effect as much as possible over time.
El proyecto GESTARR se centró fundamentalmente en la gestión municipal de los arribazones vegetales, especialmente de Posidonia oceánica.
El proyecto fue desarrollado por la Fundación Instituto de Ecología Litoral, ubicado en El Campello (Alicante), con la participación de dos municipios particularmente afectados por diferentes procesos costeros y por los efectos producidos por eventos naturales o actuaciones humanas en su franja litoral.
Para su ejecución, contó con financiación a través de la Fundación Biodiversidad, dependiente del Ministerio de Transición Ecológica (MITERD).
Among the results obtained, the coastal dynamics report includes the simulation of the prevailing waves. This has characterized the behavior of the coastal dynamics in the area, which helps to know the areas that experience less and greater dynamism during episodes of maritime storms.
Observations have been made on the beaches themselves, and a database has been created that collects the measurements made periodically on them in order to monitor changes in their width and submerged bathymetric profile to know the evolution of the seabed. This information is related to human interventions, such as the extraction of landings and the contribution of sand obtained from their screening.
At the level of Santa Pola, the results showed a generally positive evolution. 25 transects were made between all the beaches, the width of the dry beach using GPS. 76% of the transects showed a positive or stable trend. The data obtained in the submerged profiles confirm that the coastal currents in an East-West direction favour the transport of sediments towards the of Vatasa and the port of Santa Pola, causing a significant accumulation of sand on the bottoms of the beaches of Levante (20,000 m3) and Varadero (2,600 m3), which favours the replacement of sand naturally on the dry beach when calm conditions occur. Some of the observations have been conditioned by both maritime storms and heavy rains.
At the level of El Campello, the general coastal area has a relatively wide platform, where sandy substrates predominate, among which small formations of rocky bottoms stand out. The project monitored the beach of Carrer de la Mar, with three study coves between the mouth of the port and the mouth of the Seco River, establishing 12 transects and carrying out 4 bathymetric profiles, recording up to 2,400 GPS positions and up to 1,400 bathymetric points. This coastal stretch is heavily anthropized, with a large number of obstacles (dikes and breakwaters) for sedimentary transport. The presence of the port to the north and the breakwaters scattered along the beach, section the coastline causing small recirculations in each of the coves.
The distribution of sand varied throughout the period studied, moving throughout the submerged profile. 75% of the transects showed a positive or stable trend, although the observations may be conditioned by the lack of significant storms during the study period. The greatest loss of sand occurred in the southernmost section of the beach. The dry beach presented average variations in width of up to 21 m in the most affected section.
With the data obtained, it is possible to model and monitor the behaviour and evolution of these beaches, estimating their potentially more energetic areas and consequently determining areas conducive to the detachment, due to the effect of the incident waves, of plant material from the meadow. Thus, depending on the behaviour patterns of the currents, generated by the incident waves, it is possible to identify potential areas to host plant arrivals.
In both locations, the usefulness of these landings on the coastline as a natural element of cushioning the impact of the waves on the shore has been verified, controlling erosion and loss of sand. The protection of landings is especially effective during the autumn storms typical of the Mediterranean climate.
The level of vulnerability changes within the same beach depending on the width in each area, the presence-absence of landings, which reduce the rise of the water sheet, discontinuities of the sand due to natural accumulations or deficits after erosion processes, as long as they have not been altered by anthropogenic activity. such as the movement of sediments or the removal of landings due to the action of cleaning machinery.
In Santa Pola, it does not seem advisable to provide sand obtained from the sieve of Posidonia in the months of March to May, as it is a favourable period for strong storms from the east and torrential rains, which favours the transfer of sand from the dry beach to the submerged profile.
In El Campello, the degradation suffered by the coastal meadows of Posidonia oceanica in recent years is evident, confirmed by the significant reduction in the number of landings on the coast.
More time series are needed to make it possible to have more data to allow the monitoring, control and evolution of these beaches and indirectly of the state of the nearby Posidonia meadows, estimating the volume of landings and taking advantage of their value as a contingent system of sediment retention and coastal protection.
El mantenimiento de los arribazones durante la temporada baja ha favorecido la protección de las playas. Se estima una mayor pérdida de sedimentos en caso contrario, es decir, si se hubiesen retirado durante el periodo con mayor actividad hidrodinámica.
La retirada de arribazones únicamente durante la temporada alta, los aportes de arenas y las operaciones de limpieza, parecen no tener efectos contraproducentes en la dinámica de las playas. Se podría decir que las técnicas aplicadas son sostenibles, consistentes en realizar una extracción selectiva en determinadas playas y periodos del año.
En una primera fase, el sistema de recogida consiste en extraer los arribazones desde la parte interior hacia la orilla del mar. De esta forma se deja actuar a la barrera vegetal el mayor tiempo posible (retención de arenas, protección frente a oleajes, etc.) durante el periodo en el que se desarrollan las operaciones de limpieza. La fracción de arribazones situados en la zona de contacto con el mar, por tanto, son los últimos en extraerse, dilatando en el tiempo el efecto protector.
En Santa Pola, las playas donde se ha registrado la mayor concentración de arribazones y donde las praderas de Posidonia oceanica están mejor conservadas y más próximas a las playas son las de Varadero y las Calas del Este.
En El Campello, en base a las observaciones realizadas en el proyecto:
- sólo se retiran arribazones en las playas de Muchavista, Carrer La Mar, Almadraba y Amerador desde una semana antes de Semana Santa hasta el 1 de octubre.
- en el mismo período y sólo si las condiciones higiénico sanitarias así lo indican, se retiran en las Calas Enmig, Lanuza y Palmeretes.
- no se retiran nunca bajo ningún concepto en las playas de Punta del Riu, Cala Piteres, Platja barranc d’Aigües-Lloma de Reixes, Llop Marí, Illeta dels Banyets y Platja del Carritxal.
Dado el carácter piloto de este proyecto, desarrollado sólo en dos municipios, y siendo necesario disponer de más datos de series temporales y localizaciones, que permitan definir mejor el patrón de comportamiento de las playas, sería interesante su réplica abarcando nuevos municipios. Esta información resultaría particularmente relevante para realizar una gestión sostenible de las playas.
La dificultad para gestionar los arribazones, especialmente desde finales del año 2016, aconsejaron tomar medidas que mejorasen el conocimiento sobre el funcionamiento de la dinámica litoral en los municipios de Santa Pola y de El Campello, en Alicante, iniciándose un proyecto experimental para la monitorización de su erosión costera. Las observaciones comenzaron en enero de 2017 y se prolongaron hasta febrero de 2018.
El coste total de este proyecto fue de 38,712.86 € habiendo sido financiado en su totalidad con fondos públicos a través de la convocatoria de ayudas 2017 de la Fundación Biodiversidad, para la realización de proyectos en materia de adaptación.
En el marco jurídico español no existe normativa específica sobre la retirada de arribazones y/o restos vegetales depositados en las playas. Sin embargo, no se puede olvidar el importante papel ecológico que tienen en el ecosistema litoral, y aún más en el equilibrio sedimentario de numerosas playas y calas. Este papel está claramente recogido en la guía de criterios para obtener la bandera azul de las playas, que fija como criterio imperativo que las algas y restos de vegetación no deben recogerse, salvo que su acumulación y podredumbre resulten claramente molestas e insalubres.
El proyecto GESTARR ha tenido una duración de un año, desarrollándose en el período 2018-2019, si bien partía ya de las actuaciones de monitorización de playas que se iniciaron con antelación, desde enero de 2017, por lo que cabría estimar realmente unos 2 años de ejecución.
- Guillén J. et al. 2014. Guía de buenas prácticas para la gestión, recogida y tratamiento de los arribazones de algas y plantas marinas en las costas. Proyecto Seamatter LIFE11 ENV/ES/000600. Instituto Ecología Litoral. El Campello. 24 pp.
- Ibarra Marinas D. et al. 2017. El impacto del estado de conservación de la Posidonia oceanica en la erosión costera: el caso de las playas de l’Almadrava y Amerador (El Campello, Alicante). IX Jornadas de Geomorfología Litoral (Menorca, 2017). pp: 91-94.
- IEL Instituto de Ecología Litoral. 2019. Guía para gestores de playas “El papel de Posidonia oceánica en la adaptación al cambio climático. 13 pp.
- IEL Instituto de Ecología Litoral. 2019. Monitorización de la Erosión Costera en las Playas de Santa Pola. Informe Anual 2017-2018. Resumen ejecutivo. 2 pp.
- IEL Instituto de Ecología Litoral. 2019. Caracterización de la dinámica litoral de las playas de El Campello. Informe GESTARR. 66 pp.
- IEL Instituto de Ecología Litoral. 2019. Caracterización de la dinámica litoral de las playas de Santa Pola. Informe GESTARR. 90 pp.
- IEL Instituto de Ecología Litoral. 2019. Guía de divulgación “Posidonia y Cambio Climático”. 16 pp.
- IEL Instituto de Ecología Litoral. 2019. Monitorización de las playas de El Campello. Informe GESTARR. 42 pp.
- IEL Instituto de Ecología Litoral. 2019. Monitorización de las playas de Santa Pola. Informe GESTARR. 70 pp.
- EXPOSICIÓN: Posidonia oceanica y cambio climático.
- GUÍA DE DIVULGACIÓN: Posidonia oceanica y cambio climático.
- GUÍA PARA GESTORES DE PLAYAS: El papel de Posidonia oceanica en la adaptación al cambio climático.
Gabriel Soler Capdepón
Director Científico
IEL Instituto de Ecología Litoral - C/ Santa Teresa, 50 - 03560 El Campello (Alicante)
Correo electrónico: g.soler@ecologíalitoral.com
