Modelización de la evolución morfodinámica de la duna de Valdevaqueros (t.m. Tarifa) mediante la aplicación de funciones empíricas ortogonales a corto, medio y largo plazo

Memoria presentada por Dña. Marina Navarro Pons para optar al Grado de Doctora por la Universidad de Cádiz.Extreme wind conditions generated near the Strait of Gibraltar (SW Spain) have given rise to the transgressive Valdevaqueros dunefield. The dune advance has resulted in gradual invasion of the adjacent road and ecosystem. Despite restoration and control activities performed within the last decades, strong east winds have favoured dune destabilisation. The current work focuses on analyzing the dune profile evolution in the long term (years), medium term (months), short term (days) and very short term (hours). Topographic data, which were collected with a total station and a differential GPS from 1995 to 2009, were interpreted from reconstructed Empirical Orthogonal Functions (EOF). This method provides an objective way to identify the mean dune profile and therefore, to recognize morphodynamic dune changes and tendencies. Wind, humidity, rain and temperature effects on the dune behaviour were analysed from the Tarifa meteorological station. Furthermore, a sand trap was placed on three different dune profile areas during 30 min, obtaining that the sand transport at the crest was twice the amount of the sand collected at the windward and near six times greater than the sand measured at the dune foot. Sand transport rates of 140 m3 m-1 year-1, 25.5–36.5 m3 m−1 month−1, 22.52 m3 m−1 day−1 and 0.93 m3 m−1 h−1 were measured for the long-term, medium-term, short-term and very short-term periods, respectively. During an eleven-year period, the average migration rate was found to be of 17.5 m year-1, although the very short term monitoring under a severe easterly sandstorm demonstrated that the dune brink was able to experience an advance of 1.75 m in only 24 h. These values were compared with the theoretical sand transport rate for Valdevaqueros dune, based on the classic Bagnold’s equation as well as other more recent formulae, to obtain a ratio between the real and the theoretical rates for each study period. These results together with the sand drift potential following the Fryberger’s method (up to 10,000 vector units) demonstrate that Valdevaqueros is a dunefield with one of the highest sand transport capacities in Europe.265 página

Characterization of wind-blown sediment transport with height in a highly mobile dune (SW Spain)

The Valdevaqueros dune is located at one of the windiest points of Europe, where the frequent occurrence of strong easterly winds has generated a highly mobile dune. Several rotating cup anemometers in vertical array and a self-designed vertical sand trap, were placed to retain the drift sands at different heights over the surface in order to determine theoretical and actual sand transport rates in the Valdevaqueros dune system. General results show that 90% of the wind-blown sand is transported within the first 20cm above the dune crest surface. Theoretical transport rates based on different empirical formulae were 0.33 to 0.78 times the in-situ sand transport rate detected, which was 2.08·10-2kgm-1s-1 under moderate wind power (mean speed ranging from 8.4 to 17.9ms-1). Analysis of different statistical grain-size parameters helped to understand sand transport distribution at different heights

Beach nourishment effects on sand porosity variability

Article history: Received 7 June 2013 Received in revised form 7 October 2013 Accepted 10 October 2013 Available online 14 November 2013A standard assumption in coastal engineering is that the porosity of natural beach sand (non-cohesive) is 40%. However, is this assumption correct for all beach sand? This paper proposes an accurate and simplified method to assess changes in sand porosity after beach nourishment bymeans of in-situ density surveys through a nuclear densimeter. This novel application has been applied to different beaches in the southwest of Spain according to the tidal range, grain size and beachmorphology in several terms. General results showthat sand porosities range from 25.6% to 43.4% after beach nourishment works. This research can be considered a support tool in coastal engineering to find shifting sand volumes as a result of sand porosity variability after beach nourishment and later marine influence

Mobility evolution of a highly active coastal dune (SW Spain) in several terms

Extreme wind conditions generated near the Strait of Gibraltar (SW Spain) have given rise to the transgressive Valdevaqueros dunefield (Tarifa). The dune advance has resulted in gradual invasion of the adjacent road and ecosystem. Despite restoration and control activities performed within the last decades, strong east winds have favoured dune destabilisation. The current work focuses on analyzing the dune profile evolution in the long term (years), medium term (months), short term (days) and very short term (hours) from topographic data, which were collected with a total station and a differential GPS from 1995 to 2009. Sand transport rates of 140 m3 m-1 year-1, 25.5–36.5 m3 m−1 month−1, 22.52 m3 m−1 day−1 and 0.93 m3 m−1 h−1 were measured for the long-term, medium-term, short-term and very short-term periods, respectively. During an eleven-year period, the average migration rate was found to be of 17.5 m year-1, although the very short term monitoring under a severe easterly sandstorm demonstrated that the dune brink was able to experience an advance of 1.75 m in only 24 h. These values were compared with the theoretical sand transport rate for Valdevaqueros dune, based on the classic Bagnold’s equation as well as other more recent formulae, to obtain a ratio between the real and the theoretical rates for each study period. These results together with the sand drift potential following the Fryberger’s method (up to 10,000 vector units) demonstrate that Valdevaqueros is a dunefield with one of the highest sand transport capacities in Europe

Methodologies for teaching an engineering subject in different countries: comparison and results

Engineering or technical degrees are difficult to teach and, consequently, have always been characterized by a large number of academic failures. Therefore, continuous assessment has been applied to classes of similar content, related to Port and Coastal Engineering during these last years in three different Universities worldwide: University of La Republica (Montevideo, Uruguay), Nova de Lisboa (Portugal) and Cadiz (Spain). This paper presents different methodologies used to teach and evaluate these courses at each University, together with the results of the evaluations of the students who were enrolled during the current and previous stages. Generally, a decrease in the number of students who abandon the classes has been noticed together with an increase in the percentage of students who pass and an improvement of their grades, except at the University Nova de Lisboa were the results have remained stable. In addition, changes experienced in the courses are discussed herein by comparing the percentage of success in the different locations. Moreover, influence of the different methodologies and the possible reasons for these changes are also presented and analysed. As a conclusion, the improvement in educational outcomes has been achieved through the concurrence of different factors: the existence of more frequent written and/or oral exams, practical examples of case studies as well as access to specific tools of new technology and to documentation specifically prepared for the classes and available online. Evidently, the above mentioned tasks require a strong commitment and great effort by the teaching staff. If human resources diminish, as it is happening in Spain and Portugal due to the budget reduction in education, two difficult questions arise: For how long will teachers’ current effort be maintained? What impact will have their complete devotion to teaching in their research performance

Evidencias del incremento en la movilidad de dunas costeras en el último medio siglo como respuesta a la intervención humana

Given the risk of two roads being buried by the sand of two highly mobile coastal dunes (Valdevaqueros and Bolonia, SW Spain), several measures have been taken over the last half century in order to stabilize them or at least slow their progress: installation of several rows of 1-m-high concrete structures, planting of species such as Pinus pinea, Retama monosperma and Ammophila arenaria, wicker and wooden fencing, and sand mining (only performed on the Valdevaqueros dunefield). The evolution of the two dunes was investigated through the interpretation of intensive topographical monitoring and aerial photography. Average migration rates of approximately 10 m yr–1 were detected and the burial of anthropic structures has eventually occurred. This process has caused a serious regional problem, making dune management of these areas a difficult challenge. The comparison of the evolution of these two dunes has been of great importance in assessing the effect of historical human intervention and has provided a new perspective for future dune management strategies. The results obtained show that management measures based on sand removal have been proven to be unsustainable. Moreover, the monitoring methodology presented herein has proven very useful in predicting dune advance rates. For instance, the Bolonia dune could reach the nearest road in approximately 12 years.Se han tomado diferentes medidas a lo largo del último medio siglo tratando de estabilizar o al menos ralentizar el progreso de dos dunas costeras de alta movilidad (Valdevaqueros y Bolonia, SW España) dado el riesgo de enterramiento de sendas carreteras: Entre las medidas tomadas cabe destacar la instalación de filas de estructuras de hormigón de 1 m de altura, la plantación de diferentes especies (como el Pinus pinea, la Retama monosperma o la Ammophila arenaria), vallas de madera y brezo, y la extracción de arena (sólo en la duna de Valdevaqueros). La evolución de ambas dunas se ha investigado a través de la comparación de levantamientos topográficos y fotografías aéreas. Se han detectado tasas medias de avance de aproximadamente 10 m/año hasta que, finalmente, se han enterrado estructuras antrópicas. Este proceso ha causado graves problemas convirtiendo en un difícil reto la gestión de dunas de estas áreas. La comparación de la evolución de estas dos dunas ha resultado de gran importancia a la hora de evaluar el efecto de la intervención humana, y ha proporcionado una nueva perspectiva para las futuras estrategias de gestión. Entre los resultados obtenidos, debería destacarse el que la gestión basada en la retirada de arena ha resultado insostenible. Además, la metodología de seguimiento aquí presentada ha probado ser de gran utilidad al predecir las tasas de avance de las dunas. Por ejemplo, la duna de Bolonia podría alcanzar la carretera próxima en unos 12 años

Audiovisual resources as a useful tool to improve the teaching of coastal engineering (marine science bsc degree)

Numerous graduates from American Universities apply for their degree homologation for the Marine Science certificate in Spain. The Spanish Ministry of Education supports this as long as they can pass an exam based on several subjects including Coastal Engineering at the University of Cadiz. The subject of Coastal Engineering is currently being taught in the third year of the BSc degree. This is a very specific subject and unfortunately there is no adequate bibliography that allows for the breadth of knowledge needed to pass the final exam. In addition, it may be difficult for foreign students to properly prepare the subject because they cannot attend the lessons at the campus. Therefore, an innovative project was proposed to create videos where lessons are explained. These files were uploaded to the Virtual Classroom. In this way, students of the Marine Science BSc degree were also encouraged to use these audiovisual resources because not all of the enrolled students were able to attend the classes as they had clashing schedules. On the other hand, some students have an Erasmus grant and their knowledge of Spanish has not reached the required level in terms of assimilating all the given explanations. Enabling these audiovisual resources would be very useful for their studies, not only from a technical but also from a linguistic point of view. The exams from the last few years were solved and explained in documents that were also uploaded later to the Virtual Classroom in order to facilitate the study of the subject. This represented a valid and helpful alternative way in which students could prepare for their final exam. During the months of September and October a grantee was hired to assist the preparation of all the teaching material. From November to January, several PowerPoint files were prepared (including formulations, summaries and practical solved exercises) and oral explanations were implemented. The performance of the audiovisual resources was facilitated by the free software Active Presenter (http://atomisystems.com/activepresenter/). The students completed a satisfaction survey about the quality and usefulness of the audiovisual lectures, in order to assess the levels of interest and success that were achieved. According to the results obtained, these audiovisual resources can be considered to be in the public domain and hence can be uploaded to the Cadiz University repository. In order to disseminate the results of the project’s usefulness in academia, lectures explaining its methodology, results and conclusions used will be given, not only in the same faculty but also at this International Conference to further its applications to other subjects

Success on increasing number of students that pass the coastal engineering subject

During the last ten years, the ratio of students that do not take the final exam in the subject of Coastal Engineering at the University of Cadiz was 1/3 of the total number of enrolled students. Furthermore, the ratio of students who did not pass the test was 50%. Hence, only a third part of the total amount of students successfully passed the exam. In order to improve this percentage, a working procedure hypothesis was implemented and the results are shown herein. This procedure implies some “homework”, the duration of which is similar to the theoretical lessons, i.e. 2 hours a week. Assignments are not mandatory and they only represent 10% of the final mark. Weekly dedication is directly related to the main aspects of the theoretical lessons and includes practical exercises as well as the search of particular cases about the topics explained at the classes. This methodology allows the students to: a) improve their knowledge of the subject; b) check their learning progress; c) introduce them to the e-learning; d) learn complementary concepts of scientific research by using e-databases; e) refresh and update the theoretical concepts provided during the live lectures; f) add new teaching material to enhance the comprehension and study of the subject; g) feel motivated by the possibility of increasing their marks. Achievement monitoring is performed just before each lesson. This way, any possible doubts derived from the exercises resolution are clarified. Despite representing only a low percentage of the final mark, a complete dedication of the students was achieved. The application of this procedure during the previous academic year resulted in 97.4 % of the students successfully passing the final test

Coste de la limpieza “cotidiana” de playas

Más de 90.000 buques mercantes al año cruzan el Estrecho de Gibraltar de los que aproximadamente un 5% son petroleros. Ello, conjuntamente con la existencia de varios puertos con refinerías y polígonos industriales petroquímicos y la práctica del bunkering para aprovisionamiento de combustible, hace a la costa gaditana un punto de riesgo para la contaminación por hidrocarburos (Carmona et al., 2009). La Demarcación de Costas de Andalucía-Atlántico (DCAA), dependiente del Ministerio de Agricultura, Alimentación y Medio Ambiente, ha realizado en numerosas ocasiones la limpieza de su litoral debido a la polución producida por ese tipo de vertidos (Carmona et al., 2012), existiendo ya alguna bibliografía sobre cómo abordar la retirada de alquitrán y otros derivados similares de las playas (e.g. DGC 2005, CEPRECO 2006a, CEPRECO 2006b). Sin embargo, además de la fracción no volátil de los hidrocarburos, existe otro tipo de desechos, naturales y/o antrópicos, que llegan a nuestras playas y que, debido sobre todo al carácter turístico de nuestro litoral, deben ser recogidos. Por ley, esta limpieza corresponde a las autoridades locales. No obstante, debido a la escasez de su presupuesto, los municipios suelen atender prioritariamente a la limpieza de las playas más urbanas y de máxima utilización. Es por este motivo que, dentro de un espíritu de colaboración entre Administraciones, la DCAA, mediante su partida de conservación y mantenimiento, ha apoyado las tareas de los Ayuntamientos, reforzando la labor municipal en las playas más concurridas y limpiando aquellas que son menos visitadas ya sea por su lejanía del casco urbano o por su escasez de servicios. En esta ponencia se presentarán los medios humanos y materiales con los que se cuenta para esta tarea, aportando cifras de toneladas de basura retiradas y coste del trabajo, junto con una comparación superficial con los datos de otros organismos y alguna sugerencia de posibles mejoras de la productividad