Papers

coastline appear to entail some disadvantages. An innovative and interesting way of protecting a local coastal zoneby means of multifunctional artificial reefs avoids some of them. A multifunctional artificial reef is a submergedbreakwater which, besides helping to protect the local coastline, can have other purposes; in particular it may enhancethe surfing possibilities and the environmental value of the local area. The structure has several positive side effects:first, it provides an unimpaired visual amenity; second, it offers tourist and economic benefits by improving the surfingconditions. A preliminary design, achieved step-by-step, is proposed for a multifunctional artificial reef making use ofthe theory and state of the art multifunctional artificial reef design, a preliminary design, achieved step-by-step, apriliminary design is proposed. The proposed reef geometry, together with numerical and physical tests, allows theanalysis of a multifunctional reef breakwater designed to protect a stretch of the northwestern coast of Portugal.Taking into account the condition that the proposed geometry will only function properly on a sea slope bottom ofless than 1 : 50, the main choices are as follows: the upper part of the structure is delta shaped with an angle of 66and a side slope of 1 : 10, and the lower part consists of a platform whose slopes are as steep as possible. The positionof the reef should be such that the distance from the apex of the structure to the undisturbed shoreline is greaterthan 1.5 times the natural surf zone width.

Digital preservation aims at maintaining digital objects accessible over long periods of time, ensuring the authenticity and integrity of these digital objects. In such complex environments, Risk Management is a key factor to assure the normal behaviour of systems along time. Currently, the digital preservation arena commonly uses Risk Management concepts to assess repositories. In this paper, we intend to go beyond and propose a perspective where Risk Management can be used to assess existing solutions, but also to conceive digital preservation environments. Thus, we propose a Risk Management based approach to design and assess digital preservation environments, enclosing: (i) the definition of context and identification of strategic objectives to determine specific requirements and characterize which consequences are acceptable within the identified context; (ii) the identification, analysis and evaluation of threats and vulnerabilities that may affect the normal behaviour of a specific business or the achievement of the goals and conformance to the requirements identified in the context characterization; and, (iii) definition of actions to deal with the risks associated with the identified threats and vulnerabilities. We generalize and survey the main requirements, threats, vulnerabilities and techniques that can be applied in the scope of digital preservation.

Digital preservation aims at maintaining digital objects and making data accessible over long periods of time. The emerging context of e-Science imposes new scenarios and new requirements for digital preservation. This paper presents the main issues, current solutions and prominent projects for digital preservation and e-Science data management. Finally, it presents the problem to be addressed, the solutions to explore, the proposed methodology and expected contributions of the associated PhD work.

As estruturas de retenção têm vindo a ser cada vez mais utilizadas para o controlode cheias em áreas urbanas. O pré-dimensionamento destas estruturas é frequentementeefectuado através do método simplificado, também conhecido por métodoholandês, embora o dimensionamento final deva resultar da aplicação de um métodonumérico que tenha em consideração hietogramas de projecto, as características dabacia de drenagem, a geometria da estrutura de retenção e a lei de vazão dos órgãosde descarga.Dado que o dimensionamento com modelos distribuídos e hidrodinâmicos obriga àrealização de um conjunto alargado de simulações, desenvolveu-se um modelo numéricoque efectua automaticamente o cálculo iterativo das necessidades de armazenamento eda chuvada crítica de projecto, para diferentes opções de dimensionamento da estruturade retenção e dos órgãos de descarga.Os resultados obtidos pelo método holandês e pelo modelo numérico desenvolvido sãocomparados com os obtidos com o SWMM, para cenários seleccionados de um casode estudo. As potencialidades e limitações de cada método são discutidas à luz dainfluência das suas hipóteses de base nos resultados obtidos.

In this work, a video-monitoring system applicable to the study of beach morphodynamics was developed and applied to the DTM extraction of the intertidal zone of a fetch limited beach (Alfeite, Portugal). This low-cost system, intended to complement standard survey tools, has the additional benefit of enabling the continuousmonitoring of beach meso-scale process (spatial/temporal scales in the order of kilometers and years, respectively). The development of this system, based on terrestrial photogrammetric techniques, involved three main steps: i) camera calibration, where the internal camera parameters were determined in the laboratory using open-source software; ii) the development of image correction subroutines, which aimed to correct the relativelylarge image distortions induced by camera optics; this procedure revealed to be essential as the system was builtupon standard non-metric surveillance cameras; iii) the development of image rectification subroutines totransform oblique images into vertically equivalent images; this transformation was based on external camera orientation parameters obtained in the field through the surveying of ground control points. Alfeite beach DTM extraction was performed through the shoreline digitalization, in geo-referenced rectified images acquired every 10 min, during the flood. The overlapped set of shoreline curves, properly referred to a vertical datum by meansof tide measurements, characterized the intertidal beach morphology. The obtained results were compared with the ones acquired with classic survey techniques revealing very encouraging results; the overall vertical rms was 0.08 m with a maximum value of 0.15 m at 390 m of the camera.

O número de casos de estruturas de betão afectadas por reacções expansivas internas tem aumentado muito nos últimos anos, tanto em Portugal como a nível internacional. A degradação do betão por reacções químicas de origem interna engloba dois tipos de reacções expansivas: a reacção álcalis-sílica (RAS) e a reacção sulfática de origem interna (RSI). Estas duas reacções, que têm manifestações macroscópicas semelhantes (Figura 1), quando detectadas são muito difíceis de combater, não existindo ainda um método totalmente eficaz de reparação para estruturas degradadas por RAS ou RSI. Este aspecto salienta assim a necessidade da tomada de medidas mitigadoras contra a sua ocorrência no futuro.

A madeira é um material de construção versátil e com grande potencial. Noentanto, a sua susceptibilidade face à acção de agentes biológicos eatmosféricos condiciona muitas vezes o desempenho e a durabilidade dasestruturas de madeira. É assim fundamental ter estes aspectos em contadurante o projecto, a construção e a exploração das estruturas.

This paper describes a site specific study of a low energy estuarine beach sheltered from oceanic waves which presents a medium term (decade) geomorphologic stability. However, extreme meteorological events, characterized by strong winds, generate episodes of retreat of the beach face, which, under restored wave conditions, recovers in the short term. Three process-based models (a wind wave generation propagation model, a 2D-V littoral drift model and a 2D-V cross-shore morphodynamics model), frequently applied in open coastal areas but never in such low energy environments, were applied. The longshore transport was difficult to measure in the field and thus the numerical estimate was not validated. However, its uncertainty (9.6-16.1 x103 m3.year-1) was tested based on a sensitivity analysis of three influential parameters. Field measurements of meteo-oceanographic data and profile changes during a storm episode allowed the simulation of the hydrodynamics and sediment transport, and finally the verification of the numerical profile. Despite the volume of sediment extracted from the beach face being in good agreement with the observations, about 10m3.m-1, the profile geometry was not: the numerical profile exhibits an erosion scarp located bellow the retreat observed and a bar, at the beach face base, which was not observed in the field (probably flattened by the uprush and downrush flows). The effect of the passage of a catamaran was also evaluated: it generates an erosion of sediment up to 0.04m3.m-1 (depending on the catamaran velocity). Due to the beach geomorphologic characteristics the sediment transport is higher at higher tidal levels.

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