Climate, tectonics and beach erosion : the case of Espinho (nw portuguese coast)

Sea level is a very changeable surface. Furthermore, the land may also be moving, in a slower rate, generating relative sea level changes. The causes of relative sea level changes are variable, but the ones that cause more intense variations are related to climate. During Little Ice Age (LIA) Northern Hemisphere's summer temperatures fell significantly below the AD 1961–1990 range. This climate situation was responsible for a greater discharge of rivers, which could lead to a greater transportation of sediments to the coastline. During these cold periods, sea level was lower than in present time. All this could imply a coastline progradation, with the successive abandon of older beach ridges, reinforcing the sandy supply for dune building. The coastal situation should be, in some sense, the opposite of the situations that we face today. In present warm period, rivers carry less sediment than during LIA. Moreover, the recent sea level rise contributes to a coastal migration inlands and the erosion of previous beaches and dunes. Our investigation on ancient marine levels and Holocene cemented dunes suggests that the area near Esmoriz (20 km south of Porto, NW Portuguese coast) is probably subsiding. This possible subsidence, together with recent sea level rise, induced by the end of LIA, could explain the severe coastal erosion that is taking place at Espinho area (15 km south of Porto) since the middle of the XIX century. This example shows clearly the complexity of relative sea-level changes. Because of this complexity, sea level curves are not similar worldwide, as they depend on the interference of multiple time-scales phenomena

A zona costeira do Norte de Portugal : unidade e diversidade : o caso particular da região do Porto = Northern portuguese coastal zone : unity and diversity : the particular case of the Porto region

A linha de costa do Noroeste de Portugal apresenta uma notável homogeneidade quando observada num mapa de pequena escala. Tem uma orientação muito consistente, de rumo NNW-SSE desde a fronteira com a Galiza, na foz do rio Minho, ao longo de 97km até à latitude de Espinho, cerca de 14km a sul da cidade do Porto. Além de sua aparência retilínea, outra característica importante da zona costeira de Portugal é a existência da designada "plataforma litoral", que se desenvolve como uma superfície aplanada, contígua à linha de costa e geralmente separada dos relevos interiores por um alinhamento abrupto. É possível considerar vários sectores bem diferenciados dentro deste trecho com cerca de 100km de extensão. A diferenciação relaciona-se com a extensão da plataforma litoral e com o seu desenvolvimento altimétrico. O estudo dos depósitos quecobrem a plataforma litoral, feito com mais detalhe na área que rodeia a foz do Rio Douro, onde esses depósitos são bastante representativos e bem expostos, permite corroborar a hipótese de movimentações tectónicas durante o fi nal do Cenozóico.Deste modo, quer o desenvolvimento topográfi co de conjunto, quer o estudo detalhado dos depósitos correlativos sugerem a existência de compartimentos com movimentação tectónica diferenciada, ao longo de falhas herdadas dos tempostardi-hercínicos, que poderão ter continuado a atuar ao longo do Quaternário.The coastline of Northwest Portugal has a remarkable homogeneity when viewed on a small-scale map. It has a very consistent orientation towards NNW-SSE, along 122 km, from the latitude of Espinho, south of the city of Porto, up to the border with Galicia, at the mouth of the Minho River, and beyond this point up Baiona in Galicia. In addition to its straight appearance, another important feature of the coastal area of Portugal is the existence of the designated littoral platform, which develops as a fl attened surface, adjacent to the shoreline and usually separated from the interior reliefs by an abrupt alignment. One can consider several well-diff erentiated sectors within this stretch of about 100km long. The diff erentiation is related to the extension of the littoral platform and its altimetry. The study of deposits covering the littoral platform, quite detailed in the area surrounding the mouth of the Douro River, where these deposits are very representative and well exposed, seems to corroborate the hypothesis of tectonic movements during the late Cenozoic. Thus, both the topographic development and the detailed study of the deposits suggests the existence of compartments with diff erent tectonic movements along faults inherited from tardi-Hercynian times, which may continue to work during the Quaternary

Depósitos do pleistocénico superior e do holocénico na plataforma litoral da região do Porto : a morfologia das plataformas de erosão marinha e a tectónica recente

Upper Pleistocene and Holocene deposits in the coastal platform of the Porto region: the morphology of the marine platforms and neotectonics: the study of Quaternary sedimentary deposits of the coastal zone of Porto included a very detailed fieldwork and the accurate altitude definition with a GPS (Leica SR20). Luminescence dating of aeolian and lagoon deposits was performed to confirm our hypothesis about the deposits chronology and recent tectonic movements. However, the marine deposits can not be dated by TL and even OSL is quite problematic due to the small thickness of the beds. Our main goal is to characterize the several marine platforms along this coastline. It was possible to identify the present-day marine platform, some rare tiny Flandrian platform remains and also the more frequent and generally deposit bearing Eemien platform. This work has proved that even the last interglacial marine deposits have suffered some tectonic disturbance as they appear at quite different altitudes along this coastal zone

A área do S. Paio (Labruge, Vila do Conde): desafios científicos e uso de novas tecnologias

A área S. Paio corresponde a 2 pequenos afloramentos rochosos situados na costa norte de Portugal, cerca de 15km a Norte da foz do Douro. Trata-se de um local onde foi encontrado um castro da Idade do Ferro. Além disso tem múltiplos interesses sob o ponto de vista geomorfológico: arribas rectilínease praticamente verticais (prováveis planos de falha), restos de depósitos marinhos a várias altitudes e outras formas muito interessantes, como uma sapa fóssil situada a 9m. A morfologia sugere fortemente a existência de um levantamento de conjunto que possa explicar o escalonamento de depósitos. Porém essa hipótese implica a necessidade de datações por OSL, em curso. A atribuição de cotas precisas através de um GPS com correção diferencial e a utilização um ortofotomapa de alta resolução, obtido através de um VART permitiu um aperfeiçoamento do conhecimento da topografiae uma ainda maior visibilidade dos respectivos controlos estruturais

As praias entre a Foz do Douro e a Granja : algumas reflexões sobre a erosão costeira

Coastal erosion is a phenomenon that should be analyzed at a global scale. The coastal erosion is affecting an important part of the Portuguese coast. The more affected areas are the sandy coastlines (for example, the segment between Espinho and Cape Mondego), and everywhere the substratum is soft (for example, many places to the east of Olhos de Água, in Algarve). Coastal erosion is affecting beaches but also the man made structures (groins, sea walls). This is a relevant problem because beaches play an important role in the economy of the country, specially supporting the coastal tourism industry. Coastal erosion has many and inter-acting causes, so it is important to study them carefully in each context. The coastline between the mouth of the River Douro and the Granja beach is one example of the many areas affected by coastal erosion. In this coastal segment, the beaches lay over a rocky substratum (Iberian massif). Recent human interventions (construction and reinforcement of treated used waters discharger at Canidelo, detached breakwater of Aguda) caused the thinning of the beaches in the south of the structures (Francelos and Granja Beaches). The construction of new River Douro jetties may also affect this coastal segment. Our goal is to analyze the impact of this new structure and other human interventions on studied beaches. We also aim to confront this findings with the wave climate registered by Instituto Hidrogáfico. In order to accomplish these tasks we started, in April 2008, a monitoring of those beaches between Cabedelo and Granja beach. We have registered every month the beach profiles with a differential GPS. We have choose six different places, always departing from the same point and with the same direction. (...

Contribuição para o conhecimento geológico e geomorfológico da praia de Lavadores (Vila Nova de Gaia)

Lavadores' beach stands on the South of the Douro's river mouth about 2 km from Porto. It's the only sector of litoral "high" coast at the South of Douro's. This beach stays very close to the passage through the coastline of the Porto-Tomar fault, which corresponds to the contact between the Central-Iberian and Ossa-Morena zones. Posttectonics granite’s are outcropping in this beach. The fracture net seems to control the development of the coastline, imposing a rigid orientation to the cliffs as well on certain rectlineous corridors inside between the granites’ walls, which are usually abrupt. The same fracture net controls the existence of a typical block disjunction and other geomorphologic aspects of detail. We pretend to present geological and geomorphological sketches of the exposed rocks at the Lavadores beach and discuss the relationship between the geological structure (fracture net, neotectonics) and the forms due to the marine erosion

Escalonamento de plataformas de erosão marinha na praia de Fornelos (Montedor, Viana do Castelo), na perspectiva do património científico e didáctico

The present study identifies the staircase development of shore platforms at Montedor - Viana do Castelo, using the data obtained by the method of Communicating Vessels and GPS. It was found that both devices provide identical results and operation time. There were identified four different shore platforms above the actual (0,4/1,8 meters), at 2,8/3,4 - 4,5/5,5 - 6,6/7,4 and 8,5/9,2 meters. A tectono-eustatic origin of this staircase development is proposed, by excluding the influence of structural inheritance, such as sub-horizontal fracturing, in its genesis

Epidemiological surveillance system on foodborne diseases in Brazil after 10-years of its implementation : completeness evaluation

This study aimed to evaluate the data quality of the Brazilian Epidemiological Surveillance System on Foodborne Diseases (VE-DTA) through the evaluation of the completeness of the record after 10-years of its implementation. The study evaluated the measurement of completeness by quantifying ignored, incomplete or blank responses of the data items filled. The evaluation used the percentage of completion of these items regarding the total number of notifications registered in the system. We organized the results according to the general Category of completeness of the database, by year of notification and region of occurrence. We also evaluated the overall completeness percentages of the database and the completeness levels according to the degree of recommendation of completion of each variable (mandatory, essential, and complementary) by the VE-DTA manual. The system presented 7037 outbreaks of foodborne diseases. According to the completeness classification, the database presented general classification as Category 1 since it has 82.1% (n = 5.777) of variables with the level of completion up to 75.1%. We observed that 8.6% of the database was classified as category 2; 9.2% as category 3 and 0.1% as category 4. The improvement on database quality regarding completeness can positively impact on public health and public policies, reducing the number of FBDs deaths