Helena Maria Granja

Evidence for Late Pleistocene and Holocene sea-level, neotectonic and climate control in the coastal zone of northwest Portugal

The coastal zone of northwest Portugal can be subdivided into two geomorphological sectors: Sector 1, between the Minho River and the town of Espinho, where the coastal segments consist of estuaries, sandy and shingle beaches with rocky outcrops, and Holocene dune systems (foredunes and some migrating dunes with blow-outs). The estuaries and the foredunes in particular are very degraded by human activities. Sector 2, between Espinho and the Mondego Cape, where coastal lagoons and Holocene dune systems (foredunes, parabolic and transverse dunes) occur. This study deals with the macroscale, i.e. 100–1000 years, forcing by sea-level changes and neotectonic activity on the one hand, and mesoscale, i.e. 1–100 years, forcing by climate fluctuations on the other hand, on these (palaeo-)environments. It is shown in particular that sea-level changes and neotectonic activity play a dominant role in the evolution of the coastal zone since the Late Pleistocene. Sediment starvation on the shoreface is postulated to be one of the major causes for coastal erosion since at least the 15th century. The mesoscale role of climate is difficult to assess at the present stage of knowledge, mainly because of overprinting by the macroscale evolution of the coast. However, data on estuarine saltmarsh evolution in sector 1 point towards discrete changes in storminess, while the development of Medieval dune systems in sectors 1 and 2 are attributed to the Little Ice Age or, alternatively, to human occupation of the dune areas.

Some neotectonic indicators in quarternary formations of the northwest coastal zone of Portugal

Abstract In the coastal zone of northwest Portugal, between the Minho River and the Serra da Boa Viagem/Mondego Cape, evidence of structural (overthrust, tilting), sedimentological (contorted bedding, slumping) and chronological (diachronous bedding) features have been detected during the last years, which seem to indicate the occurrence of neotectonic deformation in Quaternary deposits. Recently, geophysical campaigns were initiated in order to locate the presence of tectonic accidents that could be responsible for the observed field evidence. To complement the geophysics, 45 m deep cores were drilled at some points of the area. Till now, just preliminary data are available. However, they confirm the post-Pleistocene neotectonic activity in the coastal zone of northwest Portugal.

Optical Dating of Late Quaternary Coastal Deposits in Northwestern Portugal

Abstract The northwestern coastal zone of Portugal between Mondego cape and Minho River preserves a series of fluvio-aeolian, lagoonal, and dune formations that are archives of evolution during the late Pleistocene and Holocene. The existing chronology of these formations is based mainly on radiocarbon dating of in situ organic materials. In this study, we present the results of optically stimulated luminescence (OSL) dating of these formations and discuss their implications for the existing chronostratigraphy, climate, and neotectonic changes in this area since the late Pleistocene. Three major periods of aeolian activity have been identified based on the OSL ages and are bracketed to 25–14 ka, 9.9–3.4 ka, and 1.4–0.1 ka. These OSL ages suggest intense sand deposition during oxygen isotope stage 2, the mid-Holocene, and the Little Ice Age. The dune ages in the last 500 years provide temporal constraints on the initiation of coastal erosion in the area. Further, the chronostratigraphic correlations suggest tectonic uplift in the coastal sections, between ca. 17 ka and 14 ka, and erosion due to eustatic sea-level rise.

On the interest of plant functional classifications to study community—level effects of increased disturbance on coastal dune vegetation

Abstract Coastal zones are suffering from severe changes. Dune systems are forecasted to be impacted severely by such changes. Since shifts in coastal dynamics may drive modifications in the floristic composition of plant communities, effective indicators of such changes are needed to support adaptive measures. We performe here an assessment of the relative efficiency of functional and phytosociological classifications in the analysis of structure and dynamics in foredune vegetation. Our results identified common signals but also highlighted some differences among results from different classifications with potential consequences for the monitoring of changes in dune ecosystems. The coincident signals provided by the analysed classification systems suggest that they are effective in capturing the major rules involved in the structure and dynamics of foredune vegetation. Since the disturbance regime in foredunes is mostly related to prevailing coastal dynamics, compositional shifts in phytosociological or functional spectra are thus useful in the establishment of reliable indicators and protocols to monitor changes in coastal zones.

The impact of ‘protection’ structures on the Ofir-Apúlia coastal zone (NW Portugal)

Abstract Ofir-Apulia, NW Portugal, is a resort area, which grew rapidly during the 1970s and resulted in increased rates of erosion. In response to the serious damage of buildings revetments and groins were placed in the area. As a result the buildings were temporarily protected but the consequences downdrift were grave, threatening the small village of Pedrinhas. The consequences of recent winter storms are outlined and alternative protection methods proposed.

Coastal Defense in NW Portugal: The Improbable Victory

Coastal defense in Portugal has a long history. The first attempts to resist coastal change date from early in the twentieth century, when the town of Espinho saw its most seaward streets damaged by wave impact. A coastal defense work (a “muralha”, or wall) was built. The 1980s saw the building of several groins at different locations in Portugal. The fight against the sea continued during subsequent years in a tentative effort to achieve an “artificially stable” coastal zone. Coastal retreat and thinning of beaches continued, especially downdrift of structures. The pattern has progressively revealed the inefficiency of efforts to stabilize the coastline. The underlying causes have not been addressed and indeed are poorly understood. Coastal defense is simply a temporary and palliative means of addressing the impacts of coastal erosion and, sometimes gives a false sense of security to coastal populations. In this chapter an overview of the NW Portuguese coastal defense structures is presented, their efficiency is discussed and some representative examples are described. Some recommendations are presented to create a more efficient coastal zone management policy.

Prof. Gaspar Soares de Carvalho (1920–2016)

Professor Gaspar Soares de Carvalho passed away peacefully, on Monday, 1 August 2016, at the age of 96. This was the first day of vacations of his colleagues and only a few of them got news of this sad event. He was a great and good man, a dedicated researcher, uncompromising in his beginnings, although always knowing to accept criticism. His firm character (it is better to break than yield) cost him dedicated friends but, also, enemies that attacked him, very often, indirectly. His wish to know and spirit of initiative manifested themselves along his long run. In Portugal, he was the first author of works on sedimentology and one of the pioneers studying Plio-Pleistocene stratigraphy and paleogeography. Naturalist and lover of fieldwork, he taught his disciples how to observe in the field, stimulating them to go out from their offices. His professional life as a geologist of great field experience passed not only through Portugal, but also overseas. He was a chief geologist of the Geologic Maps Division of Geology and Mines Service of Angola in 1954–58, and a researcher of the National Board of Angola Overseas Studies in 1960. He worked in Guinea-Bissau (1959), India-Goa (1960), and in Mozambique, where he was the head of the Earth Science Department of the Mozambique Scientific Research Institute (1970–75) and the head of the Institute of Scientific Research (1975–76). Unfortunately, most of his publications from these years are written in Portuguese; however, his contributions still remain. As a professor, he worked at the University of Coimbra (1944–54), University of Porto (1961– 70), and University of Minho (1976–90), where he was one of the founders of Earth Sciences Department. After his retirement in 1990, he founded EUROCOASTPortugal (being also vice-president of International EUROCOAST Federation) and also founded the Portuguese Association for Quaternary Studies (APEQ). He was the president of EUROCOAST-Portugal and of APEQ from its foundation until 2000. These organizations contributed much to the expansion and critical discussion of the knowledge of coastal zones and on the Pleistocene–Holocene of Portugal, respectively. He was also one of the founders of the multidisciplinary journal Estudos do Quaternário of APEQ.

A Multi-criteria Approach for Erosion Risk Assessment Using a New Concept of Spatial Unit Analysis, Wave Model and High Resolution DEMs

In this work, field data and model outputs were integrated, processed and analyzed in a GIS environment in order to assess the vulnerability to erosion and to produce associated risk maps using a multi-criteria approach. Erosion risk assessment methodology was developed based on morphological, hydrodynamic, and meteorological indicators that were computed using data obtained from a short term monitoring program. It was applied to a stretch on the NW coastal zone of Portugal. Comparing this methodology to previously developed ones, there are three main distinctive aspects to be considered: (i) the coastal stretch was segmented for computation of indexes (susceptibility, exposure and risk), accordingly to specific coastal types (ii) a new set of vulnerability variables is proposed; and (iii) erosion impact indicators computed from detailed building and beaches data that was extracted from aerial photos.

The recent evolution of the povoa de varzim coast, NW Portugal

Abstract Povoa de Varzim, NW Portugal is situated on a wide Quaternary abrasion platform cut in granitic rocks with some Holocene lagoonal and marine deposits lying on its surface. The area is characterized by pocket shaped beaches, tombolos and granitic headlands. The net drift on this coast is from north to south but the numerous rocky headlands have produced wave diffraction patterns which generated circulation cells. In 1927 a port was constructed with breakwaters built to protect the harbour against NW waves (the most frequent) and W-SW waves (related to storm events). After the breakwaters were built, downdrift erosion occurred south of the harbour. The volume of sediment lost and the changed dynamics of the area are outlined. Some alternatives to minimize the negative effects produced by the harbour, such as artificial beach nourishment and the development of natural tombolos are proposed.