Ana Ramos-Pereira | Universidade de Lisboa (original) (raw)

Papers by Ana Ramos-Pereira

Finisterra, Oct 28, 2013

Hydrodynamic forces over the beach sediments are the main driving factors affecting the frequency... more Hydrodynamic forces over the beach sediments are the main driving factors affecting the frequency and magnitude of morphological changes in beach systems. Most of the time, these driving factors act in a foreseeable way and do not represent any danger either to the coastal systems or to their population. However, hydrodynamic forces are also capable of inducing high morphodynamic behaviour on the beach profiles and very often in a short period of time; this endangers people and property and leads to system retreat. The most common consequences of the occurrence of this type of phenomena over the landforms are costal inundation and erosion. Still, many coastal systems, especially beach systems, have recovery mechanisms. Resilience levels have a very important role in the beach morphodynamic status and exposure to potential damaging event assessments. The Portuguese West coast has a high wave energetic environment during winter, where waves with 5 year recurrence period can reach 9.2m and storms are frequent. This research aims to access beach hazard and susceptibility to inundation and erosion. Three beach systems were selected and monitored applying sequential profiling methodology over a four year period (2004 -2007). S ta . Rita, Azul and Foz do Lizandro beaches are representative systems of the coastal stretch between Peniche and Cascais, which is a cliff dominated coast. Results from the monitoring campaigns are presented, including volume budgets, beach face slope changes, berm occurrence and heights and planimetric coastline dynamics. A hazard and susceptibility assessment diagram and zonation are proposed, including the parameterization of local flood (i.e. mean sea level, maximum spring tides, and surge and run -up levels) and erosion potentials (i.e. volume budget and beach planimetric dynamics).

Finisterra, Oct 28, 2013

Resumo -O pisoteio é um dos principais fatores de perturbação da duna frontal, originando uma red... more Resumo -O pisoteio é um dos principais fatores de perturbação da duna frontal, originando uma rede de caminhos e clareiras no meio da vegetação densa, por eliminação de plantas vulneráveis como Ammophila arenaria. em comunidades vegetais não perturbadas, à medida que A. arenaria se torna dominante, a coexistência de outras espécies é inibida, tanto pela sua estratégia de crescimento em falange, como pela diminuição da mobilidade da areia junto à superfície. Porém, a dominância desta perene, responsável pelo crescimento em altura da duna, pode ser localmente invertida após o cessar do pisoteio. Dados recolhidos em três áreas de estudo no litoral de Vila nova de Gaia em 2006, três anos após a primeira grande intervenção da Câmara Municipal no ordenamento dos acessos à praia através das dunas, sugerem que a súbita abundância de Medicago marina se relacionará com a maior disponibilidade de locais adequados ao seu recrutamento, na sequência da morte de indivíduos de A. arenaria. ao estabilizar eficazmente a areia de caminhos e clareiras de perturbação, M. marina cria condições para a colonização de variadas espécies anuais e modifica de forma significativa o gradiente de mobilidade e deposição da areia na duna frontal. Palavras -chave: Biogeomorfologia, duna frontal, perturbação, pisoteio, dinâmica de comunidades, filtros ambientais. abstract -loCal replaCeMent of AmmophilA ArenAriA by medicAgo mArinA after foredune traMpling disturbanCe. Human trampling is amongst the major causes of foredune disturbance. it creates a diffuse path network and the opening of bare--ground clearings within dense vegetation patches as a result of plant removal, namely of Ammophila arenaria. in undisturbed plant communities A. arenaria becomes dominant, and strongly inhibits the co -existence of other species, due to its phalanx growth strategy recebido: abril 2012. aceite: fevereiro 2013. 1 Professora auxiliar do Departamento de Geografia do instituto de Ciências sociais da Universidade do Minho; investigadora do CeG-iGOt-UL, núcleo sLif -sistemas Litorais e fluviais: Dinâmicas, Mudanças ambientais e Ordenamento do território.

The Encroaching Dunes of the Portuguese Coast

Journal for the history of environment and society, 2022

DOAJ (DOAJ: Directory of Open Access Journals), Jun 1, 1995

DOAJ (DOAJ: Directory of Open Access Journals), Jun 1, 2013

Quantitative approach of a non linear and scale dependant landform evolution: rate of retreat of a coastline in Portugal, Arrábida

HAL (Le Centre pour la Communication Scientifique Directe), 1995

The central part of the portuguese continental passive margin is extensively studied by portugues... more The central part of the portuguese continental passive margin is extensively studied by portuguese and french teams. On the shelf, many seismic lines have been realised and the data on submarine geological structure allows to reconstruct very precisely the history of sedimentation on the sea floor, and to link it with some phases of canyon incision. On the main land, DEM of the landforms have been constructed and some models of evolution have been proposed. On the shore line, a survey of paleo sea levels, including submarine sea stands, has permitted to establish a chronology os eustatic movements and of uplift rates. This set of data provides a good information about erosion rates, extended along various time span. The seismic profiles are used to calculate an average speed of retreat since the end of the Tortonian (7,1 millions years), because we can determine where the coast line was at this time. The average rate is 0,7 mm/year. The Eemian sea level, together with some Weichselian stands may be used to determine an average rate of coastal retreat for the last 120000 years. The rate is 5 mm/year. A very peculiar sea stand, at -7 m depth, is used to calculate a rate of retreat for a 1000 years long period, during the Holocene (5500-4500) with a very high rate of 10 mm/year. Some data is also given by present day rate of retreat, observed and measured between 1990 and 1994. The average is 1 mm/year with a great variability in space. The present day rate o retreat, when interpolated, doesn't fit with any of the other figures, neither does the holocene rate fits with the 120000 one. Though, all these rates could be found, today, on other sites of the Portuguese coast, in the same limestone material. They are commonly observed on exposed cliffs. We may propose that successive morphogenic systems, along the coast we study, have not been very different than the one we observe elsewhere today. A first discussion tries to expose why linear interpolation is impossible, in time, even if processes have remained more or less the same. A non linear model of evolution is then proposed. It relies on an arbitrary average speed of retreat which is calculated as an average during the longest know time span. If evolution were linear, all data should then be on one single straight curve. The difference between the theoretical position of data and its actual location away from the curve is used to calculate a threshold: it gives a measurement of the relative efficiency of morphogenic processes during a short period, compared with the average efficiency of all processes during long term. The originality of a morphogenic crisis may be demonstrated. Some explanations are proposed. A model is constructed and presents how sea level variations are related with the speed of coastal retreat. The speed of the sea level rise is much more important than the total amount of vertical displacement. Though, the landforms which are carved by this rise are not conserved in the morphology for very long (in this case: 100000 years). Most of the observed present landforms are a testimony of periods where erosion intensity was low. The question of morphological heritages is discussed. Tectonics are know to be quite important in this area. A comparison is attempted, but a precise quantification is at this stage of our work, not very reliable and we propose no explanation for the observed correlations. Our conclusion makes clear the difficulties in using todays figures for modelling the land forms evolution.

O estuário do Tejo das origens à contemporaneidade: o rio e as gentes

Meios, Vias e Trajetos... Entrar e sair de Lisboa. Fragmentos de arqueologia 2, 2018

Há cerca de 2,5 milhões de anos (MA), a paisagem do oeste peninsular era muito diversa da atual. ... more Há cerca de 2,5 milhões de anos (MA), a paisagem do oeste peninsular era muito diversa da atual. Num ambiente de clima quente e húmido, as paisagens litorais eram marcadas por planuras onde os cursos de água eram entrançados, com muitos canais que comunicavam com o mar por múltiplas fozes. Assim seria também a paisagem na área das penínsulas de Lisboa e de Setúbal. No litoral ocidental da Península de Setúbal, o que resta dessa paisagem litoral é ainda testemunhado pelos sedimentos, hoje cortados na arriba fóssil da Costa da Caparica, que contêm “fantasmas” de granito de Sintra, mostrando que o estuário do Tejo não existiria (Azevêdo, 1987). Só na sequência de um posterior paroxismo tectónico, o Tejo vai romper a saída para o mar, através do estuário. Para tempos mais recentes, a evolução do traçado, dos ecossistemas e das condições de navegabilidade do estuário do Tejo foram sempre condicionantes da vida humana: dos primeiros caçadores-recolectores e pescadores aos camponeses neolíticos e da “Idade dos Metais”, Fenícios, Romanos, Germanos, Árabes e Cristãos, todos viveram o rio e do rio. O que aqui procuramos trazer é um retrato, necessariamente resumido, da evolução do rio nas suas relações com as gentes desde a Pré-História à Contemporaneidade.About 2,5 million years ago, the landscape of Western Iberia was very different from the current one. In an environment of hot and humid climate, the coastal landscapes were marked by plains where the waterways were plaited, with many channels that communicated with the sea by multiple mouths. This would also be the landscape in the area of Lisbon and Setúbal Peninsulas. On the western coast of the Setúbal Peninsula, what remains of this coastal landscape is still witnessed by the sediments, now cut in the Costa da Caparica fossil cliff, which contain granite “ghosts” from Sintra, showing that the Tagus estuary would not then exist. Only after a later tectonic paroxysm, the Tagus will break off into the sea, across the estuary. For more recent times, the evolution of the layout, ecosystems and navigability conditions of the Tagus estuary have always been a determining factor of human life: from the first hunter-gatherers and fishermen to the Neolithic peasants and the “Age of Metals”, Phoenicians, Romans, Germans, Arabs and Christians, all lived the river and from the river. What we are trying to bring here is a portrait, necessarily summarized, of the evolution of the river in its relations with people from Prehistory to Contemporary times.info:eu-repo/semantics/publishedVersio

Zenodo (CERN European Organization for Nuclear Research), Dec 1, 2021

The building of dunes and sand drifts along the European coastline are generally related to clima... more The building of dunes and sand drifts along the European coastline are generally related to climatic variability and sea-level fluctuation. The last phase of dunes formation in south-western Europe coincides with the Little Ice Age (LIA) period characterized by pronounced climate variability. Historical sources retrieved from archives also report sand-drift events along the Portuguese coast. The sand invaded many agricultural fields, and settlements, forcing the inhabitants to move elsewhere. The article explores the temporal relationships between sand drift occurrences and climate, as a principal trigger for coastal dune migration. We used historical sources about sand-drift events as documentary proxies to infer the past climate variability on the Portuguese coast. Three spatial scales of climate variability were considered: i) the global climatic variability induced by the cold abrupt events over the last Millennium (LIA); ii) the regional (mesoscale) climate variability (NAO index), and iii) the local climate variability (extreme meteorological events). The paleoclimatic interpretation indicates that drifts in Portugal are related to both NAO modes, providing new insights into coastal dunes dynamics, as a response to natural drivers. However, the analysis of human activity on the coast also allowed us to better understand the relation of the local populations with their environments, highlighting those anthropogenic actions caused an additional disturbance on coastal dune dynamics.

Transgressive dune fields evolution varies along the coastline as a result of both natural factor... more Transgressive dune fields evolution varies along the coastline as a result of both natural factors and human activities. Under distinct climatic conditions and sea level fluctuation, coastal dune fields recorded intense sand drift episodes, and significant changes in their morphologies. Wind-blown sand transported inland, invaded agricultural fields, silted the rivers and estuaries and destroyed villages, forcing the inhabitants to move elsewhere. The proposed doctoral project in Physical Geography aims for the dissemination of the project -"Sea, Sand and People. An Environmental History of Coastal Dunes" (802918-DUNES-ERC-2018-STG). The main objective is to reconstruct the geomorphological evolution of transgressive dune fields during the last two centuries, as a response to environmental and anthropogenic factors and assessing the coastal dunes ecosystems vulnerability.

Records of climate changes and anthropogenic actions over dune fields in historical times

<jats:p>&lt;p&gt;Coastal dunes are very complex systems and very sensitive ... more <jats:p>&lt;p&gt;Coastal dunes are very complex systems and very sensitive to climatic variability and human actions. In Portugal, coastal dune fields have undergone major changes over historical times. The aim of the paper is focused on the coastal dune systems evolution over the last five centuries, natural and man induced (namely by deforestation and afforestation) and their transformation under the present global changes (sea level rise and coastal storms). The analysis of historical records and environmental data using a set of proxies recorded over the last 1,000 yrs, show intense aeolian activity and sand drift episodes during Little Age Period, causing serious problems for human settlements and agriculture. Coastal society have responded to the wind-blown sands fixing the dunes through afforestation. The process is well documented in the historical sources and many management measures, including abundant legislation, projects and reports were carried out by Portuguese authorities to avoid sand incursion inland. &amp;#160;According to the main report of the General Forest Administration, in the final of 18th century, was estimated an area of about 72 000 ha of free aeolian sands in need of afforestation. Thus, along Portuguese coastline, the dunes experienced a period of stability during the 20th century, due to planting of grasses and pine forest. This paper examines the pathways of the transgressive dune fields of the Central Western Portuguese coast, over various stages of coastal evolution. Mapping the morphological features between Mondego river mouth and Nazar&amp;#233;, using a combination of satellite images, aerial photographs and Lidar data we identified distinct phases of aeolian activity and landforms modification that were associated to climatic fluctuations. This coastal dune system is composed by a succession of different aeolian phases, including a littoral foredune, which lies inland with a complexity of morphologies with transverse and crescentic ridges, and also parabolic dunes. The results show that the dunes building and sand migration inland appears to be linked to the conditions of predominantly negative winter North Atlantic Oscillation index (NAOi), driven by climatic variability during Holocene/Antrhopocene. The consistency of intense sand drift episodes with abrupt cold events during Little Age Period, drastically reduced the area occupied by vegetation, causing changes in aeolian sedimentary processes. Thus, it seems that coastal dunes evolution over the past centuries have been controlled by the two-way interactions between natural conditions and human activities, shaping the Portuguese coastline. Placing historical evidence in a geographical perspective, we hope to fill the gaps in coastal zone dynamics, providing new insights of the human-landscape relationships to predict the future response of the coastal dune systems to human pressure and climate change.&lt;br /&gt;Key-words: coastal dunes evolution, geomorphological features, sand drift, anthropogenic impacts, climatic fluctuation, Western Portugal.&lt;/p&gt;</jats:p>

Cuadernos de Prehistoria y Arqueología de la Universidad de Granada, 2021

This article is the result of archaeological and paleoenvironmental investigations carried out wi... more This article is the result of archaeological and paleoenvironmental investigations carried out within the scope of the ANSOR project in the Sorraia valley (Coruche), on the left bank of the Lower Tagus. In the analysis of settlement dynamics between 5500 and 1800 a.n.e. we considered four moments: 1) The first peasant societies of the ancient Neolithic; 2) The Middle and Late Neolithic; 3) Chalcolithic; 4) The Early Bronze Age. The Sorraia valley was also framed in the framework of the Center and South of Portugal during the period under analysis. Interpretative models are presented for changes in the implantation patterns in the four stages under study, oscillating between paleoenvironmental factors and the socio-economic changes registered in the old peasant societies.

A resilience cheklist to evaluate coastal dune vulnerabiity

Periodicum Biologorum, 2000

The aim of the proposed resilience checklist is to easily evaluate foredune vulnerability when ap... more The aim of the proposed resilience checklist is to easily evaluate foredune vulnerability when applied to management. It focus on: (i) the definition of the level of pressure for each use in relation to the foredune resilience threshold, (ii) the direct identification of the system components more vulnerable and (iii) the recognition of management readjustments needed, in order to prevent or minimise impacts. The resilience checklist structure is based on a selection of relevant coastal dune vulnerability descriptors, giving information about the system sensitivity and resilience. All variables selected describe observable signs of foredune degradation or regeneration and are related to system elements susceptible of receiving management intervention. Three major degrees of biophysical vulnerability are recognised: a) Degree 0 - low sensitivity and resilience threshold not exceeded; b) Degree 1 - variable sensitivity and at the resilience threshold; c) Degree 2 - high sensitivity and resilience threshold exceeded. Each degree takes into account the system's level of degradation and the corresponding desirable level of conservation. The application example -Mira's beach southern sector- is a site under a very high summer pressure (seaside recreation and tourism). Three management phases were monitored, between 1996 and 1998. Checklist results show dune management inefficiency and an ineffective sand retention by vegetation as determinants to this foredune site vulnerability and that a planting program is still in need. However, a clear vulnerability decrease in this site was recognised.info:eu-repo/semantics/publishedVersio

Portugal: coastal dynamics: Field Trip Guide - A1

The western coast of Portugal has great geomorphological contrasts. Although the cliff littoral p... more The western coast of Portugal has great geomorphological contrasts. Although the cliff littoral prevails, there are some sandy systems associated with lagoons that are worth visiting, both because of their extension and because of the unbalanced situation and environmental vulnerability. The dynamics of the coastal systems in this exposed littoral and the management and land-use problems are the main reasons for the present environmental conflicts: (i) coastal erosion (natural and maninduced), first reported in the XIX century, which led to heavy defence structures and partial or total destruction of coastal systems, (ii) the infilling of the estuaries and lagoons, promoting their eutrophism and risking the local aquaculture communities. The present-day dynamics and Quaternary evolution are the main topics, as well as coastal zone management and conservation.info:eu-repo/semantics/publishedVersio

The Southwest Coast of Portugal

World Geomorphological Landscapes, 2020

The southwest coast of Portugal is rich in natural heritage and is framed within the Southwest Al... more The southwest coast of Portugal is rich in natural heritage and is framed within the Southwest Alentejo and Vicentine Coast Natural Park since 1995. Its complex geomorphological evolution reflects the geostructural position near the contact of the African plate and the Iberian microplate, and the relative sea-level changes and characteristics of the coastal systems. The major landform of the region is the Littoral Platform, tilted to the northwest and folded by meridian normal tectonic faults. These accidents cross a left lateral strike-slip fault—the longest NE–SW tectonic Iberian fault structure extended from Ávila (Placencia) to Messejana and to the continental margin. The Pliocene and Pleistocene sediments occurring in the Littoral Platform show a composite evolution. Seaward, the platform is undercut by the coastal cliff, which is the prevailing present-day coastal feature, with narrow beaches, in a coast with sedimentary deficit in the longshore drift.info:eu-repo/semantics/publishedVersio

Suscetibilidade ŕ inundaçăo e ŕ erosăo aplicados a praias expostas

espanolEl estuario de la Ribera Bensafrim, situado al oeste de Algarve, fue uno de los sistemas f... more espanolEl estuario de la Ribera Bensafrim, situado al oeste de Algarve, fue uno de los sistemas fluviales y marinos utilizado para evaluar la evolucion de ambientes costeros en los ultimos 5000 anos. A traves del metodo de radiocarbono, se dato la materia organica sedimentaria presente en los nucleos verticales recogidos en este estuario. Considerando el registro estratigrafico asociado con los datos cronologicos obtenidos, se utilizo un enfoque estadistico bayesiano, utilizando el software de calibracion OxCal, para obtener un marco geocronologico robusto para la secuencia sedimentaria. El analisis, basado en la construc cion de un modelo de deposicion para la secuencia sedimentaria, permitio identificar la presencia de valores atipicos (outliers), asi como establecer un marco geocronologico para los ultimos 5000 anos en el Barlavento algarvio. Mas alla de este marco, se verifica que el modelo geocronologico idealizado, asociado con la caracterizacion sedimentologica de uno de los ...

Landscapes of Portugal: Paleogeographic Evolution, Tectonics and Geomorphology

This chapter synthesizes the most relevant aspects of geology, tectonics and geomorphology of Por... more This chapter synthesizes the most relevant aspects of geology, tectonics and geomorphology of Portugal. Its main purpose is to frame, in a morphostructural point of view, the more specific chapters on Portuguese geomorphological landscapes. It includes a summary of (i) the main evolutionary stages of the Portuguese territory, as well as the present tectonic framework of Portugal’s mainland, Azores and Madeira archipelagos, and (ii) the main regional features of the geomorphological units. The synopsis is based on the scientific publications of many colleagues, physical geographers and geologists, who with their work contributed, over the years, to the geomorphologic knowledge of the country. Professor Antonio de Brum Ferreira was the “greatest teacher” of Portuguese geomorphologists, to whom many of us owe the taste, rigour, the practice and the knowledge of geomorphology.

Finisterra, Oct 28, 2013

The Encroaching Dunes of the Portuguese Coast

Journal for the history of environment and society, 2022

DOAJ (DOAJ: Directory of Open Access Journals), Jun 1, 1995

DOAJ (DOAJ: Directory of Open Access Journals), Jun 1, 2013

Quantitative approach of a non linear and scale dependant landform evolution: rate of retreat of a coastline in Portugal, Arrábida

HAL (Le Centre pour la Communication Scientifique Directe), 1995

O estuário do Tejo das origens à contemporaneidade: o rio e as gentes

Meios, Vias e Trajetos... Entrar e sair de Lisboa. Fragmentos de arqueologia 2, 2018

Zenodo (CERN European Organization for Nuclear Research), Dec 1, 2021

Records of climate changes and anthropogenic actions over dune fields in historical times

Cuadernos de Prehistoria y Arqueología de la Universidad de Granada, 2021

A resilience cheklist to evaluate coastal dune vulnerabiity

Periodicum Biologorum, 2000

Portugal: coastal dynamics: Field Trip Guide - A1

The Southwest Coast of Portugal

World Geomorphological Landscapes, 2020

Suscetibilidade ŕ inundaçăo e ŕ erosăo aplicados a praias expostas

Landscapes of Portugal: Paleogeographic Evolution, Tectonics and Geomorphology

Efectua-se a caracterização dos tipos de litoral entre Espinho e Nazaré, incluindo dados compleme... more Efectua-se a caracterização dos tipos de litoral entre Espinho e Nazaré, incluindo dados complementares, nomeadamente quanto à litologia, estrutura e evolução recente.
Procede-se à identificação e caracterização da ocupação humana, incluindo a inventariação de obras de protecção costeira existentes e outras formas de artificialização da faixa litoral.
Caracterizam-se alguns aspectos oceânicos, como sejam os movimentos das águas superficiais (marés, ondas, temporais, tsunamis ...) e as variações do nível do mar.
Propõe-se uma estratégia de gestão da faixa costeira considerada, numa perspectiva de desenvolvimento sustentável.
Fazem-se recomendações de actuações a curto, médio e longo prazo.

Characterization of the coastline types between Espinho and Nazaré (Portugal) is carried out, including complementary data, namely regarding lithology, structure and recent evolution.
Human occupation is identified and characterized, including the inventory of existing coastal protection structures and other forms of artificialization of this coastal stretch.
Some oceanic features are characterized, such as surface water movements (tides, waves, storms, tsunami ...) and mean sea level variations.
A strategy for coastal management is proposed, with a view to sustainable development.
Recommendations for short, medium and long term actions are made.

Finisterra, 2021

The building of dunes and sand drifts along the European coastline are generally related to clima... more The building of dunes and sand drifts along the European coastline are generally related to climatic variability and sea-level fluctuation. The last phase of dunes formation in southwestern Europe coincides with the Little Ice Age (LIA) period characterized by pronounced climate variability. Historical sources retrieved from archives also report sand-drift events along the Portuguese coast. The sand invaded many agricultural fields, and settlements, forcing the inhabitants to move elsewhere. The article explores the temporal relationships between sand drift occurrences and climate, as a principal trigger for coastal dune migration. We used historical sources about sand-drift events as documentary proxies to infer the past climate variability on the Portuguese coast. Three spatial scales of climate variability were considered: i) the global climatic variability induced by the cold abrupt events over the last Millennium (LIA); ii) the regional (mesoscale) climate variability (NAO index), and iii) the local climate variability (extreme meteorological events). The paleoclimatic interpretation indicates that drifts in Portugal are related to both NAO modes, providing new insights into coastal dunes dynamics, as a response to natural drivers. However, the analysis of human activity on the coast also allowed us to better understand the relation of the local populations with their environments, highlighting those anthropogenic actions caused an additional disturbance on coastal dune dynamics.