Arquitetura da água - Cais palafítico da Carrasqueira

Permitindo uma forma de habitar lugares de grande relação com a água, erguem-se um pouco por todo o mundo, sobre as águas de rios, barragens e lagos estruturas palafíticas. Em Portugal, em 1964 na aldeia da Carrasqueira, extremo sul do estuário do Sado, um cais palafítico começava a ser construído por pescadores-agricultores, que ali viviam, para combater mudanças de maré e aceder tanto a água como a terra. O barco, o abrigo e o caminho são os três elementos fundamentais da arquitetura palafítica aqui encontrada, em que a qualidade da água e da terra são determinantes para o assentamento da estrutura neste local. O rio Sado define-se como o limite geográfico e paisagístico da ocupação, é gerador de características únicas que permitem o desenvolvimento de um novo tipo de habitar que surge sobretudo de uma aproximação ao local e aos materiais que dele provêm. A Carrasqueira traduz o paradigma de uma cultura em adaptação contínua às circunstâncias adversas do meio ambiente. A pouca informação sobre o cais e a unicidade construtiva encontrado na estrutura, faz com que seja de elevada pertinência o estudo, sob o ponto de vista construtivo, da arquitetura palafítica da vila piscatória da Carrasqueira, enquanto matéria mutável sensível às mudanças ambientais e espontâneas. Pretende-se clarificar e identificar as singularidades da arquitetura de expressão espontânea da Carrasqueira, intrinsecamente ligada tanto à água do rio Sado, como à terra que a limita e corporiza. Para o estudo construtivo serão elaborados:  Mapas de desenvolvimento do cais;  Um registo fotográfico das estruturas;  Desenhos, realizados originalmente no decorrer desta investigação no local, de forma a criar um maior entendimento da forma de construção entre as diferentes peças e partes de cada uma das estruturas.  Construção de uma estrutura palafítica.  Vídeo, enquanto registo das fases do trabalho prático mostra parte do trabalho desenvolvido no processo construtivo. A produção dos documentos mencionados testemunha um tipo de vida invulgar na História da Arquitetura Portuguesa. O contacto com locais, pescadores, trabalhadores e gentes da terra também ajudará a entender os sistemas construtivos utilizados, pelo conhecimento construtivo por experiência própria, e proximidade das matérias-primas; ABSTRACT: Allowing life in floodplain areas, palaffitic structures take advantage from water, and appear a bit all over the world. The stilts portray a way of living changing and giving identity to the places and population. In Portugal, 1964 year, in Carrasqueira village, located on the southwest Sado’s river, facing the river side and land, a palaffitic piers was built, to fight the tide changing and allowed the population to get as close as they could to water and reach the land easier when they were coming from the fishing activity. The continuously adaptation of lifestyle in order to follow and adjust themselves to nature shows how strong and unique this culture and people are. The boat, the shelter and the paths are the three fundamental elements used in Carrasqueira’s palaffitic architecture. Water and land, construction and nature, this beautiful balance is only possible because of the river and its qualities. Also the time roles an important paper in the process, it changes with the growing of the main materials. This investigation has the goal to study the palaffitic piers of Carrasqueira by the constructivist point of view, as a spontaneous structure that began with the available materials and was continuously changing and adjusting to fit the land, the lifestyle and the needs of the population that was living there. Clarifying and identifying the singularities of this construction is what the study wants to achieve. Maps, photography’s and intensive drawings will be making on the process. A palaffitic structure will be build and the part of the building process will be available for watch on a short-video, filmed by then. The contact with locals will probably assume the biggest part of the work in main to understand their way of thinking and the process of their work.

TECTONIC CONTROLS ON FLUVIAL LANDSCAPE DEVELOPMENT IN CENTRAL-EASTERN PORTUGAL: INSIGHTS FROM LONG PROFILE TRIBUTARY STREAM ANALYSES

This study examines the long profiles of tributaries of the Tejo (Tagus) and Zêzere rivers in central eastern Portugal (West Iberia) in order to provide new insights into the patterns, timing and controls on drainage development during the Pleistocene to Holocene incision stage. The long profiles were extracted from lower order tributary streams associated with the trunk drainage of the Tejo River and one main tributary, the Zêzere River (Fig. 1). These streams flow through a landscape strongly influenced by variations in bedrock lithology (mainly granites and metasediments), fault structures delimiting crustal blocks with distinct uplift rates, and a base-level lowering history (tectonic uplift / eustatic). The long profiles of the tributaries of the Tejo and Zêzere rivers record a series of transient and permanent knickpoints. The permanent knickpoints have direct correlation with the bedrock strength, corresponding to the outcropping of very hard quartzites or to the transition from softer (slates/metagreywaques) to harder (granite) basement. The analyzed streams/rivers record also an older transient knickpoint/knickzone separating: a) an upstream relict graded profile, with lower steepness and higher concavity, that reflects a long period of quasi-equilibrium conditions reached after the beginning of the incision stage; and b) a downstream reach displaying a rejuvenated long profile, with steeper gradient and lower concavity, particularly for the final segment, which is often convex (Fig. 2). The rejuvenated reaches testify the upstream propagation of several incision waves that are the response of each stream to continuous or increasing crustal uplift and dominant periods of base-level lowering by the trunk drainages, coeval of low sea level conditions. The long profiles and their morphological configurations enabled spatial and relative temporal patterns of incision to be quantified for each individual tributary stream. The incision values of streams flowing in uplifted blocks of the Portuguese Central Range (PCR) (ca.380-280 m) indicate differential uplift and are higher than the incision values of streams flowing on the adjacent South Portugal planation surface – the Meseta (ca. 200 m). The normalized steepness index, calculated using the method of Wobus et al. (2006), proved to be sensitive to active tectonics, as lower ksn values were found in relict graded profiles of streams located in less uplifted blocks, (e.g. Sertã stream in the PCR), or in those flowing through tectonic depressions. Fig. 1 – Geological map of the study area. 1 – fluvial terraces (Pleistocene); 2 – sedimentary cover (Paleogene and Neogene); 3 – slates and metasandstones (Devonian); 4 – slates and quartzites (Silurian); 5 – quartzites (Ordovician); 6 – slates and metagreywackes (Precambrian to Cambrian); 7 – slates, metagreywackes and limestones (Precambrian); 8 – granites and ortogneisses; 9 – diorites and gabros; 10 - fault. SFf – Sobreira Formosa fault; Sf – Sertã fault; Pf – Ponsul fault; Gf – Grade fault. The differential uplift indicated by the distribution of the ksn values and by the fluvial incision was likely accumulated on a few major faults, as the Sobreira Formosa fault (SFf), thus corroborating the tectonic activity of these faults. Due to the fact that the relict graded profiles can be correlated with other geomorphic references documented in the study area, namely the T1 terrace of the Tagus River (with an age of ca. 1 Myr), the following incision rates can be estimated: a) for the studied streams located in uplifted blocks of the PCR, 0.38 m/kyr to 0.28 m/kyr; b) for the streams flowing on the South Portugal planation surface, 0.20 m/kyr. The differential uplift inferred between crustal blocks in the study area corroborates the neotectonic activity of the bordering faults, which has been proposed in previous studies based upon less robust data. Fig. 2 – Longitudinal profile of the Nisa stream a tributary of the Tejo River. Note the equilibrium relict profile upstream the older transient knickpoint (hatched line) and the downstream rejuvenated profile (continuous line). Legend: tKP – transient knickpoint; rKp – resistant knickpoint; Mt – schist and phyllite; Gr – granite; Hf – hornfels; Og – orthogneisse. In the inset Distance – Slope plots, fill circles correspond to the relict graded profile, crosses correspond to the rejuvenated profile located downstream the older transient knickpoint (tKP).

Tectonic and lithological controls on fluvial landscape development in central-eastern Portugal: Insights from long profile tributary stream analyses

This study examines the long profiles of tributaries of the Tagus and Zêzere rivers in Portugal (West Iberia) in order to provide new insights into patterns, timing, and controls on drainage development during the Quaternary incision stage. The studied streams are incised into a relict culminant fluvial surface, abandoned at the beginning of the incision stage. The streams flow through a landscape with bedrock variations in lithology (mainly granites and metasediments) and faulted blocks with distinct uplift rates. The long profiles of the analyzed streams record an older transitory knickpoint/knickzone separating (1) an upstream relict graded profile, with lower steepness and higher concavity, that reflects a long period of quasi-equilibrium conditions reached after the beginning of the incision stage, and (2) a downstream rejuvenated long profile, with steeper gradient and lower concavity, particularly for the final reach, which is often convex. The rejuvenated reaches testify to the upstream propagation of several incision waves, interpreted as the response of each stream to increasing crustal uplift and prolonged periods of base-level lowering by the trunk drainages, coeval with low sea level conditions. The morphological configurations of the long profiles enabled spatial and relative temporal patterns of incisions to be quantified. The incision values of streams flowing on the Portuguese Central Range (PCR; ca. 380–150 m) are variable but generally higher than the incision values of streams flowing on the adjacent South Portugal Planation Surface (SPPS; ca. 220–110 m), corroborating differential uplift of the PCR relative to the SPPS. Owing to the fact that the relict graded profiles can be correlated with the Tagus River T1 terrace (1.1–0.9 My) present in the study area, incision rates can be estimated (1) for the streams located in the PCR, 0.38–0.15 m/ky and (2) for the streams flowing on the SPPS, 0.22–0.12 m/ky. The differential uplift inferred in the study area supports the neotectonic activity of the bordering faults, as proposed in previous studies based upon other geological evidence.

Tectonic and lithological controls on fluvial landscape development in central-eastern Portugal: Insights from long profile tributary stream analyses

This study examines the long profiles of tributaries of the Tagus and Zêzere rivers in Portugal (West Iberia) in order to provide new insights into patterns, timing, and controls on drainage development during the Quaternary incision stage. The studied streams are incised into a relict culminant fluvial surface, abandoned at the beginning of the incision stage. The streams flow through a landscape with bedrock variations in lithology (mainly granites and metasediments) and faulted blocks with distinct uplift rates. The long profiles of the analyzed streams record an older transitory knickpoint/knickzone separating (1) an upstream relict graded profile, with lower steepness and higher concavity, that reflects a long period of quasi-equilibrium conditions reached after the beginning of the incision stage, and (2) a downstream rejuvenated long profile, with steeper gradient and lower concavity, particularly for the final reach, which is often convex. The rejuvenated reaches testify to the upstream propagation of several incision waves, interpreted as the response of each stream to increasing crustal uplift and prolonged periods of base-level lowering by the trunk drainages, coeval with low sea level conditions. The morphological configurations of the long profiles enabled spatial and relative temporal patterns of incisions to be quantified. The incision values of streams flowing on the Portuguese Central Range (PCR; ca. 380–150 m) are variable but generally higher than the incision values of streams flowing on the adjacent South Portugal Planation Surface (SPPS; ca. 220–110 m), corroborating differential uplift of the PCR relative to the SPPS. Owing to the fact that the relict graded profiles can be correlated with the Tagus River T1 terrace (1.1–0.9 My) present in the study area, incision rates can be estimated (1) for the streams located in the PCR, 0.38–0.15 m/ky and (2) for the streams flowing on the SPPS, 0.22–0.12 m/ky. The differential uplift inferred in the study area supports the neotectonic activity of the bordering faults, as proposed in previous studies based upon other geological evidence.