DURAO, Vitor C. M.. Análise Urbana de Territórios Construídos: Os Aterros na Baixa e na Frente Ribeirinha de Lisboa, Portugal. []. , 12, 1, pp.17-30. ISSN 1646-8872.

^lpt^aNa antiguidade, o território onde Lisboa foi gradualmente crescendo e tornando-se cidade, era formalmente muito diferente do actual porque o rio Tejo o banhava em parte. As modificações de carácter natural, como o assoreamento do próprio rio, tiveram importância na modificação do território primigénio mas foi a criação, pelo homem, de espaços planos nos terrenos baixos e lodosos onde chegavam ribeiras ao Tejo e sobre as praias e margens do rio que proporcionou tão grande e significativa transformação que se iniciou há mais de dois milénios. A formação/transformação do território teve influência significativa na identidade de Lisboa que já nos séculos XIV-XV se consolidou como assentamento portuário e de comércio marítimo, para o que muito contribuiu a formação ao longo do rio, de amplos espaços planos aptos a essas utilizações. Os espaços planos criados por aterros, tiveram uma efectiva transcendência sobre a forma urbana ao modificar a forma do próprio suporte - o território, que em vez de enseadas e pequenas praias, foi sendo transformado numa plataforma que relegou a cidade para o interior com pouco contacto com o rio, apesar de possibilitar muitos e diversificados usos que facilitaram por sua vez a contínua readaptação da cidade enquanto se afirmava no plano político, económico, ao nível nacional e internacional. A frente ribeirinha, criada fora das muralhas, como espaço de mediação entre a cidade e o rio, tem desde a sua formação características ambíguas, que conduzem a compreendermos este espaço como sendo simultaneamente da cidade e do rio. Estas características mantêm-se na actualidade, porque as muitas transformações formais e de usos que ao longo do tempo aqui se verificaram não alteraram esta característica genética, até a vincaram, devido à actual separação entre a cidade e o rio que é realizada pela linha do caminho-de-ferro e avenida ribeirinha, representantes actuais das muralhas da cidade. Isso diferencia-a da Baixa de Lisboa que apesar de ter nascido também fora das muralhas foi integrada na cidade pelo crescimento da urbe nas colinas envolventes, pelo fecho da muralha da ribeira e por se consolidar o seu tecido urbano que, ao longo do tempo, alteraram tanto o seu carácter de arrabalde que a transformaram no centro da cidade antiga e no espaço de excelência da cidade. Na actualidade, a frente ribeirinha é apreciada pela qualidade urbana e amplitude de vistas que proporciona, pela identidade que fortalece, pelo valor simbólico que lhe é intrínseco, pela sua própria história, pelas funções portuárias, comerciais, lúdicas e turísticas que possibilita mas continua a não ter uma relação de proximidade com a cidade devido à existência da linha de caminho-de-ferro e de vias de grande fluxo de tráfego na sua frente que os planos de melhoramentos da frente ribeirinha não resolvem por não estabelecerem a permeabilidade necessária.^len^aThe territory, in which Lisbon grew up and later became a city, was in Antiquity quite different from its present form, mostly because it was partly flooded by the river Tagus. The natural changes, such as the silting up of the river itself, were important in modifying the original territory but it was the construction of landfills by man, on muddy and low grounds where the brooks flowed in Tagus and on the beaches and river banks, that eventually led to a large and significant transformation that began as far as two millennia ago. Classification of landfill areas result of the crossing of information from the areas where it took place with construction periods. Landfills started in sludge lands located in the downtown creek, later over the beaches and since the end of the 19th century, over the river itself. This practice allowed the creation of plain and vast public areas, managed by the central or municipal administration. Since the 14th century or earlier, this allowed to adapt the city at a functional level to the objectives of the creation of an important hub for international maritime trade, taking advantage of Lisbon’s excellent location. This was a persistent achievement carried on by many generations with a main objective: the political, economical and urban adaptation of Lisbon to the permanent changes in society. The riverfront, outside the walls, while a mediator between the city and the river, has had since its formation ambiguous characteristics that lead to understand this space as belonging both to the city as to the river. These characteristics remain at present because many changes of form and uses that over time have been noticed here did not alter this genetic trait, they actually emphasized it due to the current separation between the city and the river which is made by the railway and riverside avenue, the today’s replicas of the erstwhile city walls. This differentiates it from the downtown city centre that despite being also born outside the walls was integrated into the city by its growth in the surrounding hills, by the river’s walls enclosure and by the consolidation of its urban framework that, over time, altered so deeply its character of suburbs that have transformed it into the old city centre and in the city’s place of excellence. Today, the riverfront is appreciated because of its urban quality and the extent of views that provides, the identity that strengthens, the intrinsic symbolic value, its own history and, ultimately, by the port, commercial, recreational and touristic activities it provides, despite the ambiguity enclosed in this space. However, the Lisbon riverfront and the downtown area are built on landfill terrains which are among the most dangerous places as far as environmental risks are concerned, as demonstrated in the 1755 Earthquake which destroyed part of the city’s buildings and was followed by a tsunami which went through all of the downtown area and was the main cause of death of most of the population. On the one hand, it is necessary to continue to expand the city to these areas, as it happened recently with the 1998 Lisbon World Exposition, on the other hand, it is fundamental that such expansion takes caution and minimizes the impact on the fragile riverfront areas. There is a close relationship between the human accomplishments and the territories where such accomplishments take place. In riverfront or coastal systems and other sensitive areas of the territory, such a relationship becomes more difficult to achieve in a sustainable way but it is also more necessary because of the natural constraints. Both the downtown area and the riverfront where built at a time when knowledge was very different from nowadays and the risks where not perceived in the same way, even with the knowledge that existed at the time. Currently, the intervention in this areas must take into account the concern to decrease the environmental risks, which must take place at a monitoring level, by taking precaution on the interventions, namely on buildings, and also by taking action to help reduce detected problems. It is a culture of balance between the constructive aspects of the territory, the environmental risks and the high historic value of the urban spaces and buildings, a heritage which is the symbol of Lisbon in the world.

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