Browsing by Author "Prada, S."
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- O inventário nacional do património geológico: abordagem metodológica e resultadosPublication . Prada, S.; PRADA, SUSANAA existência de um inventário nacional de património geológico é fundamental para se poderem implementar estratégias de geoconservação. Este trabalho apresenta a metodologia usada no desenvolvimento do mais completo inventário de geossítios, realizado até ao momento em Portugal, assim como os principais resultados obtidos. O inventário vai integrar o Sistema de Informação do Património Natural e o Cadastro Nacional dos Valores Naturais Classificados, ambos geridos pelo Instituto de Conservação da Natureza e da Biodiversidade.
- Tectónica da Ponta de São Lourenço, Ilha da MadeiraPublication . PRADA, SUSANA; Madeira, J.; Fonseca, P. E.; Silveira, A.; Prada, S.; Rodrigues, C. F.The tectonics of Madeira Island is, in its generality, still quite unknown. A structural characterization togeth er with the formulation of hypothesis contributing to this problematic is, in our opinion, of extreme impor tance to relate this context with the regional and global tectonic models. The Ponta de São Lourenço, in Madeira Island, exhibited an unusual situation for studies of this nature, due to the diversity of lithologies found there, as well as the presence of excellent natural cross-sections originated by marine erosion. In terms of tectonics, the studied area is dominated by accidents of distensive nature, organized in two out standing families: E-W and NW-SE. From these structures the most important are: a dyke swarm, very dense and with an approximate WNW-ESE direction; and a fracture pattern where we highlight the Seixal Machico (N50ºW, subvertical), Pedra Furada (E-W, 70ºN) and Estreito (N50ºW, 70ºN) faults. The analysis of those structures suggests a distensive tension field with minimum compression axis (s3) oriented with NNE-SSW direction, and maximum compression axis (s1) subvertical, related to the weight of the lytho static column (gravitical origin). This tension field suggests a hotspot rift model, similar to the one proposed by WALKER (1987), for shield volcanoes of the Hawaiian kind. This tension field seems to have a constant space-temporal orientation, with probable neotectonic activity. It is also proposed a tectonic control of vol canism, confirmed by the presence of aligned volcanic structures with the same directions previously described. It is equally proposed the existence of a structural control of the coast line and the landforms in the area.
- The use of detention basins to reduce flash flood hazard in small and steep volcanic watersheds - a simulation from Madeira IslandPublication . Vieira, I.; Barreto, V.; Figueira, C.; Lousada, S.; Prada, S.Madeira, like many mountainous volcanic islands, is susceptible to flash floods. Throughout its history, about 40 large events resulted in more than 1200 victims and countless damages. Recently, urban areas expanded greatly, leading to a higher exposure of the population to flash floods. In order to analyse ways to reduce vulnerability and decrease hazard in the urbanised, flash flood prone watershed of the Machico River, the construction of detention basins (DB) is simulated. A hydrological and hydraulic model was performed to determine if they would be a viable option to protect downstream populations. Modelling suggests that two 12 m high outlet structures, and a storage capacity of 111 298 m3 (DB1) and 121 095 m3 (DB2), would reduce peak discharge by 72%, from a precipitation event with a return period of 100 years. Two identified sen sitive Sections (S) had their fill rates reduced from 130.6% to 79.6% (S1) and from 128.6% to 33.4% (S2), thus preventing channel overflow. A concise eco nomic analysis was made in terms of implementation and maintenance costs, as well as a SWOT analysis highlighting that DB should be regarded as a viable engineering solution to reduce vulnerability to flash floods hazards in volcanic islands with small, steep, and urbanised watersheds.