Influência das alterações climáticas no dimensionamento de passagens hidráulicas
Data
2019-04-03
Título da revista
ISSN da revista
Título do Volume
Editora
Resumo
Em Portugal, o projeto de órgãos de recolha de água pluvial é realizado com base em curvas de Intensidade-Duração Frequência (IDF) cujos parâmetros estão definidos na legislação em vigor, nomeadamente no Decreto Regulamentar nº 23/95 de 23 de agosto (DR 23/95). O DR 23/95 define três regiões pluviométricas em Portugal Continental e os valores dos dois parâmetros das curvas IDF a considerar em cada região. Estas curvas IDF foram desenvolvidas no pressuposto da estacionariedade do regime de precipitação e a partir de séries anuais de intensidade máxima de precipitação para Lisboa (localizadas na região pluviométrica A) e extrapoladas para o resto do país, assumindo que a intensidade média da chuva diminui 20% na região Nordeste (região B) e aumenta 20% nas regiões montanhosas com maior altitude. Contudo, o campo da precipitação apresenta variabilidade espacial incompatível com as regiões pluviométricas definidas e têm vindo a ser observadas alterações no regime de precipitação enquanto as projeções dos modelos climáticos para o futuro sugerem alterações no regime de precipitação, em particular na frequência e intensidade de ocorrência de eventos de precipitação extrema. Este estudo teve como objetivo avaliar as potenciais alterações no regime de precipitação intensa em Portugal e as consequências dos futuros projetos de engenharia, nomeadamente no dimensionamento das passagens hidráulicas (PH) em vias de comunicação. Foram avaliados e comparados os resultados do dimensionamento realizado com dados observados para o passado recente e para diferentes períodos e cenários de clima futuro. A principal contribuição deste estudo consistiu na avaliação do impacto das alterações nos parâmetros climático e a criação de novas curvas IDF. Após o tratamento dos dados e a sua correção, foi possível quantificar e avaliar as alterações no regime de precipitação intensa. Assim, utilizando os novos valores das curvas IDF, procedeu-se ao dimensionamento de duas PH em três regiões diferentes, onde se verificou o impacto que as alterações tiveram no valor da altura da lâmina de água na secção das PH. De forma a concluir que as obras realizadas no passado recente poderão apresentar deficiências de dimensionamento e como deverão ser dimensionadas as futuras obras hidráulicas. Apesar do dimensionamento de PH depender de um grande conjunto de fatores e a altura da lâmina de água ser o resultado de uma combinação de fatores, os resultados permitem concluir que as alterações climáticas projetadas para o futuro implicam alterações no dimensionamento de PH. Averiguou-se ainda uma disparidade no dimensionamento de PH, utilizando os valores dos modelos climáticos em comparação com a legislação vigente, e ainda uma distribuição não homogénea em três regiões distintas, tal como preconizado na legislação em vigor.
In Portugal, the rainwater harvesting project is carried out on the basis of IntensityDuration-Frequency curves (IDF), whose parameters are defined in the legislation, namely Implementing Decree nº 23/95 of August 23 (DR 23/95). This legislation defines three rainfall regions in Portugal and the values of the two parameters of the IDF curves to be considered in each region. These IDF curves were developed on the assumption of stationarity of the precipitation regime and from annual series of maximum precipitation intensity for Lisbon (located in rainfall region A) and extrapolated to the rest of the country, assuming that the average rainfall intensity decreases by 20% in the Northeast region (region B) and increases by 20% in mountainous regions with higher altitude. However, the rainfall field presents high spatial variability incompatible with the defined rainfall regions and changes in the precipitation regime have been observed while the projections of the future climate models suggest changes in the precipitation regime, in particular the frequency and intensity of occurrence of extreme precipitation events. This dissertation aimed to evaluate the potential changes in the intense rainfall in Portugal and the consequences on future engineering projects, mainly in the design of hydraulic passages (PH) in communication routes. The results of the sizing were evaluated and compared with data observed for the recent past, for different periods and future climate scenarios. The main contribution of this study consisted in the evaluation of the impact of the changes in the climatic parameters, and the creation of new IDF curves. After the data treatment and its correction, it was possible to quantify and evaluate the changes in the regime of intense precipitation. Then, using the new values of the IDF curves, two PH were designed in three different regions, where the impact of the changes in the height of the water slide in the PH section was verified. In order to conclude that constructions of the recent past may present design deficiencies and how future hydraulic construction should be designed. Although PH design depend on many factors and the height of water slide is the result of a combination of others factors, the results allow to conclude that future climate changes imply changes in the PH design. It was still ascertained a difference in the PH design, using the values of the climatic models in comparison with current legislation, as well as a nonhomogeneous distribution of the values in three distinct regions, as recommended in the current legislation.
In Portugal, the rainwater harvesting project is carried out on the basis of IntensityDuration-Frequency curves (IDF), whose parameters are defined in the legislation, namely Implementing Decree nº 23/95 of August 23 (DR 23/95). This legislation defines three rainfall regions in Portugal and the values of the two parameters of the IDF curves to be considered in each region. These IDF curves were developed on the assumption of stationarity of the precipitation regime and from annual series of maximum precipitation intensity for Lisbon (located in rainfall region A) and extrapolated to the rest of the country, assuming that the average rainfall intensity decreases by 20% in the Northeast region (region B) and increases by 20% in mountainous regions with higher altitude. However, the rainfall field presents high spatial variability incompatible with the defined rainfall regions and changes in the precipitation regime have been observed while the projections of the future climate models suggest changes in the precipitation regime, in particular the frequency and intensity of occurrence of extreme precipitation events. This dissertation aimed to evaluate the potential changes in the intense rainfall in Portugal and the consequences on future engineering projects, mainly in the design of hydraulic passages (PH) in communication routes. The results of the sizing were evaluated and compared with data observed for the recent past, for different periods and future climate scenarios. The main contribution of this study consisted in the evaluation of the impact of the changes in the climatic parameters, and the creation of new IDF curves. After the data treatment and its correction, it was possible to quantify and evaluate the changes in the regime of intense precipitation. Then, using the new values of the IDF curves, two PH were designed in three different regions, where the impact of the changes in the height of the water slide in the PH section was verified. In order to conclude that constructions of the recent past may present design deficiencies and how future hydraulic construction should be designed. Although PH design depend on many factors and the height of water slide is the result of a combination of others factors, the results allow to conclude that future climate changes imply changes in the PH design. It was still ascertained a difference in the PH design, using the values of the climatic models in comparison with current legislation, as well as a nonhomogeneous distribution of the values in three distinct regions, as recommended in the current legislation.
Descrição
Dissertação de Mestrado em Engenharia Civil
Palavras-chave
Passagens Hidráulicas , Alterações climáticas , Precipitação extrema , Intensidade máxima de precipitação