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Alteração do uso do solo e condições de escoamento na sub-bacia do rio de Loures
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Orientador(es)
Resumo(s)
As alterações no uso do solo têm como consequência a substituição de áreas permeáveis para impermeáveis, aumentando o escoamento superficial na bacia hidrográfica. Estes episódios podem ter influência natural e humana, sendo esta última o ponto central deste trabalho, o qual tem como principal objetivo estudar as dinâmicas de alteração do uso e ocupação do solo ocorridas nos últimos 30 anos e a sua influência na ocorrência de cheias, na bacia hidrográfica do rio de Loures.
Durante o desenvolvimento do projeto foi essencial a modelação hidrológica com o programa HEC-HMS onde, a partir de cenários de precipitação intensa, e por meio de métodos cinemáticos, estimaram-se os caudais de ponta de cheia, considerando o impacto das dinâmicas territoriais na impermeabilização do solo, conseguindo assim aferir-se a sua influência no que toca à infiltração da água e escoamento superficial, com reflexo nos picos de cheia e nos caudais específicos.
Pela análise dos resultados obtidos através da modelação hidrológica, verificamos através dos hietogramas e hidrogramas de cheia, as perdas iniciais por infiltração, bem como os caudais de ponta de cheia e os caudais específicos de cada sub-bacia. Entre 1995 e 2018, a região que engloba a bacia do rio de Loures sofreu alterações significativas, no que toca ao uso e ocupação do solo, tendo-se verificado um aumento de 9,6 % de áreas artificializadas. Registou-se também o aumento de caudal específico na secção crítica meridional da bacia hidrográfica, na ordem dos 0,28 m3/s.
Tendo a situação deste local piorado, com o aumento significativo da artificialização, sobretudo em tecido urbano, durante o período de 1995 até 2018, conclui-se pela ocorrência do agravamento das condições de escoamento e, consequentemente pelo aumento da propensão para ocorrência de cheias na bacia hidrográfica do rio de Loures.
Changes in land use result in the replacement of permeable areas with impervious ones, increasing the amount of surface runoff in the watershed. These episodes can have both natural and human influences, and human influence is the central point of this work, with the main objective being to study the dynamics of changes in land use and occupation that have occurred over the last 30 years and their influence on the occurrence of floods in the Loures river basin. During the development of the project, hydrological modeling with the HEC-HMS software was essential. Using intense rainfall scenarios and kinematic methods, peak discharges were estimated, considering the impact of territorial dynamics on soil imperviousness, thus gauging their influence on water infiltration and surface runoff, with a reflection on peaks discharges and specific discharges. By analyzing the results obtained from the hydrological modelling, we can verify the initial losses due to infiltration, as well as the peak discharges and the specific flows for each sub-basin through the hyetograms and flood hydrographs. Between 1995 and 2018, the region encompassing the Loures river basin underwent significant changes in terms of land use and occupation, there was a 9,6% increase in artificialized areas. There was also an increase in the specific flow in the critical southern section of the river basin, in the order of 0.28 m3/s. As the situation at this location has worsened, with a significant increase in impervious areas, especially in urban areas, during the period from 1995 to 2018, it is concluded that runoff conditions have worsened and, consequently, the possibility of flooding in the Loures river watershed has increased.
Changes in land use result in the replacement of permeable areas with impervious ones, increasing the amount of surface runoff in the watershed. These episodes can have both natural and human influences, and human influence is the central point of this work, with the main objective being to study the dynamics of changes in land use and occupation that have occurred over the last 30 years and their influence on the occurrence of floods in the Loures river basin. During the development of the project, hydrological modeling with the HEC-HMS software was essential. Using intense rainfall scenarios and kinematic methods, peak discharges were estimated, considering the impact of territorial dynamics on soil imperviousness, thus gauging their influence on water infiltration and surface runoff, with a reflection on peaks discharges and specific discharges. By analyzing the results obtained from the hydrological modelling, we can verify the initial losses due to infiltration, as well as the peak discharges and the specific flows for each sub-basin through the hyetograms and flood hydrographs. Between 1995 and 2018, the region encompassing the Loures river basin underwent significant changes in terms of land use and occupation, there was a 9,6% increase in artificialized areas. There was also an increase in the specific flow in the critical southern section of the river basin, in the order of 0.28 m3/s. As the situation at this location has worsened, with a significant increase in impervious areas, especially in urban areas, during the period from 1995 to 2018, it is concluded that runoff conditions have worsened and, consequently, the possibility of flooding in the Loures river watershed has increased.
Descrição
Palavras-chave
Cheias Precipitação Uso e ocupação do solo Infiltração Escoamento