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The deadliest storm of the 20th century striking Portugal: flood impacts and atmospheric circulation
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Orientador(es)
Resumo(s)
The deadliest storm affecting Portugal since, at least, the early 19th century, took place on the 25 and 26
November 1967 causing more than 500 fatalities. This work aims to assess the most relevant aspects of
this episode. This includes describing the associated meteorological conditions and key hydrological
characterisation such as the level of exceptionality of the observed precipitation at different temporal
scales, or the estimation of peak discharge values in 20 small river catchments affected. Additionally,
from a human impact perspective we provide a full account of all the main socio-economic impacts, particularly
the numbers and location of victims (dead, injured, homeless and evacuated).
Based on the sub-daily time series of a representative station, and its Intensity–Duration–Frequency
curves, we have found that the exceptionality of this rainfall event is particularly linked to rainfall intensities
ranging in duration from 4 to 9 h compatible with return periods of 100-years or more. This range of
time scale which are similar to the estimated concentration time values of the hydrographic basins
affected by the flash flood event. From a meteorological perspective, this episode was characterised by
strong convection at the regional scale, fuelled by high availability of moisture over the Lisbon region
associated with a low pressure system centered near Lisbon that favoured the convective instability.
Most victims were sleeping or were caught by surprise at home in the small river catchments around
the main Lisbon metropolitan area. The majority of people who died or who were severely affected by the
flood lived in degraded housing conditions often raised in a clandestine way, occupying flood plains near
the stream beds. This level of destruction observed at the time is in stark contrast to what was observed
in subsequent episodes of similar amplitude. In particular, since 1967 the Lisbon area, was struck by two
comparable intense precipitation events in 1983 and 2008 but generating considerably fewer deaths and
evacuated people.
Descrição
Palavras-chave
Extreme precipitation Lisbon Flash floods Natural hazard Atlantic storms
Contexto Educativo
Citação
Trigo, Ricardo M., Ramos, Catarina, Pereira, Susana da Silva, Ramos, Alexandre M., Zêzere, José, & Liberato, Margarida L.R. (2016). The deadliest storm of the 20th century striking Portugal: flood impacts and atmospheric circulation. Journal of Hydrology 541, 597–610. https://doi.org/10.1016/j.jhydrol.2015.10.036
Editora
Elsevier