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Floods in southern Portugal: their physical and human causes, impacts and human response
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Autores
Orientador(es)
Resumo(s)
Floods have been the most deadly natural disasters in Portugal during the last century,
followed by earthquakes. The type of flood known as a ‘progressive flood’ mainly affects the larger
basins, such as that of the Tagus River, and results in a large inundated area. These floods are caused
by heavy rains associated with a westerly zonal circulation that may persist for weeks. The system of
dams within the basin reduces the frequency of flooding, but cannot ‘tame’ the river. The dam system
has even contributed to an increase in the peak flow, as in the 1979 flood. Nevertheless, these floods
are not a danger for the human population. In contrast, flash floods are more dangerous and deadlier
than progressive floods, as demonstrated in 1967 and 1997. They affect the small drainage basins and
are caused by heavy and concentrated rainfall, created by convective depressions (active cold pools
or depressions caused by the interaction between polar and tropical air masses), active in the south
of the country, in the Lisbon region, Alentejo and the Algarve. Deforestation, soil impermeability,
chaotic urbanization, building on floodplains, the blockage of small creeks or their canalisation,
and the building of walls and transverse embankments along the small creeks all contribute to the
aggravation of this kind of flood.
Descrição
Palavras-chave
Dams Flood types Fluvial regime Large and small drainage basins Portugal
Contexto Educativo
Citação
Ramos, C., & Reis, E. (2003). Floods in southern Portugal: their physical and human causes, impacts and human response. Mitigation and Adaptation Strategies for Global Change, 7, 267–284. https://doi.org/10.1023/A:1024475529524
Editora
Springer