A study by the University of Aveiro (UA) that integrated numerical models with high spatial resolution, adapted to each place, concludes that the water level “will rise, but without catastrophism.”
According to this study, in the Tagus estuary, in the year 2055, 10.9 square kilometers of urban areas will be flooded due to the combined effect of the tide, the rise in the mean sea level and as a consequence of extreme meteorological phenomena, which can occur once every 100 years.
By 2100, that figure will be 14.9 square kilometers, and the researchers predict that about 66 square kilometers of agricultural and grazing land will be flooded by 2055.
It is estimated that more than 6,500 people could be affected by the flooding of the Tagus estuary in 2055. By 2100 the number of people affected will exceed 12,500.
Likewise, in terms of urban areas, in the Ria de Aveiro there will be 6.4 square kilometers of flooded area in 2055 and eight in 2100, at the mouth of the Mondego 1.4 in 2055 and 1.7 in 2100 in the estuary do Sado 5.6 in 2055 and 6.7 until 2100 and in Ria Formosa 3.6 square kilometers in 2055 and 4.4 until 2100.
“The numbers are not alarming, despite all the damage resulting from the loss of territory”, considers João Miguel Dias, from the University of Aveiro.
As for the agricultural and pasture areas flooded, and the number of inhabitants affected, the calculations of the research team point to 57 square kilometers in 2055 and 62.6 in 2100, with more than 10,500 people affected in 2055 and 13,100 in 2100, in Ría de Aveiro, while in Foz do Mondego with 33 square kilometers in 2055 and 36 in 2100, with around 600 people affected in 2055 and 800 in 2100.
For the Sado Estuary, the forecast is 43.5 square kilometers in 2055 and 44.9 by 2100, with more than 2,500 people affected in 2055 and some 5,000 by 2100, while for the Ria Formosa it is 3.6 kilometers square by 2055 and 4.4 by 2100, with some 2,200 people affected by 2055 and 2,500 by 2100.
The researchers point out that multiple factors intervene in the value of the maximum water level in estuaries, derived from the increase in the average sea level due to climate change.
“The average rise in sea level of half a meter, for example, does not necessarily imply a rise of half a meter in the maximum water level in the entire estuary,” they say.
“The forecasts of flooding in national estuaries that have been released are exaggerated and considerably higher than those obtained in this study, since they result from works that ignore the physical processes that determine the propagation of the flood wave through the estuaries,” explains the researcher from the Center for Environmental and Sea Studies (CESAM) and the Department of Physics (dfis).
Another member of the research team, Carina Lopes, states that it was found that “the energy of the flood wave is strongly dissipated during the flooding of the tidal and alluvial plains and that this dissipation translates into a reduction in the maximum water level, and consequently of the extension of the flood”.
“This mechanism is particularly important in the Ria de Aveiro and in the Tagus and Mondego estuaries, which have extensive tidal and alluvial plains,” says Carina Lopes.
The size of the estuary mouth is another factor that determines the amplitude of the flood wave: “we found that the flood wave is strongly attenuated during its propagation along narrow and shallow mouths, as is the case of the estuary of Aveiro and the Mondego estuary”, say the researchers.
The UA researchers also found that “the flood wave is amplified in the regions upstream of the entrance to the Tagus and Sado estuaries, due to their divergent geometric configuration.”
However, they note, “this amplification does not translate into an increase in the flooded area, since the regions adjacent to the entrance of these estuaries have relatively high levels.”
The study, in which Magda Sousa, Américo Ribeiro, Humberto Pereira, João Pinheiro and Leandro Vaz, all CESAM/dfis researchers, also participated, seeks to provide “a global vision of the physical mechanisms that determine the magnitude of floods in estuaries with different geomorphological characteristics” and advises the application of numerical models instead of simplified models of flooding in estuarine systems.
Source: Observadora
