Numerical study of one of the major natural disasters in Iberia in the XX century

What is it about?

A hindcast of the strongest storm that occurred in the 20th century in the Iberian coast was carried out using a suite of atmospheric, oceanic and estuarine models. The models were carefully validated with available data, and the validation was complemented by sensitivity analyses. Overall, the models are shown to provide an accurate simulation of the coastal hydrodynamics, and, in particular, of the water levels and inundation in the Tagus estuary.

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Why is it important?

It is the first numerical study performed for the atmospheric and ocean conditions of the storm of 1941. The quantitative and qualitative validations show that the models adequately reproduce this type of extreme events. It is shown that the regional surge and the setup induced by swell are the two main drivers of the inundation. In particular, the modulation of the wave setup by tides induces a semi-diurnal signal which is amplified by resonance inside the estuary. The ability of the model to reproduce a storm that occurred so many years ago, in 1941, opens interesting perspectives to investigate other extreme events. The total area threatened by inundations grows from 25 km2, if the 1941 event were to happen today, to 77 km2 if sea level rises by 0.5 m. A present-day worst case scenario, obtained by combining the 1941 storm with an extreme tidal range, would flood over 40 km2 of agricultural land. These results will support risk analyses and the definition of adaptation measures to cope with future extreme events.