Abstract
Abstract. According to the DISASTER database the 20–28 December 1909 event was the hydro-geomorphologic event with the highest number of flood and landslide cases that occurred in Portugal in the period 1865–2010 (Zêzere et al., 2014). This event also caused important social impacts over the Spanish territory, especially in the Douro Basin, having triggered the highest floods in more than 100 years at the river's mouth in the city of Oporto. This work has a dual purpose: (i) to characterize the spatial distribution and social impacts of the December 1909 hydro-geomorphologic DISASTER event over Portugal and Spain; (ii) to analyse the meteorological conditions that triggered the event and the spatial distribution of the precipitation anomalies. Social impacts that occurred in Portugal were obtained from the Disaster database (Zêzere et al., 2014) whereas the data collection for Spain was supported by the systematic analysis of Spanish daily newspapers. In addition, the meteorological conditions that triggered the event are analysed using the 20th Century Reanalysis data set from NOAA and precipitation data from Iberian meteorological stations. The Iberian Peninsula was spatially affected during this event along the SW-NE direction spanning from Lisbon, Santarém, Oporto, and Guarda (in Portugal), to Salamanca, Valladolid, Zamora, Orense, León, and Palencia (in Spain). In Iberia, 134 DISASTER cases were recorded (130 flood cases; 4 landslides cases) having caused 89 casualties (57 due to floods and 32 due to landslides) and a further total of 3876 affected people, including fatalities, injured, missing, evacuated, and homeless people. This event was associated with outstanding precipitation registered at Guarda (Portugal) on 22 December 1909 and unusual meteorological conditions characterized by the presence of a deep low-pressure system located over the NW Iberian Peninsula with a stationary frontal system striking the western Iberian Peninsula. The presence of an upper-level jet (250 hPa) and low-level jet (900 hPa) located SW–NE oriented towards Iberia along with upper-level divergence and lower-level convergence favoured large-scale precipitation. Finally, associated with these features it is possible to state that this extreme event was clearly associated with the presence of an elongated Atmospheric River, crossing the entire northern Atlantic Basin and providing a continuous supply of moisture that contributed to enhance precipitation. This work contributes to a comprehensive and systematic synoptic evaluation of the second most deadly hydro-geomorphologic DISASTER event that has occurred in Portugal since 1865 and will help to better understand the meteorological system that was responsible for triggering the event.
Highlights
In the Iberian Peninsula, extreme precipitation events that occur during winter (December-January-February-March) have been historically associated with progressive flooding events in the major rivers (Salgueiro et al, 2013), and exceptionally with flash floods that typically occur in small watersheds or urban areas (Llasat et al, 2005; Fragoso et al, 2012) and landslide events
The spatial distribution of the societal impacts will be explored per hydrographic basin whereas the results of the damage indices are presented per region
This study provides the first comprehensive assessment of a major hydro-geomorphologic event that occurred in Iberia in the last 150 years, including: (i) the spatial and temporal characteristics of the societal impacts based on newspapers analysis; (ii) the corresponding spatial distribution of precipitation anomalies using recently digitized daily precipitation data; and (iii) the meteorological conditions that triggered the event using the 20 CR
Summary
These events have been the source of major socio-economic impacts, with human and material damage (Barriendos and Rodrigo, 2006; García et al, 2007; VicenteSerrano et al, 2011; Trigo et al, 2014, 2015). These extreme events have been evaluated based on case studies, like for instance the large flood in the Guadiana River in 1876 (Trigo et al, 2014), the November 1967 flash flood in the Lisbon region (Trigo et al, 2015), the 10 June 2000 flash flood in Catalonia (Llasat et al, 2003), and the 20 February 2010 flash floods in Madeira (Fragoso et al, 2012). Major floods that occurred in the Iberian Peninsula were extensively analysed in the Tagus Basin (Benito et al, 2003; Salgueiro et al, 2013; Machado et al, 2015) and to a lesser extent in the Douro Basin (e.g. Morán-Tejeda et al, 2012)
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