Historical flash floods retromodelling in the Ondara River in Tàrrega (NE Iberian Peninsula)

Flash floods in the Ondara River have caused many fatalities and damages in the town of Tàrrega in the last 400 yr. Unfortunately, no flow records are available. <br><br> However, floods can sometimes be reconstructed thanks to available historical information: limnimarks, written accounts and archaeological surveys. Indeed, from these data and using the retromodelling method on three different scenarios to take into account morphology changes, the peak flows of the seven greatest floods occurred in Tàrrega since the 17th century were estimated. <br><br> The results showed that the heaviest flood's specific peak flow (10.7 m<sup>3</sup> s<sup>−1</sup> km<sup>−2</sup>) ranks among the highest ever modelled or measured in similar-sized catchments in the Western Mediterranean region. The results pointed out, as well, that the changes in channel's morphology (mainly, the disappearance of a mediaeval bridge under sediment) caused by one of the floods increased the hydraulic capacity of a crucial cross-section. All this resulted in modest floods invading the town less often, but with much faster and, thus, more destructive flows. <br><br> A preliminary estimation of the results' uncertainty was 4% for great floods and 18% for modest floods. <br><br> The reconstructed peak flows will be introduced in a database for a future use in climatic and hydrological studies

Low-frequency atmospheric variability patterns and synoptic types linked to large floods in the lower Ebro River basin

This study analyzes the atmospheric variability that caused the largest floods affecting the town of Tortosa in the mouth of the Ebro River (northeast Iberian Peninsula). The Tortosa flood database and flood marks in the nearby town of Xerta are used to define the more relevant flooding episodes (discharges > 2900 m3s−1) of the 1600-2005 period. We explore the atmospheric variability based on low-frequency patterns and synoptic types applying a multivariable analysis to grids at sea-level pressure and geopotential at 500 hPa provided by the 20th Century V3 Reanalysis Project for the instrumental period (since 1836). Output from the Last Millennium Ensemble Project was used to analyze the sea-level pressure over the pre-instrumental period (before 1836). Our analysis includes 33 flood episodes. Four synoptic types are related to floods in Tortosa since 1836, characterized by low-pressure systems that interact with the Mediterranean warm air-mass and promote the atmosphere destabilization. Flooding in Tortosa is related to relative high values of solar activity, positive Northern Hemisphere temperature anomalies and NAO in positive phase. This indicates that the major floods are related to zonal atmospheric circulations (west to east cyclone transfer). During winter, the main impact of the floods is located at the western part of the basin, while the Pyrenean sub-basins are affected during autumn. The major finding is that similar flood behavior is detected since 1600, improving our understanding of past climates, enhancing the knowledge base for some aspects and impacts of climate change and reducing uncertainty about future outcomes

Reconstruction of the 1874 <i>Santa Tecla</i>'s rainstorm in Western Catalonia (NE Spain) from flood marks and historical accounts

The Santa Tecla flash flood, a very heavy event occurred in western Catalonia (NE Spain) in 1874, was reconstructed with hydraulic and hydrological modelling tools in three basins. The hydrograph obtained in a first step and the basin soil moisture information ultimately allowed the estimation of the range of the rainstorm magnitude which caused the flash flood. The reconstruction of historical floods has proved useful to improve the flood probability analysis, especially in ungauged basins

Low-Frequency Atmospheric Variability Patterns and Synoptic Types Linked to Large Floods in the Lower Ebro River Basin

This study analyzes the atmospheric variability that caused the largest floods affecting the town of Tortosa, Spain, in the mouth of the Ebro River (northeast Iberian Peninsula). The Tortosa flood database and flood marks in the nearby town of Xerta are used to define the more relevant flooding episodes (discharges.2900 m s) of the 1600-2005 period. We explore the atmospheric variability based on low-frequency patterns and synoptic types applying a multivariable analysis to grids at sea level pressure and geopotential at 500 hPa provided by the twentieth-century V3 Reanalysis Project for the instrumental period (since 1836). Output from the Last Millennium Ensemble Project was used to analyze the sea level pressure over the pre-instrumental period (before 1836). Our analysis includes 33 flood episodes. Four synoptic types are related to floods in Tortosa since 1836, characterized by low pressure systems that interact with the Mediterranean warm air mass and promote atmospheric destabilization. Flooding in Tortosa is related to relative high values of solar activity, positive Northern Hemisphere temperature anomalies, and NAO in positive phase. This result indicates that the major floods are related to zonal atmospheric circulations (west-to-east cyclone transfer). During winter, the main impact of the floods is located at the western part of the basin, and the Pyrenean subbasins are affected during autumn. The major finding is that similar flood behavior is detected since 1600, improving our understanding of past climates, enhancing the knowledge base for some aspects and impacts of climate change, and reducing uncertainty about future outcomes. SIGNIFICANCE STATEMENT: A total of 33 large floods (.2900 m s) were registered since 1600 in Tortosa, Spain, located at the mouth of the Ebro River (northeast Iberian Peninsula). They occur associated with low pressure systems that interact with the Mediterranean warm air mass promoting atmospheric destabilization. The floods in Tortosa are also associated with other important processes occurring at significantly longer time scales: high values of solar activity, positive Northern Hemisphere temperature anomalies, and NAO in positive phase, indicating that the major floods are related to zonal atmospheric circulations. The major finding is that we detect similar flood behaviors since 1600, improving our understanding of past climates, enhancing the knowledge base for some aspects and impacts of climate change, and reducing uncertainty about future outcomes

The “Prediflood” database of historical floods in Catalonia (NE Iberian Peninsula) AD1035–2013, and its potential applications in flood analysis

“Prediflood” is a database of historical floods that occurred in Catalonia (NE Iberian Peninsula), between the 11th century and the 21st century. More than 2700 flood cases are catalogued, and more than 1100 flood events. This database contains information acquired under modern historiographical criteria and it is, therefore, suitable for use in multidisciplinary flood analysis techniques, such as meteorological or hydraulic reconstructions

Geomorphic Hazards in Spain

An overview of the main geomorphic hazards in Spain is presented. For each one of the processes analysed (floods, landslides, sinkholes, and coastal hazards), a brief description of their distribution, socioeconomic effects, and main causes is given. The main lines of research undertaken in recent times on these hazards, including development of new tools or techniques, are discussed. Finally, legislation and land-use planning measures for mitigation of risks due to such processes are described