The extreme floods in the Ebro River basin since 1600 CE

Abstract

Reliable and complete knowledge of the historical floods is necessary for understanding the extreme hydrological dynamics of the rivers, their natural variability and anthropic changes. In this work we reconstruct the most important floods of the Ebro basin during the last 400 years in different areas of the basin. The analysis is based on four different areas: the Ebro River at Zaragoza, the Cinca River at Fraga, the Segre River at Lleida, and the Ebro River near its mouth at Tortosa. Based on a documentary research, we have first obtained relevant information about the initial conditions (rainfall duration and distribution, snow cover influence) and the maximum flood heights that allow to reconstruct the maximum peak flows by using hydraulic models and to calculate the subbasins contributions. The results show four main types of extreme floods: a) those affecting simultaneously all the subbasins with the highest peak discharges (Ebro at Tortosa in 1787: 0.15 m s km); b) those originated at the western basin, upstream from Zaragoza, with an Atlantic origin, presenting moderate maximum peak flows, caused by persistent winter rainfall and where snowmelt significantly contributes to the flood; c) those originating at the central Pyrenean subbasins, with Mediterranean origin, occurring, with high peak discharges. These mainly occur during autumn as a consequence of rainfalls of different duration (between 3 days and 1 month), and without significant snow thawing and d) finally, less frequent but very intense flash floods events centered in the Lower Ebro area with low peak flows. In terms of frequency, two different periods can be distinguished: from 1600 until 1850, the frequency of events is low; since 1850 the frequency of events is clearly higher, due to an increase of the climatic variability during last stages of the Little Ice Age. From the 1960's reservoirs construction modifies discharges regime.

Hydrogeomorphic Impacts of Floods in a First-Order Catchment: Integrated Approach Based on Dendrogeomorphic Palaeostage Indicators, 2D Hydraulic Modelling and Sedimentological Parameters

“…The two-dimensional IBER model (version 2.5.1) was applied to the hydraulic modelling of the selected reach [53]. This is an established software that was applied to the estimation of palaeoflood discharges of small [18] to large rivers [35,45]. An unstructured mesh, which comprised almost 200,000 elements with an average size of 0.3 m, was developed over the reach.…”

“…As mentioned, two-dimensional hydraulic models have been successfully applied to peak discharge reconstructions in ungauged or poorly gauged catchments of various sizes and environments [18,[32][33][34][35]. This peak discharge is mostly defined not as the single deterministic value but rather as a range of values due to uncertainties inherent in the process of the estimation [36].…”

Potential and Limitations of Open Satellite Data for Flood Mapping

“…The land use of the floodplain is primarily cultivated land, urban areas (Zaragoza, with approximately 600,000 inhabitants and other minor towns) and natural vegetation along the riverbanks. The floodplain is affected by periodic floods, particularly in the winter and spring seasons with several extreme events [47]. In the February-March 2015 period, several events of heavy rainfall occurred in the upper and middle basin of the Ebro River [48].…”

Soil particle size distribution and induced soil carbon transport by ephemeral gully erosion in Mediterranean mountain arable land

“…In 2012, the fallow cereal field selected for this study experienced an exceptional rainfall event of long duration (19 to 21 October) and high intensity (between 200 and 260 mm). The exceptional rainfall event mainly happened in the French and Spanish central western Pyrenees and in the central part of the Ebro River basin (Figure 1a), which is one of the great rivers of the Mediterranean basin and has a mean annual discharge of 428 m 3 s ‐1 (Balasch et al, ). The most intense rainfall was concentrated in the headwaters of the Aragón and Gállego Rivers and in a small sector of the central part of the Ebro Basin, in the region of Las Cinco Villas (Lana‐Renault et al, ; Serrano‐Muela et al, ) where the field is located.…”