The 2-3 November 2015 flood of the Sió River (NE Iberian Peninsula): a flash flood that turns into a mudflow downstream / J. Balasch, J. Ruiz, R. Rodríguez, J. Tuset, X. Castelltort, M. Barriendos, D. Pino, J. Mazon



En: European Geosciences Union General Assembly. "Geophysical Research Abstracts". Viena : [s.n.], 2016, p. 1


Historical and recent evidence shows that many floods in the interior of Catalonia (NE Iberian Peninsula) usually have such a great sediment load that can even alter the hydraulic behaviour of the flow. This is especially true in catchments with a great proportion of agricultural soils, which are the main source of sediment. The night of 2-3 November 2015 torrential rains fell on the headwaters of the Sió River catchment (508 km2); the subsequent flood caused four deaths and many damages along the stream. The hydrological, hydraulic and sedimentary characteristics of this recent flood have been analysed in order to gain a better insight on the characteristics of the major historical floods in the same catchment. The rainfall height on the headwaters was between 139 and 146 mm in ten hours, with a maximum intensity of about 50 mm h-1. In the rest of the catchment it rained much less (22-71 mm). The agricultural soils in the headwaters show evidence of intense erosion by laminar and concentrated Hortonian overland flow in their superficial layer (Ap1; 10 cm), which uncovered the more compact underlying layer (Ap2). The peak flow in the headwaters (Oluges) was 90 m3 s-1 (that is, a specific peak flow near 1 m3 s-1 km-2) and it diminished downstream: 40 m3 s-1 in the centre of the catchment (Oluges + 27 km) and 15 m3 s-1 in the outlet (Oluges + 54 km). The suspended sediment load was 10-15.