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River Flow 2014, p. 1711-1719

DOI: 10.1201/b17133-228

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Floods in the Guadalquivir river (Southern Spain)

This paper is available in a repository.
This paper is available in a repository.

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Postprint: policy unknown
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Abstract

The impacts of high-stage fluvial discharge events on the Upper Guadalquivir River (Southern Spain) as well as the Guadalbullón and Guadiana Menor tributaries are studied in this work. Better insight into the recent morphological evolution of the rivers was derived from consideration of the association of sediment deposits, modelled two-dimensional hydraulic conditions, riparian vegetation and instrumental data. We alert on the continuous channel narrowing of Guadalquivir River and the coloni-sation of bars by non-flexible riparian vegetation as observed in high-resolution orthophotos from 1956 up to present days, opposite to non-regulated tributary widen (e.g. Guadabullón river). Highly-accurate two-dimensional numerical simulations in the presence of riverbank defences and dams, which are veri-fied with radar images from Terrasar-X satellite, show that the predominant mode of sediment transport (bedload) can be impeded by actual dams promoting sedimentation, higher water surface elevation during floods and higher risk. The main anthropogenic factors identified in the present study that increase the flood potential are: the land use legacy in the basin since Roman period, soil management and destruction of the vegetation cover in rural areas, owing to larger runoff and contributing to reservoir sedimentation, soil and gully erosion processes; non-optimised hydraulic structures that promote aggradation in the main channel and the formation of slackwater deposits that are later colonised by non-flexible riparian vegeta-tion, decreasing consequently the water drainage capacity of the Guadalquivir River. weeks leading to slowly variations of the water level and hydrograph. Flood impacts and damages were as severe as for the most catastrophic episode occurred in 1963 that routed 2850 m 3 s −1 , i.e. between fifty and one hun-dred percent more than during recent floods, cor-responding with return periods of about 50–100 yr. Taking into account the previous series of floods during years 20–30 and 58–63, and the future sce-narios affected by climate change (Solomon et al. 2007, Vargas-Amelina and Pindado 2013), the risk of occurrence of new events requires mitigation strategies based on better knowledge of flooding processes. So this work is aimed at better under-standing the circumstances that contributed to increase the impacts of recent floods with lower peak flow rates than 1963 yr by presenting an inte-grated description and multidisciplinary study of