ANALYSIS AND MODELLING OF SEDIMENT TRANSFER IN MEDITERRANEAN RIVER BASINS Suspended sediment dynamics during flushing flows in a large impounded river (the lower River Ebro) Alvaro Tena & Damià Vericat & Ramon J. Batalla Received: 27 September 2013 /Accepted: 16 September 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract Purpose The aim of this work was to improve the understand- ing of the spatial and temporal dynamics of suspended sedi- ment transport during flushing flows in a large regulated river, the lower River Ebro (NE Spain). Materials and methods Relationships between sediment and discharge (i.e. discharge (Q)–suspended sediment concentra- tions (SSC)) were examined during six flushing flows using continuous discharge and turbidity records obtained at six monitoring sections distributed along the lower Ebro River for the 2008–2011 period. Results and discussion Analyses revealed marked spatial and temporal patterns. At the spatial scale, the Q–SSC relation- ships were mostly influenced by the different routing velocity of discharge and sediment waves. At the upstream sections, the sediment peak usually preceded peak discharge (i.e. clock- wise loop); however, flow routing through the 85-km channel length tends to increase the lag between them, modifying the hysteresis towards counter-clockwise patterns in the down- stream direction. At the temporal scale, the season when the artificial releases were performed strongly influenced the sed- iment availability, with similar-magnitude flushing flows gen- erating higher sediment peaks in autumn than in spring. Conclusions These results are of great interest in order to reinforce the flushing flows programme in the lower Ebro River, so as to help achieve the sustainability of the riverine and deltaic ecosystems. Keywords Dams . Flushing flows . Hysteresis . River Ebro . Suspended sediment transport 1 Introduction Knowledge of sediment fluxes in river basins, as well as their controlling parameters, is fundamental to understand the over- all behaviour of rivers. A deeper understanding of sediment transport dynamics is crucial for many catchment manage- ment purposes (Alexandrov et al. 2003), from the assessment of contaminants associated with fluvial sediments (Konhauser et al. 1997) to the restoration of fluvial sediment-dependent habitats such as riparian and estuarine wetlands (Steiger et al. 2001). In impounded rivers, sediment transfer between source and depositional areas is disrupted by dams. This alters the processes which control the sediment transport below the dams. For instance, variables whose influence on sediment transport in natural rivers is fundamental (i.e. rainfall intensity, plant cover, sediment source connectivity, etc.) become less important downstream of the dams. The main processes con- trolling sediment transport downstream of the dams are nota- bly influenced by channel hydraulics and energy conditions, e.g. bed and bank erosion (Kondolf 1997; Vericat and Batalla 2006), conveyance and sediment storage (Asselman 1999; Bača 2008; Tena et al. 2012), breakup and re-establishment of the armour layer (Vericat et al. 2006), as well as tributary Responsible Editor: Axel Bronstert Electronic supplementary material The online version of this article (doi:10.1007/s11368-014-0987-0) contains supplementary material, which is available to authorized users. A. Tena (*) : D. Vericat : R. J. Batalla Fluvial Dynamics Research Group–RIUS, Department of Environmental and Soil Sciences, University of Lleida, 25198 Lleida, Catalonia, Spain e-mail: alvaro.tena@macs.udl.cat D. Vericat : R. J. Batalla Forest Sciences Centre of Catalonia—CTFC, 25280 Solsona, Catalonia, Spain R. J. Batalla Catalan Institute for Water Research—ICRA, 17003 Girona, Catalonia, Spain J Soils Sediments DOI 10.1007/s11368-014-0987-0