title: Geomorphic status of regulated rivers in the Iberian Peninsula.
abstract: River regulation by dams modifies flow regimes, interrupts the transfer of sediment through channel networks, and alters downstream bed dynamics, altogether affecting channel form and processes. So far, most studies on the geomorphic impacts of dams are restricted to single rivers, or even single river stretches. In this paper we analyse the geomorphic status of 74 river sites distributed across four large basins in the Iberian Peninsula (i.e. 47 sites located downstream of dams). For this purpose, we combine field data with hydrological data available from water agencies, and analyse historical (1970) and current aerial photographs. In particular, we have developed a Geomorphic Status (GS) index that allows us to assess the physical structure of a given channel reach and its change through time. The GS encompasses a determination of changes in sedimentary units, sediment availability, bar stability and channel flow capacity. Sites are statistically grouped in four clusters based on contrasted physical and climate characteristics. Results emphasise that regulation changes river's flow regime with a generalized reduction of the magnitude and frequency of floods (thus flow competence). This, in addition to the decrease downstream sediment supply, results in the loss of active bars as they are encroached by vegetation, to the point that only reaches with little or no regulation maintain exposed sedimentary deposits. The GS of regulated river reaches is negatively correlated with magnitude of the impoundment (regulation). Heavily impacted reaches present channel stabilization and, in contrast to the hydrological response, the distance and number of tributaries do not reverse the geomorphic impact of the dams. Stabilization limits river dynamics and may contribute to the environmental degradation of the fluvial ecosystem. Overall, results describe the degree of geomorphological alteration experienced by representative Iberian rivers mostly because of regulation, challenging the successful long-term implementation of river basin management programmes.
authors.affiliation: Fluvial Dynamics Research Group - RIUS, University of Lleida, Lleida, E-25198 Catalonia, Spain. Electronic address: globera@macs.udl.cat.
authors.forename: G
authors.initials: G
authors.lastname: Lobera
authors.affiliation: Department of Geography, Prehistory and Archaeology, University of the Basque Country, 01006 Vitoria-Gasteiz, Spain.
authors.forename: P
authors.initials: P
authors.lastname: Besné
authors.affiliation: Fluvial Dynamics Research Group - RIUS, University of Lleida, Lleida, E-25198 Catalonia, Spain; Forest Sciences Centre of Catalonia, Solsona, E-25280 Catalonia, Spain; Institute of Geography and Earth Sciences, Aberystwyth University, Ceredigion SY23 3DB, Wales, UK.
authors.forename: D
authors.initials: D
authors.lastname: Vericat
authors.affiliation: Fluvial Dynamics Research Group - RIUS, University of Lleida, Lleida, E-25198 Catalonia, Spain; School of Natural Sciences and Psychology, Liverpool John Moores University, L3 3AF Liverpool, UK.
authors.forename: J A
authors.initials: JA
authors.lastname: López-Tarazón
authors.affiliation: Fluvial Dynamics Research Group - RIUS, University of Lleida, Lleida, E-25198 Catalonia, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Tena
authors.affiliation: Faculty of Science and Technology, University of the Basque Country, 48080 Bilbao, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Aristi
authors.affiliation: Faculty of Education, University of the Basque Country, 01006 Vitoria-Gasteiz, Spain.
authors.forename: J R
authors.initials: JR
authors.lastname: Díez
authors.affiliation: Department of Geography, Prehistory and Archaeology, University of the Basque Country, 01006 Vitoria-Gasteiz, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Ibisate
authors.affiliation: Faculty of Science and Technology, University of the Basque Country, 48080 Bilbao, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Larrañaga
authors.affiliation: Faculty of Science and Technology, University of the Basque Country, 48080 Bilbao, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Elosegi
authors.affiliation: Fluvial Dynamics Research Group - RIUS, University of Lleida, Lleida, E-25198 Catalonia, Spain; Forest Sciences Centre of Catalonia, Solsona, E-25280 Catalonia, Spain; Catalan Institute for Water Research, Girona, E-17003 Catalonia, Spain.
authors.forename: R J
authors.initials: RJ
authors.lastname: Batalla
mesh_terms: D017753:Ecosystem; D055868:Floods; D062070:Hydrology; D045483:Rivers / Q000737:chemistry*; D013030:Spain; D014872:Water Movements
keywords: Dams; Flow regulation; Geomorphic Status; Iberian rivers