Breakup and reestablishment of the armour layer in a large gravel-bed river below dams: The lower Ebro

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dc.contributor.author Garcia, C.
dc.contributor.author Vericat, Damià
dc.contributor.author Batalla, Ramon J.
dc.date.accessioned 2011-04-21T14:14:01Z
dc.date.available 2011-04-21T14:14:01Z
dc.date.issued 2006
dc.identifier.citation Garcia , C , Vericat , D & Batalla , R J 2006 , ' Breakup and reestablishment of the armour layer in a large gravel-bed river below dams: The lower Ebro ' Geomorphology , pp. 122-136 . en
dc.identifier.other PURE: 159117
dc.identifier.other dspace: 2160/6696
dc.identifier.uri http://hdl.handle.net/2160/6696
dc.description Vericat, D., Batalla, R.J., Garcia, C. (2006). Breakup and reestablishment of the armour layer in a large gravel-bed river below dams: The lower Ebro. Geomorphology, 76: 122-136 Sponsorship: Spanish Ministry of Science and Technology funding REN2001-0840-C02-01/HID en
dc.description.abstract Changes in armour layer during floods under supply limited conditions are little known. This paper describes the breakup and the reestablishment of the bed armour layer in the regulated gravel-bed Ebro River during a flooding period. The study was conducted over a 28-km study reach from 2002 to 2004. The surface, subsurface and bed load grain size distribution constitute the bases for the analysis of bed-armouring dynamics. The results indicate that the magnitude of floods controlled the degree of armouring of the river bed. The initial mean armouring ratio was 2.3, with maximum values reaching 4.4. Floods in the winter of 2002–2003 (Q8) caused the breakup of the armour layer in several sections. This resulted in the erratic bed load pattern observed during the December 2002 flushing flow and in the increase in bed load transport during successive events. Most grain size classes were entrained and transported, causing river bed incision. The mean armouring ratio decreased to 1.9. In contrast, during low magnitude floods in 2003–2004 (Q2), the coarsest fractions (64 mm) did not take part in the bed load while finer particles were winnowed, thus surface deposits coarsened. As a result, the armour layer was reestablished (i.e., the mean armouring ratio increased to 2.3), and the supply of subsurface sediment decreased. The supply and transport of bed material appear to be in balance in the river reach immediately below the dam. In contrast, the transport of medium and finer size classes in the downstream reaches was higher than their supply from upstream, a phenomenon that progressively reduced their availability in the river bed surface, hence the armour layer reworking. en
dc.format.extent 15 en
dc.language.iso eng
dc.relation.ispartof Geomorphology en
dc.title Breakup and reestablishment of the armour layer in a large gravel-bed river below dams: The lower Ebro en
dc.type Text en
dc.type.publicationtype Article (Journal) en
dc.contributor.institution Aberystwyth University en
dc.contributor.institution Centre for Catchment and Coastal Research en
dc.description.status Peer reviewed en


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