Print Email Facebook Twitter Armor breakup and reformation in a degradational laboratory experiment Title Armor breakup and reformation in a degradational laboratory experiment Author Orru, C. (TU Delft Environmental Fluid Mechanics) Blom, A. (TU Delft Rivers, Ports, Waterways and Dredging Engineering) Uijttewaal, W.S.J. (TU Delft Environmental Fluid Mechanics; TU Delft Rivers, Ports, Waterways and Dredging Engineering) Date 2016-06-09 Abstract Armor breakup and reformation was studied in a laboratory experiment using a trimodal mixture composed of a 1mm sand fraction and two gravel fractions (6 and 10mm). The initial bed was characterized by a stepwise downstream fining pattern (trimodal reach) and a downstream sand reach, and the experiment was conducted under conditions without sediment supply. In the initial stage of the experiment an armor formed over the trimodal reach. The formation of the armor under partial transport conditions led to an abrupt spatial transition in the bed slope and in the mean grain size of the bed surface, as such showing similar results to a previous laboratory experiment conducted with a bimodal mixture. The focus of the current analysis is to study the mechanisms of armor breakup. After an increase in flow rate the armor broke up and a new coarser armor quickly formed. The breakup initially induced a bed surface fining due to the exposure of the finer substrate, which was accompanied by a sudden increase in the sediment transport rate, followed by the formation of an armor that was coarser than the initial one. The reformation of the armor was enabled by the supply of coarse material from the upstream degrading reach and the presence of gravel in the original substrate sediment. Here armor breakup and reformation enabled slope adjustment such that the new steady state was closer to normal flow conditions. To reference this document use: http://resolver.tudelft.nl/uuid:43fb9a49-0a25-4da0-b5c2-7bd481a62ebf DOI https://doi.org/10.5194/esurf-4-461-2016 ISSN 2196-6311 Source Earth Surface Dynamics (ESurf), 4 (2), 461-470 Part of collection Institutional Repository Document type journal article Rights © 2016 C. Orru, A. Blom, W.S.J. Uijttewaal Files PDF esurf_4_461_2016.pdf 3.84 MB Close viewer /islandora/object/uuid:43fb9a49-0a25-4da0-b5c2-7bd481a62ebf/datastream/OBJ/view