Anabranching in mixed bedrock-alluvial rivers: the example of the Orange River above Augrabies Falls, Northern Cape Province, South Africa

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dc.contributor.author Tooth, Stephen
dc.contributor.author McCarthy, T. S.
dc.date.accessioned 2008-12-15T16:26:24Z
dc.date.available 2008-12-15T16:26:24Z
dc.date.issued 2008-12-15
dc.identifier.citation Tooth , S & McCarthy , T S 2008 , ' Anabranching in mixed bedrock-alluvial rivers: the example of the Orange River above Augrabies Falls, Northern Cape Province, South Africa ' ' , pp. 235-262 . en
dc.identifier.other PURE: 104788
dc.identifier.other dspace: 2160/1660
dc.identifier.uri http://hdl.handle.net/2160/1660
dc.description Tooth, Stephen, McCarthy, T.S., (2004) 'Anabranching in mixed bedrock-alluvial rivers: the example of the Orange River above Augrabies Falls, Northern Cape Province, South Africa', Geomorphology 57(3-4) pp.235-262 en
dc.description.abstract Anabranching is characteristic of a number of rivers in diverse environmental settings worldwide, but has only infrequently been described from bedrock-influenced rivers. A prime example of a mixed bedrock-alluvial anabranching river is provided by a 150-km long reach of the Orange River above Augrabies Falls, Northern Cape Province, South Africa. Here, the perennial Orange flows through arid terrain consisting mainly of Precambrian granites and gneisses, and the river has preferentially eroded bedrock joints, fractures and foliations to form multiple channels which divide around numerous, large (up to 15 km long and 2 km wide), stable islands formed of alluvium and/or bedrock. Significant local variations in channel-bed gradient occur along the river, which strongly control anabranching style through an influence on local sediment budgets. In relatively long (>10 km), lower gradient reaches (0.0013) within the anabranching reach, local transport capacity exceeds sediment supply, bedrock crops out extensively, and channels flow over an irregular bedrock pavement or divide around rocky islands. Channel incision into bedrock probably occurs mainly by abrasion, with the general absence of boulder bedforms suggesting that hydraulic plucking is relatively unimportant in this setting. Mixed bedrock-alluvial anabranching also occurs in a number of other rivers worldwide, and appears to be a stable and often long-lived river pattern adjusted to a number of factors commonly acting in combination: (1) jointed/fractured granitoid rock outcrop; (2) erosion-resistant banks and islands; (3) locally variable channel-bed gradients; (4) variable flow regimes. en
dc.format.extent 28 en
dc.language.iso eng
dc.relation.ispartof ' en
dc.title Anabranching in mixed bedrock-alluvial rivers: the example of the Orange River above Augrabies Falls, Northern Cape Province, South Africa en
dc.type Text en
dc.type.publicationtype Article (Journal) en
dc.contributor.institution Institute of Geography & Earth Sciences en
dc.description.status Peer reviewed en


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