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Bankfull hydraulic geometry; the role of in-channel vegetation and downstream declining discharges in the anabranching and distributary channels of the Gwydir distributive fluvial system, southeastern Australia

Journal Article


Abstract


  • Australian rivers frequently exhibit long periods of lowor no flow, trees and shrubs that growon the channel bed,

    and discharges that decline downstream. Four channels of the Gwydir distributive fluvial system (Gwydir and

    Mehi Rivers; Carole and Moomin Creeks) greatly contrast the hydraulic geometry of most other rivers,

    particularly in the way they respond to changes in discharge downstream. Data describing 167 cross sections

    across all four streams are assembled into standard exponential bivariate hydraulic geometry plots, with the

    relationships shownto exist outside the range of previously investigated downstreamchanges (i.e., in contrast to

    the commonly obtained exponents for width [b], depth [f], and velocity [m] of ~0.5, ~0.4, and ~0.1, respectively).

    Comparatively low exponents for width (b=0–0.4) and high values for velocity (m=0.26–0.42) reflect the

    importance of slope in accommodating changes in discharge. In sharp contrastwith nearly all previous hydraulic

    geometry investigationswhere discharge increases downstreamand slope decreases, in theGwydir systemslope

    declines in sympathywith discharge resulting in a marked downstreamdecline in streampower. The presence of

    in-channel vegetation is also argued to be a highly significant influence on the downstreamhydraulic geometry of

    these streams. Because these streams are frequently dry, trees grow in abundance on the bed, appearing to

    displace the flow laterally and causing the channels to widen and shallow downstream — an adjustment that

    contrasts the high mud content of the boundary. The result is a very different hydraulic geometry in this

    anabranching-distributary system to that commonly described for other types of river.

Publication Date


  • 2011

Citation


  • Pietsch, T. J. & Nanson, G. C. (2011). Bankfull hydraulic geometry; the role of in-channel vegetation and downstream declining discharges in the anabranching and distributary channels of the Gwydir distributive fluvial system, southeastern Australia. Geomorphology, 129 (1-2), 152-165.

Scopus Eid


  • 2-s2.0-79953799536

Ro Metadata Url


  • http://ro.uow.edu.au/scipapers/3780

Has Global Citation Frequency


Number Of Pages


  • 13

Start Page


  • 152

End Page


  • 165

Volume


  • 129

Issue


  • 1-2

Abstract


  • Australian rivers frequently exhibit long periods of lowor no flow, trees and shrubs that growon the channel bed,

    and discharges that decline downstream. Four channels of the Gwydir distributive fluvial system (Gwydir and

    Mehi Rivers; Carole and Moomin Creeks) greatly contrast the hydraulic geometry of most other rivers,

    particularly in the way they respond to changes in discharge downstream. Data describing 167 cross sections

    across all four streams are assembled into standard exponential bivariate hydraulic geometry plots, with the

    relationships shownto exist outside the range of previously investigated downstreamchanges (i.e., in contrast to

    the commonly obtained exponents for width [b], depth [f], and velocity [m] of ~0.5, ~0.4, and ~0.1, respectively).

    Comparatively low exponents for width (b=0–0.4) and high values for velocity (m=0.26–0.42) reflect the

    importance of slope in accommodating changes in discharge. In sharp contrastwith nearly all previous hydraulic

    geometry investigationswhere discharge increases downstreamand slope decreases, in theGwydir systemslope

    declines in sympathywith discharge resulting in a marked downstreamdecline in streampower. The presence of

    in-channel vegetation is also argued to be a highly significant influence on the downstreamhydraulic geometry of

    these streams. Because these streams are frequently dry, trees grow in abundance on the bed, appearing to

    displace the flow laterally and causing the channels to widen and shallow downstream — an adjustment that

    contrasts the high mud content of the boundary. The result is a very different hydraulic geometry in this

    anabranching-distributary system to that commonly described for other types of river.

Publication Date


  • 2011

Citation


  • Pietsch, T. J. & Nanson, G. C. (2011). Bankfull hydraulic geometry; the role of in-channel vegetation and downstream declining discharges in the anabranching and distributary channels of the Gwydir distributive fluvial system, southeastern Australia. Geomorphology, 129 (1-2), 152-165.

Scopus Eid


  • 2-s2.0-79953799536

Ro Metadata Url


  • http://ro.uow.edu.au/scipapers/3780

Has Global Citation Frequency


Number Of Pages


  • 13

Start Page


  • 152

End Page


  • 165

Volume


  • 129

Issue


  • 1-2