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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Record number 439324
Title Sediment discharge division at two tidally influenced river bifurcations
Author(s) Sassi, M.G.; Hoitink, A.J.F.; Vermeulen, B.; Hidayat, H.
Source Water Resources Research 49 (2013)4. - ISSN 0043-1397 - p. 2119 - 2134.
DOI https://doi.org/10.1002/wrcr.20216
Department(s) Hydrology and Quantitative Water Management
WIMEK
Publication type Refereed Article in a scientific journal
Publication year 2013
Keyword(s) depth-integrated model - open-channel flow - suspended sediment - settling velocity - secondary flow - load transport - boundary-layer - particles - suspension - roughness
Abstract [1] We characterize and quantify the sediment discharge division at two tidally influenced river bifurcations in response to mean flow and secondary circulation by employing a boat-mounted acoustic Doppler current profiler (ADCP), to survey transects at bifurcating branches during a semidiurnal tidal cycle. The ADCP collecting flow velocity and acoustical backscatter data was used to quantify suspended sediment discharge, adopting a recently introduced calibration procedure. Measured profiles of flow velocity and sediment concentration allowed us to compute spatiotemporal distributions of the shear velocity, the roughness length and the Rouse number. Spatiotemporal distributions of the settling velocity were obtained by combining the Rouse number and shear velocity estimates with in situ measurements from a laser particle size analyzer. Bed-load transport rates were inferred from shear stress estimates. The concentration field shows a direct response to bed shear stress, stressing the alluvial context of the system. The flow in the bifurcation regions is characterized by counter rotating secondary-flow cells, which stretch over the full width and depth of the cross sections in the downstream branches, and persist throughout the entire tidal cycle. The pattern of secondary flow suggests the flow approaching the bifurcation is concentrated in two independent threads. A two-cell structure inhibits the exchange of sediment that would occur in case a single cell would stretch over the full channel width. The division of suspended sediment primarily depends on the upstream transverse profile of the suspended sediment concentration, which is in turn dependent on geometrical factors such as upstream curvature.
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