Author(s): Roy M. Frings; Willem Ottevanger; Kees (C.J.) Sloff

Linked Author(s): Roy M. Frings, w ottevanger, Kees (C.J.) Sloff

Keywords: Downstream fining; dune sorting; longitudinal bed profile; meander migration; overbank deposition; river bifurcation; sand-bed river; selective transport; Rhine River

Abstract: Downstream fining of river bed sediments is well known for gravel-bed rivers, but also occurs in sand-bed rivers. The objective of this study was to determine the effect of selective transport processes, dune sorting, overbank deposition, channel migration and river bifurcations on downstream fining in sandy lowland rivers subject to relative sea level rise, tidal water level variations and increasing river width. A numerical simulation model was built using the Delft3D software. Selective suspended-load transport appeared to be dominant over selective bed-load transport. Dune sorting and channel migration increase fining rates, but overbank deposition has an opposite effect. River bifurcations affect the fining rate because of their effect on the sediment supply to bifurcating lowland rivers. Downstream fining was found to develop within decades, but it took few centuries before the longitudinal bed profile and the fining rate attained dynamic equilibrium. A comparison of the modelled fining rates with those observed in the Rhine River shows reasonable agreement.

DOI: https://doi.org/10.1080/00221686.2011.561000

Year: 2011