Author(s)

A. Schmidt, T. Brudy-Zippelius, R. Kopmann & M. Imiela

Abstract

Upstream of the last barrage of the river Rhine at Iffezheim sedimentation takes place at a rate of about 150,000 m³ per year leading to severe problems related to flood protection. In the past this material was dredged periodically and was used for the extension of a mole in the upstream part of the barrage. Because of the great amount of material to be dredged and the associated ecological aspects, this is a matter of great economic concern. However, as the measures taken in the past are not applicable any longer and the recurrent accumulations considerably reduce the level of flood protection the responsible authority is urgently looking for an appropriate and environmentally compatible sediment management strategy. The most obvious way to decrease costs for maintenance dredging, transportation and disposal is to reduce the amount of sediments to be dredged, i.e. to prevent the particles transported in suspension from settling above the barrage at that high rate. This may be achieved by changing the hydrodynamic situation close to the barrage e.g. by the installation of flow guiding structures or an appropriate operation of the weir. Periodically flushing of artificially resuspended sediments may support the aspired objective. In this paper results from a two-dimensional hydrodynamic model and from a two-dimensional morphodynamic model are presented to describe the processes close to the barrage. Flow structures at different discharges are analysed and are compared to results from field measurements, in particular with respect to the area of sedimentation. The effectiveness of a flow guiding structure to minimize sedimentation is demonstrated and suggestions are made for further investigations. Keywords: sedimentation, suspended load, hydrodynamic model, morphodynamic model, eddy, flow guiding structure, barrage, river Rhine, Iffezheim.

Keywords

sedimentation, suspended load, hydrodynamic model, morphodynamic model, eddy, flow guiding structure, barrage, river Rhine, Iffezheim.