ABSTRACT
A model-based investigation of the hydrodynamic and morphodynamic effects of artificial gravel islands within the large navigable Austrian Danube River is presented. An artificial island was implemented 500 m in length and around one fourth of the river channel wide. Numerical simulations of discharges from low flow to a 100-year flood were performed using the hydrodynamic model RSim-3D and the sediment transport model iSed. Morphologies investigated included variations of widths and heights of the gravel island as well as a complete removal. Artificial gravel islands were found to yield comparable effects as groynes on hydro- and morphodynamics. The presence of the island had almost no effect on the water levels upstream for a 100-year flood. Flow velocities and bed shear stresses as well as subsequent erosive processes increased in the river channel in the presence of the island for low to mean discharges, but remained almost constant during flood discharge.
