ABSTRACT
The authors discuss the use of a 1-D model or a 2-D model for the evolution of the bed between the levees while the spreading of water and sediment over the floodplains is simulated using a 2-D model. A 1-D model cannot represent the asymmetrical behaviour of the flow in the bends but makes easier the estimate of the variations of the sediment transport capacity along the river if the bed geometry is complex. For the case of the Agly river floods, results in terms of water elevation and bed evolution are compared for a simplified geometry of the bed. The two models (coupled 1-D/2-D or full 2-D) provide quite similar processes in the flood plain but different erosion rates of the main channel bed. Because differences of both results to observations are large, one cannot decide which model provides the more relevant results.
