Morphological development of the Rhine river delta at the lake of Constance

The solids which are forming the delta of the river Rhine at the lake of Constance consists mainly of fine material. To prevent the silting of the harbours near to the river mouth, lateral dams are being built to convey the suspended material into deeper parts of the lake. To achieve a more "natural look" of the delta, it is planned to partly lower the levees. The aim is to get local depositions in the overbank region without affecting the flood protection safety upstream of the river mouth. With this restoration measures one hopes to improve the ecological situation. The impact of different levee configurations on the development of the delta was investigated with the help of a physical and a numerical model. The numerical model is based on a shallow water approach. The sediment transport can be carried out for different grain size classes and suspended load and bedload are treated separately. The models were validated by comparing it with field measurements of the morphological changes which took place during a period of about six month.