Bed level change in the Upper Rhine Delta and Niederrhein

The Rhine reach comprising the Niederrhein and the Upper Rhine Delta is characterized by a long history of engineering interventions. The area is densely populated and the Rhine, the main inland waterway in Europe, justifying the need for such measures. Interventions have had a strong impact on morphodynamic channel characteristics. We use bed level data collected since 1926 to assess large scale bed level change in the Upper Rhine Delta and Niederrhein. The field data show various trends both at the large scale and locally. A reduction of the main channel slope is observed in the Waal and the IJssel branches of the Rhine Delta, achieved through bed degradation. In the Pannerdensch Kanaal-Nederrijn-Lek branch, the morphoynamics are controlled by three weirs, downstream of which degradation has developed. The downstream half of the Niederrhein has degraded, resulting in a slope increase. Most of the domain has remained relatively stable for at least 20 years. The observed trends provide insight on the river response to interventions, which helps to better understand degradation processes, in model calibration, and in anticipating future change of channel geometry.