Modelling the morphological effects of longitudinal dams in the Midden-Waal

The longitudinal Dams have been constructed in the Waal River as a new river training measure to sustain its ecosystem services, navigability and provide more room for the river. In this study, we investigate the effects of the longitudinal dams on the river morphology. Long-term morphological simulations (for 30 years) have been conducted. Many variants have been considered in this study. The main variants are modelling the river reach with and without the dams. Furthermore, variants are defined to investigate the effects of the side channel inlet opening on the flow distribution and river morphology. The study displays that the longitudinal dams are able to maintain the main channel navigability. However, the current design provides local deposition, in the main channel, downstream km 912, around km 918 and between km 919 to km 921. This deposition may need to be verified and investigated further. The study also shows that the inlet opening influences the morphological changes in main channel and the side channels, especially for the Dreumel and Ophemert reaches. Despite the valuable insights from these results, for more detailed investigation and evaluation of the longitudinal dams in the Midden Waal, some further investigations are recommended.