In the framework of the project "Ruimte voor Rijntakken" (Room for the Rhine Branches), several measures have been devised to achieve a decrease of the water levels at peak discharges. A wide range of fourteen measures has been proposed, among which, lowering the existing groynes by someone to two metres. Lowering the groynes along certain reaches of the river will increase the flow area in addition to reducing the effective roughness in the groynes' region during high water conditions. However, if the groynes are lowered, the balance of hydrodynamic forces acting on the groyne fields will change, and there will be a morphological impact on the river system. To carry on with the proposed plan a thorough understanding to the effect of lowering the groynes on the morphology of the river is necessary.
To that end, the aim of this thesis was set to study the morphological interaction between the groyne fields and the main channel of a river; with the intention to address some concerns for the river manager. This thesis covers a range of stales.