Room for the River IJssel Delta South

Witteveen+Bos advised contractor Boskalis, which was part of Isala Delta, the combination of Boskalis and Van Hattum Blankevoort that was in charge of this project. We were involved in almost all design work for this project.

The summer bed of the IJssel was lowered to give more room to the water at high water levels, resulting in a drop in water levels. The summer bed of the (Lower) IJssel was lowered over a distance of more than seven kilometres between Kampen and the Eilandbrug, near the river mouth. The dredging was done with a cutter suction dredger and by excavating the bottom. Thus, the river bottom was deepened. 

In addition, the Reevediep was constructed, an (overflow) area with a channel for recreational boating. On both sides of the channel, 16 km of primary defences (dykes) were constructed. Maximum use was made of the material in the project area to realise these dykes. For example, the core of the dykes was built with the sand produced by the summer bed lowering.

The Reevediep is a water discharge bypass: a new distributary of the IJssel, south of Kampen, which forms an extra connection between the IJssel and the Drontermeer. This way, in extreme circumstances, the high water is drained before it reaches the city of Kampen. During the high-water situation in December 2023, the value of the bypass was already demonstrated. The Reevediep also acts as a buffer for rising water from the IJsselmeer.

On the side of the IJssel, an inlet has been built with a bridge construction, over which the N763 Kamperstraatweg has been placed. Next to this inlet system, a fish passage has been constructed. A sluice on the IJssel side has also been constructed for the benefit of recreational boating. It is crossed by a fixed bridge. This lock can be completely flooded at high water levels.

The spatial quality of the area was also improved, including 400 hectares of new, wet delta nature in the Reevediep, including walking, hiking and cycling paths. The development of four floodplains, Zalkerbosch, Scherenwelle, Koppelerwaard and Onderdijkse Waard, between Kampen and Zwolle improves the spatial quality in the river area. This mainly involves the preservation and enhancement of the special natural values of the IJssel Delta and its accessibility. Since part of the project area has been realised in a Natura 2000 area, a new reed marsh has been created to compensate. Space has been created on a climate dike for a new residential area for Kampen.

Within this project, various engineering structures such as locks, bridge, inlet work and pumping stations were realised and the road network and water management in the area were thoroughly revised. While Boskalis carried out the ground, road and water works and nature development, Van Hattum en Blankevoort took care of the engineering works, including the inlet system, bridges, locks and pumping stations.

The way of working within this project was special: team Ruimte voor de Rivier Kampen moved into a previously empty school building in 2015. There, clients, contractors and implementers, around 100 people in total, worked intensively together on the project.