The Grebbedijk is located along the north bank of the Rhine River, protecting an extensive low-lying and densely populated area between two natural heights. Behind the dyke, local people live, work and play, enjoying nature and the recreational areas.
With climate change in mind, the Vallei and Veluwe district water board asked Lievense, now part of WSP, to create a design for dyke reinforcement. Sustainability and the consideration of future trends were central to the improvements; the Grebbedijk reinforcement also provided an opportunity to explore sociocultural and environmental objectives such as further nature and recreational development. Within this project, a new method was developed to quantify and compare the sustainability of the design options.
One of the ways that a dyke can fail is through a form of internal erosion called piping, so we proposed an alternative technique that saved space and costs, called a "sand-barrier". Locally excavated clay and sand will improve the dyke’s stability.
One example of multifunctional design is the new footpath on the dyke, which improves safety for users and serves as a breakwater so that the dyke did not have to be raised as high. Another is the integration of the "Grebbelinie" monument (this was a defense line that played an important role during WWII). To avoid damage due to the dyke reinforcement, the monument will be restored in a sensitive manner.
Through a unique and intensive participation process, residents, visitors, local businesses and other parties submitted their goals for the dyke, as well as their priorities for improvement.