“Something nice is starting to grow” says Henk Meuldijk the day after an excursion and knowledge exchange event to the pilot location. He is referring to the plants and bushes on the pilot section at the Houtribdijk in lake Marken in The Netherlands. In 2014 EcoShape and Rijkswaterstaat constructed a 400 meter long test site along the dike here. The aim was to test how to reinforce a dike in a lake with sand, to gain more knowledge about the design of this type of dikes. (continued below picture).
Meuldijk is project leader of the upcoming reinforcement of the entire 25 km long Houtribdijk between Enkhuizen and Lelystad, starting in 2018. The pilot delivers valuable knowledge for his project. “We know quite a lot about sandy sea dikes. Not so for dikes in a lake. It turns out these two types of dike differ fundamentally.”
Some of the results have already been used in the design of the sandy reinforcement. “We used new ways to calculate the amount of sand we need to reinforce the dike. And we now know how the body of sand is shaped after a few years. We also know more about how to maintain the dike once we finished constructing it. We learned about the best type of vegetation. For instance, we will not use willows on the sandy reinforcement dike because maintenance is too expensive and because they will block the view from the Houtribdijk. The pilot enables us to make better informed choices.”
The pilot runs until the beginning of 2018. Monitoring will continue after that, but then on the entire stretch of the reinforced Houtribdijk. Meuldijk: “We will measure ecology, sand transport and development of vegetation. I also hope to be able to find a PhD student to deepen the understanding of the sandy reinforcement. The knowledge we gain here can be applied in The Netherlands and abroad.”