Can an artificial sandy forebank be an alternative to traditional dike upgrade approaches in lakes? The sandy forebank created directly alongside the Houtrib Dike in the Markermeer lake (near Lelystad in the Netherlands) could provide a positive answer to that question. The forebank has the potential to considerably reduce the wave impact on the dike, and perhaps to make less drastic measures to strengthen the dike necessary. A solution of this kind is cheaper and more sustainable, and it enhances the natural values and leisure potential of the locality. Interest in natural dike upgrades is increasing both in the Netherlands and worldwide.
In 2014, in collaboration with Rijkswaterstaat and Ecoshape, we created a forebank consisting of 70,000 cubic metres of sand near Trintel Harbour. Cameras on the sheet pile wall provide daily assessments of the wave impact on the sandy bank. Continuous hydrodynamic and meteorological measurements are also made. In addition, we are making periodical measurements of the slope to determine morphological development and vegetation dynamics. These data constitute important input that will allow us to answer the question of to what extent we can design a safe, stable and cost-efficient forebank. The first results are expected in 2016. Deltares will be responsible for the monitoring over the next four years. We are also helping to develop knowledge as a part of the project, for example by designing tools. The pilot project near Lelystad is part of the Second Flood Protection Programme (HWBP-2) organised by the Dutch government and water authorities.
Flood protection remains important and this project shows that it can also be done in a natural and sustainable way.