Construction
The project consists of three pilot studies. In two locations along the Frisian IJsselmeer coast sand nourishments are applied.
For the Workumerwaard this is constructed as a sand ridge parallel to the coast, while for Oudemirdum this is constructed as a hook perpendicular to the coast. At both locations, the morphological changes and ecological effects are followed closely in time. For a third location, Hindeloopen, a model study is conducted to gain insight into the functioning of the coastal system and to explore the chances of measures based on the principles of Building with Nature for this area.
The Workumerbuitenwaard location was managed by the provincial nature organization It Fryske Gea. As one of the experiment’s initiators, it expected the sand engine to create favourable conditions for establishment of pioneer vegetation. The damming of the lake in 1933 suddenly stopped the tidal regime, whereupon ecosystem succession stopped. Macrophyte coverage was low or absent along this part of the coast. The sand engine was positioned some 500 m off the coast, in the wave breaking zone. This zone forms the transition between the shallow water plateau and the deeper lake water. Wave energy was expected to move the sand from here in a north-easterly direction. In the summer of 2011 a 31,000 m3 sand nourishment was deposited, creating a 500 m by 50 m elongated sand engine parallel to the coast.
The Oudemirdum location and design were different. At this location, the existing dikes had not passed the safety assessment and were in need of reinforcement. The sand engine’s main role here was wave attenuation. The hope was that by reducing the height of the waves impacting the dike, investments in dike reinforcement could be reduced or delayed. The Frisian water authority contributed to the experiment here because it was interested in the strategy’s potential to mediate engineered dike reinforcements. At this location, the sand nourishment was positioned close to the shore on the boundary between a recreational area and a protected nature area (see the figure). The shape and closeness of the sand engine to the coast were influenced by the desire to create a hard boundary between recreation (wind surfing) and the protected area. Thus, in the winter of 2013, an 11,500 m3, 500 meter hook-shaped sand engine was constructed.
