Behind the research facility of NIOZ in Yerseke lie 12 concrete basins that are flooded during high tide and easy to reach during low tide. Within these basins experiments are performed on how biodiversity can be enhanced on subtidal, hard structures like dikes or pillars of wind farms. To meet current safety standards dikes need to be reinforced. In subtidal parts this is usually done through adding a layer of rock material or steel slag (a waste product of the steel industry with a high density). These reinforcements are often applied in soft sediment areas or on dikes with a high nature value. These locations often receive special protection due to their high natural value. The hard structures provide shelter for the European lobster and other important target species. Dike reinforcements can only take place when this natural value is preserved or compensated.
The aim of Rijkswaterstaat is to protect the nature value of the subtidal parts of the dike through the addition of 'eco-tops'. These eco-tops exist of a ridge or pile of rocks which facilitate the reestablishment of the target species as well as a sheltered area that allows a faster sediment deposit.