Oyster dam (‘Oesterdam’)
Although the Oyster dam remained open, the tides in the Oosterschelde would change. Because the mouth of the Oosterschelde was reduced, less sea water could flow in and out. Salt marshes and mudflats were threatened, because the difference between high and low tides had been reduced. Two dams on the east side of the Oosterschelde reduced its surface area, enhancing the tidal movements. In the north-east, the Philips dam had sealed off the Krammer (about 3,500 hectares of water) from the Oosterschelde. The Oyster dam closed off another 1,000 hectares of water on the east side. Because of the enclosure of these areas, the water level in the Oosterschelde had to be raised by 2.7 metres. The oyster culture in Yerseke was saved because of the dams. Also, the dams made sure that the Scheldt-Rhine canal was no longer harmed by the tides. The dams protected the areas that lied behind them against high water levels, together with the Oosterschelde barrier.
The Oyster dam is the longest ‘delta work’ with a length of eleven kilometres. By connecting Tholen to South-Beveland, the Zoom lake was created. This was part of the Scheldt-Rhine connection, which connects the port of Antwerp to the river Waal. The Zoom lake would have reached Bergen op Zoom if the Markiezaat quay was not there. This dam was constructed between 1981 and 1983 to facilitate the construction of the Oyster dam. Because of the construction of the Markiezaat quay, the water between the Markiezaat quay and the Oyster dam became the Zoom lake. To understand where exactly the Oyster dam was placed, in relation to the Markiezaat quay, more needs to be explained about the section of the Oyster dam. If you were to fly over the dams from an eastern direction, one would successively see the Oosterschelde, the Oyster dam, the Zoom lake, the Markiezaat quay, the Markiezaat lake and the coast of North Brabant.
The lake of Tholen (‘Tholense Gat’), the water between Tholen and North Beveland, was closed by the sustained raising of the seabed. This was much cheaper than closing the lake by means of stones, with or without a cableway. As the work progressed, the gap that needed to be closed became smaller. The amount of water flowing through remained equal however. Because of that, the current continually increased. It was to be expected that the closing and raising of the last hundred metres would become a long-lasting and expensive job. Therefore, the lake was not completely closed until the Oosterschelde barrier was finished. The slides of the barrier could then be closed to eliminate the tidal movements. Eventually, the Oyster dam was finished in 1986.