Zandkreek Dam

Zandkreek Dam
Video: Zandkreek Dam
Shortly after the barrier in the Hollandse IJssel was finished, the construction of the Sand Creek dam begun. This was one of the two dams, which would connect Walcheren, North-Beveland and South-Beveland, according to the ‘Three Islands plan’.

Spearheads

The Sand Creek dam could not be put into place instantly. There were eight aspects which had to be taken into account, to ensure the construction would be a success.
1. The closure of the dam had to take place during low water levels, and preferably during the period of neap tide, which occurs twice a month.
2. The caissons could not be sunk down during rates of flow higher than 0.8 metres per second.
3. The caissons had to be sunk by means of a crane, which ensured that the caissons would be placed in a straight line.

Final situation after finishing the Zandkreekdam and sluice
Final situation
4. After a caisson was placed, a top-piece needed to be attached. This had to be done before high tide, because the height of the caisson without the top piece was only one metre above Amsterdam Ordnance Zero, whereas high tide was 1.5 metres above Amsterdam Ordnance Zero. If the top piece was not installed in time, the caisson would be flooded during high tide.
5. On the day of the placement of the caissons, the sand and the stones should be dumped at both sides of the dam, since the water could flow under the caissons.
6. The joints between the caissons needed to be filled.

The flow danger

The Sand Creek dam has a length of 830 metres and connects South-Beveland to North-Beveland, between Goes and Kortgene. The Sand Creek dam separates the (salty) Oosterschelde from the (fresh) Lake of Veere. The dam which closes the Lake of Veere on the side of the North Sea is called the ‘Veerse Gat’ dam. The construction of the Sand Creek dam was necessary because otherwise the ‘Veerse Gat’ dam could not have been built. If the Sand Creek dam was built after the ‘Veerse Gat’ dam, there would have been serious problems as a result of the tidal movements. To understand this, we have to return to the caissons. These concrete blocks were placed one by one in the closing gap. The smaller the remaining gap, the stronger the flow. The flow would become so strong that the last caissons would not be able to be placed. If the ‘Veerse Gat’ dam would have been placed without the Sand Creek dam, the seawater could also have caused problems via the back side.

Caissons

Like many other dams, caissons played an important part during the construction of the Sand Creek dam. The caissons which were used for the Sand Creek dam were 11 metres long, 7.5 metres wide and 6 metres high. This is about as large as a semi-detached house. The caissons were built near the village Kats on the island North-Beveland. However, the manufacture process turned out to be harder than originally expected.

A crane is placing caissons for the Zandkreekdam
Installation caissons
The walls of the caissons in particular, caused many problems. For this reason, it was decided to make these parts somewhere else and then put them together in Kats. One by one, the caissons were placed next to one another, and as a result the dam was gradually built. However, the caissons were not placed on the bottom of the sea. The seabed could sink under the enormous weight of the concrete. So, before the caissons were placed, the seabed was covered with a thick layer of plunging stone. The gaps between the stones were filled with gravel and sand, to prevent the water from flowing through the ‘threshold’. The caissons would be covered with a layer of sand afterwards. The Sand Creek dam was completed in 1960.

The construction

The placement of caissons for the Zandkreekdam
Placement of caissons
The closure of the eastern side of the Lake of Veere by the Sand Creek dam was completed as follows. A good week for the placement of the dam was at the end April and the beginning of May. Firstly, a hollow caisson was put into position. At the time when the tidal movements were as weak as possible, the caisson was sunk. On April 29th, the first caisson was placed. On May 2nd, another six were sunk. Because of the strong currents, only four caissons could be placed on May 3rd. After this, all that was left was a gap of 20 metres. This opening was closed by two attached caissons, on May 4th. During the placement, these last caissons were sailed against the flow. Fortunately, the flow was not so strong, and so, on May 4th, at 2:22 PM, the task was completed.

A special crane was used to ensure that the caissons were placed at right angles to the plunging stones. After the caissons were placed, they were filled with large amounts of gravel and sand. Extra top-pieces were attached to make them higher. Consequently, sand was dumped at the caissons for nine days, and as a result they stood very firmly. Following that, an asphalt layer and a road were built.

Bridge and lock

The lift-lock at Zandkreek
Lift-lock Zandkreek
After the dam was finished, a bridge and a lock were built which allowed ships to reach Middelburg and Vlissingen through the Lake of Veere and the Canal through Walcheren. Without these facilities, ships would have had to sail around Walcheren via the North sea to reach the Westerschelde.