Philipsdam
The Philipsdam is a compartmentalisation dam constructed as part of the Delta Works in the Netherlands. It separates water of the lakes Krammer and Volkerak from the Oosterschelde, and connects the Grevelingendam to Sint Philipsland.
History, design, and construction
Design and optioneering
The need for the dam
In 1974, it was decided by Rijkswaterstaat and the Den Uyl cabinet to construct the Oosterscheldekering as a storm surge barrier at the mouth of the Oosterschelde, instead of completely closing off the tidal inlet at that location. The construction of the Oosterscheldekering required the compartmentalisation of the basin.The compartmentalisation model chosen involved the construction of the Philipsdam, the Oesterdam, and a discharge channel for managing the level and quality of the lake that would then form behind the dams. The overall project was also required to create a freshwater lake for water management purposes, ensure a tide-free navigation on the Scheldt-Rhine connection, and achieve a tidal difference of 2.7m at Yerseke.
Optioneering and preliminary design
To prevent unacceptable flow velocities from being realised in the Scheldt-Rhine Canal during the works, the closing phases of both the Philipsdam and the Oesterdam had to be coordinated with each other. A number of alternatives to the final location of the Philipsdam and the lock complex were investigated, with an important consideration being the preservation of valuable intertidal areas along with considerations of the closure method to be employed.The decision-making process for the nature and location of the Philipsdam involved a comprehensive consideration of multiple factors, leading to the selection of the variant at a sandbank known as Plaat van de Vliet as the preferred option. Key considerations included: The connection of the damn to the Grevelingendam instead of the southern shore of Goeree-Overflakkee was chosen to allow for the option of turning the Grevelingenmeer into a freshwater basin by feeding it via a discharge sluice from the Krammer, which was ultimately decided against. The benefit of this route is that it also removed the requirement for an additional road bridge across the Krammer instead connecting it to the existing road over the Grevelingendam.Hydrology and soil mechanics: The Plaat van de Vliet option was favoured for its hydrological aspects, which were thought to cause minimal disruption to flow speeds in the Krammer during construction. The flow speeds in the Krammer were expected to increase by 20% as long as the Slaak was still open, due to the construction of the work island with salt control basins on the Plaat van de Vliet. The increase in flow speeds along the sandbank known as the Plaat van Oude Tonge was anticipated to be less than 10%. No significant impact was expected on the Zijpe. Soil mechanics considerations favoured an eastern connection to St.-Philipsland to ensure the stability of the dam and minimise ground settlement risks.
| Waterway | Max. Ebb Speed | Max. Ebb Volume | Max. Flood Speed | Max. Flood Volume |
| Slaak | 0.9 | 2000 | 0.75 | 2000 |
| Krammer | 1.05 | 11000 | 1.05 | 12500 |
The road connection on the south side of the dam required significant research during the design stage, as it runs through vulnerable nature reserves.
Construction
Construction on the Philipsdam commenced in 1976, starting with the creation of a 96-hectare temporary work island on a sandbank known as Plaat van de Vliet.Eighteen months after initiation, the island's construction concluded, paving the way for the commencement of the locks aimed at facilitating inland navigation and accommodating yachts. By 1983, the Krammer locks complex was completed, and the dam was officially inaugurated on 2 February 1987. A second lock for yachts was added in 1994.
The Philipsdam functions as a dam, a fresh-salt water separator, and a lock system. It mitigates tidal influences within the Scheldt-Rhine connection, ensuring the Port of Antwerp remains accessible. To the dam's west lies saltwater, while to its east, freshwater flows from the Waal and Bergse Maas.
On the dam's saltwater side, the Oosterschelde's water level is maintained, ensuring the conservation of salt marshes and mudflats vital for oyster farming. The freshwater side supports extensive vegetation due to its drier conditions. The inclusion of a lock complex facilitates the passage of ships, featuring an innovative system for fresh-salt water separation.
In addition to the main road over the crest of the dam, there is a parallel road on its eastern side which was constructed to offer access to recreational zones. The dam's southern route was deliberately positioned as far west as possible from the Plaat van Vliet and Krammerse Slikken, maximising the recreational potential of these mudflats. Efforts were made to preserve the ecological and tidal areas of the Slaak, while minimising the impact on agricultural land in Sint Philipsland.