Buoyant dam provides protection to the city of Spakenburg.
In the near future, the historical centre of the Dutch town of Spakenburg will be protected against flooding by a rising dam, powered by the upward force of the water. With its total length of 335 metres, this floating dam will be the longest in the world. The dam – 80 centimetres in height – will be submerged in the road surface surrounding the historical fishing harbour, to prevent the dam from influencing the sights of the historical centre. The dam will be fixed into the raised embankment alongside the new harbour.
The project is part of the dam improvement alongside the Zuidelijke Randmeren (Southern Border Lakes) and the Eem River, passing through the Water Board Valley and the Veluwe national park. The national programme for the prevention of high water, the ‘Hoogwaterbeschermingsprogramma’ is funding the project. Construction will start in the autumn of 2016.
The tender for this project, called by the water board, was won by the Dutch building consortium Van Heteren (Hengelo)/Jansen Venneboer (Wijhe). The project called for an innovative solution, and the rising dam design was the best match for the design requirements. The project asked for the solution to blend into the historical centre, taking up little space and with a maximum deployment time of three hours, requiring only a few employees of the water board.
Example for other cities
The technique is supplied by the Belgian company Aggéres. Although the technique has been used before, on different locations worldwide, the Spakenburg project will be the first time it is constructed at such a large scale and as part of the primary water barrier. This will make this a good example for other historical city centres in the Netherlands, such as Dordrecht.
The water barrier will float upwards as a result of the rising water level in the harbours. This water will fill the steel container holding the dam. The dam is made from a light weight plastic, with a steel cover. The incoming water will push up the dam.
The dam will be incorporated into the road surface surrounding the historical harbour (approximately 60 metres of the Turfwal and some 115 metres of the Oude Schans). The embankment lining the new harbour (Kerkemaat) is raised 60 centimetres; this elevation will hold the dam (about 160 metres). The park on the south side of the new harbour (Weikamp) will be redesigned, in order to fulfil its water containing function.
There will be no new water barrier at the other length of the marina (Havendijk). This will remain ‘outside the dam’. The buildings there have been built to withstand high water.
High Water Protection Programme
As a result of the construction of the floating dam, the water barrier at Spakenburg will meet the current requirements, to withstand water levels that occur during north-western storms at wind force 12. This is the requirement that all dams alongside the Zuidelijke Randmeren and the Eem must meet. Because these dams protect a large area against high water levels, this construction is called the ‘primary water barrier’, and the requirements for these barriers have been determined by the State. The construction of the floating dam is funded by the national High Water Protection Programme, a cooperative body of the Dutch water boards and the Department of Waterways and Public Works.