Lock + aquaduct = naviduct
Capacity at the Krabbegat Lock in the Houtrib Dike between Enkhuizen and Lelystad was seriously overstretched, especially in the summer. The roadway led over the lock via a drawbridge, which meant that boats as well as cars often had to endure long waiting times. This prompted Rijkswaterstaat (the Directorate-General for Public Works and Water Management) to build a new lock complex to the east. Zwarts & Jansma became involved in the design at an early stage, for the overall architectural aspects and the buildings of this largely civil work.
The complex consists of two lock-chambers, each 120 metres long and 12 metres wide. These function independently and are suitable for both merchant and pleasure craft. The roadway travels under the lock, and in the new situation it is simultaneously a lock and an aqueduct. This new civil engineering type was dubbed a ‘Naviduct’.
The location of the control building is dictated by the optimization of sightlines. The position of the control room is elevated to afford the best possible overview of the complex and is thus kept separate from the two-storey substructure. Functions that have no need for a view are incorporated in the substructure.
The elevated position of the lockkeeper in the superstructure is exploited to make the control building room into an eye-catching building, despite its small proportions compared with the big lock complex. The control room has an unusual and attractive form that is recognizable from a long way away. The finish of the control building, clad with shining stainless steel, stands in sharp contrast with the heavy, stony substructure. The orthogonal substructure is partially embedded in the embankment to accentuate its heavy, solid character. The transparent glass stairwell connecting the sub- and superstructures exaggerates the floating effect of the lockkeeper’s control building.
For the nature development around the Naviduct, a landscaping and ecological design was drafted in collaboration with landscape architect Lodewijk Baljon. Surplus silt (2 million cubic metres) from the digging of the locks was used to raise an embankment on the IJsselmeer, thus creating a habitat for wildlife to thrive undisturbed. This structure also has a protective function, as a windbreak for vessels sailing into and from the IJsselmeer.