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A 42-kilometre-long dam strengthens the tides in the Wadden Sea by means of wave resonance so that water from IJsselmeer can continue to be discharged into the Wadden Sea despite the rising sea level
Strengthened tides as the answer to rising seas
The Resonator is a 42-kilometre-long dam south of the Afsluitdijk, the dyke between the sea and IJsselmeer. It lengthens the tidal basins in the Western Wadden Sea, so that original waves and reflected waves reinforce each other. This is known as wave resonance. This strengthening of the tides in the Wadden Sea makes the low water here lower. It means that despite the rising sea level it will be possible to discharge water from IJsselmeer into the Wadden Sea for the next hundred years.
The Resonator is inspired by the first plan Cornelis Lely drew up for the Afsluitdijk. This would have placed the Afsluitdijk much further to the south. A committee led by Nobel Prize winner Hendrik Lorentz calculated that due to wave resonance the tide here could become three times as strong, which might cause problems during the construction of the Afsluitdijk. For this and other reasons Lely's plan was modified and the dyke placed more to the north where it would 'only' double the tidal strength. The Resonator reinforces the tide to roughly the same extent as calculated by Lorentz for the southern version of the Afsluitdijk. Much taller dykes are therefore required to cope with the high water levels. The IJsselmeer water is discharged via a sluice complex in the Resonator dam and the existing discharge sluices in the Afsluitdijk. The tidal current flows in and out of the Resonator through a six-kilometre-long gap in the Afsluitdijk oversailed by a bridge (Lelybrug) high enough for ships to pass underneath.
Between Resonator and Afsluitdijk is a dynamic brackish water ecosystem, as this is where freshwater and salt water converge. Here, redirected currents carve new channels and ebb-tidal shoals.
A calm freshwater lake, Friese Randmeer, occupies the space between the coast of Friesland and the Resonator. This area, which can be used for pleasure boating in small craft, increases Friesland's potential for water sports.
The Resonator dam is a varied flood defence landscape shaped by natural processes and with space for recreation. Sand fills and and dredging sludge from the IJsselmeer and Markermeer lakes lay the basis for three landscape types named after shallows in the former Zuiderzee inlet. Wieringer Vlaak is a brackish landscape of salt marshes generated by tidal dynamics. Kreilerbaai is an inland lake surrounded by islands opposite the coastal town of Stavoren. Here there is room for camp sites, yacht harbours and holiday chalets in an expansive dune landscape. Steenplaat Archipel is an extensive island pattern of shallows, reed marshes and marshy woodland opposite the village of Makkum; a place where birds can breed in peace and quiet.
The Afsluitdijk retains its unique character in these new circumstances. New duties to perform are not in its interest. Nor is there any need to heighten the Afsluitdijk within the accretion of the Resonator. Just the road is made higher as the tides to either side of the dyke have been given free play. Travellers on the motorway can look out over the crest of the dyke to the Wadden Sea and experience the great expanse round about.
The cycleway once squeezed between the crest of the Afsluitdijk and the motorway is moved to the south side of the dyke. Cyclists are now less inconvenienced by the onslaught of traffic and have a view of the landscape of water and sandbanks in the Resonator.
Place of education: AvB Amsterdam | Specialization: landscape architecture | Tutors: Rob van Leeuwen, Berdie Olthof, Arjan Karssen
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