The Deltaworks brought safety to Zeeland, the province that was devastated by the 1953 flood disaster. Safety used to be secured at the expense of nature.
Today, however, nature conservation is as important as flood protection. In half a century, insights have radically changed.
Letting seawater in, instead of keeping it out. That’s what the sluices of the Haringvliet, a former North Sea bay, will do in a couple of years time. It’s the first step towards the recovery of the natural eco-system behind the Deltaworks’ sluices.
Nature is no longer the neglected child at Rijkswaterstaat, the Dutch Department of Public Works and Water-management. This fact emerged at the symposium ‘Deltaworks or working on the delta,’ organised by Civil Engineering’s student society, Water-management.
When the sluice was built thirty years ago, the salty sea at Haringvliet was turned into a fresh water lake. The sluice was only opened at low tide to discharge river water. From 2005, however, the sluice gates will be left slightly ajar most of the time, admitting seawater into the former bay. ”At first, the flow opening will be a few hundred square metres. That’s tiny, compared to what it used to be, but it offers direct possibilities for the migration of fish,” explains J.W.M Kuijpers, of Rijkswaterstaat’s Directorate for the Zuid-Holland Region. Also, the tidal movement will return, although in a reduced form of only a few centimetres.
Compensation
A transition zone between fresh and salt water will be created, requiring the water intakes for drinking water and agriculture to move further away from the sea. The sluice gates, therefore, will not only be closed in the spring, but also when the seawater’s salt concentration exceeds a certain limit.
In 2015, the sluice gates will be opened to one third of their height. Kuijpers: ”To open the slides immediately would be very expensive, because compensation would have to be paid to farmers, local water administrators and drinking water companies.”
Looking back on half a century of Deltaworks, Professor H. Saeijs notes that the original plans consisted mainly of concrete and steel, and all was focussed on keeping the sea out. ”At the time, all sea coves were to be closed. Later on, it appeared possible to keep them open, like the Westerschelde,” he says.
The Oosterschelde’s storm tide dam, which only closes when water levels are dangerously high, was the first dam that also took the environment into account.
Nowadays, the Deltaworks would be constructed differently, with nature being interfered with as little as possible, according to Saeijs, so that in future nature wouldn’t have to be restored.
With the opening of Haringvliet’s sluice gates, nature isn’t restored yet. At the lake’s bottom, there’s lots of contaminated sludge. Much remains to be done in order to make nature natural again.
The Deltaworks brought safety to Zeeland, the province that was devastated by the 1953 flood disaster. Safety used to be secured at the expense of nature. Today, however, nature conservation is as important as flood protection. In half a century, insights have radically changed.
Letting seawater in, instead of keeping it out. That’s what the sluices of the Haringvliet, a former North Sea bay, will do in a couple of years time. It’s the first step towards the recovery of the natural eco-system behind the Deltaworks’ sluices.
Nature is no longer the neglected child at Rijkswaterstaat, the Dutch Department of Public Works and Water-management. This fact emerged at the symposium ‘Deltaworks or working on the delta,’ organised by Civil Engineering’s student society, Water-management.
When the sluice was built thirty years ago, the salty sea at Haringvliet was turned into a fresh water lake. The sluice was only opened at low tide to discharge river water. From 2005, however, the sluice gates will be left slightly ajar most of the time, admitting seawater into the former bay. ”At first, the flow opening will be a few hundred square metres. That’s tiny, compared to what it used to be, but it offers direct possibilities for the migration of fish,” explains J.W.M Kuijpers, of Rijkswaterstaat’s Directorate for the Zuid-Holland Region. Also, the tidal movement will return, although in a reduced form of only a few centimetres.
Compensation
A transition zone between fresh and salt water will be created, requiring the water intakes for drinking water and agriculture to move further away from the sea. The sluice gates, therefore, will not only be closed in the spring, but also when the seawater’s salt concentration exceeds a certain limit.
In 2015, the sluice gates will be opened to one third of their height. Kuijpers: ”To open the slides immediately would be very expensive, because compensation would have to be paid to farmers, local water administrators and drinking water companies.”
Looking back on half a century of Deltaworks, Professor H. Saeijs notes that the original plans consisted mainly of concrete and steel, and all was focussed on keeping the sea out. ”At the time, all sea coves were to be closed. Later on, it appeared possible to keep them open, like the Westerschelde,” he says.
The Oosterschelde’s storm tide dam, which only closes when water levels are dangerously high, was the first dam that also took the environment into account.
Nowadays, the Deltaworks would be constructed differently, with nature being interfered with as little as possible, according to Saeijs, so that in future nature wouldn’t have to be restored.
With the opening of Haringvliet’s sluice gates, nature isn’t restored yet. At the lake’s bottom, there’s lots of contaminated sludge. Much remains to be done in order to make nature natural again.
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