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Dieren en planten

Water en land

Mens en Milieu

Coastal protection   Sand nourishments   
Sand nourishment on Texel, Foto Fitis,

Sand nourishments along the Dutch coast

Dunes are built and eroded away by the wind. Sometimes, more sand washes away than washes ashore, creating a negative sand balance. Since 1979, the Dutch Department of Public Works has been compensating coastal erosion by spouting sand onto the beaches of the Dutch coast. This has been the major form of coastal protection since 1990, In 1993, a new method was developed, whereby large amounts of additional sand are dumped on the fore banks. The goal is to maintain the coastline of 1990.

On Texel

Beach nourishment Texel, ca.1995, Ecomare, Sytske Dijksen

On Texel, the first beach nourishment occurred in 1979 along the coast by Eierland. In 1984 and 1985, extra sand was added to the beaches of De Koog and Eierland. Since 1990, two to three million cubic meters of sand are sprayed onto the beaches of Texel almost every year. As far as coastal protection is concerned, Texel is the most expensive ground in the Netherlands. In order to limit the costs, a 550-meter long dam was constructed perpendicular to the coast near Eierland in 1995. Nevertheless, sand nourishments remained a necessity. The first forebank nourishments near Texel took place in 2002 and 2003.

  • Where from and where to
    Beach nourishment, Ecomare

    The sand is extracted from areas which usually lie a number of kilometers away from the shore and at least 20 meters deep. Sand from dredged channels is also used for nourishments. Between 1990 and 2000, around seven million cubic meters of sand was extracted every year. In 2008, around 12 million cubic meters of sand was needed. It is expected that this amount will have to increase to combat sea-level rise.
    Even the beaches of the eastern and north Frisian Islands are regularly supplied with new sand. In 1998/1999, almost all of the beaches of Baltrum and Wangerooge (in Germany) were lost during heavy winter storms. Sylt is continually threatened with sand loss.

  • Sucked-up benthic (bottom) animals and treasures
    Many stones are spouted onto the beach, Foto Fitis,

    The sand used for beach nourishments is sucked up far away from the coastline at a depth of more than twenty meters. It is often easy to see on the beach that the sand comes from elsewhere. Benthic animals normally are not found very often on the beach are among the sucked-up sand. Benthic fish such as plaice and turbot land on the beach after a trip through the hopper, making an easy meal for coastal birds. Other examples of sucked-up treasures from the bottom are fossil bones from a walrus, early-Middle Age coins and silver rings and flint stone instruments from banks in the North Sea which used to be inhabited. During sand nourishments in Zeeland, fossilized shark and ray teeth are often found in the sand on the beach. This sand comes from a sandbank situated close to the coast.

  • Forebank nourishments
    A fore bank nourishment, Foto Fitis,

    An underwater nourishment was performed for the first time in the Netherlands in 1993, along the coast of Terschelling. It was time for a sand nourishment on the north shore of the island. Forebank nourishments are cheaper than beach nourishments since the sand does not have to be transported as far. Much more sand can be used for coastal defence for the same budget. In addition, there are no inconveniences on the beach.
    Two million cubic meters of sand was dumped right in front of the Terschelling coast, at a depth of around six meters. Based on experience in Australia and the United States, it was expected that the receding shoreline could be compensated by introducing a kind of pavement in front of the coast. This expectation was proven true. The experimental fore bank nourishment near Terschelling had such favourable effects that the Department for Public Works now applies the method in many other coastal areas.

  • Ecological effects

    The ecological effects of the underwater supplementation on Terschelling were studied using a grant from the European Community. The research concentrated on the extent and duration of the disturbance on the sea life living on the underwater bank. Approximately six months after the supplementation, the density of the benthic fauna was around half of what it was before supplementation. Shellfish in particular had declined. Worms and crustaceans recovered more quickly.
    Two years after the supplementation, the density of the benthic animals was again comparable to the original situation. Only the cut trough shells, the banded wedge shell and the sea potato did not recover.
    This pattern of recovery shows that there are not many risks for sea fish in relation to forebank nourishments. Fish species found a lot in coastal water (plaice, sole, dab, brill, turbot) eat mainly worms and crustaceans, species which recover quickly. The risks for diving ducks, such as common scoters, is greater. These ducks consume primarily shellfish that live on banks. When such a bank has been disturbed by sand nourishments, it can take several years before the ducks can find food again.
    Comparable effects occur in areas where sand is exploited. Worms and crustaceans recover quickly, while considerable damage is done to long-living species, such as bivalve shellfish and sea potatoes.
    Because sand nourishments have ecological and geological consequences, the Natura 2000 regulation requires a study of the effects on the sea fauna, both where the sand is exploited and where it is to be dumped. To avoid any possible delays due to legal discussions, Rijkswaterstaat had an environmental effect report performed on sand exploitation (2008-2012). The results showed that negligible effects occurred down to a depth of 2 meters. Deeper exploitation down to 6 meters even decreased the amount of damaged surface area. In the meantime, regulations have been formulated, which include keeping a 500-meter distance from spisula shellbanks and taking into account times in the year when birds are foraging and seals are nursing.