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Dieren en planten

Water en land

Eierland, 1995, Ecomare, Sytske Dijksen

Coastal protection

In the Netherlands, the dunes form a natural sandy sea defence, together with the beach and the underwater banks, and is continually changing under influence of natural forces. The sea is building new coasts in some places while eroding away coasts elsewhere. The rest of the Dutch defence line consists of sea dikes dams and piers. Nowadays, methods such as sand nourishments have been developed to maintain the natural sea defences. The least spectacular, but actually the most important form of coastal protection, is management of the beach ridges (the outer row of dunes).

  • Coastal protection in the wadden region

    Sand nourishment is the most often applied method for protecting coastal regions from flooding in the Netherlands, while Germany and Denmark use outer dike salt marshes as an important part of their coastal defence.
    Coastal protection is not performed everywhere on the islands. If the coast is not being threatened, nature is allowed free play. For example, there is no coastal protection on the German islands Nigehörn, Scharhörn, Memmert and Mellum, with the exception of a few small coastal works necessary to protect the homes of the island managers. Nor is there any extensive coastal protection on the Dutch islands Rottummeeroog and Rottumeerplaat.

  • Sea-level rising and North Sea coast

    As of the 21st century, there is no doubt any longer among scientists and politicians that the temperature on earth is rising, causing various glaciers and polar caps to melt. Being a 'nether' land means that extra regulations must be taken to reassure safety from the rising North Sea. Lots of suggestions and studies are constantly being made, such as islands off the coast, raising sea dikes, wider beaches, a Second Delta Plan, etc.
    The Delta Committee was re-installed in September 2007 by the Dutch government to investigate how to protect the country best from climate change and sea-level rising for over a century. They reported their Delta Plan, 'Working together with water', in September 2008 to the Parliament, presenting twelve recommendations for adaptations to the Dutch coast and inland waters. Their general recommendation is to urgently and drastically increase the safety of the Netherlands; based upon their suggestions, it will cost 1.3 to 1.9 billion euros per year up till 2050.
    Some of major recommendations of the Delta Committee are the following:
    1 - gradually broaden the North Sea coast with sand nourishments spread out over a hundred years to allow nature to develop;
    2 - gradually raise the water level in the IJsselmeer by a maximum of 1.5 meters, to insure the capability of releasing excess water without having to pump;
    3 - protect the Rijn estuary region on both the sea-side and river-side with movable flood barriers;
    4 - provide flood areas for excess riverwater from the Maas and Rijn in the Krammer-Volkerak, the Zoommeer, the Grevelingen and possibly the Oosterschelde;
    5 - increase the lifespan of the Oosterschelde flood barrier; it is now made to work till 2075;
    6 - stregthen and raise sea and river dikes;
    7 - keep the Westerschelde and New Waterway open; it must also be possible to close off the New Waterway if necessary.
    Further recommendations and detailed information can be found on the website (see Weblinks, below). Executing the Delta Committee's advice means supplementing 85 million cubic meters of sand per year, which is seven times more than what is needed anno 2008.
    The first reactions from environmental groups and political parties were generally positive. However, there was also criticism from others questioning the costs per year. Are the costs for safety or do they also include new economic development. And perhaps various activities should move to safer areas instead of spending millions to keep dry feet. Needless to say, more discussion will come before any action takes place.

  • Weak links
    Weak areas in the Dutch sea dikes, Ecomare

    There are fourteen weak links in the primary dunes in the northern part of North-Holland. The costs for enforcing all of the weak spots is estimated at 432 million euros (2008).
    The Hondsbossche and Pettemer sea dikes form weak links along the Dutch coast because they are 1.5 and 4 meters too low to withstand a possible superstorm. In April 2008, three options for re- enforcing the dunes between Petten and Den Helder reached the Environmental Effect Report stage.
    Enforcement of the weak link between Hook of Holland and the harbour of Scheveningen began in the autumn of 2008 and is expected to take three years. The beach will be extended by 200 meters seaward. Drifting sand will result in natural growth of the dunes, adding to the enforcement.
    One of the most serious problems such a mega-sand nourishment will cause is the loss of forage area for 10,000 birds. Although they do not serve the purpose they were built for (preventing erosion), the breakwaters along the coast have become important sources of food for gulls, oystercatchers, turnstones, sandpipers. Mussels, sea snails, crabs and starfish live among the stones. The sand nourishment as planned will bury the breakwaters in tons of sand. The Water Board recognizes the importance of the breakwaters and hopes to find a solution to this problem.
    Researcher Bram Bliek from Swasek Hydraulics presented a plan in 2008 to pack the Hondsbossche en Pettemer sea dike in with sand, creating a 200-meter long sandy beach. In addition, 4 to 5 million cubic meters of sand nourishment is necessary to maintain this body of sand along the coast between IJmuiden and Den Helder every year. Wind and currents will take care of all sand transportation, carrying sand to where it is needed.

  • Earlier days

    People were building terpen in the Bronze Age (2600 years ago), which functioned as refuge when the sea rose. Many terpen have been excavated, but others can still be found. Those on the German Halligen still serve as protection for tidal floods.

  • Protection of North Sea coasts elsewhere

    All of the countries around the North Sea incur coastal erosion of some kind. But not all countries are actively involved in maintaining the present coastline. The coast of Norwich in eastern England is made up of dunes and beaches. Hundreds of meters of dunes have disappeared since the late 1980s. The only beach defence are wooden poles placed in 1959 to break the waves. Although the poles have never been maintained and are rotting away, they proved to still have effect, especially noticeable when several hundred meters were removed. The British budget only provides 46 million euros per year to protect its entire coast (17,800 kilometer) compared to the 1 billion euros annually recommended by the Delta Commission for the Dutch coast (~350 kilometers).
    Belgium, on the other hand, was among the first in the early 1990s to use fore-bank sand nourishments to protect its coast. The difference with the Netherlands, where one attempts to maintain the coastline as it was, the Belgians are most concerned about safety.
    In 2005, the North Sea Coastal Managers Group initiated a network of coastal managers from the five North Sea countries, referred to as Safecoast. The project Chain of Safety started at the same time. While Safecoast deals with the effects of climate change on managing the coasts, Chain of Safety works more on the human problems when floods or other disasters occur. Both projects are supported by the European Community and fall under the Interreg program for interregional cooperation.
    In 2008, the two projects had a joint final conference. One of the results of the Safecoast project included a preliminary risk analysis for the entire North Sea region. The greatest increase in the risk of flooding up to 2050 is expected in the Central Netherlands, the Thames and Humber estuaries, the coast of West-Flanders, Antwerp, Hamburg and Bremen. Project leader Niels Roode hopes that instead of acting after the fact, which has always been the case up till now, this project will encourage the North Sea countries to act before the crisis occurs.

  • Coastal activities versus the coastal ecosystem

    The major target of coastal protection is aimed at protecting people. A secondary target is preserving various habitats, such as the dunes. However, there is not usually much thought given to protecting beach fauna. In his oration speech, Prof. G.M. Janssen describes the effects of human activity along the coast in relationship to the fauna found in the sand. He pleads for the acknowledgement that a beach is not just made up of sand. It has its own ecology that is ignored particularly when preparing the beach for recreational activities and other uses. Important links in the food chain live in the wet sands along the coast.
    It is obvious that dumping sand on the beach or forebanks during sand nourishments buries any life that was on or near the surface. But one doesn't think twice about the damage done to fauna living in the sand by driving with a vehicle along the waterline. Birds fly away, but the animals they pick out of the sand are squashed. Big culprits are mechanical methods for cleaning beaches from marine litter.