5

islands

1000

hectares of new land

30 million m3

of sediment used

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The challenge

With nearly one third of the country below sea level, people living in the Netherlands are faced with the constant risk of flooding. As a result, over the centuries, the Dutch have become world renowned for their expertise in water management. The Afsluit and Houtrib Dikes are two examples of spectacular waterworks projects that provide protection to millions of people. But they have also had unintended negative consequences for nature. The dikes have created two lakes, Lake IJssel and Lake Markermeer, water which was previous connected to the North Sea. In Lake Markermeer, now that the water is no longer subject to the tides, the marine environment is stagnant, and there is a high concentration of sediments like sand, clay, and silt. This combined with the lack of landmass in the lake means that Lake Markermeer is a hostile environment for fish, birds, and other living creatures. The Dutch wildlife conservation NGO Natuurmonumenten and the Dutch Ministry of Public Works decided to take steps to stimulate life in Lake Markermeer.

The solution

The construction, dredging, and marine services company Boskalis devised a plan to build a number of islands in the lake, with the goal of creating a new nature reserve: a place for plants and animals to flourish. Boskalis asked our experts to help with the design of the islands and help ensure they won’t be blown or washed away over time. The islands also needed to be outfitted with various dunes, mudflats, jetties, and other natural barriers to help create a safe environment for fish to spawn and birds to feed and nest.


The result is the Marker Wadden Islands, an archipelago that is similar to the Wadden Islands along the coast at the North Sea. The first phase of the project involved the creation of five new islands: 1000 hectares of new landmass. These islands are made completely out of sand, clay, and silt that was taken from the bottom of Lake Markermeer. In total, 30 million cubic meters of sediment was used to make the islands. Arcadis experts in sand morphology helped ensure the long, sandy shores of the islands provide adequate protection for the swamp lands and shallows behind them. This creates attractive areas for fish and other wildlife. In contrast to traditional structures such as steep dams and dikes, the gradually sloping natural banks create a dynamic transition between land and water. This has given Lake Markermeer a totally new look and has also improved the ecosystem for plants and animals.

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    The Marker Wadden Islands are also a treasure trove for science. The islands form a living laboratory for researchers studying how best to develop new natural systems. Arcadis experts worked together with experts from Boskalis, Wtteveen+Bos and Vista in order to deliver this revolutionary project. Arcadians contributed to the design of the islands, maintenance of the sandy shores, stakeholder engagement and we managed the licensing procedures.

The impact

The construction of the Marker Wadden Islands transforms Lake Markermeer into a more dynamic environment that enriches animal and plant life. The first phase of the project was completed in 2020 with the establishment of the five new islands and the surrounding shallow wetlands. By far, the largest part of the Marker Wadden consists of closed nature reserves. However, one of the islands is also open to the public and includes a visitor center, a play area for children, hiking trails and a watchtower.


The intended results were already visible during construction, when scores of birds descended upon the project site. This included numerous endangered species. The new nature reserve has also helped with the recovery of the underwater landscape. Arcadians have contributed valuable expertise, which has helped transform a desolate, manmade lake, into a marine environment that is teeming with life.


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