Deltares: Maintaining the Dutch Coast

Rijkswaterstaat needs millions of cubic meters of sand every year to maintain the Dutch coast and protect it from the coastal erosion caused by major storms.

That sand comes from the seabed. A permit is needed to extract the sand and an environmental impact report is needed in turn to obtain a permit.

Rijkswaterstaat works with the LaMER foundation – the platform for the commercial bodies that extract fill sand – on this permit and report.

They called in Deltares to study more than eighty areas and determine how suitable they are for the extraction of sand for beach nourishment and fill sand over the next ten years.

The sand can be found between the continuous NAP -20 m line and the twelve-mile limit.

Extraction is inappropriate in areas with, for example, ecological value, where there are cables in the seabed, with navigation channels or wind farms (now or in future), or where other man-made structures are located.

The structure of the seabed is also important.

Identifying potential locations for sand extraction

Combining these exclusion areas with the Mineral Information System developed by Deltares in collaboration with TNO resulted in the identification of more than eighty potential locations for sand extraction.

The geological structure of these areas will have to be studied to see whether they may be suitable for sand extraction in the next ten years.

Deltares is currently looking at all of these locations to determine the structure of the seabed and to see whether it contains rocks, peat and silt layers, to determine the structure of the sand grains, and to establish how much silt will be released if sand is extracted.

The study began in mid-June and publication of the resulting report is planned for late October.

On the basis of the recommendations, Rijkswaterstaat will then select the areas for the extraction of the millions of cubic meters of sand needed to maintain the Dutch coast in the next ten years and for the extraction of fill sand.

The report will serve as a background document for the environmental impact report.