Investigating possibilities for sand extraction off the Dutch coast
Rijkswaterstaat -the Dutch authority responsible for the design, construction, management and maintenance of the main infrastructure facilities in the Netherlands- needs millions of cubic metres 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. Rijkswaterstaat and the LaMER foundation 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 -20m 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.
Structure of the seabed
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 disturbed silt can make the water turbid and have a negative ecological impact on the North Sea and Wadden Sea. These impact assessments are important for the environmental impact report. Initially, the study will identify the areas that are most and least promising in geological terms.
This will be done in collaboration with various private bodies and the Dutch Geological Service (TNO) on the basis of existing information and knowledge. Areas about which information is sparse will also be identified. The next step will be to go to sea on the Zirfaea, a Rijkswaterstaat survey vessel, to conduct borings. A second vessel will carry out geophysical surveys to map out the suitability of the selected prospecting areas in greater detail.
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 metres 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.
