Is sand becoming scarce?

Seismic sand model

Sand is used for many different purposes such as for our coastal defense, but also in construction as filler sand or to make concrete and in glass and electronics. Sand expert Tommer Vermaas knows all about it. As chief project manager of the Aggregates Information System, he accurately maps our Dutch sand reserves at sea.

Tommer: "We are working on an improvement of the earlier model where we are now adding another source of information: seismic data. Whereas a borehole gives information at a single point, seismic data gives it along a line. It is measured from a ship, and along the entire sailing line you get a 2D image of the subsurface. This gives us a more detailed picture of the sand layers under the seabed. Before, only drilling was used."

"I like putting the puzzle of the subsoil together and want to solve practical issues. These range from wind turbines we want to build at sea, dike safety and also sand. As a coastal geologist, I mainly study coastal development and how everything is preserved in the subsoil."

3D Model

If in the Netherlands we don’t consider the availability of sand in our spatial planning, we will run into problems in the long run. Cables or wind farms, for example, might then be in the way for sand extraction. Then it becomes much more expensive to extract suitable sand. It is important to keep enough sand available for our coastal defenses and construction in the long term.

Together with TNO - Geological Survey of the Netherlands, we are making a new subsurface model of the sand mining area in the North Sea on behalf of Rijkswaterstaat. We are now using detailed 3D modelling in it to map where each type of sand is located.

This also allows us to calculate how much sand there is. As manager of the North Sea, Rijkswaterstaat also uses this model when granting permits or planning cable routes or wind farms, for example.

The extraction of sand is of national importance. Sand is necessary to keep coastal safety in order, and sand is also needed in construction. It is therefore very important that we have a good understanding of the sand reserves in the Netherlands.

Quirijn Lodder, senior water safety advisor, Rijkswaterstaat

Serious sand shortage

"Here in the Netherlands, we still have enough sand, but in other places in the world it is scarce. Shortages are also not easy to solve because it is expensive to move sand over long distances," says Tommer.

"We have to keep an eye on our supplies for the long term. You must be able to access it and you need specific sand for different applications. If we lay a cable through the North Sea or build houses, we cannot remove the sand underneath. In IJmuiden, you can bring sand ashore easily because of the harbour. But the area where we can extract sand from the sea is limited by cables, pipelines, wind farms and a busy shipping route. Therefore, sand is scarce there anyway."

"It does not look like grains of sand may disappear altogether soon, but suitable sand cannot always be found nearby. Sometimes this makes it financially unattractive to extract that sand. Then there is scarcity after all. In the Netherlands, we don't have to worry yet when it comes to coastal defense sand, but we must keep it in mind."

Sand thieves

Globally, there is cause for alarm, Tommer points out. The sand issue received a lot of attention in 2022 due to a report by the United Nations Environment Programme UNEP. Helena van der Vegt, coastal researcher at Deltares, contributed to this. Among other things, this report warns of a shortage of construction sand in developing countries. This can lead to criminal practices, such as sand extraction from beaches without a permit.

Helena explains that there are different types of sand. "Construction sand should be angular and coarse (large grains), so that the grains hook firmly together. This sand is mainly found on the mainland in the Netherlands. Sand grains start out coarse and angular but gradually wear down and thus become finer (smaller grains) and rounder, as they continue to flow with the river and are blown by the wind."

Sometimes there is a lack of knowledge. Then sand is removed somewhere, causing damage in other places. In Vietnam, for example, where sand was extracted from the Mekong River, which then no longer reaches the delta, resulting in flooding.

Dune and desert sand cannot be used in construction because the sand grains are too fine and round. Thus, desert countries may have to import sand anyway.

Helena van der Vegt, coastal researcher Deltares

Sand status in the Netherlands

In the Netherlands, we have sand management under control, says Tommer. "Because of all our laws and regulations, we handle it responsibly in the Netherlands. We have also been nourishing our coasts with sand for 35 years."

Efforts are being made by UNEP to make all global data more transparent. Awareness and dialogue on sand have increased. There is also increasing attention to it in the media.

Tommer: "Another nice example is Vietnam, where several projects are ongoing and Deltares also provides sand supply advice. There, they are now more conscious about sand, both in rivers and at sea."

Sustainable sand management

Sand extraction from the North Sea requires extensive testing first, says Tommer. "Suppose we need two million cubic metres of sand for raising, selling or for construction. Then we first check where this is available and to what depth we need to go. We also study what sand there is and what the effects on ecology are if we take it out."

Tommer explains: "When we nourish the beach, we look for sand similar to what is already there. We preferably don't have clay or stones on the beach. That's not good for ecology, nor is it nice for people enjoying the beach walking barefoot there. For our coastal defenses, we take sand further out to sea, where we expect no adverse effects on our beaches. Otherwise, you would be carrying water to the sea."

In sand extraction, you damage the seabed, taking away shells and other life. That is why an environmental impact assessment (EIA) study is carried out by a consultancy company. For the EIA Deltares specifically looks at the effects of sand extraction on ecology in the North Sea and the Wadden area. This mainly concerns fine material which is released when you extract sand from the sea floor. Those fines contain food for marine life, but too many fines also block light and can have adverse effects on the ecosystem.

Subsurface data shows what material has been deposited at the location of the datapoint. Using geological knowledge, you can then reconstruct the system that deposited that sediment. Once you understand that system, you can predict what you can expect at locations where there is no data. This way you can predict where you might encounter sand, how certain this prediction is and whether that sand is easily accessible.

Romée Kars, Geologist, TNO Geological Survey of the Netherlands

Alternatives to sand

Tommer says we need to look for solutions where you can build with less sand, such as other construction techniques, lighter building materials like wood and recycling of raw materials. "Because we have concrete houses that are heavy, we need to put a good layer of sand underneath to keep it stable. A lot of sand goes into the concrete itself, of course.

More drilling and seismic data

Tommer: "In the Netherlands, we are working with the Geological Survey and Rijkswaterstaat to further improve the model with new data." Abroad, there is still a lot to investigate and often little is known about sand availability. You can't see what's under the ground with satellites, for that, drilling must be done, and seismic data must be available.

"We look at the cores from the North Sea in our lab in Delft", Tommer points out. "Every year boreholes are planned to get more insight into availability of our sand, and form input for the model we built. We then want to know how the sediment was deposited in the borehole. For example, did it come from rivers, sea or land ice? And how old is it? With that knowledge, we can better predict whether a clay layer occurs locally or over a larger area, and that gives more insight into the variation in sand composition. After all, a borehole is only a 10 cm wide, a few metres away the subsurface can be very different again."

What is your dream?

"I think it's incredibly beautiful that in the Netherlands we collect so much data and invest in properly mapping sand resources. As a geologist, that's a dream!"