Delta Life 11

Deltares, MARCH 2019 19 More information: maaike.blauw@deltares.nl Not all sand is suitable for use in construction or for raising coasts. Desert sand, for instance, is too uniformand doesn't provide enough grip. The amount of sand in a single location can be small. Alternatively, a project may be too far away. Under these conditions, sand extraction will not be economically feasible. Worldwide, we currently need more sand than the amount formed by the pulverisation and wearing of rocks, river beds and mountains. That is leading to the depletion of our supplies. More­ over, in areas where regulation is inadequate, sand extraction is increasingly resulting in damage to the natural environment and the loss of biodiversity. Sand extraction even results in crime. Research by Temple University in the United States, for example, showed that the demand for sand in India exceeds supplies from legal sources three times over. That has led to the establishment of a 'sand mafia' that extracts sand illegally and is happy to use violent methods. Poorly regulated sand extraction at seamakes coastal areas particularly vulnerable to ero- sion and sea level rise. In deltas like the Mekong in Vietnam, salty seawater is pene­ trating further inland, causing the salinisation and degradation of drinking water supplies and agri- cultural land. Not all countries have their own sand reserves. However, all countries do need sand. This issue needs to be addressed internationally if sand extraction is to be sustainable. Geo­ logical services and research and coastal institutes can play an important role here. Deltares knows where sand has accumulated in the past and where it is accumulating now. By combining this information with our morphology expertise, we know which sand can be extracted, and where, in a sustainable way without impacting natural values or coastal foundations. In the Netherlands, most sand is extracted in the North Sea. But things are busy there. Fishing, oil and gas extraction, shipping, wind farms, nature and, in the future, per­ haps the expansion of Schiphol airport: all these things take up space. Deltares - in collabora­ tion with TNO - has been studying the North Sea for more than fifty years. So this is one of the most intensively researched areas in the world. Even so, no more than 0.01% of the bed has actually been bored and studied. Precisely because use patterns are becoming so intensive, the Dutch government has asked Deltares to produce even more detailed charts of the subsur­ face below the bed of the North Sea. By combining bore studies with seismo­ logical and geological expertise, we can esta­ blish a clear picture of the quality and availability of sand. Deltares and sand