Delta Life 7

DELTARES, MARCH 2017 23 Alliance between Deltares and industry produces innovative techniques and creates new market opportunities for business. MAPPING OUT THE FLOOR OF THE NORTH SEA T he seabed consists of layers of material such as sand, clay, peat and gravel. If we dig in the wrong places, the ecology can suffer and the coast could even be eroded. A clear picture of the seabed is needed to minimise the impact on the environment when extracting sand for nourishment operations. We can, for example, limit the impact of the release of clay into the water. Marine Sampling Holland BV is part of a consortium that identifies locations for sand extraction. Cees Laban, a con- sultant with MSH: 'We had to team up with others to map out such a large area in the North Sea. It was a huge logistical effort that had to be completed in a short period of time.' New drilling techniques MSH specialises in offshore research. Over the past forty years, the company has analysed materials on and below the seabed throughout the world using sampling and geo- technical equipment. Government authorities, dredging contractors and research institutes use this information when, for example, they build offshore wind farms or dredge ports. MSH studied the Dutch coast in the summer and autumn of 2016. Technicians collected 350 samples –'sediment cores' – that went down to a depth of six metres below the seabed. Cees Laban: 'Technical challenges such as large waves and the irregular seabed slowed the study down. But that also led to the development of new drilling techniques from the vessels.' Suitable for worldwide application At the same time, the crew used geophysical equipment fromDeltares to visualise the layers below the seabed. Geologists at Deltares and TNO-GSN analysed the sediment cores, after which Wiertsema & Partners determined the granular distribution. These analyses help to assess the environmental impact when issuing permits to dredging companies for the appropriate locations and depths. 'The sand from these areas will be enough to maintain the Dutch coast during the next decade.' The collaboration between Deltares and MSH will boost the international experience of MSH and provide Deltares with reliable information for seabed research. This knowledge can be applied throughout the world to help local authorities and dredging contractors use rawmaterials from the sea efficiently, economically and sustainably. The hydraulic vibrocorer on board the MV Zirfaea takes samples of sand, gravel or clay using a seven-metre-long boring pipe. IMAGE G. HARINGSMA KNOWLEDGE IN OPERATION