The seabed-sediment map shows the composition of the upper half meter of the North Sea seabed. This information is an important prerequisite for applications in the shallow offshore domain, such as the installation of cables and pipelines, sand extraction, and ecological habitat suitability analyses. The map therefore provides a scientific basis for policy, nature management, spatial planning, and the sustainable use of the North Sea.
Four map layers
The seabed-sediment map consists of four map layers, three of which show the classified proportions of mud, sand, and gravel. Three Folk classification systems were used to classify these sediment types. The fourth map layer shows the mud content. Further down on this page, the three Folk classifications used and the mud-percentage map are explained in more detail.
Data origin and application
The seabed-sediment map is based on decades of geological research, supplemented with recent data from publicly funded projects, including contributions from external parties. Examples include data from exploratory surveys for offshore wind farm development and sand extraction in coastal areas.
The map represents the North Sea seabed divided into grid cells of 100 by 100 meters. For each grid cell, a random forest algorithm predicts seabed composition based on data from sediment samples and bathymetry (water depth measurements), derived from the EMODnet bathymetric grid.
To ensure a representative continuity at the maritime boundaries, data from a buffer zone of approximately 10 kilometers around the Dutch sector of the North Sea were used.
Reliability and use
The seabed-sediment map is an overview product intended for use at national or regional scale. However, the quality and density of available samples may vary per location. In addition, the geology of the seabed may vary considerably from one location to another.
In the map viewer, these uncertainties are visualized for each grid cell and can be viewed by selecting “Likelihood of prediction”, providing direct insight into how reliable the prediction is at a specific location.
Patterns such as linear artefacts on the map may occur in areas where bathymetric data of varying quality have been used, or where different measuring methods have been applied.
Updates
The most recent update includes further improvements in map coverage by fully mapping the areas along the coastline. In addition, updated bathymetric data from EMODnet have been applied, and a new feature has been added: the mud-percentage map.
The four map layers in the map viewer
Folk classification systems
The three Folk classification systems are based on the proportion of mud (clay and silt; grain size <63 µm), sand (63 µm – 2 mm), gravel (>2 mm – 63 mm), and coarser material (stones, cobbles, and boulders; >63 mm).
The classifications follow internationally used standards for sediment classification (Folk classification and EUNIS), as applied within EMODnet. The ternary diagrams show the different Folk classes for mud, sand, and gravel. The class for coarser materials is not shown.
Folk 16: Detailed representation
This is the most detailed representation and the international standard with 16 sediment classes.
Folk 7: Simplified representation
This map combines several sediment types. Folk 7 is particularly suitable when a simplified representation of the whole Dutch North Sea seabed is needed for reports or overview maps.
Folk 5: Representation based on EUNIS
This classification aligns with the European Union Nature Information System (EUNIS). This is the standard for mapping European habitat types and biodiversity.
Ternary diagrams of the different Folk classifications.
Mud percentage
The mud-percentage map provides a more accurate insight into variations in the mud content than the Folk classifications. As a result, subtle spatial variations become visible, even within areas assigned to the same Folk class.
This makes the mud-percentage map particularly suitable for analyses in which detailed sediment composition is important. The map therefore forms an important addition for applications in the shallow offshore domain of the North Sea.
Citation
TNO-GDN (2026) Seabed-sediment map (V2.0). TNO - Geological Survey of the Netherlands, https://www.dinoloket.nl/en/subsurface-models/map; accessed on dd-mm-yyyy.
Downloading the seabed-sediment map
The seabed-sediment maps can be downloaded via the map viewer using the download function.
Contact
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