Expertise group Geomodelling
The Geological Survey of the Netherlands (GDN) has developed four models for the shallow subsurface (up to 500 metres deep) based on the hundred thousand drillings and cone penetration tests in the DINO database. The GDN also develops models for the deep subsurface up to a depth of 4 to 5 thousand metres.
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Behind the scenes at our expertise group Geomodelling
Subsurface models use all the available knowledge to produce the most faithful representation possible of the subsurface. They predict strata structure and characteristics, including the gases and fluids present.
The models for the integrated basic geological information and links to other databases enable specific questions to be answered, like the risks of subsurface intervention, the construction of infrastructure above and below the ground, production of gravel, sand, clay, limestone and groundwater, subsidence predictions or the use of geothermal heating.
Excisions can be made from the models for specific purposes, such as the sandy gully systems of the Rhine and Maas in the Holocene layer of South Holland. The model then reveals the presence of surrounding continual sand layers (sand paths) through clay and peat layers at different depths as well as information about the granular composition of the sand.
The subsurface models are freely available online.
DGM and REGIS
In the Digital Geological Model (DGM) the Dutch subsurface is built by digitally stacking the lithostratigraphic layers in the subsurface on top of each other from a depth of 500 metres to the surface.
The DGM provides insight into the stratification through thickness and depth planes, thereby making clear the spatial relationships of the layers on a regional scale as map images and profiles.
REGIS-II (REgional Geohydrological Information System) is the hydrogeological refinement of the DGM in which each geological layer (formation) is subdivided into layers whose permeability is good (sandy) and poor (clayey). These layers have been assigned mean geohydrological parameters for use in groundwater studies.
GeoTOP and NL3D
GeoTOP provides a detailed three-dimensional image of the subsurface up to a depth of 30 metres below the surface, that part of the subsurface most intensively used by man. It refines the upper side of the DGM and REGIS-II whereby the subsurface is divided into millions of voxels (little blocks) of 100 x 100 x 0.5 m. Each voxel contains information on the type of soil and the corresponding physical and chemical attributes.
The fourth model is NL3D, a low-resolution variant of GeoTOP with voxels of 250 x 250 x 1 m. NL3D provides information on the soil structure up to a depth of 50 m for the whole of the Netherlands.