NATIONAL 3D MODELS AS INPUT FOR DECISION-SUPPORT SYSTEMS

TNO – Geological Survey of the Netherlands (GSN) develops and maintains four national 3D subsurface models, ranging in depth from kilometres to 10’s of meters. The upper 50 m of the subsurface is modelled with voxel models which represent the internal heterogeneity of geological units in great detail. Our voxel models contain two main geological properties: geological unit and lithology, which form the basis for adding other properties, such as organic matter content, hydraulic conductivity or shear-wave velocity.

In this presentation we will focus on three application domains: (1) the use of our national GeoTOP voxel model in assessing risks on a regional scale that are the result of human intervention in the natural system; (2) the construction of detailed voxel models for a site-specific application on a local scale, and (3) the use of an offshore voxel model for aggregate resource estimations.

On a regional scale, GeoTOP is used by third parties in predicting land subsidence, a major problem in the densely populated western part of the country. Another application is the estimation of ground motion acceleration caused by human-induced earthquakes in the Groningen gas field. In both applications, the standard GeoTOP properties geological unit and lithology were used as “carrier” for application-specific variables (organic matter content, shear wave velocity).

On a local scale, the GeoTOP workflow was used to build a high-resolution voxel model of the subsurface of a 55 km long dike along a northern branch of the River Rhine, that protects the central part of the Netherlands from flooding. The water authority is using the model in its maintenance program of the dike, e.g. for optimizing additional data acquisition.

Our offshore voxel model is designed to support aggregate resource estimations on the Dutch North Sea. Results are being used by the Directorate-General for Public Works and Water Management (Rijkswaterstaat) in their decision-support system. This DSS is subsequently used in finding solutions for an optimal planning of offshore space for an increasing number of applications: windfarms, shipping routes, nature reserves, fishing grounds and mining of aggregates.

These examples show that geological voxel models can be deployed for a wide range of applications from regional to local scale.