URBAN-SCALE 3D SUBSURFACE MODELING OF ROTTERDAM (THE NETHERLANDS)

TNO-Geological Survey of the Netherlands (TNO-GSN) produces a diverse suite of nation-wide 3D subsurface models, ranging from the deep subsurface to shallow depth. The most detailed model is GeoTOP, schematizing the subsurface up to a depth of 50 m in voxels of 100 by 100 by 0.5 m. For each voxel the model provides estimates of the geological unit and lithological class, including uncertainties. GeoTOP can also be populated with an expanding range of derived parameters, for example hydraulic conductivity and geochemical reaction capacity.

Up to now however, the information contained within geological models like GeoTOP is not particularly suited to be used in 3D urban planning processes. Geological models usually do not provide information on the desired properties of the shallow subsurface in the appropriate detail. Furthermore, man-made ground is generally only poorly schematized and geological subsurface information is not easily interoperable with above-ground, CAD-based spatial information.

To improve the applicability of GeoTOP in urbanized regions TNO-GSN and the Municipality of Rotterdam have collectively developed methods for urban-scale subsurface modeling in a fluvial-deltaic setting. Focus has been particularly on:

• Improving model resolution by increasing the amount and diversity of input data. Apart from traditional borehole data, historic maps have been used, as well as geotechnical measurements, for example cone penetration test data.
• Improving characterization of man-made deposits, for example by using archaeological research.
• Integrating 3D visualization of geology, subsurface infrastructure and above-ground information.

We will show that the resulting urban-scale 3D subsurface model provides the detail necessary to make the right decisions in 3D spatial planning issues. As such, the urban-scale model assists the Municipality of Rotterdam in assessing current and future subsurface-related risks, as well as taking full benefit of the opportunities the subsurface provides.