Geophysical mapping and 3D geological modelling to support urban planning: A case study from Vejle, Denmark

The increasing population density in existing urban areas often leads to the development of areas previouslyomitted due to construction risks. We suggest a comprehensive interpretation strategy exemplifying how planningmaps should classify areas depending on risk and opportunities. The first steps of the interpretation strategyinvolve a review of the purpose of the project, followed by the acquisition of high-density geophysical data. In thesubsequent steps, geophysical data in conjunction with GIS data are used for constructing a detailed highresolution3D geological voxel model. Specific geotechnical properties are assigned to the interpreted geologicalunits based on in situ vane shear tests and the standard penetration test. In the final step of the interpretationstrategy, two planning maps containing the three relevant themes are combined into one conclusive map demonstratingthe recommended use of different parts of the area for future urbanisation. An isopach map showingthe depth of the layers suitable for the foundation is combinedwith a map showing the areas flooded by the VejleStream during a 50- and 100-year event as well as habitat protected areas. Thus, the resulting planning mapsshow the most suitable locations of blue areas (lakes, wetlands), green areas (parks, etc.) and grey areas (buildings,roads) for future development.The adopted interpretation strategy can be successfully applied in similar situations to reduce the risks associatedwith urban development.