The role of 3D modelling in the urban geological map of Catalonia
Vilà, Miquel; Torrades, Pau; Pi, Roser; Albalat, David; Monleon, Ona
published: Dec 1, 2016
ArtNo. ESP171016704006, Price: 29.00 €
The Urban Geological Map of Catalonia Project focuses on the geological characterisation of county capitals and towns with a population larger than 10 000. This represents 131 municipalities hosting ~6.2 million inhabitants and a study area of 2200 km 2 . To address the underground geological structure and properties of the geological units it has been established a set of 3D modelling methods, which are based on: (i) Comparing digital terrain models from different ages to determine elevation changes produced on the last century; (ii) delineating contour lines at 5 metre intervals and seriated cross-sections taking into account borehole data, geomorphological features, detailed geological mapping and H/V measures; (iii) compartmentalisation of geological horizons in sectors where bedding orientation is approximately constantly separated by lines of locally sharp curvature; (iv) interpolation of multiple 2D sections and contour lines after a detailed structural analysis of the data; and (v) creating regular grids of regional planar geological structures derived from the interpolation of field measurements of the dip and the dip direction. These methods pay special attention to the structure of the near surface, the part of the underground, which most directly influences the urban environment. 3D reconstructions depend on available information and the geological, geomorphological and anthropogenic features of each study area. The comparison of multi-temporal digital terrain models is especially useful to define the geometry of certain artificial deposits. The main Quaternary and Neogene surfaces are primarily reconstructed by contour lines. The reconstruction of the Palaeogene and Mesozoic horizons are built from the integration of contour lines, cross-section traces and hinge lines related to dip domains. The reconstruction procedure for the main Palaeozoic horizons and the faults is usually based on interpolating master cross-sections and contour lines. Presently, the role of 3D modelling in the Urban Geological Map of Catalonia Project is oriented to derivate different components of the 1:5000 scale geological map sheets, such as the pre-Quaternary basement map, the cross-sections, and the isopach map of the drift deposits. To improve the development and the sustainability of the Catalan cities, we advocate that, in the coming years, we must strive in the integration of the 3D geological models in their urban planning systems. The combination of the different 3D geological modelling techniques presented in this work represents a methodological sound basis to reconstruct the subsurface of these urban areas.