The use of GIS-based 3D geological tools to improve hydrogeological models of sedimentary media in an urban environment

Abstract

A software platform was developed to facilitate the development of 3D geological models of sedimentary media for hydrogeological modelling, especially for urban environments. It is composed by a geospatial database and a set of tools that enable the user to perform an accurate stratigraphic analysis. The geospatial database is used for the management of a large amount of different data types coming from different sources (geophysical logs, borehole logs, hydraulic tests, etc.). Its structure allows us to store accurate and very detailed geological borehole-log description that can be straightforwardly generalized and further upscaled. The set of stratigraphic analysis instruments, working within a Geographical Information System (GIS) environment, has been set up to facilitate the geological data interpretation. Detailed stratigraphic columns of the selected boreholes can be generated using customized queries. Creating automatically a geological profile is further possible by displaying the boreholes lithological columns and the geophysical and geotechnical field-tests’ results together with the defined stratigraphic units. Based on an interactive analysis environment is created, where the user is able to analyze and to define the possible existing correlation surfaces, units, and faults. The obtained information represented by the geological units/subunits can be then converted within a 3D environment. The resulted 3D features could be used within the same GIS environment or by external software packages for further stochastic analysis or to build up 3D geological and hydrogeological models. Starting from an accurate and very detailed geological description, the software allows us to represent in three dimensions (3D) the heterogeneity of the sedimentary media and their spatial distribution. Thus, it shows how connectivity implemented into hydrogeological models among the different sedimentary bodies plays an important role. Results are shown consisting in a case study located in the Besos River Delta, in the metropolitan area of Barcelona, on the Mediterranean coast in NE Spain.