GIS and Geostatistics for 3D geological and hydrogeological modeling of fluvial deposits

In specific geological contexts, such as alluvial environments, the lithology is highly heterogeneous and laterally variable. As a result, a large number of lithological data are collected (generally random and under sampled) for stratigraphic reconstruction. The integrated management of geo-lithologic data causes major methodological problems, because data obtained from geognostic investigations have to be normalized and correlated. Data are often affected by their degree of precision, a detail depending on the investigation technique and on the geologist’s interpretation. This paper presents a methodological approach to organizing, integrating, and interpolating subsoil, mechanical (boreholes, penetration tests), and geophysical (seismic profiles, resistivity sounding) investigations for the construction of a three-dimensional geological model supported by geographical information systems and geostatistics. A practical application concerning the lower Foglia river alluvial deposits (Northern Marche, Italy) was carried out to investigate the geometry of these sedimentary bodies. This integrated approach offers many advantages for the understanding and in-depth visualization of the geometry of the deposits. Moreover, it allows for the acquisition of qualitative and quantitative information about hydrogeological settings, which is useful for water resources exploitation and protection. The achieved goals are the design of a data management workflow for geo-lithological data, the construction of a threedimensional geological model of the lower Foglia river alluvial plain, a comparison between the geological sections obtained from the model and those made in a traditional manual fashion, and, in addition, new stratigraphic and hydrogeological considerations about the study area.