Abstract
This study presents the results of a research project financed by the Lazio Regional Government. The research focused on defining an integrated model of recent alluvial deposits in the Tiber River. To achieve this objective, geological boreholes were made to monitor the aquifer and in situ and laboratory tests were carried out. The data obtained were used to detail stratigraphic aspects and improve the comprehension of water circulation beneath the recent alluvial deposits of the Tiber River in the urban area of Rome, between the Ponte Milvio bridge and the Tiber Island. The stratigraphic intervals recognised in the boreholes were parameterised based on their litho-technical characteristics. The new data acquired, and integrated with existing data in the database of Institute of Environmental Geology and Geoengineering of the Italian National Research Council, made it possible to produce a three-dimensional model of the lithologies in the study area. The model of the subsoil, simplified for applied reasons, was described in hydrostratigraphic terms: three different lithotypes were subjected to piezometric levels monitoring. Finally, the research generated a numerical hydrological model in a steady state. In general, this study demonstrates how a numerical hydrogeological model calibrated by piezometric monitoring data can support the construction of a geological model, discarding or confirming certain hypotheses and suggesting other means of reconstructing sedimentary bodies.
Highlights
This article describes the results of the activities defined in the research contract between the Institute of Environmental Geology and Geoengineering of the Italian National Research Council (IGAG-CNR) and Geoplanning-Servizi per il Territorio as part of the project “TIBER–Innovation in the field of geotechnics for the definition of tools, methods and procedures aimed at the building of a new model of subsoil,” financed by the Lazio Regional Government
Results of the geolithologic model and 3D voxel model show the distribution of facies and, the hydraulic conductivities in the modelled area, which vary spatially
The central channel belt of complex 4b, due to its elongated geometry and high hydraulic conductivity, can facilitate preferential flowpaths, which could control contaminant transport; being in direct contact with the Tiber River, it ensures the exchange between groundwater and surface water
Summary
A detailed facies analysis was made on these boreholes, keeping to the specific recommendations provided in the literature of fluvial deposits [29,30] which include the sequence boundary (SB), the first transgressive surface (ts), and the maximum flooding surface (mfs) (See Figure 2a–c; after [28]) These key surfaces identify substantial changes to the general configuration of the facies in the various depositional environments in relation to the variations between the space of accommodation and the sedimentation rate, driven by: the variations in sea level, the hydraulics of the system, the compaction of alluvial terrains, tectonics, climate, and the sedimentary supply [26,27,31,32,33,34,35]. For a detailed investigation of this type of hydraulic relation, this study included the planning of a continuous monitoring of the alluvial complex
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