Fluvial and fluvioglacial systems in the Milan Plain

This work refers to the detailed quantitative rebuilding of the textural characteristics of the subsoil of the Milan plain. The central point of the study is the organization and codification of the numerous data concerning the wells for water (7853 stored), 3472 of which have stratigraphic logs. The stratigraphic data have been codified in a database, extracted and elaborated in GOCAD (Geological Object Computer Aided Design). Three-dimensional georeferenced objects are then created, and each stratigraphic level of the wells is assigned a percent value of the textural classes – gravels, sands and clay – extracted from the database. The spatial data of the study area (topographic surface and aquifer bottom) have been elaborated by a GIS and subsequently converted into GOCAD format. A 3D grid has built between the surfaces and each cell assumes proportional form. The calculation grid has been created with regular cells of 250m each side and variable thicknesses from 1.8 to 2.3m, for a total of 207 rows, 267 columns and 96 layers. The percentages of gravel, sand and clay are attributed to each cell located in correspondence with the 3D georeferenced wells. Using the "Discrete Smooth Interpolator" (DSI), the values have been interpolated in all three-dimensional spaces defined by the 3D grid, and the three-dimensional rebuilding of the textural distribution of the subsoil of the Province of Milan has been realized. The model translates quantitatively not only the traditional aquifers, but deeper aquifers as well, which are not commonly studied and never quantified in their structure. The rebuilding of the 3D distribution of textural parameters can be considered as the departure point for many hydrogeological applications, such as the mode of propagation and distribution of the polluting, the hydrogeological system mass balance evaluation, and the flow and transport models.