Tomografie di resistività elettrica a supporto della modellazione idrologica: applicazioni su un argine dell'Adige

The seepage phenomena that occur through artificial (and natural) embankments play a crucial role in determining the hydraulic risk of a given area. Therefore, an appropriate characterization of the domains affected by these processes is necessary to better understand them. In this study we present the extended characterization, by means of electrical resistivity tomography (ERT) and hydrological modelling, of part of an artificial levee of the Adige River and of the alluvial plain nearby in Salorno (BZ, northern Italy). This part of the levee is subjected to seepage during flooding events, which consists in the movement of water from the river to the alluvial plain through the embankment itself. This process takes place despite the injection of jet-grouting in the core of the embankment, which was performed in order to increase the hydraulic seal of the artificial structure. More in detail, our work consists in the acquisition of several 2D ERT cross-sections distributed homogeneously within the study area (i.e. on the embankment, at the embankment toe and on the alluvial plain), aimed at reconstructing the material distribution in subsoil. The combination of the information thus obtained with other direct data (e.g. stratigraphic surveys and hydrometric measurements), helped us developing a 2D hydrological model describing the water flux within the embankment, from the river to the plain. The simulations, performed thanks to the SEEP2D code (Aquaveo), show that one of the main reasons triggering the seepage phenomenon could be the height of the jet-grouting injections, which end inside a permeable material. From the results of the hydrologic modelling it also emerges that the efficiency of the hydraulic defence could be greatly reduced by the presence of discontinuities within the barrier itself. In conclusion, in this work we highlighted that the combination of ERT and hydrological modelling is particularly suitable for this kind of applications, providing rather fast, cost-effective, and spatially distributed information