The ancient Roman aqueduct of Karales (Cagliari, Sardinia - Italy): applicability of geophysics methods to finding the underground remains

Detection of the buried antique Roman aqueduct, which supplied fresh water to the ancient town of Karales (Cagliari, Italy), is not a trivial problem because of the small size of its cross section, its depth (about 10m), and of the presence of shallow conductive layers. In order to determine the best geophysical method to use in the research of the conduit, a test was carried out over a well-known section of the underground aqueduct in its extra-urban part. Taking into account the geological features of the site, time-domain electromagnetic (TEM), very low-frequency (VLF) and electrical tomography methods were chosen. The test was conducted over several profiles. The results showed that among the electrical resistivity arrays, theWenner–Schlumberger is themost suitable for the detection of the conduit some metres in depth, whereas the other electrical methods did not have enough resolution to distinguish between the aqueduct and other non-related anomalies at the requested depth. The TEM method also showed good capability to detect the presence of the aqueduct in spite of very conductive superficial layers.With the exception of one profile, all VLF profiles showed anomalies that could be correlated to the aqueduct.