Two electrical surveys by resistivity profiles on the ancient site of Eretria, Euboea Island, Greece, have detected an important channel giving way to a flood coming from the neighboring hills. Several profiles show characteristic anomalies for different investigation depths. Their unsymmetrical aspect suggests that fine deposits to the North and coarse deposits to the South have been separated and this can be related to the deltaic evolution of the site and the seashore modifications. -- AATA