 The Marecchia river runs through its valley and the plain in a very large riverbed and, after confluence with the Ausa, it flows into the Adriatic sea through a deviator between San Giuliano Mare and Rivabella, while the ancient riverbed is used in its last section as the city's harbour.The Marecchia, usually with little water flow, was subjected to periodic, destructive floods near its mouth, where the riverbed became narrow after various bends