By the second quarter of the 2nd century AD, Imperial Rome was supplied with foodstuffs and materiel from across the Mediterranean through a network of ports on the Tyrrhenian coast of Italy. Portus and Ostia were the most important of these, the former as the principal maritime port and the latter as town and fluvial port, and together with the emporium at Rome and the port at Centumcellae (Civitavecchia) formed part of what has been defined at the “port system” of Imperial Rome. Central to the success of this was the fact that Rome, Portus and Ostia were connected by the Tiber and interlinked by a system of artificial canals and roads that together facilitated the movement of supplies and export between the Mediterranean and Rome. Research since 2005 has provided important new evidence for the position, character and function of three new canals that, together with known canals within Portus itself, help us better understand the inter-relationships between Portus, Rome, Ostia and the broader Mediterranean. This paper, which is interdisciplinary in scope, and draws upon recent archaeological, epigraphic, geo-archaeological and geophysical evidence, provides an interpretative overview of all the canals that focuses upon their functions. It begins with an analysis of the canals established by Claudius and then goes on to discuss the significance of the two new canals established by Trajan. In particular, the paper takes into account recent geo-archaeological evidence from the canal that run southwards from Portus to Ostia, and that which ran from the Tiber to the coast lying to the north of Portus.