Navigable canals contribute to the improvement of connectivity between marine, coastal and inland waterways networks. This paper questions the location of active canals during the Roman period in relation to their archaeological and geographical contexts in which they were excavated. During the Roman period, literary and archaeological evidence reveal that most of the canals were dug in lowlands, coastal plains, and especially in river deltas. Locally, canals connected fluvial and/or coastal port-cities to inland waterways and maritime routes (e.g. Ostia-Portus, Ravenna, Aquileia, Alexandria). Additionally, some canals could have had a regional relevance in interconnecting fluvio-coastal port systems or possibly organising wider port systems. We identified three types of coastal settings that hosted regional projects of canals or actual constructed canals: (1) river deltas with the Nile delta as the archetype; (2) overlapping or contiguous deltaic plains similar to the Northern Adriatic coastal plain; and (3) separated coastal or deltaic plains, categories in which most of the Mediterranean port systems fit, especially the coastal port system of Rome. This paper explores the potential of these fluvio-coastal landscapes in which canals may have contributed in establishing interconnected port systems.