The Canopic branch, the largest relict Nile distributary, once flowed across the NW Nile delta of Egypt to the Mediterranean. This study focuses on the Canopic's evolution at the delta margin and in Abu Qir Bay seaward of the coast. Information from historic documents, integrated with data from geographical, geological, and archaeological exploration in the bay, indicates that the Canopic distributary was active from ∼4000 B.C. to the end of the 1st millennium A.D. Fluvial discharge persisted through pre-Dynastic, Dynastic, Greek, Roman, Byzantine and early Arabic time. The channel flowed to two sites, Herakleion and Eastern Canopus, established by the Greeks as navigational gateways for trade in the delta and surrounding region. Eastern Canopus functioned until the mid-8th century A.D. At that time, flow in the Canopic had decreased markedly, and Nile water was diverted to the east, through the Bolbitic-Rosetta branch. By the end of the first millennium A.D., Nile water was channeled in the Rosetta and Damietta distributaries, and the Canopic branch eventually converted to a canal and drain system.

The Canopic promontory across which the branch flowed, and the 2 ancient sites located at the promontory coast near Canopic channel mouths, subsided beneath the waters of the bay after the 8th century. Submergence was a response to interaction of eustatic sea-level rise, annual floods, growth-faulting, soft-sediment deformation and other natural processes. As the Canopic promontory subsided, Abu Qir Bay attainted a marked concave-seaward shape and its shoreline shifted southward. This geoarchaeological investigation helps distinguish the long-term impact of natural events from that of increased human activity. This distinction is of practical importance for the highly populated and vulnerable delta margin that continues to experience submergence and erosion.