The canal system and Tiber delta at Portus. Assessing the nature of man-made waterways and their relationship with the natural environment

Abstract

Results of the ongoing archaeological survey and excavations at Portus and the surrounding hinterland of the Tiber delta have revealed a system of large artificial canals and associated structures relating to the Imperial and Late Antique port, and associated agrarian practice and secondary industries practiced in the delta area. These man-made features have demonstrable links to the geomorphology of the Tiber delta, with canals making use of the dune cordons and variations in the sediments across the wetland. The methodology used to map the archaeological and geomorphological features in the study area has included topographic survey, geophysical survey, using magnetometry, and Ground Penetrating Radar, and analysis of air photographic evidence together with other sources of data including satellite imagery. To these non-intrusive techniques have been added borehole data collected by colleagues as part of the Portus Project (www.portusproject.org), and evidence for canal and waterfront construction relating to excavation at the site of Portus. This paper presents a detailed methodology of the fieldwork to date, and assesses some of the preliminary results of the archaeological survey, focusing on evidence for the system of large canals linking the port with the river Tiber, and the Tiber to the coast. It also focuses upon a reassessment of some of the canal features by comparing coring evidence collected during the excavation seasons at Portus by colleagues at the CNRS-Lyon with results of the geophysical survey. The paper also advances possible avenues for future investigation and research, and draws upon the results of the survey to provide an overview of evidence for the organization of land in the delta and wetland surrounding the port complex, including a system of smaller canals and land divisions.