The ancient morphology of the Po Plain in the area of Bologna (Italy)

Abstract

A multidisciplinary approach has permitted to reconstruct the ancient morphology of the Po Plain north of Bologna. Covering an area of about 766 square kilometres, the territory is characterized by the presence of a considerable number of fluvial ridges. At the time of the Roman colonisation in the II century B.C. the plain was far more even as compared to today. The absence of ridges is borne out by the large number of archaeological finds that have been found in situ. Streams flowed carving their sediments, as is still the case along the left side of the Po. Roman centuriazione patterns confirm this hypothesis. Centuriazione is a land subdivision practice adopted by the Romans which strongly takes into account the morphological aspects of a territory as one of its functions was to facilitate surface water flow-off. If ancient morphology had been characterized by ridges and depressions, as is the case today, this type of system would have been unsuitable to ensure drainage. For it to have effectively performed this essential function the morphology at the time must have been far more uniform and homogeneous than what it currently is. The process of aggradation, which has given rise to the formation of the numerous ridges found today, presumably began in the third century A.D. and continued throughout the Middle Ages. The riverbeds thus came to find themselves above the level of the surrounding plain so that the hydraulic set up was upset and large portions of the territory were lost control of.