À Chelles (Seine-et-Marne), rue Gustave-Nast, des fouilles ont été menées par l’Inrap dans un contexte archéologique dense associé à une agglomération gallo-romaine. Elles ont révélé la présence d’un port gallo-romain, situé en bordure d’un ancien bras de la Marne graduellement abandonné au profit d’un bras secondaire. Son étude montre qu’il a été établi dans un environnement marqué par une très forte sédimentation alluviale, liée à la perte d’énergie progressive du chenal. Les données archéologiques et géoarchéologiques documentent les efforts apportés à l’entretien de la rive de ce port, convexe et donc propice au dépôt d’alluvions, et permettent de suivre son évolution marquée par de nombreux états distincts qui traduisent une adaptation à l’évolution du cours d’eau.
In Chelles (Seine-et-Marne), on Gustave-Nast street, excavations were performed by Inrap in a dense archaeological context associated with an ancient town. They revealed the presence of an ancient port, located along the bank of an old branch of the Marne river. Archaeological and geoarchaeological data document the efforts made to maintain the riverbank, making it possible to reconstruct its evolution over time. The study of the remains of this port has identified four distinct developmental phases.-Phase 1, around 35 BC: a riverbank fastening set-up, composed of branches and logging waste, several wooden posts, and possibly included a light, make-shift wharf structure, was installed in the hopes of stabilizing the bank. This installation cannot yet really be considered a significant port facility. -Phase 2, around 25 BC: a half-box wharf –with 17 planks supported by 14 oak posts– and an angle abutting the riverbank, allows this sector of the town at this time to be assigned the role of a real port allowing for the docking of merchant ships. -Phase 3, around 17 AD: a doubling of the previous wharf, more modest and less robust, was built 2 m towards the river in an attempt to thwart its siltation. Several consolidations are attested to. -Phase 4, around 70 AD: a much smaller structure, formed of two parallel stone walls associated with wooden posts, was established at the western border of the port area and more than 7 m from the original ancient riverbank. This is the final development in connection with the river in the space investigated; the activity on the shore was then reduced and only a potter’s oven can be associated with it. The extent of the excavation has only allowed for the study of the western part of the port facilities, which may continue further east. The general development reflects a rapid decline in activity in connection with the gradual flooding of the Marne channel, due to massive alluvial inflows. The latter are related to erosion due to the development of agriculture across the Marne watershed, which also led to the establishment of an increasingly marked flood regime. The riverbanks sustained various activities and endeavors aimed at maintaining access to water –digging, dredging, depositing backfill, and more advanced developments toward the north in hopes of following the river– an effort which could not be maintained for more than a century and which reflects a veritable race after the river. The large quantity of dolia dating to the 1st c. AD and found scattered around the city, however, seems to indicate that port activity must have continued elsewhere, possibly further to the east. The harbor was therefore established on the convex riverbank of an old meander, in an environment marked by very strong alluvial sedimentation linked to the progressive loss of energy from the channel, its migration northward, and its subsequent abandonment in favor of another secondary branch of the Marne located 2 km further south. This resulted in the intersecting meander that can be recognized today and which is already visible on 18th c. maps. The displacement may have had a partly anthropogenic origin, despite its inheritance of a late-glacial morphogenesis, but the existing data does not allow for a definitive answer to this question. Whatever the case, the channel migration certainly had a major influence on local and regional territories, in particular on the relationship that may have existed between the ancient town of Chelles and its possible artisanal suburb of Gournay-sur-Marne. The dating of the displacement is yet to be specified, but would appear to be later than or contemporary to the Roman period and was already in place in the Middle Ages.
