Chapitre 9. Le chaland Arles-Rhône 3 dans la batellerie gallo-romaine : étude typologique et interprétation historique
Authors: Rieth Eric 
Published: January 2018

Chapter 9. The arles-rhône 3 barge within gallo-roman water transport : a typological study and historical interpretation
A return to the Rhône-Saône tradition : The evolution of archaeological issues on the one hand, the increase in archaeological sources over the last decade on the other (nine barge wrecks dating from the 1st to 3rd centuries AD excavated in the Rhône-Saône basin) and also the development of methods of excavation, recording and post-excavation management of archaeological data have all led to a modification and up-dating of the historical questions surrounding Gallo-Roman river craft architecture. The Rhône-Saône architectural tradition is attested from the 1st century AD with the wrecks of Place Tolozan in Lyon (30 AD), the old bridge at Chalon-sur-Saône (50-70 AD) and the Arles-Rhône 3 (50s AD). And we can add those of the Parc Saint-Georges in Lyon dated from the 1st to 3rd century AD, as well as the Arles-Rhône 5 wreck (provisionally dated to between 51BC and 135 AD). These wrecks were bottom-based constructions and fall within an “ extended log boat” architecture, with the exception of the PSG Ep. 8 (circa 55 AD) whose bottom-based construction is entirely planked. The most significant characteristics of the Rhône-Saône tradition of river craft architecture are based on technical influences of a Mediterranean and maritime origin. There is the systematic luting with pitch cloth to ensure watertightness of seams between the assembled pieces (a common characteristic of all the wrecks) : the pre-assembly of the bottom strakes using non-plugged tenons in mortises (the Tolozan, Chalon-sur-Saône and PSG Ep. 8 wrecks) : the use of nailed strips of lead covering the internal seams of the bottom and sides similar to the “ palâtres” of river craft architecture (PSG Ep. 2 et Ep. 4 wrecks). Along with these three characteristics shared with maritime naval construction there is a fourth that harks back to an architectural tradition that is specifically fl uvial and represents a sort of “ memory” of log boat architecture. It is the use of conifer half-trunks in the sides of barges of extended log boat structure. The Arles-Rhône 3 and the Rhône-Saône tradition : One of the three architectural signatures of Mediterranean maritime origin is present on the Arles-Rhône 3 wreck : watertightness by means of pitch cloth. Meanwhile, the architectural signature of continental and fluvial origin is most remarkably attested in the sides made of half-trunk fir wood, some 26 m long each. Alongside these characteristics common to boats of the Rhône-Saône tradition, there are other original characteristics that can be qualified as “ boatyard” architectural signatures, the most remarkable of which, from the structural point of view, is the mixed nature of the bilge strakes : monoxylous bilges for the “ body”/ major part of the hull ; composed and assembled for the stern ; mixed bilges (composed and assembled, associated with monoxylous bilges) for the prow. When considering the morphology, the most visible original architectural signature of the Arles-Rhône 3 barge concerns the geometry of the hull, which fi ts into the class of “ polygonal boats of octagonal type” as established by Béat Arnold. However, the proportional geometry is quite particular and is characterised by an elongation coefficient (ratio length/ width) of 1/ 10, which is higher than the river barge wrecks of the Gallo-Roman tradition, where the mean is between 1/ 6 and 1/ 7. Such a slender hull is a particularity associated with the very long rising bow. Another illustration of the morphological originality of the Arles-Rhône 3 barge is to be seen in the section of the hull reserved for the cargo. This occupies almost the half of the flotation rectangle, whereas in the De Meern 1 wreck, for example, nearly three quarters of this same rectangle was dedicated to the hold. These two figures reveal two architectural and functional choices. For one high elongation coefficient, of similar value, we witness the existence of two very different geometries, which in the case of the De Meern 1 translates into a simplicity of form favouring the space for the cargo, and in the case of the Arles-Rhône 3 means a greater complexity of form to the detriment of the space reserved for cargo. The central question to be asked is how to interpret these boatyard architectural signatures of the Arles-Rhône 3 barge. In terms of weight, the “ heaviness coefficient” (ratio of light displacement [bare hull] to 1 m of hull length) of the Arles-Rhône 3 wreck is calculated at 0,26 t/ m, whereas the PSG Ep. 4 wreck, of the same tradition and comparable length, stands at 0,67 t/ m, nearly three times greater. These figures confirm that fact the builders of the Arles barge chose a relatively light construction matched with a very high elongation coefficient L/ W of 1/ 10. As for the loading capacity, the “ profitability coefficient” (ratio between carriage and 1 m of hull length) is 0,69 t/ m for the Arles-Rhône 3 wreck and 1,96 t/ m for the PSG Ep. 4. This coefficient, as regards the economy of water transport, appears much more favourable in the case of the PSG Ep. 4 wreck than that of the Arles-Rhône 3 barge. All the same, this difference in “ profitability coefficient”, as an absolute value, in relation to the loading capacities will probably have to be seen relatively as a function, on the one hand, of the nature of the transport (short haul up and downstream from Arles in the case of the Arles-Rhône 3 and long distance for the PSG Ep. 4) and on the other, depending on the different navigation conditions of the sections of the Rhône-Saône basin under consideration.
The Arles-Rhône 3 barge and the port city of Arles : One of the important questions that arises is the role of the city of Arles and its sea-river port, as a place of exchange and of technical influences, within the Rhône-Saône architectural tradition. The impressive dimensions and the structural complexity of the Arles-Rhône 3 barge demonstrate that the boatyards of Arles, beyond their access to supplies of sizeable wood, had a technical expertise in terms of knowledge and know-how that can only be understood in relation to past technical practices that integrated influences from Mediterranean maritime shipyards. The Arles-Rhône 3 thus reproduced an architecture similar to vessels from long before its construction. The building of a boat of 31 m in length, like the Arles-Rhône 3, raises two principal questions : that of the nature of the boatyard and its technical, economic and human (specialist workforce) resources, and that of the use of the barge. Who chartered it, for what, in what context and with what means ? The penetration of Roman influence into Gaulle along the Rhône-Saône axis and the strategic position of Arles at the interface between Mediterranean influences in maritime construction techniques and those riverine influences from the hinterland, leads one to consider the importance of the Arles boatyards and their role in the development and diffusion upstream of the Rhône-Saône architectural tradition.