Geomorphological evidence for fluvial change during the Roman period in the lower Rhone valley (southern France)

The hydrological and geomorphological dynamics of the lower Rhone river (southern France) are studied during the Roman period (2nd–1st centuries BC, 2nd–3rd centuries AD). The crossing of archaeological and radiocarbon dating methods allow to study events at a pluridecadal to centennial scale. From the Avignon town to the delta, the 15 sites where Roman fluvial dynamics were recorded show higher flooding frequencies, higher energy levels during floods, rises in the marshes or groundwater levels, and/or active morphological dynamics such as channel migrations from 1st century BC to 1st–2nd centuries AD, with respect to the encircling periods. Although this fluvial change does not reach the amplitude of great climatic events such as the Little Ice Age in the Rhone valley, we show that it is also perceived in other parts of the catchment and could have a climatic origin. However, this event is not recorded in the immediate Mediterranean environment of the lower Rhone, so that the Rhone appears to efficiently transmit a foreign climatic change.