Between the Rhone and the Massif des Maures, geomorphological research
, radiocarbon dating and archaeological excavation has revealed synchr
onous variations in morphological evolution produced by changes in cli
mate. Following one or more torrential protohistoric phases, the later
Iron Age and Gallo-Roman civilizations were marked by a reduction in
runoff from slopes and a lowering of the water level in marshy areas.
This was probably due to drier climatic fluctuations linked to a more
even seasonal rainfall distribution. The early Middle Ages and the beg
inning of Modern Times correspond to a renewed increase in rainfall, t
he erosive effects of which have been exacerbated by human activity.