FLUVIAL DYNAMICS, RISK AND HUMAN OCCUPATION IN THE FLUVIAL-ESTUARINE PLAIN OF THE GARONNE
Anne Colin, Florence Verdin (Ausonius, CNRS, University of Bordeaux 3)
Physical Geography laboratory of Meudon (LGP - UMR 8591)
LIENSs UMR 7266), La Rochelle
Duration: 1.5 years (1st September 2012 – 31st December 2013)
This project falls within the Topic I.1 of the Cluster of excellence (Adaptations, appropriation of spaces and Man/environment interactions) and complete the thematics relating to the Man/fluvial environment interactions on which we have been working since 2010, in the frame of the regional programme “Estuary and Medoc Coastline populations during protohistoric and ancient periods”. It already helps to specify the archaeological and hydrographical map (palaeochannels) of test sites during the studied periods (to which the Middle Ages can be added).
However, whereas the fluvial-estuarine plain of the Garonne/Gironde, which results from the encounter of the river and the Atlantic Ocean, makes rises and diffluences inevitable, the impact of hydrological risks on local populations is yet to be determined. And yet, it is an essential step to understand the dynamics of land use by these populations, especially in those times during which the societies we are studying were very responsive to environmental change.
Addressing properly this fluvial risk implies to fully know the flood/diffluence conditions of the palaeochannels of the Garonne. Contrary to other big drainage basins (Rhône, Loire, Seine and Rhine) which were the object of several studies, the Garonne’s one remains unknown. To assess the spatiotemporal variability of hydrological risks over the last 4,000 years and, especially, to find out about the state of the channels which existed during occupation phases, it is therefore necessary to reconstitute the geography of the alluvial plain and the complete stratigraphy of the reference archaeological sites’ palaeochannel fill. A programme of deep sedimentary core sampling, combined with geophysical prospecting will help to measure the influence of hydroclimatic variability, sea level fluctuations and human land use in the main environmental cycles.