Morphosedimentary behaviour of the deltaic fringe in comparison to the relative sea-level rise on the Rhone delta
Résumé
For the first time, mareographic data obtained by the 'Compagnie du Salin du Midi' have been used to estimate the relative sea-level rise (RSLR) in the Rhone delta. The results were compared with the data obtained in the Marseille region which is known to be a tectonically stable zone, at least, on the secular time scale. The magnitude of relative sea-level rise is equal to 2.1 mm/year, from which 1 mm/year could be attributed to subsidence. The morphosedimentary behaviour of the deltaic fringe has been analyzed in order to see if the amount of sediment input is sufficient to allow the wetlands to continue to exist with RSLR. The horizontal variations (erosion and progradation) have been quantified from land surface changes obtained by shoreline variation analysis. The vertical accretion is measured using isotopic dating (137Cs). It appears that the eastern part of the mouth of the Rhone is characterized by high sediment input, sufficient enough to offset the recent rise of sea level. The western part remains vulnerable due to the lack of sediment in this area.