Comparison of estuarine sediment record with modelled rates of sediment supply from a western European catchment since 1500

Clément Poirier (1) , Cyril Poitevin (2) , Eric Chaumillon (2)

1 M2C - Morphodynamique Continentale et Côtière
2 LIENSs - LIttoral ENvironnement et Sociétés

Marine and estuarine sediment records reporting impacts of historical land use changes exist worldwide, but they are rarely supported by direct quantified evidence of changes in denudation rates on the related catchments. Here we implement a spatially-resolved RUSLE soil erosion model on the 10 000 km2 Charente catchment (France), supplied with realistic scenarios of land-cover and climate changes since 1500, and compare the results to a 14C-dated estuarine sediment record. Despite approximations, the model correctly predicts present-day Charente river sediment load. Back-cast modelling suggests that the Charente catchment is an interesting case where the sediment supply did not change despite increase in soil erosion resulting from 18th-century deforestation because it was mitigated by drier climate during the same period. Silt-sand alternations evidenced in the sediment record were correlated with sub-decadal rainfall variability.

Mots clés: Marennes-Oléron Bay; Land cover; Rainfall; Little Ice Age; Gironde Estuary

Domaines: Stratigraphie; Géomorphologie

Clément Poirier, Cyril Poitevin, Eric Chaumillon. Comparison of estuarine sediment record with modelled rates of sediment supply from a western European catchment since 1500. Comptes Rendus Géoscience, 2016, 348 (7), pp.479--488. ⟨10.1016/j.crte.2015.02.009⟩. ⟨hal-01242097⟩