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Contribution of diffuse hillslope erosion to the sediment export of French rivers

Abstract : Soil erosion is one of the major drivers of landscape evolution in Western Europe. However, depending on the land use characteristics and on the geological and topographical settings, miscellaneous forms of erosion may lead to a very diverse morphological evolution. A key element is the connection between the hillslope and the river. In this context, the objective of this study is to investigate to what extent eroded soil particles contribute to river sediment exports for the major French basins. The hillslope erosion rates are deduced from a distributed pan-European assessment of hillslope, rill, and interrill erosion by water, which was quantified by interpolation of erosion plot data as a function of topographical, land use, and pedological parameters. Sediment fluxes were mainly assessed from the French river quality database using an improved rating curve approach from the daily discharge data (IRCA), which allows estimation of the mean annual suspended sediment load. A similar approach based on the same datasets was used to calculate the mean annual dissolved load over the same period. The resulting mean annual suspended sediment loads show that French rivers export approximately 50 Mt of sediments per year to the seas, including ca. 17 Mt as particulate matter, corresponding to a specific sediment yield of ca. 0.4 t ha−1 yr−1. No relationship was found between the mass of the exported sediment and the size of the drainage basins, but large differences were observed between the different basins. For the Seine river basin and the Rhône river basin, the estimated average gross erosion rates are comparable, with ca. 1.14 t ha−1 yr−1 for the Rhone and ca. 1.80 t ha−1 yr−1 for the Seine. In contrast, the Rhône exports ca. 10 times more than the Seine River. The ratio of gross erosion to sediment exports calculated in this work ranges from 6.8% for the Seine to more than 100% for the Rhône. To explain these variations, we propose the use of indices that represent the landscape patchiness and connectivity.
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https://hal-brgm.archives-ouvertes.fr/hal-00770215
Contributeur : Olivier Cerdan <>
Soumis le : vendredi 4 janvier 2013 - 16:37:16
Dernière modification le : jeudi 24 septembre 2020 - 16:00:35

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Olivier Cerdan, Magalie Delmas, Philippe Négrel, Jean-Marie Mouchel, Emmanuelle Petelet-Giraud, et al.. Contribution of diffuse hillslope erosion to the sediment export of French rivers. Comptes Rendus Géoscience, Elsevier Masson, 2012, 344 (11-1), pp.636-645. ⟨10.1016/j.crte.2012.10.011⟩. ⟨hal-00770215⟩

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