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3. Rate of soil denudation from plot scale to river system in different social and physical environments

Author

Cerdan, Olivier, Bizeul, Rémi, Evrard, Olivier, Foucher, Anthony, Landemaine, Valentin, Minella, Jean, Pak, Lai-Ting, Salvador-Blanes, Sebastien, Cerdan, Olivier, Bizeul, Rémi, Evrard, Olivier, Foucher, Anthony, Landemaine, Valentin, Minella, Jean, Pak, Lai-Ting, and Salvador-Blanes, Sebastien

Abstract

The negative effects of soil erosion vary widely including pollution and siltation of water bodies, reduced crop yields, organic matter loss, diminished water storage capacity. These adverse effects generate significant consequences on developing as well as modern societies, possibly leading to land abandonment and the decline of rural communities and therefore posing fundamental social challenges. While protection of the soil resources is rightfully considered an important target of environmental policy, it is crucial to accurately understand the impacts of soil erosion and allocate funds for mitigation. Achieving this requires a precise assessment of erosion rates and their geographical distribution. as well as the targeting of funds to remedy soil erosion requires a correct assessment of the amount of erosion that is occurring and of its geographical distribution. Accurate quantification of soil erosion is not only essential for environmental policy but also holds scientific significance. Recent studies stressed the importance of comprehending human-induced impacts on sediment fluxes as well as their potential effects on global biogeochemical cycles. This need is even accentuated in a context where there is a demand to assess with reasonable confidence the impact of rapid climate and land use changes on these budgets. This crucial information is often lacking. To measure the rates and geographical extent of soil erosion, both indirect and direct methods have been used. Indirect methods generally measure soil profile truncation or sediment accumulation relative to a reference soil horizon, exposed or buried reference object (such as roots, foundations…), or to the loss or accumulation of tracers. These methods are more suitable for studying historical erosion. To assess current erosion rates, direct methods, typically plot or catchment monitoring and field-based measurements (e.g. mapping of erosion features) are preferred. Among these, field-based methods are mos

Published
2024

4. Diagnostic multiscalaire de la vulnérabilité des aquifères karstiques face au risque ruissellement-érosion

Author

MAURIE, Aurélien, primary, PATAULT, Edouard, additional, LANDEMAINE, Valentin, additional, Jérôme, LEDUN, additional, DAVID, Pierre-Yann, additional, CERDAN, Olivier, additional, DEMAN, Marielle, additional, MARDUEL, Benoit, additional, FOSSA, Manuel, additional, CLOSET, Jean-François, additional, OUVRY, Jean-François, additional, PENNEQUIN, Didier, additional, and FOURNIER, Mathieu, additional

Published
2023
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12. Runoff observatories: from processes analysis to improved modelling

Author

Grangeon, Thomas, Cerdan, Olivier, Landemaine, Valentin, Vandromme, Rosalie, Desprats, Jean-François, Salvador-Blanes, Sébastien, Vanhooydonck, Pierre, Gaillot, Arthur, Manière, Louis, Pene-Galland, Isabelle, Evrard, Olivier, Foucher, Anthony, Ledieu, Lauriane, Simonneau, Anaëlle, Ouvry, Jean- François, Pak, Lai, Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), GéoHydrosystèmes COntinentaux (GéHCO EA6293), Université de Tours (UT), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Géochimie Des Impacts (GEDI), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Biogéosystèmes Continentaux - UMR7327, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Association Régionale pour l'Etude et l'Amélioration des Sols (AREAS), Fonctionnement agroécologique et performances des systèmes de cultures horticoles (UPR HORTSYS), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), Département Performances des systèmes de production et de transformation tropicaux (Cirad-PERSYST), Université de Tours, Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
ruissellement par saturation, [SDU]Sciences of the Universe [physics], saturation-excess runoff, soil properties, rainfall, [SDE]Environmental Sciences, ruissellement hortonien, pluviométrie, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDV.SA.SDS]Life Sciences [q-bio]/Agricultural sciences/Soil study, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Infiltration-excess runoff, propriété des sols
Abstract

International audience; Runoff events are usually very concentrated in both space and time, and are therefore challenging to monitor. They result from the interactions of rainfall characteristics with both soil surface and intrinsic characteristics and catchment morphology. To improve our understanding of this complex process, five observatories were installed to monitor the runoff response of eleven catchments to natural rainfall events. Measurements were performed with a high frequency (≤ 15 min-time step) and over long time periods (1.5 to 11 years). 1640 rainfall-runoff events were extracted from rainfall and discharge time series. Statistical analyses were performed in order to determine significant triggering factors. The rainfall-runoff response of each catchment is highly variable, but some common features were identified across contrasted catchments. Under highly variable soil types, the catchment runoff exhibited contrasted patterns. Soil surface state, and land use were demonstrated to highly affect runoff. The scattering in the rainfall-runoff relationship demonstrated the key role of the initial soil moisture and rainfall characteristics. Lessons learnt from previous studies in these various environments, as well as their consequences on runoff understanding and modelling are discussed.; Le ruissellement est un phénomène épisodique et localisé, donc difficile à mesurer. Il résulte de l'interaction de nombreux facteurs, dont les caractéristiques intrinsèques et de surface du sol, la morphologie du bassin versant, mais également les caractéristiques pluviométriques. Afin d'améliorer la compréhension de la genèse et de la propagation du ruissellement au sein de bassins versants de tête, cinq observatoires du ruissellement sont présentés, incluant 11 bassins versants. Pour chacun d'entre eux, la pluie et le ruissellement sont mesurés sur le terrain à haute fréquence (≤ 15 min) pendant des durées longues (1,5 à 11 ans). 1640 évènements pluvio-ruisselants sont extraits de ces chroniques en continu et statistiquement analysés, afin de cerner les facteurs influant significativement le ruissellement. La réponse ruisselante de chaque bassin versant est extrêmement complexe mais permet d'identifier des comportements communs. L'importance des caractéristiques des sols est montrée, ainsi que celle de leur occupation, de leurs états de surface et état hydrique. La dispersion de la relation pluie-débit observée au sein de chacun des observatoires permet par ailleurs de montrer et de quantifier l'impact des caractéristiques pluviométriques sur la lame d'eau ruisselée. Les leçons tirées de chacun des observatoires et leurs conséquences sur la compréhension et la modélisation du ruissellement dans différents contextes sont discutées.

Published
2020
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13. Evaluation de l'efficacité des politiques publiques pour les actions visant à réduire les impacts du ruissellement et de l'érosion en Haute-Normandie

Author

Patault, Edouard, Jérôme, Ledun, Landemaine, Valentin, Soulignac, Arnaud, Richet, Jean-Baptiste, Fournier, Matthieu, Rinaudo, Jean-Daniel, Ouvry, Jean François, Cerdan, Olivier, Laignel, Benoît, Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS), Association Régionale pour l'Etude et l'Amélioration des Sols (AREAS), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Université de Rouen NormandieBRGMAREASAgence de l'Eau Seine-NormandieConseil Départemental de Seine-MaritimeConseil Départemental de l'Eure, Université de Rouen Normandie - UMR CNRS 6143 M2C, BRGM, AREAS, and EVAPORE

Subjects
[SDE.IE]Environmental Sciences/Environmental Engineering, [SDE.MCG]Environmental Sciences/Global Changes, [SDE]Environmental Sciences, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDE.ES]Environmental Sciences/Environmental and Society
Published
2020

14. Les observatoires du ruissellement : comprendre les processus pour améliorer les modélisations

Author

Grangeon, Romain, Cerdan, Olivier, Landemaine, Valentin, Vandromme, Rosalie, Desprats, Jean-François, Salvador-Blanes, Sebastien, Vanhooydonck, Pierre, Gaillot, Arthur, Maniere, Louis, Pene-Galland, Isabelle, Evrard, Olivier, Foucher, Anthony, Ledieu, Lauriane, Simonneau, Anaëlle, Ouvry, Jean-François, Pak, Lai-Ting, Grangeon, Romain, Cerdan, Olivier, Landemaine, Valentin, Vandromme, Rosalie, Desprats, Jean-François, Salvador-Blanes, Sebastien, Vanhooydonck, Pierre, Gaillot, Arthur, Maniere, Louis, Pene-Galland, Isabelle, Evrard, Olivier, Foucher, Anthony, Ledieu, Lauriane, Simonneau, Anaëlle, Ouvry, Jean-François, and Pak, Lai-Ting

Abstract

Le ruissellement est un phénomène épisodique et localisé, donc difficile à mesurer. Il résulte de l'interaction de nombreux facteurs, dont les caractéristiques intrinsèques et de surface du sol, la morphologie du bassin versant, mais également les caractéristiques pluviométriques. Afin d'améliorer la compréhension de la genèse et de la propagation du ruissellement au sein de bassins versants de tête, cinq observatoires du ruissellement sont présentés, incluant 11 bassins versants. Pour chacun d'entre eux, la pluie et le ruissellement sont mesurés sur le terrain à haute fréquence (≤ 15 min) pendant des durées longues (1,5 à 11 ans). 1640 évènements pluvio-ruisselants sont extraits de ces chroniques en continu et statistiquement analysés, afin de cerner les facteurs influant significativement le ruissellement. La réponse ruisselante de chaque bassin versant est extrêmement complexe mais permet d'identifier des comportements communs. L'importance des caractéristiques des sols est montrée, ainsi que celle de leur occupation, de leurs états de surface et état hydrique. La dispersion de la relation pluie-débit observée au sein de chacun des observatoires permet par ailleurs de montrer et de quantifier l'impact des caractéristiques pluviométriques sur la lame d'eau ruisselée. Les leçons tirées de chacun des observatoires et leurs conséquences sur la compréhension et la modélisation du ruissellement dans différents contextes sont discutées.

Published
2020

15. Analysis of off-site economic costs induced by runoff and soil erosion: example of two areas in the northwestern European loess belt for the last two decades (Normandy, France)

Author

Patault, Edouard, primary, Ledun, Jérôme, additional, Landemaine, Valentin, additional, Soulignac, Arnaud, additional, Richet, Jean-Baptiste, additional, Fournier, Matthieu, additional, Ouvry, Jean-François, additional, Cerdan, Olivier, additional, and Laignel, Benoit, additional

Published
2021
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16. Analyse coût-bénéfice du programme d’actions visant à réduire les impacts du ruissellement et de l’érosion en Haute-Normandie : évaluation des actions passées et projections futures sur le bassin versant de la Lézarde

Author

Patault, Edouard, primary, Soulignac, Arnaud, additional, Landemaine, Valentin, additional, Ledun, Jérôme, additional, Allard, Erwan, additional, Fournier, Matthieu, additional, Ouvry, Jean-François, additional, Cerdan, Olivier, additional, and Laignel, Benoit, additional

Published
2021
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17. Les observatoires du ruissellement : comprendre les processus pour améliorer les modélisations

Author

Grangeon, Thomas, primary, Cerdan, Olivier, additional, Landemaine, Valentin, additional, Vandromme, Rosalie, additional, Desprats, Jean-François, additional, Salvador-Blanes, Sebastien, additional, Vanhooydonck, Pierre, additional, Gaillot, Arthur, additional, Maniere, Louis, additional, Pene-Galland, Isabelle, additional, Evrard, Olivier, additional, Foucher, Anthony, additional, Ledieu, Lauriane, additional, Simonneau, Anaëlle, additional, Ouvry, Jean-François, additional, and Pak, Lai Ting, additional

Published
2020
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21. Spatial and temporal dynamics of soil erosion across different landscapes

Author

Cerdan, Olivier, Landemaine, Valentin, Foucher, Anthony, Evrard, Olivier, Grangeon, Thomas, Vandromme, Rosalie, Salvador-Blanes, Sebastien, Pak, Lai-Ting, Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), GéoHydrosystèmes COntinentaux (GéHCO EA6293), Université de Tours, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Géochimie Des Impacts (GEDI), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université Francois Rabelais [Tours], Association Régionale pour l'Etude et l'Amélioration des Sols (AREAS), Université de Tours (UT), Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2018

22. Tracing the sources and dynamics of contaminated sediment in coastal rivers draining the main Fukushima radioactive fallout plume using gamma-emitting radionuclides and carbon/nitrogen stable isotopes (2011-2017)

Author

Evrard, O., Laceby, J. Patrick, Onda, Yuichi, Hayashi, Seiji, Tsuji, Hideki, Huon, Sylvain, Lefèvre, Irène, Jaegler, Hugo, Landemaine, Valentin, Vandromme, Rosalie, Cerdan, Olivier, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Géochimie Des Impacts (GEDI), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Alberta Environment and Parks (AEP), Université de Tsukuba = University of Tsukuba, National Institute for Environmental Science [Fukushima], Institut d'écologie et des sciences de l'environnement de Paris (iEES), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Recherche Agronomique (INRA), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), ANR-11-RSNR-0002,AMORAD,AMORAD1(2011), ANR-11-JAPN-0001,TOFU,Traçage des conséquences environnementales du tsunami provoqué par le séisme de TOhoku et de l'accident de FUkushima(2011), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut National de la Recherche Agronomique (INRA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Evrard, Olivier, AMORAD1 - - AMORAD2011 - ANR-11-RSNR-0002 - RSNR - VALID, and Great Tohoku Earthquake - Traçage des conséquences environnementales du tsunami provoqué par le séisme de TOhoku et de l'accident de FUkushima - - TOFU2011 - ANR-11-JAPN-0001 - JAPON - VALID

Subjects
[SDE] Environmental Sciences, [SDE.MCG] Environmental Sciences/Global Changes, [SDU.STU.GM] Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDE.MCG]Environmental Sciences/Global Changes, [SDE]Environmental Sciences, [SDU.STU.HY] Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDV.SA.SDS]Life Sciences [q-bio]/Agricultural sciences/Soil study, [SDV.SA.SDS] Life Sciences [q-bio]/Agricultural sciences/Soil study, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, [SDU.ENVI] Sciences of the Universe [physics]/Continental interfaces, environment
Abstract

International audience; Fieldwork was conducted every 6 months between 2011 and 2017 to monitor the dispersion of sediment contaminated with radionuclides in rivers draining the main Fukushima radioactive pollution plume (~500 km²). Fine sediment was systematically collected at the same locations (n=47) and analysed for gamma-emitting radionuclides (including 137Cs and 110mAg). A selection of samples was also analysed for carbon/nitrogen concentrations and isotopes. Organic matter analyses showed that paddy fields provided the main source of contaminated sediment to the rivers shortly after the accident. The spatial variations of the 110mAg:137Cs activity ratio in soils were used to demonstrate the very rapid export of sediment to the Pacific Ocean. However, this tool could only be used during the first campaigns, because of the quick decay of 110mAg. Overall, radiocesium concentrations measured in sediment deposits decreased by ~90% between 2011 and 2017. This may be explained by remediation works, by a massive export of material during typhoons and by the occurrence of landslides or channel bank erosion that supply material sheltered from the Fukushima fallout to the river network. Consequently, 6 years after the accident, most of the residual radioactive contamination is found in forests and in dam reservoirs. The analysis of sediment cores collected in a reservoir confirmed the significant storage of contaminated material in these lakes and that paddy fields provided their main source. Ongoing research focuses on the development of a soil erosion model and on the quantification of the impact of remediation works.

Published
2018

23. Coupled Modeling of Hydro-Sedimentary Transfer Processes and Socio-Economic Dynamics Evaluating Public Policies to Control Runoff and Erosion: Case Study in Normandy (France)

Author

Patault, Edouard, primary, Ledun, Jérôme, additional, Landemaine, Valentin, additional, Soulignac, Arnaud, additional, Richet, Jean-Baptiste, additional, Ramaekers, Fanny, additional, Cabaz, Boris, additional, Cikowski, Natacha, additional, Fournier, Matthieu, additional, Ouvry, Jean-François, additional, Rinaudo, Jean-Daniel, additional, Cerdan, Olivier, additional, and Laignel, Benoit, additional

Published
2019
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24. Contribution of bank erosion to the sediment budget of a drained agricultural lowland catchment

Author

Cerdan, Olivier, Foucher, Anthony, Vandromme, Rosalie, Salvador-Blanes, Sébastien, Gay, Aurore, Landemaine, Valentin, Evrard, O., Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), GéoHydrosystèmes COntinentaux (GéHCO EA6293), Université de Tours (UT), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Géochimie Des Impacts (GEDI), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Cerdan, Olivier, Université de Tours, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
", [SDU.STU.GM] Sciences of the Universe [physics]/Earth Sciences/Geomorphology, sediment, bank erosion, [SDU.STU.HY] Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDV.SA.SDS]Life Sciences [q-bio]/Agricultural sciences/Soil study, [SDV.SA.SDS] Life Sciences [q-bio]/Agricultural sciences/Soil study, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, [SDU.ENVI] Sciences of the Universe [physics]/Continental interfaces, environment
Abstract

International audience; Following the shift towards more intensive agriculture in cultivated lowlands in Europe, field sizes have increased and stream valley meanderings have been removed and realigned along new straight field borders. These modifications have led to profound alterations of the hydromorphology of the streams. To test the impact of these modifications, the long-term and current volumes of sediment originating from stream banks were calculated as they provided potential sources of sediment in a large pond located at the outlet of a small agricultural lowland basin under strong anthropogenic pressure. Bank erosion was measured using several methodologies, i) over a short period using a set of erosion pins along a small stream (1400 m long) to quantify the material exported during a single winter season (2012/2013); ii) over the last 69 years using an original approach involving the comparison of a compilation of three-dimensional historical stream redesign plans from 1944 vs. new measurements conducted in 2013 (DGPS and LiDAR data); iii) over several decades by using tracers (137Cs) that can differentiate between surface and subsoil erosion. At the catchment scale, total sediment exports were estimated from 1945 to 2013 combining seismic imagery and core dating in the lake. Sediment exports decreased with time, from 300 t. km–2.yr–between 1954 and 1980 to 95 t. km–2.yr–1 between 1980 and 2013. Today, erosion rates recorded at the outlet of the catchment vary between 90–102 t.km–2.yr–1. Therefore, the order of magnitude of the mean export rate is approximately 180 t. km–2.yr–1 for the last 70 years.The contribution of channel banks to this sediment export was the highest (~30%) between 1954 and 1980 when the ditches were constructed. For the entire period since the landscape modification, the contribution of bank erosion is lower but still reaches 20%. Bank erosion can therefore be considered as a significant contributor to the sediment budget of the lowland catchments that have been redesigned after the 2nd world war in Western Europe.

Published
2017

25. Predicting Sediment Discharge at Water Treatment Plant Under Different Land Use Scenarios Coupling Expert-Based GIS Model and Deep Neural Network.

Author

Patault, Edouard, Landemaine, Valentin, Ledun, Jérôme, Soulignac, Arnaud, Fournier, Matthieu, Ouvry, Jean-François, Cerdan, Olivier, and Laignel, Benoit

Abstract

Excessive sediment discharge at karstic springs and thus, water treatment plants, can be highly disruptive. It is essential for catchment stakeholders and drinking water supplier to reduce the impact of sediment on potable water supply, but their strategic choices must be based on simulations, integrating surface and groundwater transfers, and taking into account possible changes in land use. Karstic environments are particularly challenging as they face a lack of accurate physical description for the modelling process, and they can be seen as a black-box due to the non-linearity of the processes generating sediment discharge. The aim of the study was to assess the sediment discharge variability at a water treatment plant according to multiple realistic land use scenarios. To reach that goal, we developed a new coupled modelling approach with an erosion-runoff GIS model (WaterSed) and a deep neural network. The model was used in the Radicatel catchment (106 km2 in Normandy, France) where karstic spring water is extracted to a water treatment plant. The sediment discharge was simulated for five designed storm projects under current land use and compared to three land use scenarios (baseline, ploughing up of grassland, eco-engineering, best farming practices). Daily rainfall time series and WaterSed modelling outputs extracted at connected sinkholes were used as input data for the deep neural network model. The model structure was found by a classical trial and error procedure, and the model was trained on two significant hydrologic years. Evaluation on a test set showed a good performance of the model (NSE = 0.82), and the application of a monthly-backward chaining nested cross validation revealed that the model is able to generalize on new datasets. Simulations made for the three land use scenarios suggested that ploughing up 33 % of grasslands would not increase significantly sediment discharge at the water treatment plant (5 % in average). In the opposite, eco-engineering and best farming practices will significantly reduce sediment discharge at the water treatment plant (respectively in the range of 10-44 and 24-61 %). The coupling of these two strategies is the most efficient since it affects the hydro-sedimentary production and transfer processes (decreasing sediment discharge from 40 to 80 %). The coupled modelling approach developed in this study offers interesting opportunities for sediment discharge prediction at karstic springs or water treatment plant under multiple land use scenarios. It also provides robust decision-making tools for land use planning and drinking water suppliers. [ABSTRACT FROM AUTHOR]

Published
2020
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26. Érosion des sols et transferts sédimentaires sur les bassins versants de l’Ouest du Bassin de Paris : analyse, quantification et modélisation à l’échelle pluriannuelle

Author

Landemaine, Valentin, Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS), Normandie Université, Benoit Laignel, Olivier Cerdan, and Matthieu Fournier

Subjects
Effet d’échelle, Scale effect, Érosion, Bassin versant, Modélisation, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Watershed, Surface runoff, Modelling, Ruissellement
Abstract

The impacts of accelerated soil erosion are particularly important on the loess plateaux of Normandy, and are therefore studied since several decades. The works performed at the scale of the agriculture plot show erosion rates among the greatest in Europe, as a consequence of intensive agriculture practices on unstructured loamy soils, especially vulnerable to surface water runoff and erosion.; Les impacts de l’érosion accélérée des sols sont particulièrement présents au niveau des plateaux lœssiques normands, et sont à ce titre étudiés depuis plusieurs décennies. Les travaux menés à l’échelle de la parcelle agricole montrent des taux d’érosion parmi les plus élevés d’Europe en raison d’une agriculture intensive sur sols lœssiques peu structurés particulièrement sensibles au ruissellement et à l’érosion. Cependant, les premiers bilans d’export réalisés à l’exutoire de quelques bassins versants normands indiquent des taux d’érosion extrêmement faibles en comparaison. Ces différences notables sont liées au stockage des produits érodés au sein du bassin versant avec le changement d’échelle spatiale. Toutefois, la connaissance de l’effet d’échelle restait jusqu’à présent limitée aux bassins versants élémentaires. Ce travail de thèse propose d’étendre notre compréhension du fonctionnement global de ces hydrosystèmes, par une étude approfondie du continuum sédimentaire, depuis les zones de production du ruissellement et de l’érosion sur les parcelles agricoles, jusqu’à l’exutoire du bassin versant.

Published
2016

27. Connectivity and scale effect on sediment fluxes dynamic from the hillslope to the river basin

Author

Cerdan, Olivier, Landemaine, Valentin, Vandromme, Rosalie, Gay, Aurore, Laignel, Benoît, Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), AMORAD, Centre National de la Recherche Scientifique (CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Caen Normandie (UNICAEN), and Normandie Université (NU)

Subjects
sediment, connectivity, river, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, hillslope
Abstract

International audience; The phenomena of erosion and sediment transport are often observed with a time lag and / or space within a watershed, especially between the upstream and downstream areas. This difference between runoff and erosion assessments that depends on the size of observation is commonly called the "scale effect". This effect has often been studied globally and reduced runoff and erosion rates are generally reported as one moves from the local to the regional level.To quantify the scale effect, local erosion models are often linked to the empirical concept of SDR (Sediment Delivery Ratio): the ratio of exported sediment at the outlet of a drainage system on the gross erosion that occurred locally. This empirical parameter is used as a connectivity factor to estimate the contribution of net soil losses to sedimentary basins exports. A recent renewed interest on these topics has led the development of more or less elaborate variants that propose a conceptualization of the (es) connectivity (s) of the landscape to describe the sedimentary flows within watersheds.In general, these concepts allow apprehending the spatial variability of flow in heterogeneous environments and for events / climates not too extreme. Their use is more difficult when the flows are constrained by the production process. A limit also appears when trying to cover too large a range of spatial scales, because beyond a spatial succession of (re) detachment and deposition processes a new nature of process can emerge. We will rely on several measured database of erosion / sediment transport at different scales and in diverse geomorphological contexts to illustrate and discuss the relevance of these concepts.

Published
2016

28. Soil erosion and sediment transfers on the watersheds of the western Paris Basin: analysis, quantification and modelling at a pluri-annual time scale

Author

Landemaine, Valentin, Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS), Normandie Université, Benoit Laignel, Olivier Cerdan, Matthieu Fournier, and Weill, Pierre

Subjects
Effet d’échelle, [SDU.STU.GM] Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Scale effect, Érosion, Watershed, Surface runoff, [SDU.ENVI] Sciences of the Universe [physics]/Continental interfaces, environment, Modelling, Ruissellement, Bassin versant, Modélisation, [SDU.STU.HY] Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment
Abstract

The impacts of accelerated soil erosion are particularly important on the loess plateaux of Normandy, and are therefore studied since several decades. The works performed at the scale of the agriculture plot show erosion rates among the greatest in Europe, as a consequence of intensive agriculture practices on unstructured loamy soils, especially vulnerable to surface water runoff and erosion., Les impacts de l’érosion accélérée des sols sont particulièrement présents au niveau des plateaux lœssiques normands, et sont à ce titre étudiés depuis plusieurs décennies. Les travaux menés à l’échelle de la parcelle agricole montrent des taux d’érosion parmi les plus élevés d’Europe en raison d’une agriculture intensive sur sols lœssiques peu structurés particulièrement sensibles au ruissellement et à l’érosion. Cependant, les premiers bilans d’export réalisés à l’exutoire de quelques bassins versants normands indiquent des taux d’érosion extrêmement faibles en comparaison. Ces différences notables sont liées au stockage des produits érodés au sein du bassin versant avec le changement d’échelle spatiale. Toutefois, la connaissance de l’effet d’échelle restait jusqu’à présent limitée aux bassins versants élémentaires. Ce travail de thèse propose d’étendre notre compréhension du fonctionnement global de ces hydrosystèmes, par une étude approfondie du continuum sédimentaire, depuis les zones de production du ruissellement et de l’érosion sur les parcelles agricoles, jusqu’à l’exutoire du bassin versant.

Published
2016
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29. Archivages croisés de la dynamique hydro-sédimentaire et de l'histoire des activités polluantes dans le bassin de la Seine : le point sur une carotte sédimentaire prélevée dans l'Eure

Author

Patault, Edouard, Debret, Maxime, Copard, Yoann, Sabatier, Pierre, Landemaine, Valentin, Desmet, M., Fournier, Matthieu, Portet-Koltalo, Florence, Reyss, J.L., Laignel, Benoît, Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS), Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Chimie Organique et Bioorganique : Réactivité et Analyse (COBRA), Institut Normand de Chimie Moléculaire Médicinale et Macromoléculaire (INC3M), Institut de Chimie du CNRS (INC)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Université Le Havre Normandie (ULH), Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie Organique Fine (IRCOF), Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Océan et Interfaces (OCEANIS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Environnements, Dynamiques et Territoires de Montagne (EDYTEM), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie Organique Fine (IRCOF), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut Normand de Chimie Moléculaire Médicinale et Macromoléculaire (INC3M), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Université Le Havre Normandie (ULH), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDE]Environmental Sciences, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2015

30. Role of river bank erosion in sediment budgets of catchments within the Loire river basin

Author

Gay, Aurore, Cerdan, Olivier, Poisvert, Cécile, Landemaine, Valentin, Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), GéoHydrosystèmes COntinentaux (GéHCO EA6293), Université de Tours (UT), Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS), Université de Tours, and Gay, Aurore

Subjects
[SDE] Environmental Sciences, sediment budgets, [SDE]Environmental Sciences, vegetated banks, flow discharge
Abstract

Quantifying volumes of sediments produced on hillslopes or in channels and transported or stored within river systems is necessary to establish sediment budgets. If research efforts on hillslope erosion processes have led to a relatively good understanding and quantification of local sources, in-channel processes remain poorly understood and quasi inexistent in global budgets. However, profound landuse changes and agricultural practices have altered river functioning, caused river bank instability and stream incision. During the past decades in France, river channelization has been perfomed extensively to allow for new agricultural practices to take place. Starting from a recent study on the quantification of sediment fluxes for catchments within the Loire river basin (Gay et al. 2013), our aim is to complete sediment budgets by taking into account various sources and sinks both on hillslope and within channel. The emphasis of this study is on river bank erosion and how bank erosion contributes to global budgets. A model of bank retreat is developed for the entire Loire river basin. In general, our results show that bank retreat is on average quite low with approximately 1 cm.yr-1. However, a strong variability exists within the study area with channels displaying values of bank retreat up to ~10 cm.yr-1. Our results corroborate those found by Landemaine et al. 2013 on a small agricultural catchment. From this first step, quantification of volumes of sediment eroded from banks and available for transport should be calculated and integrated in sediment budgets to allow for a better understanding of basin functioning

Published
2014

31. Estimating of suspended sediment loads of rivers in the Seine downstream basin and coastal rivers in Southeastern Channel

Author

Landemaine, Valentin, Cerdan, Olivier, Laignel, Benoît, Fournier, Matthieu, Copard, Yoann, Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS), and Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)

Subjects
[SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology
Abstract

Sediment exports in rivers constitute the essential of materials transfer from the land surface to the ocean and contribute significantly to the transfer of nutrients, pesticides, heavy metals which can affect water quality. Such problems of water pollution are particularly present at the Norman loess plateaus because soil erosion is a frequent phenomena and mudslides are common. In this context, the quantification of sediment load, as well as the short and long term variability analysis are a key component for any sustainable management project of water resources. The quantification of sediment fluxes is based on turbidity, suspended sediment concentrations (SSC) and discharge measurements. These measurements must be made with sufficient high frequency for integrating temporal variability of SSC and flows. However, the cost of a high frequency monitoring limits their use at large scale. In France, discharges are monitored using daily frequency (Banque Hydro), while SSC are measured in monthly or bimonthly frequency under the national water quality survey system (RNB). With these low frequency measurements, an algorithm must be used to reconstruct SSC temporal variability and to estimate a sediment flux. Many estimation algorithms have been developed in recent decades, from the simplest to the most elaborate, but no consensus has been reached on the use of a particular algorithm because of the complexity of SSC-discharge relationship. In this study, the analysis focuses on eight Channel coastal watersheds and nine Seine watersheds in the downstream part. We have a several years of high-frequency measurements on nine watersheds with highly variable area (10 km2 to 10,000 km2) and low-frequency measurements for all watersheds. From these data, we compared the statistical performance of eleven algorithms to estimate sediment fluxes conventionally used in the literature. These algorithms are: averaging estimator, ratio estimator, linear interpolation, rating curve and multi sediment rating curve (MRC). From the results, the MRC algorithm had the best performance in terms of bias and precision between real and estimated sediment loads. This algorithm has been used to determine the sediment loads of all watersheds. On the Seine downstream basin, sediment fluxes from tributaries range from 171,000 t/year to 945,000 t/year depending on the year. This represents between 3% and 9% of sediment fluxes passing into the Seine. Finally, the long term variability analysis showed a high variability from year to year depending on climatic conditions. This study suggests the need to investigate fluxes over several years, to extract representative orders of magnitude and to quantify uncertainties.

Published
2014

34. The scale dependency of erosion and runoff for two agricultural catchments in the Western Paris Basin, France.

Author

Cerdan, Olivier, Landemaine, Valentin, Laignel, Benoit, Evrard, Olivier, Salavador-Blanes, Sébastien, Grangeon, Thomas, Vandromme, Rosalie, and Laceby, Patrick

Subjects
*AGRICULTURAL pollution, *SOIL erosion, *EROSION, *GEOMORPHOLOGY, *WATERSHEDS, *SOIL depth, *SOIL topography
Abstract

A major challenge in geomorphology is reconciling the disparity between runoff coefficients and erosion rates from the field to the catchment scale. In the European loess belt, a decrease of runoff coefficients and erosion rates occurs with increasing spatial scales. Indeed, it is important to understand the scale dependency of run-off and erosion to manage the off-site impacts of accelerated soil erosion. Accordingly, a continuous simulation of the scale dependency of runoff and erosion, from the field scale to the catchment scale (100 – 1000 km²) was conducted with the Water and Sediment (WaterSed) model for two catchments (Andelle-756 km², and Austreberthe-214 km²) over 12 years (>1000 events). Scale effects were evident with a 100-fold decrease in runoff coefficients and sediment delivery ratios between the field scale and the catchment scale. In spite of a low variability of the annual rainfall (19%), the inter-annual variability of the runoff volume (37%) and erosion rates (92%) at catchment outlets were high. The inter-annual variability of runoff and erosion was closely linked to the number of extreme events per year and their distribution through the year, in particular during periods with highly crusted soil surface states. For these high magnitude events, a complex distributed modelling approach was not necessary as the ability of the soil surface and of the landscape to retain overland flows are largely exceeded. The seasonality of soil surface characteristics also affected the scale dependency of runoff and erosion, from the field scale to the catchment scale. However, this is only observed up to a certain spatial extent, i.e. where hillslope erosion processes are governed by hortonian overland flow. When saturation flows are generated, topography and soil depth become the dominant factors. Understanding runoff and sediment response at different scales should focus on the location and amount of runoff and sediment production within the catchment and the capacity of the downstream flow path to retain or transfer overland flow and sediment. Furthermore, this study demonstrates the need to implement model that represent both hortonian and saturation flows when simulating erosion events at the catchment scale. [ABSTRACT FROM AUTHOR]

Published
2019

35. Uncontrolled deforestation and population growth threaten a tropical island's water and land resources in only 10 years.

Author

Foucher A, Evrard O, Rabiet L, Cerdan O, Landemaine V, Bizeul R, Chalaux-Clergue T, Marescaux J, Debortoli N, Ambroise V, and Desprats JF

Subjects
Tropical Climate, Biodiversity, Humans, Madagascar, Comoros epidemiology, Agriculture methods, Ecosystem, Conservation of Natural Resources, Population Growth, Islands
Abstract

Rapid demographic growth in tropical islands can exacerbate conflicts and pressures on natural resources, as illustrated by the French island of Mayotte where resources are limited. In only 10 years, uncontrolled migration and population growth (+80% of population between 2002 and 2021) have led to a pronounced 3600% increase in deforestation rates (2010-2014) and an intensification of agricultural practices, escalating conflicts over limited land, water, and biodiversity resources. Implementing an original multi-proxy approach to sediment cores, our study reveals a staggering 300% acceleration in erosion during the first wave of migration (2011-2015), followed by a further 190% increase (2019-2021) under sustained migratory and demographic pressures. Sedimentary DNA analysis provided insights into increased connectivity and community changes. By 2050, the population of this region will increase by 74 and 103%, in Comoros and Madagascar islands, respectively. Urgent conservation measures are needed to avoid major socio-environmental crises and to protect resources for future generations.

Published
2024
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