3 results on '"Delsinne, N."'
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2. Pluri-millenial to pluri-annual evolution of the sediment wedge at the River Seine mouth. Natural and anthropogenic controls
- Author
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Delsinne, N., 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 Caen, Tessier Bernadette(bernadette.tessier@unicaen.fr), and Delsinne, Nicolas
- Subjects
sismique THR ,[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere ,The river Seine mouth ,coastal sedimentary prism ,[SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere ,prisme littoral ,man-made modifications ,cartes bathymétriques ,hydro-meteorological time series ,climatic factors ,aménagements ,carottes sédimentaires ,comblement estuarien ,bathymetric charts ,sedimentary cores ,macrotidal environment ,Embouchure de la Seine ,estuarine infilling ,seismic VHR ,facteurs climatiques ,environnement macrotidal ,Holocène ,[SDU.STU.MI] Sciences of the Universe [physics]/Earth Sciences/Mineralogy ,chroniques hydro-météorologiques ,[SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy - Abstract
A sediment wedge, about 20 m thick, has emplaced at the mouth of the River Seine during the Holocene transgression. Two main methodological approaches have been developed to determine the controlling factors of its construction and morphosedimentary evolution: (1) very high resolution seismic investigation coupled with vibro-coring for studing the pluri-millenial evolution; (2) historic bathymetric chart comparison to analyse the centennial to pluri-annual evolution during the last two centuries. The long term (Holocene) evolution is controlled on one hand by the rate of sea level rise, on the other hand by the position of the main fluvial incision. The tidal inlet system remains active all along the construction above the incision, whereas the adjacent areas, particularly in the South, have filled rapidly. During the last two centuries, the infill can be divided into 3 main stages: from 1834 to 1875, the mouth is a wide migrating channelized system; from 1875 to 1960: supratidal areas develop and lateral infill occurs; from 1960 to now-days: the infill is mainly up-to downstream and marked by the development and rapid seaward progression of two tidal longitudinal bars. The impact of natural factors on this recent evolution is hard to identify as management works during this period are major; they are assumed to be the controlling agents. However high frequency climatic cycles such as the NAO (North Atlantic Oscillation) seem to play a significant role in the morphodynamic behaviour of the tidal mouth during the most recent period, as since the 1980's no more major managements have been performed., A l'embouchure de l'estuaire de la Seine, un prisme sédimentaire d'une vingtaine de mètres d'épaisseur s'est mis en place au cours de la transgression holocène. L'étude des facteurs de contrôle de sa construction et de son évolution morphosédimentaire a été menée selon deux approches : (1) à partir de données sismiques et de carottage pour étudier l'évolution à long terme (pluri?millénaire) ; (2) à partir de données cartographiques anciennes pour l'étude des évolutions à moyen et court terme (pluri-décennale à pluri-annuelle) depuis les deux derniers siècles. L'évolution à long terme du prisme (construction holocène) est contrôlée d'une part par la vitesse de remontée du niveau marin, d'autre part par la position initiale de l'incision majeure de la Seine. C'est à l'aplomb de celle-ci que le système d'embouchure reste actif tout le long de la construction, tandis que dans les secteurs adjacents, notamment au sud, le système se comble rapidement. L'évolution du prisme depuis deux siècles se caractérise par un comblement progressif comprenant trois stades. 1834-1875 : vaste système divagant ; 1875-1960 développement des zones supratidales et comblement latéral du système interne ; 1960-2003 : comblement amont-aval du système par développement et progression vers le domaine marin de deux barres sableuses longitudinales. Le contrôle des aménagements dans cette évolution est considéré comme majeur et l'impact des facteurs naturels est extrêmement difficile à extraire. L'influence de cycles climatiques haute fréquence comme la NAO (North Atlantic Oscillation) est néanmoins sensible pour la période la plus récente (depuis 1980), période marquée par l'arrêt des aménagements.
- Published
- 2005
3. Modelling sand/mud transport and morphodynamics in the Seine river mouth (France): an attempt using a process-based approach
- Author
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Waeles, Benoit, Le Hir, Pierre, Lesueur, P, Delsinne, N, Waeles, Benoit, Le Hir, Pierre, Lesueur, P, and Delsinne, N
- Abstract
The mouth of the Seine River estuary (France) has undergone marked morphological evolution over several decades mainly due to engineering works aimed at improving access to Rouen and Le Havre harbours. The intertidal areas are decreasing in size and the lower estuary is accumulating sediment and prograding. In order to understand and better describe the major morphological behaviours of the estuary, a morphodynamic numerical model was developed within the Seine-Aval program. At the end of the 1st part of the research program, a validated fine sediment transport model (3D) was available (Le Hir et al., 2001b). As the present morphological study addresses medium-term issues (a few decades), and because of the need to investigate impacts of local structures or events, we chose to use the so-called "process-based approach" starting from the existing model. First, the existing model was upgraded to account for (suspended) sand transport, and to achieve coupling between morphological changes and sediment transport. Erodability of the sediment accounts for the respective proportions of mud and sand. Simulations starting from an arbitrary surficial sediment cover show that the model is able to reproduce realistic sediment patterns. For example, it is able to change the sediment nature on the intertidal flat near Le Havre from sand to mud. Observed structures of suspended sediment are also reproduced: fine particles mainly follow the turbidity maximum whereas significant concentrations of sand grains in suspension are found where the hydrodynamic stresses are intense. Concerning morphodynamics, simulations with real forcing over one year are discussed. The effect of waves on the bathymetric evolution of the mouth is shown and the sensitivity of morphodynamics to the coupling procedure is tested.
- Published
- 2007
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