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| Registros recuperados: 58 | |
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| Alzieu, Claude; Abarnou, Alain; Bassoullet, Philippe; Boutier, Bernard; Chiffoleau, Jean-francois; Crenn, Isabelle; Derrien, Annick; Erard-le Denn, Evelyne; Gourmelon, Michele; Guiliaud, Jean-françois; Silva Jacinto, Ricardo; Le Cann, Pierre; Le Guyader, Françoise; Le Hir, Pierre; L'Yavanc, Jacky; Mauvais, Jean-louis; Menard, Dominique; Michel, Pierre; Monbet, Yves; Pommepuy, Monique; Quiniou, Francoise. |
| Port activities require continuous or occasional dredging of considerable quantities of sediments : approximately 50 million m3 along the French coastline. A large proportion of the dredgings is authorized for dumping at sea in geographically delimited areas and following an impact evaluation of their potential harmfulness to the marine environment. The environmental risks assessment linked to dredging operations relies on knowledge related to several scientific disciplines contributing to changes in the regulations. This work, intended both for managers and for environmental scientists and engineers, is designed to take stock of the current state-of-the-art in the field of sediment contamination and related ecotoxicological hazards, along with a review of... |
| Tipo: Text |
Palavras-chave: Regulations; Management; Impact; Contaminants; Dredging; Réglementation; Gestion; Impact; Contaminants; Dragages. |
| Ano: 1999 |
URL: http://archimer.ifremer.fr/doc/1999/rapport-1040.pdf |
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| Diaz, Melanie; Grasso, Florent; Le Hir, Pierre; Caillaud, Matthieu; Thouvenin, Benedicte. |
| Coastal environments are directly influenced by terrigenous inputs coming from rivers through estuaries. Quantifying the amount of nutrients and contaminants brought by sediments from continental areas to the sea is of major interest for marine resource protection. The complexity of the intra-estuarine dynamics, associated with the strong variability of meteorological forcing makes it difficult to quantify the residence time of particles within the estuary and the accumulation and dispersion areas offshore the mouth. Moreover, the dynamics of fine sediment trapping areas in the adjacent continental shelf (e.g. temporary or permanent storage such as the “West-Gironde Mud Patch” (WGMP) ) remains extremely challenging to address. Based on a realistic... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00514/62559/66913.pdf |
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| Diaz, Melanie; Grasso, Florent; Le Hir, Pierre; Sottolichio, Aldo; Caillaud, Matthieu; Thouvenin, Benedicte. |
| Coastal environments are directly influenced by terrigenous inputs coming from rivers through estuaries. Quantifying the amount of nutrients and contaminants transported by sediments from continental areas to the sea is crucial for marine resources protection. However, the complexity of estuarine dynamics makes it difficult to quantify sediment fluxes from field measurements alone and requires numerical modeling. Thus, using a realistic 3D hydrodynamic and sediment transport model, this study aims at evaluating the influence of model empirical parameters on sediment fluxes and estimating uncertainties on mud and sand transfers at a macrotidal estuary mouth. A sensitivity analysis, considering changes in sediment transport parameters, revealed that the... |
| Tipo: Text |
Palavras-chave: Sensitivity analysis; Sediment fluxes; Numerical modeling; Mud; Sand; Gironde Estuary. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00617/72897/71906.pdf |
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| Le Hir, Pierre. |
| After a brief reminder on the sediment composition and facies, the paper reviews water-sediment exchanges that require to account for sediment transformation in Coastal Environment modelling. Physical processes (consolidation, bed armouring, liquefaction) and bio-chemical processes (organic matter mineralisation, adsorption/desorption, precipitation/dissolution, bioturbation…) are briefly reviewed, as well as usual modelling methods. The need for a guide book on the required minimal modelling, depending on the arisen questions, is put forward. |
| Tipo: Text |
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| Ano: 2007 |
URL: https://archimer.ifremer.fr/doc/00480/59151/61780.pdf |
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| Grasso, Florent; Mengual, Baptiste; Le Hir, Pierre; Walther, Régis; Verney, Romaric. |
| L'embouchure de l’estuaire de la Seine a subi de fortes altérations morphosédimentaires au cours du dernier siècle et son évolution se poursuit encore actuellement. La question du devenir du système et des habitats associés est donc posée, en tenant compte d'éventuels changements environnementaux ou climatiques. La modélisation morphosédimentaire a pour ambition de simuler le devenir de la morpho-bathymétrie, en rendant compte des couplages entre processus hydrodynamiques, transports de sédiment et évolution de la morphologie. Le projet MORPHOSEINE vise à exploiter l'outil de modélisation MARS3D CurviSeine mis en place par l’Ifremer dans le cadre des programmes Seine-Aval (SA) 4 et 5, afin de répondre à l'attente concernant l'évolution possible de... |
| Tipo: Text |
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| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00684/79630/82353.pdf |
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| Dufois, Francois; Garreau, Pierre; Le Hir, Pierre; Forget, P. |
| Simulations of both currents and waves were performed throughout the year 2001 to assess the relative contribution of each to their overall erosive potential on the Gulf of Lions shelf. Statistical analysis of bottom shear stress (BSS) was compared to sediment grain-size distribution on the bottom. The hydrodynamic features of the bottom layer coincide with the distribution of surficial sediments, and three areas with different hydro-sedimentary characteristics were revealed. (i) The sandy inner shelf ( < 30 m) area is a high-energy-wave dominated area but may be subjected to intense current-induced BSS during on-shore winds along the coast and during continental winds mainly in the up-welling cells. (ii) The middle shelf (30-100 m) is a low-energy... |
| Tipo: Text |
Palavras-chave: Gulf of Lions; 3D modelling; Bottom shear stress; Sediment transport. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-6305.pdf |
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| Mengual, Baptiste; Le Hir, Pierre; Cayocca, Florence; Garlan, Thierry. |
| This study describes the building of a common erosion law for fine sand and mud, mixed or not, in the case of a typical continental shelf environment, the Bay of Biscay shelf, characterized by slightly energetic conditions and a seabed mainly composed of fine sand and muddy sediments. A 3D realistic hydro-sedimentary model was used to assess the influence of the erosion law setting on sediment dynamics (turbidity, seabed evolution). A pure sand erosion law was applied when the mud fraction in the surficial sediment was lower than a first critical value, and a pure mud erosion law above a second critical value. Both sand and mud erosion laws are formulated similarly, with different parameters (erodibility parameter, critical shear stress and power of the... |
| Tipo: Text |
Palavras-chave: Sand-mud mixture erosion; Numerical modelling; Non-cohesive to cohesive transition. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00394/50588/51280.pdf |
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| Mengual, Baptiste; Cayocca, Florence; Le Hir, Pierre; Draye, Robin; Laffargue, Pascal; Vincent, Benoit; Garlan, Thierry. |
| Sea trials were performed on two zones with different fishing efforts on the continental shelf of the Bay of Biscay ('Grande-VasiSre' area of muddy sand) in order to assess particulate matter resuspension and seabed disturbances (i.e., penetration, reworking, grain size changes) induced by different types of trawls. Optical and acoustic measurements made in the water column indicate a significant trawling-induced resuspension mainly due to the scraping action of doors. It manifests as a highly dynamic turbid plume confined near the seabed, where suspended sediment concentrations can reach 200 mg l(-1). Concentration levels measured behind an "alternative" configuration (trawls with jumper doors instead of classical doors penetrating the sediment) are... |
| Tipo: Text |
Palavras-chave: Bottom trawling; Sedimentresuspension; Seabed disturbance; Erosion flux; Bay of Biscay. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00353/46428/51396.pdf |
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| Orvain, Francis; Le Hir, Pierre; Sauriau, Pierre-guy. |
| Previous studies have shown that the gastropod Hydrobia ulvae destabilizes the top layers of fine-grained sediments. This process is mediated by the formation of a "biogenic" fluff layer that includes tracks, faecal pellets and mucus. This fluff layer has been shown to be easily resuspended before general bed erosion. In order to examine how fluff layer and bed. erosion interact, flume experiments were performed with fluid sediments of varying water contents. Ten thousand snails were placed and allowed to crawl for 5 h on the sediment surface, and then the resuspended sediment mass was measured in response to step-wise shear stress increases. Two distinct erosion phases were observed: (1) initial resuspension of the fluff layer and (2) the subsequent bed... |
| Tipo: Text |
Palavras-chave: Gastropoda; Erosion sediment; Bioturbation; Cohesive sediment; Marine sediment. |
| Ano: 2003 |
URL: http://archimer.ifremer.fr/doc/2003/publication-805.pdf |
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| Bourillet, Jean-francois; Jouanneau, J.m.; Macher, Claire; Le Hir, Pierre; Naughton, F. |
| The Quaternary sequence of the Armorican continental shelf in the Bay of Biscay is setting down above one regional erosion surface, which has been produced by successive transgressions that occurred during the last deglaciations. The few meters of the sequence covers the Holocene period and it is composed by two clean and sandy units at the base followed by thin (few decimetres) clayed sand unit and mud (few millimetres) unit in the top. The two upper units form the improperly called "La Grande Vasière" area over 8,000 km2. The settlement of these sedimentary units occurred since 8,000 C14 years BP, previously to other coastal mud fields setting of the shelf. Historical grain size data show that the mud field has lost part of the fine content during the... |
| Tipo: Text |
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| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/acte-6243.pdf |
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| Jacobs, Walter; Le Hir, Pierre; Van Kesteren, Walther; Cann, Philippe. |
| Results of a large number of erosion tests on artificially generated and relatively dense sand-mud mixtures are presented. Soil sample compositions are varied concerning clay-silt and sand-silt ratio, and clay mineralogy. The experimental set-up consists of a re-circulating small-scale rectangular erosion flume with unidirectional flow conditions. The erosion threshold and erosion rate are studied through step by step increasing the flow rate during a test. Results clearly indicate time-decreasing erosion during which individual flocs are randomly eroded, and time-independent (steady) erosion during which both sand and mud particles are continuously and uniformly eroded. These two erosion types appear to be floc and surface erosion, respectively... |
| Tipo: Text |
Palavras-chave: Erosion; Sand-mud mixtures; Clay; Sediment structure; Critical shear stress; Strength. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00041/15252/12678.pdf |
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| Dufois, Francois; Verney, Romaric; Le Hir, Pierre; Dumas, Franck; Charmasson, Sabine. |
| In this study a three-dimensional sediment transport model was developed. The model accounts for both current and wave forcing on the sediment and was implemented over the Gulf of Lions. A two-way nesting technique was used to focus on the Rhone River prodelta which is considered as a sink for riverine sediment. In addition, to understand the resuspension of trapped sediment over the Rhone prodelta, an in situ experiment, called SCOPE, was conducted during the winter 2007/2008. The experiment consisted of measuring hydro-sedimentary parameters using a mooring station comprising a current profiler (ADCP) and an altimeter (acoustic transducer) located in the eastern part of the Rhone prodelta. The three-dimensional transport model was validated using these... |
| Tipo: Text |
Palavras-chave: Sediment transport; Gulf of Lions; Rhone prodelta; 3D modelling; ADCP; ALTUS. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00165/27584/25743.pdf |
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| Le Hir, Pierre; Cayocca, Florence; Waeles, Benoit. |
| Mixed sediments are constituted of cohesive and non-cohesive materials with distinct behaviours that numerical models traditionally manage separately. This paper first introduces a rapid state of the Art in sediment transport modelling in order to point out the specific requirements for process-based models applied to mixed sediments. Based on a preliminary study by Waeles et al. (2007), which showed the validity of the advection approach to compute fine sand transport, a complete modelling strategy is described: it is applied to the suspended transport of sand and mud mixtures, and accounts for consolidation of mixed sediments. Special care is paid to the realistic representation of the structure and density of sand and mud mixtures, and to the... |
| Tipo: Text |
Palavras-chave: Sediment transport modelling; Mixed sediment; Sand; Mud; Suspension; Consolidation. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00028/13952/12567.pdf |
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| Registros recuperados: 58 | |
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