Consulta: creatorFacets:"Le Hir, Pierre"
Registros recuperados: 58
Data/hora: 16/06/2024 11:29:50

Dual-frequency ADCPs measuring turbidity
Provedor de dados: 5
Autores: Jourdin, Frederic; Tessier, Caroline; Le Hir, Pierre; Verney, Romaric; Lunven, Michel; Loyer, Sophie; Lusven, Andre; Filipot, Jean-francois; Lepesqueur, Jeremy.
A pair of self-contained acoustic Doppler current profilers (SC-ADCPs) operating with different frequencies were moored on a muddy sea bottom at about 20 m depth in the Bay of Vilaine off the French Atlantic coast. With their acoustic beams oriented upwards, the SC-ADCPs ensonified most of the water column. The results of several months of in situ recorded echo intensity data spanning 2 years (2003 to 2004) from the dual-frequency ADCPs are presented in this paper. The aim was to estimate suspended particle mass concentration and mean size. A concentration index CI is proposed for the estimation of particle concentration. Based on theory the CI-unlike the volume backscatter strength-does not depend on particle size. Compared with in situ optical data, the...
Tipo: Text
Ano: 2014
URL: https://archimer.ifremer.fr/doc/00213/32427/30896.pdf

Etude d'impact du rejet des eaux d'exaure du tunnel sur l'environnement marin
Provedor de dados: 5
Autores: Monbet, Yves; Delpech, Jean-paul; Le Hir, Pierre.
En 1983, plus de 20 millions de voyageurs et près de 20 millions de tonnes de marchandises ont traversé la Manche ou la Mer du Nord entre la Grande-Bretagne et le continent. Ces échanges sont trois fois supérieurs à ceux enregistrés en 1970, ce qui représente une augmentation annuelle de l'ordre de 10 %. Les prévisions les plus réalistes tablent actuellement sur une augmentation moyenne légeretnent supérieure à 4 % par an d'ici l'an 2000, ce qui équivaut à plus que doubler à cette date le trafic actuel. Pour répondre à une telle demande, il a été nécessaire d'envisager différentes solutions permettant de faire face à l'augmentation prévue.
Tipo: Text
Ano: 1987
URL: http://archimer.ifremer.fr/doc/00080/19124/16719.pdf

Suspended Sediment Dynamics in the Macrotidal Seine Estuary (France) - Part 2: Numerical Modeling of Sediment Fluxes and Budgets Under Typical Hydrological and Meteorological Conditions
Provedor de dados: 5
Autores: Schulz, Elisabeth; Grasso, Florent; Le Hir, Pierre; Verney, Romaric; Thouvenin, Benedicte.
Understanding the sediment dynamics in an estuary is important for its morphodynamic and ecological assessment as well as, in case of an anthropogenically controlled system, for its maintenance. However, the quantification of sediment fluxes and budgets is extremely difficult from in-situ data and requires thoroughly validated numerical models. In the study presented here, sediment fluxes and budgets in the lower Seine Estuary were quantified and investigated from seasonal to annual time scales with respect to realistic hydro- and meteorological conditions. A realistic three-dimensional process-based hydro- and sediment-dynamic model was used to quantify mud and sand fluxes through characteristic estuarine cross-sections. In addition to a reference...
Tipo: Text
Palavras-chave: Macrotidal estuary; Sediment fluxes; Numerical modelling; Mud/sand; Wind/waves; River discharge.
Ano: 2018
URL: http://archimer.ifremer.fr/doc/00416/52772/53640.pdf

Erosions, dépots et transits sédimentaires associés dans le bassin de Marennes-Oléron
Provedor de dados: 5
Autores: Le Hir, Pierre; Kervella, Stephane; Walker, Patrice; Brenon, Isabelle.
Managing sediments in the bate de Marennes-Oleron (Atlantic coast of France) can be achieved providing particulate fluxes at the scale of the basin are available as well as tidal and meteorological conditions during which major transports occur A sediment dynamics model accounting for tide- and wave-induced sand and mud transport has been applied to the Pertuis Charentais area Consolidation of pure mud and mixtures of sand and mud is accounted for The model validation is achieved by current and turbidity measurements, local altimetric surveys during one year and pressure measurements for waves on the tidal flat An asymmetry between eastern and western halves of the bay is observed on turbidity signals in agreement with a residual circulation from north to...
Tipo: Text
Ano: 2010
URL: http://archimer.ifremer.fr/doc/00019/13034/10302.pdf

Modélisation des turbidités en Bretagne sud et validation par des mesures in situ
Provedor de dados: 5
Autores: Tessier, Caroline; Le Hir, Pierre; Dumas, Franck; Jourdin, F.
A hydrodynamic and sediment model of South Brittany is calibrated with ADCP measurements, which allow to estimate hydrodynamic forcing and concentration of suspended particulate matter. The exercise of comparison between observed and simulated concentrations reveals that turbidity is highly dependant on numerous strongly coupled sedimentary and physical processes.
Tipo: Text
Palavras-chave: Waves; ADCP; Acoustical backscattering; Modelisation; Turbidity; Vagues; ADCP; Rétrodiffusion acoustique; Modélisation; Turbidité.
Ano: 2008
URL: http://archimer.ifremer.fr/doc/2008/publication-6300.pdf

Formulating Fine to Medium Sand Erosion for Suspended Sediment Transport Models
Provedor de dados: 5
Autores: Dufois, Francois; Le Hir, Pierre.
The capacity of an advection/diffusion model to predict sand transport under varying wave and current conditions is evaluated. The horizontal sand transport rate is computed by vertical integration of the suspended sediment flux. A correction procedure for the near-bed concentration is proposed so that model results are independent of the vertical resolution. The method can thus be implemented in regional models with operational applications. Simulating equilibrium sand transport rates, when erosion and deposition are balanced, requires a new empirical erosion law that involves the non-dimensional excess shear stress and a parameter that depends on the size of the sand grain. Comparison with several datasets and sediment transport formulae demonstrated the...
Tipo: Text
Palavras-chave: Sand; 1DV model; Erosion rate; Suspended sediment transport.
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00276/38763/37304.pdf

Golfe Normano-Breton - Etude Régionale Intégrée
Provedor de dados: 5
Autores: Le Hir, Pierre; Bassoullet, Philippe; Erard, E.; Blanchard, Michel; Hamon, Dominique; Jegou, Anne-marie.
Ce rapport en 6 volumes est le résultat d'une étude pluridisciplinaire (6 thèmes correspondant aux volumes du rapport), réalisée sur un secteur géographique bien délimité, présentant des caractéristiques physiques et biologiques particulières (très fort marnage, grande hétérogénéité des fonds, forte production biologique à base de mollusques filtreurs…), et siège d'activités humaines importantes et diversifiées (essentiellement basées sur l'exploitation des ressources du milieu). L'étude fait suite à un Livre Blanc établi en 1982, synthétise les données existantes, et les complète par des travaux originaux sur la connaissance des mécanismes naturels, en particulier de ceux qui ont une relation directe ou indirecte avec les activités humaines (processus...
Tipo: Text
Ano: 1986
URL: http://archimer.ifremer.fr/doc/00047/15837/13240.pdf

Development and validation of a sediment dynamics model within a coastal operational oceanographic system
Provedor de dados: 5
Autores: Cayocca, Florence; Verney, Romaric; Petton, Sebastien; Caillaud, Matthieu; Dussauze, Morgan; Dumas, Franck; Le Roux, Jean-francois; Pineau-guillou, Lucia; Le Hir, Pierre.
The rising interest in environmental and ecosystem dynamics have lead coastal oceanographers to not only investigate the “traditional” physical parameters describing the ocean state and its dynamics (e.g. temperature, salinity, currents, water levels in coastal areas), but to also account for the dynamics of parameters describing its biogeochemical components. To that end, MARS3D regional and coastal modelling system has been coupled to ecosystem modules (ECO-MARS3D, ECO3M) as well as sediment dynamics modules (MARS3D-SEDIM): sediment, nutrient and primary production contents can be considered as the lower level environment and ecosystem descriptors of the “biogeochemical” ocean. Early investments into physical and biological analysis at the regional scale...
Tipo: Text
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00194/30572/29015.pdf

Impact du régime du barrage d'Arzal sur la stratification a l'embouchure de la Vilaine : étude par modélisation numérique
Provedor de dados: 5
Autores: Le Hir, Pierre; Duchene, C.; Merel, A; De Nadaillac, G.; Merceron, Michel; Breton, Marguerite.
The rate of flow of the fresh water releases at the Arzal Dam into the Vilaine is likely to influence the haline structure of Vilaine Bay. In order to determine the rate of flow that causes a minimum downstream stratification, a vertical two-dimensional mathematical modelling of the Vilaine's estuary was undertaken. We obtain very similar stratification flows for different fresh water release scenarios, in spite of the rather different desalinisations and currents.
Tipo: Text
Palavras-chave: Water release; Stratification; Estuary; Numerical model; Vilaine; Rejet de barrage; Stratification; Estuaire; Modèle numérique; Vilaine.
Ano: 1986
URL: https://archimer.ifremer.fr/doc/1986/rapport-2654.pdf

Amélioration de la salubrité des eaux conchylicoles de l'estuaire de l'Elorn et du Nord de la Rade de Brest - Etude du milieu marin
Provedor de dados: 5
Autores: Le Hir, Pierre; Breton, M; L'Yavanc, J.
Afin de préciser les rejets où il est préférable d'intervenir pour réduire les contaminations des secteurs conchylicoles de l'Elorn et du Nord de la rade de Brest, un calcul de dilution de chacun des rejets a été mené à l'aide d'un modèle mathématique. Après une description des courants de marée calculés dans tout le secteur d'étude, des figures de dilution sont présentées. L'impact de chaque rejet se déduit facilement.
Tipo: Text
Ano: 1987
URL: http://archimer.ifremer.fr/doc/00103/21460/19041.pdf

Modelling Pb and Cd dynamics in the Seine estuary
Provedor de dados: 5
Autores: Thouvenin, Benedicte; Gonzalez, Jean-louis; Chiffoleau, Jean-francois; Boutier, Bernard; Le Hir, Pierre.
The Seine estuary (France) is currently one of the world's most contaminated estuaries, due in particular to its high cadmium and lead content. Proper understanding of contaminant transfer, transformation and retention mechanisms throughout the estuary and up to the adjacent marine zone require a range of studies involving data collections, experiments, and modeling tool. A multivariable transport model (SiAM-3D) was used to simulate dissolved and particulate transport and it is applied to several calculation grids; a speciation model (MOCO) was used to select key species and obtain a schematic system representation. The coupled model for Cd and Pb was compared with field measurements. The complementary character of various tools (model applied to annual...
Tipo: Text
Palavras-chave: 3D modeling; Cd and Pb trace metals; Seine estuary.
Ano: 2007
URL: http://archimer.ifremer.fr/doc/2007/publication-3009.pdf

Modèle hydro-sédimentaire du bassin de Marennes-Oléron : présentation et principaux résultats
Provedor de dados: 5
Autores: Raillard, Olivier; Le Hir, Pierre; Lazure, Pascal.
Depuis plusieurs années l'écosystème conchylicole de Marennes-Oléron est l' objet de modélisations de complexité croissante qui tendent à intégrer de plus en plus de processus physiques et biologiques (Bacher, 1989 ; Raillard, 1991) afin d'accroître le réalisme et le champ d'investigation de l'outil (Héral et al., 1991 ) . Confrontés au problème de la variabilité spatiale et temporelle des concentrations du matériel dissous et particulaire de l'eau, les travaux les plus récents ont pu mettre en évidence les limitations des modèles d'écosystème qui asservissent spatialement et temporellement la représentation des processus physiques à celle des mécanismes biologiques (Raillard, 1991). Le but de cette étude est de développer une modélisation de l'écosystème...
Tipo: Text
Palavras-chave: Modèle hydro-sédimentaire; Concentration particulaire; Concentration dissoute; Production primaire; Production secondaire; Bassin de Marennes Oléron; Charente Maritime Dep.
Ano: 1992
URL: http://archimer.ifremer.fr/doc/00102/21305/18918.pdf

Influence des conditions hydrométéorologiques sur les flux et bilans sédimentaires en estuaire de Seine
Provedor de dados: 5
Autores: Grasso, Florent; Schulz, Elisabeth; Le Hir, Pierre; Verney, Romaric; Thouvenin, Benedicte.
La dynamique sédimentaire à l’embouchure de l’estuaire de Seine est principalement contrôlée par les forçages hydrométéorologiques (débit, vent, vagues, marée) et les fortes pressions anthropiques (endiguement, dragage, clapage). La compréhension et la quantification de la dynamique des flux sédimentaires en suspension (sable/vase) est un enjeu majeur, autant d’un point vu écologique (ex. turbidité, envasement) que financier (ex. gestion des chenaux de navigation). La mise en place de réseaux de mesure in situ permet une meilleure compréhension de la dynamique sédimentaire de l’estuaire, mais leur caractère local rend difficile toute estimation des flux et bilans sédimentaires. Pour répondre à ces questions, cette étude s’appuie sur la modélisation...
Tipo: Text
Palavras-chave: Dynamique hydro-sédimentaire; Sable/vase; Estuaire de Seine; Modélisation numérique; Mesures in situ; Dragage; Flux résiduels et bilans; Année/trimestres.
Ano: 2016
URL: http://archimer.ifremer.fr/doc/00348/45928/45621.pdf

Modélisation hydro-sédimentaire de la baie du Mont Saint-Michel
Provedor de dados: 5
Autores: Cayocca, Florence; Dussauze, Morgan; Le Hir, Pierre; Bassoullet, Philippe; Jestin, Herve.
A numerical model for hydrodynamics and sediment transport is applied to Mont Saint Michel Bay, where ecological concerns are related to sediment transfers. Recent current datasets recorded on the tidal flat show the wind influence on the currents during neap tide. They are compared to model outputs. The simulation of sediment transfers driven by tides and waves accurately mimics the sediment repartition in the Bay.
Tipo: Text
Palavras-chave: Turbidité; Sédiments cohésifs; Modèle; Courant; Mont Saint Michel.
Ano: 2006
URL: http://archimer.ifremer.fr/doc/2006/acte-6274.pdf

Etude de l'estuaire de la Seine - Modélisation numérique des phénomènes physiques
Provedor de dados: 5
Autores: Salomon, Jean-claude; Le Hir, Pierre.
Les zones côtières, et les estuaires en particulier, fournissent au bien-être de l'homme et à son activité économique une aide très appréciable. Contrairement au milieu terrestre pauvre en eau, et au milieu marin pauvre en éléments nutritifs, les estuaires riches de ces deux constituants sont un lieu de vie privilégié. On connait le rôle de frayère et de nurserie qu'ils jouent pour de très nombreuses espèces. Ces estuaires sont actuellement utilisés comme collecteurs des rejets industriels et domestiques. Bien que ces rejets lorsqu'ils sont convenablement traités et dilués ne soient pas obligatoirement néfastes, il est de première utilité de pouvoir juger de leurs effets selon leur nature, leur localisation et leur importance, pour ne pas mettre en danger...
Tipo: Text
Ano: 1981
URL: http://archimer.ifremer.fr/doc/00105/21638/19219.pdf

Spatio-temporal variations in intertidal mudflat erodability: Marennes-Oleron Bay, western France
Provedor de dados: 5
Autores: Orvain, Francis; Sauriau, Pierre-guy; Le Hir, Pierre; Guillou, Gael; Cann, Philippe; Paillard, Michel.
A portable erosion device (ERIS) was deployed in November 2000 and May 2001 to investigate the spatio-temporal variation of fine-grained sediment erosion over a transect on the intertidal mudflats of Marennes-Oleron Bay, western France. The objective was to relate changes in bed erodability over diurnal emersion periods to bioturbation, rapid changes in sediment characteristics, and microphytobenthos biomass.   Macrofaunal assemblages were dominated by the bivalve, Scrobicularia plana, on the upper mudflat, and by the gastropod, Hydrobia ulvae. on the middle mudflat. A power relationship was obtained where tau(cr) was plotted as a function of sediment density. Results from the upper part of the mudflat deviated from this relationship due to bioturbation by...
Tipo: Text
Palavras-chave: EPS; Microphytobenthos; Erodability; Intertidal mudflat; Sediment; Scrobicularia plana; Hydrobia ulvae; Bioturbation; Resuspension; Eris.
Ano: 2007
URL: http://archimer.ifremer.fr/doc/2007/publication-3779.pdf

Aide mémoire de dynamique sédimentaire. 7ème édition
Provedor de dados: 5
Autores: Le Hir, Pierre.
This aide-mémoire is not a lesson on sedimentary dynamics but more of a calculation form. Its use implies a good knowledge of the involved processes. This report presents the basic formulations used for the calculation of the hydrodynamic forcings as well as the main sediment behavioural laws, in order to help the reader conduct a basic sediment transportation calculation.
Tipo: Text
Palavras-chave: Bottom shear stress; Boundary layer; Mathematical modelling; Transport rate; Cohesive sediments; Non cohesive sediments; Sediment dynamics; Contrainte de cisaillement au fond; Couche limite; Modélisation mathématique; Fonctions de transport; Sédiments cohésifs; Sédiments non cohésifs; Dynamique sédimentaire.
Ano: 2008
URL: http://archimer.ifremer.fr/doc/2008/rapport-6273.pdf

Remaniements sédimentaires superficiels sur l'estran occidental de la baie du Mont Saint-Michel
Provedor de dados: 5
Autores: Bonnot-courtois, C; Bassoullet, Philippe; Tessier, B; Cayocca, Florence; Le Hir, Pierre; Baltzer, A.
In order to define and quantify the rhythm and amplitude of the processes of erosion and sedimentation on broad tidal flats, in situ measurements of sediment elevation have been performed in the western part of the Mont-Saint-Michel bay. The amplitude of reworking is generally low (&lt; ± 5 cm), and variable from west to east. The wind influence on tidal currents and surficial reworking emphasizes erosion phases rapidly followed by accretion of similar amplitude on the whole tidal flat. A numerical model for hydrodynamics and sediment transport is applied to Mont Saint Michel Bay, where ecological concerns are related to sediment transfers.
Tipo: Text
Palavras-chave: Sediment transport; Numerical model; Erosion sedimentation budget; "In situ" measurements; Tidal sandy mud flat; Transport sédimentaire; Modèle numérique; Bilan érosion sédimentation; Mesures in situ; Estran sablo vaseux.
Ano: 2008
URL: http://archimer.ifremer.fr/doc/2008/publication-6279.pdf

Bottom trawling contribution to the spatio-temporal variability of sediment fluxes on the continental shelf of the Bay of Biscay (France)
Provedor de dados: 5
Autores: Mengual, Baptiste; Le Hir, Pierre; Cayocca, Florence; Garlan, T.
Based on experiments, a trawling-induced erosion dynamics was included in a 3D realistic and pre-validated hydro-sedimentary model so as to assess its contribution to the overall regional sediment dynamics in the specific case of the Bay of Biscay continental shelf. The effect of trawling was investigated throughout a 5-year period in terms of horizontal/vertical fluxes and changes in seabed mud content, and compared to the natural variability of sediment fluxes at different spatio-temporal scales. Trawling is shown in the model to significantly contribute to sediment re-suspension, and changes in the seabed at the scale of the shelf. The contribution of trawling to re-suspension is &gt;80% during the high fishing season at many locations on the outer...
Tipo: Text
Palavras-chave: Sediment fluxes; Bottom trawling; Numerical modelling; Bay of Biscay; Continental shelf.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00500/61146/64574.pdf

Modélisation environnementale de l'estuaire de la Seine
Provedor de dados: 5
Autores: Bacq, Nicolas; Cugier, Philippe; Grasso, Florent; Le Gendre, Romain; Le Hir, Pierre; Lemoine, Jean-philippe; Riou, Philippe; Schulz, Elisabeth; Thouvenin, Benedicte; Verney, Romaric.
Dans le cadre du programme de recherche Seine-Aval 5, différentes stratégies de modélisation numérique sont mises en place pour aider à répondre aux questionnements scientifiques et sociétaux associés au fonctionnement physique, biologique, chimique et écologique de l'estuaire de la Seine (ex. projets RESET et HYMOSED). Les forçages météo-marins (vent, vague, marée) et hydrologique (débit) contrôlent le fonctionnement hydro-morpho-sédimentaire et biogéochimique de l'estuaire, modifiant ainsi les paramètres environnementaux de l’estuaire amont jusqu’à la baie de Seine (ex. nature des fonds, courant, turbidité, salinité, température, oxygène dissous, chlorophylle-a). La modélisation de ces paramètres, ainsi que leur évolution face à différents scénarios...
Tipo: Text
Ano: 2015
URL: http://archimer.ifremer.fr/doc/00284/39480/37966.pdf

Dragages et environnement marin Etat des connaissances
Provedor de dados: 5
Autores: 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

Accumulation and dispersion dynamics of mud and sand particles in a continental shelf under estuarine influence: a numerical modelling analysis (Gironde, France)
Provedor de dados: 5
Autores: 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
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00514/62559/66913.pdf

Modeling mud and sand transfers between a macrotidal estuary and the continental shelf: influence of the sediment-transport parameterization
Provedor de dados: 5
Autores: 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

Physique du sédiment et des eaux interstitielles : stratégies de modélisation pour les besoins en environnement côtier
Provedor de dados: 5
Autores: 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
Ano: 2007
URL: https://archimer.ifremer.fr/doc/00480/59151/61780.pdf

Modelling mud transport in a macrotidal estuary
Provedor de dados: 5
Autores: Le Hir, Pierre; Bassoullet, Philippe; L'Yavanc, Jacky.
In order to determine the fate of the fine particles and adsorbed contaminants in·a short macrotidal èstuary, a mathematical modelling system for cohesive suspended mater transport and bottom evolution, including a new consolidation algorithm, is developed. An analysis of successive erosion, transport and deposi~ion processes due to tidal forcing is given and comparisons with field data are provided. A description of mean-term bottom variations has been attempted and is partially validated by differential soundings.
Tipo: Text
Palavras-chave: Dynamique des sédiments cohésifs; Estuaire Morlaix; Tassement des vases; Modèle mathématique; Érosion; Dépôt; Cohesive sediment dynamics; Estuary; Erosion; Deposition; SoiT consolidation; Mathematical modelling.
Ano: 1988
URL: https://archimer.ifremer.fr/doc/00682/79379/81909.pdf

Contraintes de fond dans le Golfe du Lion générées par les houles et les courants
Provedor de dados: 5
Autores: Dufois, Francois; Garreau, Pierre; Le Hir, Pierre.
Simulated data of both currents and waves for the entire year 2001 are used in order to assess their statistical contribution to the erodability power over the shelf of the Gulf of Lion. Bottom circulation patterns are also analysed in response to wind forcing. A method to compute the skin friction component of the total bottom shear stress is then proposed and compared with a classical method.
Tipo: Text
Palavras-chave: MARS 3D; Golfe du Lion; Contraintes de peau; Contraintes de fond; Courants; Houles.
Ano: 2006
URL: http://archimer.ifremer.fr/doc/2006/publication-6306.pdf

MORPHOSEINE. Modélisation de l’évolution morphosédimentaire de l’estuaire de la Seine
Provedor de dados: 5
Autores: 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
Ano: 2021
URL: https://archimer.ifremer.fr/doc/00684/79630/82353.pdf

Modèle hydro-sédimentaire du bassin de Marennes-Oléron : présentation et principaux résultats. 1992
Provedor de dados: 5
Autores: Raillard, Olivier; Le Hir, Pierre.
Le bassin conchylicole de Marennes-Oléron fait l'objet d'une étude par modèle mathématique. L'outil est élaboré par étapes successives qui voient la mise en jeu de nouveaux processus et l'introduction de nouvelles variables (Bacher, 1989 ; Raillard, 1991). La forte variabilité spatio-temporelle des matériaux dissous et particulaire de la baie a focalisé l'attention sur les processus hydrodynamiques. Les modèle de couplage des processus physiques et biologiques développés jusqu'à présent ont privilégié la représentation des phénomènes biologiques en moyennant dans le temps et l'espace les phénomènes physiques. Un tel choix s'est avéré inadapté pour simuler la variabilité spatiale et temporelle du bassin de Marennes-Oléron (Raillard, 1991). L'objectif du...
Tipo: Text
Palavras-chave: Modèle hydro-sédimentaire; ¨Production primaire; Production secondaire; Simulations; Bassin de Marennes Oléron; Charente Maritime.
Ano: 1993
URL: http://archimer.ifremer.fr/doc/00102/21302/18922.pdf

Wave- and current-induced bottom shear stress distribution in the Gulf of Lions
Provedor de dados: 5
Autores: 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 ( &lt; 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

Modelling Fine Sediment Dynamics: Towards a Common Erosion Law for Fine Sand, Mud and Mixtures
Provedor de dados: 5
Autores: 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

Evolution morphodynamique cross-shore d’un estran vaseux
Provedor de dados: 5
Autores: Monbet, Valerie; Maisondieu, Christophe; Le Hir, Pierre.
The main goal of this study consists in evaluating the combined effect of cross-shore waves and current on the long term evolution of a mud flat profile. An original method is used to create a database of realistic wind fields and sea states. These data are applied to a numerical model of sediment transport and morphological changes. A description of long term simulations is proposed.
Tipo: Text
Palavras-chave: Morphodynamique; Estran vaseux; Courant de marée; États de mer; Mer du vent.
Ano: 2006
URL: http://archimer.ifremer.fr/doc/00203/31429/29824.pdf

Observations de l'Ifremer sur la demande d'amélioration du chenal de navigation dans l'estuaire de la Gironde
Provedor de dados: 5
Autores: Manaud, Francois; Bassoullet, Philippe; Dreves, Luc; Le Hir, Pierre; L'Yavanc, Jacky; Prouzet, Patrick; Quintin, Jean-yves.
Tipo: Text
Ano: 2003
URL: http://archimer.ifremer.fr/doc/00269/38070/36185.pdf

Influence of bottom trawling on sediment resuspension in the 'Grande-Vasière' area (Bay of Biscay, France)
Provedor de dados: 5
Autores: 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

A model of fluff layer erosion and subsequent bed erosion in the presence of the bioturbator, Hydrobia ulvae
Provedor de dados: 5
Autores: 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

"La Grande Vasière" mid-shelf mud belt : Holocene sedimentary structure, natural and anthropogenic impacts
Provedor de dados: 5
Autores: 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
Ano: 2006
URL: http://archimer.ifremer.fr/doc/2006/acte-6243.pdf

Erosion threshold of sand-mud mixtures
Provedor de dados: 5
Autores: 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

Behaviour of a floc population during a tidal cycle: laboratory experiments and numerical modelling
Provedor de dados: 5
Autores: Verney, Romaric; Lafite, Robert; Brun-cottan, Jean Claude; Le Hir, Pierre.
An approach combining laboratory experiments and numerical modelling was used to investigate the behaviour of a floc population during an idealized tidal cycle. The experiment was conducted on suspended sediments at a concentration of 93 mg l−1 collected in the field. It was based on a jar test device to reproduce tidal-induced turbulence and coupled with a CCD camera system and image post-processing software to monitor floc size distribution. At the same time, a 0D size-class based aggregation/fragmentation model (FLOCMOD) was developed to simulate changes in the floc population over the tidal cycle. Experimental results revealed strong variability of the behaviour of microfloc and macrofloc populations with respect to the varying shear rates observed in...
Tipo: Text
Palavras-chave: Flocculation; Tidal cycle; Laboratory experiment; FLOCMOD; OD model; Sensitivity analysis; Optimization.
Ano: 2011
URL: http://archimer.ifremer.fr/doc/00027/13846/11020.pdf

Impact of winter storms on sediment erosion in the Rhone River prodelta and fate of sediment in the Gulf of Lions (North Western Mediterranean Sea)
Provedor de dados: 5
Autores: 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

Numerical modelling of heterogeneous sediment transport: new insights for particulate radionuclide transport and deposition
Provedor de dados: 5
Autores: Rivier, Aurélie; Le Hir, Pierre; Bailly Du Bois, Pascal; Laguionie, Philippe; Morillon, Mehdi.
A sediment transport module which solves simultaneously bedload and suspended load is developed, in a context of multiclass sediment transport. Different approaches are used to simulate each transport mode: (i) bedload transport results from divergence of transport capacity and (ii) suspension transport is solved using erosion and settling fluxes associated with advection/diffusion equation. A focus is made on the significance of hiding and exposure processes in case of heterogeneous sediment bed. Their influence is strong on bedload sediment transport, and induces specific trends of sediment sorting in sand dunes. The application to heterogeneous sediment dynamics in the macrotidal area of the Normand Breton Gulf (English Channel), show that hiding and...
Tipo: Text
Palavras-chave: Sediment transport; Numerical modelling; Hiding; Exposure; Bedload; Suspension.
Ano: 2017
URL: http://archimer.ifremer.fr/doc/00394/50580/51274.pdf

Dynamics of sand and mud mixtures: a multiprocess-based modelling strategy
Provedor de dados: 5
Autores: 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

Preface of the CSR Supplement Issue: Proceedings of the 9th International Conference on Nearshore and Estuarine Cohesive Sediment Transport Processes
Provedor de dados: 5
Autores: Le Hir, Pierre; Toorman, Erik; Cayocca, Florence; Verney, Romaric.
Tipo: Text
Ano: 2011
URL: http://archimer.ifremer.fr/doc/00041/15250/12620.pdf

Analysis of mixed-sediment consolidation experiments
Provedor de dados: 5
Autores: Grasso, Florent; Le Hir, Pierre; Bassoullet, Philippe.
Estuarine sediment transport models require that a time variation of erodibility due to consolidation be taken into account. If numerical modelling of mud sedimentation and consolidation is currently satisfactory, simulation of mud-sand mixture consolidation is more problematical. This is partly due to mixed-sediment processes, as hindered settling and segregation, not well understood yet. Hence, based on extensive settling columns experiments, the aim of this study is to improve our understanding of mud-sand mixture consolidation for varying concentrations (54 to 600 kg/m3) and large sand contents (15 to 80%). Firstly, we observed that for a given initial mass concentration and sand content the final consolidation appeared independent from the initial...
Tipo: Text
Palavras-chave: Settling column experiments; Consolidation; Sedimentation; Mud/sand mixtures; Sand segregation; Gelling concentration.
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00206/31727/30129.pdf

Numerical modelling of mixed-sediment consolidation
Provedor de dados: 5
Autores: Grasso, Florent; Le Hir, Pierre; Bassoullet, Philippe.
Sediment transport modelling in estuarine environments, characterised by cohesive and non-cohesive sediment mixtures, has to consider a time variation of erodibility due to consolidation. Generally, validated by settling column experiments, mud consolidation is now fairly well simulated; however, numerical models still have difficulty to simulate accurately the sedimentation and consolidation of mixed sediments for a wide range of initial conditions. This is partly due to the difficulty to formulate the contribution of sand in the hindered settling regime when segregation does not clearly occur. Based on extensive settling experiments with mud-sand mixtures, the objective of this study was to improve the numerical modelling of mixed-sediment consolidation...
Tipo: Text
Palavras-chave: Mud-sand mixtures; Hindered settling; Consolidation; Experiments; Numerical modelling; Segregation.
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00254/36539/35168.pdf

Modelling sand/mud transport and morphodynamics in the Seine river mouth (France): an attempt using a process-based approach
Provedor de dados: 5
Autores: Waeles, Benoit; Le Hir, Pierre; Lesueur, P; Delsinne, N.
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...
Tipo: Text
Palavras-chave: Sand and mud mixtures; Sediment transport modelling; Morphodynamics.
Ano: 2007
URL: http://archimer.ifremer.fr/doc/2007/publication-7404.pdf

Circulation and suspended sediment transport in a coral reef lagoon: The south-west lagoon of New Caledonia
Provedor de dados: 5
Autores: Ouillon, S.; Douillet, Pascal; Lefebvre, J. P.; Le Gendre, Romain; Jouon, Aymeric; Bonneton, P.; Fernandez,; Chevillon, C.; Magand, O.; Lefevre, J.; Le Hir, Pierre; Laganier, R.; Dumas, Franck; Marchesiello, P.; Madani, A. Bel; Andrefouet, S.; Panche, J. Y.; Fichez, R.
The south-west lagoon of New Caledonia is a wide semi-open coral reef lagoon bounded by an intertidal barrier reef and bisected by numerous deep inlets. This paper synthesizes findings from the 2000-2008 French National Program EC2CO-PNEC relative to the circulation and the transport of suspended particles in this lagoon. Numerical model development (hydrodynamic, fine suspended sediment transport, wind-wave, small-scale atmospheric circulation) allowed the determination of circulation patterns in the lagoon and the charting of residence time, the later of which has been recently used in a series of ecological studies. Topical studies based on field measurements permitted the parameterisation of wave set-up induced by the swell breaking on the reef barrier...
Tipo: Text
Palavras-chave: Hydrodynamics; Suspended sediment; New Caledonia; Coral reef lagoon; Sediment; Turbidity; Resuspension.
Ano: 2010
URL: http://archimer.ifremer.fr/doc/00014/12526/9401.pdf

Modelling the effects of macrofauna on sediment transport and bed elevation: Application over a cross-shore mudflat profile and model validation
Provedor de dados: 5
Autores: Orvain, Francis; Le Hir, Pierre; Sauriau, Pierre-guy; Lefebvre, Sebastien.
Tipo: Text
Palavras-chave: Modelling; Sediment dynamics; Erodability; Bioturbation; Macrofauna; Biota; Sediment stability.
Ano: 2012
URL: http://archimer.ifremer.fr/doc/00079/19055/18610.pdf

Sedimentary processes in a shellfish farming environment, Mont Saint Michel Bay, France
Provedor de dados: 5
Autores: Cayocca, Florence; Bassoullet, Philippe; Le Hir, Pierre; Jestin, Herve; Cann, Philippe.
Mont Saint Michel Bay is a 30 km wide bay located on the French side of the English Channel. The tidal range reaches 14 m during spring tides, which leads, along with the gentle slope of the bathymetry, to a tidal flat up to 11 km wide. The sedimentary coverage exhibits strong longshore and cross-shore gradients, with purely muddy environments to the west of the domain, and pure sands to the east, where the natural channels of three incoming rivers induce rapid morphological changes. The contributions of tides and waves to sedimentary processes are analysed by means of numerical modelling and results of field observations. Maximum tidal bottom shear stresses are shown to account for the sediment distribution throughout the bay, while the longshore gradient...
Tipo: Text
Ano: 2008
URL: http://archimer.ifremer.fr/doc/2008/publication-6278.pdf

Suspended Sediment Dynamics in the Macrotidal Seine Estuary (France) - Part 1: Numerical Modeling of Turbidity Maximum Dynamics
Provedor de dados: 5
Autores: Grasso, Florent; Verney, Romaric; Le Hir, Pierre; Thouvenin, Benedicte; Schulz, Elisabeth; Kervella, Youenn; Fard, I. Khojasteh Pour; Lemoine, J. -p.; Dumas, Franck; Garnier, Valerie.
Tidal pumping, baroclinic circulation and vertical mixing are known to be the main mechanisms responsible for the estuarine turbidity maximum (ETM) formation. However, the influence of hydro-meteorological conditions on ETM dynamics is still not properly grasped and requires further investigation to be quantified. Based on a realistic 3-dimensional numerical model of the macrotidal Seine Estuary (France) that accounts for mud and sand transport processes, the objective of this study is to quantify the influence of the main forcing (river flow, tides, waves) on the ETM location and mass changes. As expected, the ETM location is strongly modulated by semidiurnal tidal cycles and fortnightly timescales with a high sensitivity to river flow variations. The ETM...
Tipo: Text
Palavras-chave: Estuary; Mud; Sand; Hydrodynamics; Turbidity maximum; Waves; Measurement; Modeling.
Ano: 2018
URL: http://archimer.ifremer.fr/doc/00416/52770/53638.pdf

Accounting for Rough Bed Friction Factors of Mud Beds as a Result of Biological Activity in Erosion Experiments
Provedor de dados: 5
Autores: Guizien, Katell; Orvain, Francis; Duchene, Jean-claude; Le Hir, Pierre.
The average bed shear stress and bed friction factor of samples with any roughness was derived from the head loss between upstream and downstream of a test section in an erosion tunnel. The method was validated in both hydraulically smooth (plexiglass; Reynolds number less than 25,000) and rough regimes (calibrated particles with known roughness). As a first step toward using this method on natural sediment, this method was tested with experimental mesocosms assembled from field collected materials (sieved sediments; diatoms). Bed shear stress measurement precision was high enough in the experiments to detect a positive significant relationship between bed friction factor and core roughness. The observed bed friction factor increase could be related to...
Tipo: Text
Palavras-chave: Bed roughness; Friction factor; Mud beds; Biological activity; Erosion experiments.
Ano: 2012
URL: http://archimer.ifremer.fr/doc/00117/22807/20617.pdf

Interacting effects of Hydrobia ulvae bioturbation and microphytobenthos on the erodibility of mudflat sediments
Provedor de dados: 5
Autores: Orvain, Francis; Sauriau, Pierre-guy; Sygut, A; Joassard, Lucette; Le Hir, Pierre.
Microphytobenthos-macrofauna sediment interactions and their effects on sediment erodability were examined in laboratory experiments. Sediment beds were manipulated in a tidal mesocosm to produce diatom mats in exponential or in stationary phases of development after 6, 8 or 11 d of culture. These sediment beds were used in flume experiments to investigate the influence of bioturbation by the gastropod Hydrobia ulvae on both sediment and pigment resuspension as a function of the physiological state of the microphytobenthic mats. In most experiments, only a surface layer was resuspended. A model was used to analyse in detail the contribution of each variable to this surface-layer erosion. Bioturbation was the major factor controlling resuspension, and its...
Tipo: Text
Palavras-chave: Sediment; Bioturbation; Erosion; Model; Hydrobia ulvae; Physiological state; Microphytobenthos; Resuspension.
Ano: 2004
URL: http://archimer.ifremer.fr/doc/2004/publication-3780.pdf

PREVIMER: A contribution to in situ coastal observing systems
Provedor de dados: 5
Autores: Charria, Guillaume; Repecaud, Michel; Quemener, Loic; Menesguen, Alain; Rimmelin-maury, Peggy; L'Helguen, Stephane; Beaumont, Laurence; Jolivet, Aurelie; Morin, Pascal; Mace, E; Lazure, Pascal; Le Gendre, Romain; Jacqueline, Franck; Verney, Romaric; Marie, Louis; Jegou, Paul; Le Reste, Serge; Andre, Xavier; Dutreuil, Vincent; Regnault, Jean-pierre; Jestin, Herve; Lintanf, Herve; Pichavant, Pascal; Retho, Michael; Allenou, Jean-pierre; Stanisiere, Jean-yves; Bonnat, Armel; Nonnotte, Lidwine; Duros, Wenceslas; Tarot, Stephane; Carval, Thierry; Le Hir, Pierre; Dumas, Franck; Vandermeirsch, Frederic; Lecornu, Fabrice.
To design a prototype for an Integrated Ocean Observing System (IOOS), at least three components are mandatory: a modeling platform, an in situ observing system and a structure to collect and to disseminate the information (e.g. database, website). The PREVIMER project followed this approach and in order to sustain model applications, PREVIMER has developed, funded and organized part of in situ observing networks in the Bay of Biscay and the Channel. For a comprehensive system, focus was addressed on fi xed platforms (MAREL MOLIT, MAREL Iroise, Island network and D4 for sediment dynamics), ships of opportunity (RECOPESCA program and FerryBoxes), and coastal profi lers (ARVOR-C/Cm). Each system is briefl y described and examples of scientifi c results...
Tipo: Text
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00197/30785/29143.pdf

Suivi de flotteurs dans la zone Loire Vilaine
Provedor de dados: 5
Autores: Kerdreux, Michel; Merceron, Michel; Le Hir, Pierre; Breton, Marguerite.
During one month in summer of 1985 the courses of ten drifters, dropped at the mouth of Loire and Vilaine Rivers, were monitored. Results show:  -the marked influence of wind on the movement of this region's bodies of water, -the possibility of an intrusion of the Loire's waters in Vilaine Bay, -the very likely absence of any influence of the Loire's waters in the bottom waters' anoxia that occurred in Vilaine Bay during the summer of 1982.
Tipo: Text
Palavras-chave: Anoxia; Vilaine; Currents; Drifters; Anoxie; Vilaine; Loire; Courants; Flotteurs.
Ano: 1986
URL: http://archimer.ifremer.fr/doc/1986/rapport-2653.pdf

Etude d'impact du rejet des eaux d'exhaure du tunnel sur l'environnement marin
Provedor de dados: 5
Autores: Monbet, Yves; Delpech, Jean-paul; Le Hir, Pierre.
En 1983, plus de 20 millions de voyageurs et près de 20 millions de tonnes de marchandises ont traversé la Manche ou la Mer du Nord entre la Grande-Bretagne et le continent. Ces échanges sont trois fois supérieurs à ceux enregistrés en 1970, ce qui représente une augmentation annuelle de l'ordre de 10 %. Les prévisions les plus réalistes tablent actuellement sur une augmentation moyenne légèrement supérieure à 4 % par an d'ici l'an 2000, ce qui équivaut à plus que doubler à cette date le trafic actuel. Pour répondre à une telle demande, il a été nécessaire d'envisager différentes solutions permettant de faire face à l'augmentation prévue.
Tipo: Text
Ano: 1987
URL: http://archimer.ifremer.fr/doc/00103/21458/19039.pdf

Influence of morphological changes on suspended sediment dynamics in a macrotidal estuary: diachronic analysis in the Seine Estuary (France) from 1960 to 2010
Provedor de dados: 5
Autores: Grasso, Florent; Le Hir, Pierre.
Estuaries are subject to extensive morphological changes through human activities, such as deepening and narrowing via dredging and channelization. The estuary sediment load, characterised by the estuarine turbidity maximum (ETM), can severely increase in response to channel deepening, shifting the estuary from a natural to hyperturbid state. The main processes driving the estuarine circulation, hydrology and sediment dynamics are relatively well known. However, their relative influence on suspended sediment concentration (SSC), as well as their role in the transition toward hyperturbid estuaries, is still a subject of debate. Therefore, this study aims at investigating the relative contribution of key estuarine drivers (gravitational circulation and tidal...
Tipo: Text
Palavras-chave: Estuary deepening and narrowing; Sediment dynamics; Turbidity maximum; Tidal asymmetry; Stratification; Numerical modelling; Morphological changes.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00479/59046/65965.pdf

Modélisation du fonctionnement HYdro-MOrpho-SEDimentaire de l’estuaire de la Seine [HYMOSED]. Volet « Modélisation »
Provedor de dados: 5
Autores: Grasso, Florent; Le Hir, Pierre.
Le projet HYMOSED (« Modélisation du fonctionnement HYdro-MOrpho-SEDimentaire de l’estuaire de la Seine ») du programme de recherche Seine-Aval 5 (déc. 2013 – mar. 2017) a eu pour objectif d’apporter une meilleure compréhension du fonctionnement hydro-morpho-sédimentaire de l’estuaire de la Seine des échelles de temps événementielle à annuelle. Cela s’est traduit par : (1) une analyse fine de la dynamique du bouchon vaseux, (2) la quantification des flux et bilans sédimentaires (sables/vase) pour différents scénarios hydrométéorologiques caractéristiques et (3) l'analyse de l’évolution morpho-sédimentaire à l'embouchure. Afin de répondre de manière pertinente à ces questions, ce projet s’est appuyé sur un important travail de validation du modèle...
Tipo: Text
Ano: 2017
URL: http://archimer.ifremer.fr/doc/00412/52381/53170.pdf

Modeling mud transport in a macrotidal estuary
Provedor de dados: 5
Autores: Le Hir, Pierre; Bassoullet, Philippe; L'Yavanc, Jacky.
In order to determine the fate of the fine particles and adsorbed contaminants in a short macrotidal estuary, a mathematical modelling system for cohesive suspended mater transport and bottom evolution, including a new consolidation algorithm, is developed. An analysis of successive erosion, transport and deposition processes due to tidal forcing is given and comparisons with field data are provided. A description of mean-terrn bottom variations has been attempted and is partially validated by differential sounding.
Tipo: Text
Ano: 1988
URL: http://archimer.ifremer.fr/doc/00080/19146/16741.pdf

Synthèse des études relatives à la modelistion de l'oxygène dissous dans l'estuaire de la Loire
Provedor de dados: 5
Autores: Thouvenin, Benedicte; Le Hir, Pierre; Maurice, Laurence; Romana, Louis-alexandre.
A la demande de l'Association pour la Protection de l'Environnement de l'Estuaire de la Loire, une étude sur le cycle de l'oxygène dissous a été entreprise. Un modèle mathématique a été développé en plusieurs étapes, associé à des études sur le cycle de la matière organique dans le système bouchon vaseux/crème de vase et au développement d'un modèle de transport sédimentaire. Après la mise en place d'un modèle d'advection-dispersion dans l'estuaire, qui reproduit l'évolution de l'oxygène dissous sur un cycle lunaire, l'application du modèle de transport sédimentaire a permis le perfectionnement du modèle d'oxygène dissous, qui tient compte alors des variables particulaires aussi bien que dissoutes et décrit les variations de l'oxygène pendant cinq mois....
Tipo: Text
Ano: 1995
URL: http://archimer.ifremer.fr/doc/00082/19289/16884.pdf

Golfe Normano-Breton. Bilan des connaissances
Provedor de dados: 5
Autores: Blanchard, Michel; Chardy, Pierre; Chaussepied, Marcel; Dao, Jean-claude; Le Hir, Pierre; Jegou, Anne-marie; Larsonneur, C.; Loarer, Ronan; Manaud, Francois.
Ce document a été élaboré dans le cadre de la préparation d'un programme d' "étude régionale intégrée" du golfe normano-breton. Réalisé dans des délais très courts, il ne constitue pas un inventaire exhaustif des travaux effectués dans le golfe mais une illustration par grands secteurs disciplinaires de l'état actuel des connaissances. Son objectif est de cerner les domaines à développer dans le cadre d'une programmation poly-disciplinaire orientée vers la gestion de l'espace littoral. La présentation par disciplines fondamentales de l'océanographie (physique, sédimentologie, biologie) est associée à un bilan de l'utilisation du milieu, faisant apparaître la diversité et la complexité des problèmes à résoudre. En effet, point privilégié entre la Manche...
Tipo: Text
Ano: 1982
URL: http://archimer.ifremer.fr/doc/00450/56186/57739.pdf