Dover Strait Research Articles

Fast hydrodynamic model for medium- and long-term dispersion in seawater in the English Channel and southern North Sea, qualitative and quantitative validation by radionuclide tracers

The database for medium- and long-term model validation using 125Sb released by the La Hague reprocessing plant includes 1400 measurements performed between 1987 and 1994 in the English Channel and the North Sea and data for each release since 1982. Antimony-125 has a conservative behaviour in water masses over a period of several years. These data can be used qualitatively and quantitatively to compare the measured concentrations with the calculated ones and quantities of tracers. Tritium measurements are also available for model calibration. A two-dimensional hydrodynamic model has been developed to allow repetitive long-term simulations. This model uses a database of residual tidal currents calculated using the Lagrangian barycentric method [Salomon, J.C., Guéguéniat, P., Orbi, A., Baron, Y., 1988. A Lagrangian model for long-term tidally induced transport and mixing. Verification by artificial radionuclide concentrations. In: Guary, J.C., Guéguéniat, P., Pentreath, R.J. (Eds.), Radionuclides: A Tool for Oceanography, Cherbourg 1–5 June, 1987. Elsevier Applied Science Publishers, London, New York, pp. 384–394]. The area covered by the model includes the English Channel, the southern North Sea and the Irish Sea with a mesh size of 1 km. The main adjustment parameters of this model are the sources of wind data used and the calculation method for evaluating wind stress at the sea surface. With these parameters, the fluxes of radionuclides and water masses in the English Channel and the North Sea were balanced for the whole period of field measurements (1987–1994). The correlation factor between individual measurements in seawater and calculation results is 0.88 with an average error of ±54%, the error attributable to the measurement process being 15% on average. The mean flux through the Dover Strait is 126,000 m 3 s −1, close from the one obtained from previous studies [Salomon, J.C., Breton, M., Guéguéniat, P. 1993. Computed residual flow through the Dover Strait. Oceanologica Acta 16 (5–6) (1993) 449–455; Bailly du Bois, P., Salomon, J.C., Gandon, R., Guéguéniat, P. 1995. A quantitative estimate of English Channel water fluxes into the North Sea from 1987 to 1992 based on radiotracer distribution. Journal of Marine Systems 6 (5–6) (1995) 457–481; Prandle, D., Ballard, G., Flatt, D., Harrison, A.J., Jones, S.E. Knight, P.J., Loch, S. McManus, J. Player, R. Tappin, A., 1996. Combining modelling and monitoring to determine fluxes of water, dissolved and particulate metals through the Dover Strait. Continental Shelf Research 16 (2) (1996) 237–257]. This model appears as a robust tool for modelling long-term dispersion at a low computation cost (it takes less than 1 h to simulate one year on a personal computer). It could forecast consequences of controlled or accidental releases of soluble substances in seawater under realistic conditions or calculate water masses fluxes and transit times.

Types of internal structure and external morphology of submarine dunes under the influence of tide- and wind-driven processes (Dover Strait, northern France)

The expression of tide- and wind-driven processes in the internal architecture and external morphology of very large submarine dunes is investigated at a dune field located in the central part of the Dover Strait (Southern North Sea). Current measurements and sediment transport calculations enable quantification of the dominant tide- and wind-driven processes, and very high resolution seismic recordings are used to analyse internal structure and external morphology of dunes. In the study area, moderate to storm winds induce temporary currents that can lead to the reversal of sediment transport direction and induced erosive processes on the seabed. Dune master-bedding consists of extended erosive surfaces with 9–11° slopes that bound storm-generated sets of cross-beds, 1.5–4.85 m thick (2.65 m on average). Three types of architectures are observed within the dune field, and occasionally within single dunes. These types, which display a strong linkage between internal structure and external morphology, consist of: (1) asymmetric dunes with cosets, which dip in the direction of the marked external asymmetry of the dunes; (2) dunes with a complex external morphology composed of mega-herringbone structures, each displaying an opposing progradation direction; and (3) dunes with a symmetric megaripple bedding unit at their summit. The diversity of the internal architecture and external morphology results from the variable combinations of tide- and wind-driven processes occurring in the study area. The asymmetry of tidal peak current velocity and the relative strength of wind-driven currents are the parameters that have the most important influence on dune architecture. Asymmetric dunes with cosets result from a strong asymmetry in tidal peak current velocity, which is reversed only slightly during storms. Dunes with mega-herringbone structures and dunes with symmetric megaripple units at their summit are observed in areas where the asymmetry of the tidal peak current velocity is negligible, allowing reversal of the sediment transport and dune migration directions each time moderate winds blow. The latter architectural type is specific to sand-rich areas. The different dune architecture types display strong geometrical similarities to structures observed in dunes from other shelf environments where driving processes are different. This implies that a study based only on a geometric description of internal structures will not enable the reconstitution of ancient depositional environments. A better discriminant criteria seems to be the thickness of the second-order sets of cross-beds which is correlated with specific hydro-sedimentary processes. Dune height also probably has an important influence on the thickness of second-order sets of cross-beds, as dune height and set thickness display a clear relationship in the present study.

Spatio-temporal changes of the near-bottom mesozooplankton from the English Channel

The near-bottom mesozooplankton was caught by a four net suprabenthic sledge on six sites in the English Channel during both spring and autumn. Taxa richness showed no significant difference between seasons, nevertheless diversity (H′), evenness (J) and normalized rarefaction number of taxa E(S91) were higher in autumn than in spring at each site except at Site 2 offshore Plymouth, where Calanus helgolandicus dominated at both seasons. Copepods dominated in abundance at each site in spring while crustacean larvae were dominant in autumn except at Site 2 offshore Plymouth, where copepods remained dominant and, at Site 6 in the Dover Strait, where no significant difference occurred between copepod and crustacean larvae abundances. Four assemblages were distinguished depending on the season. Abundance was higher during the day than at night as a result of a mesozooplankton concentration in the near-bottom layer during the daytime. Moreover, three vertical patterns of suprabenthic mesozooplankton were identified according to their distribution above the near-bottom layer: taxa distributed homogeneously in the four nets; taxa concentrated in nets 2 and 4, and taxa concentrated in the three upper nets.

Fog funnelling through the Strait of Dover

Fog funnelling through the Strait of Dover

A tectonic inversion by steps during the Cenozoic : the Dover Strait

Abstract The Boulonnais is a dome incised by a former marine gulf inset into a zone of tectonic inversion from the Middle Eocene, which was already partly excavated at least at the Upper Eocene. New sedimentological and paleopedological data obtained within the Boulonnais, completed with old seismic profiles, allow a better understanding of the inversion process which developed step by step. The initial breaching probably took place in the late Eocene. The Dover Strait was probably opened during the Lutetian, a part of the Oligocene and the late Neogene. Oligocene and Pliocene faunal assemblages are identical on both sides of the Strait. It was closed again for tectonic and eustatic reasons in the early Quaternary and reopen subsequently just before the Last Interglacial. The opening is related to the evolution of the Western Channel and of its paleovalley system. The inversion of the Variscan front accommodates most of the shortening induced by the Pyrenean Orogen on the western border of the European plate. The inversion of the Dover Strait region is almost synchronous with those of other basins of the Channel and North Sea areas. Tectonic, geomorphologic and climatic implications of this dynamic are discussed within the western European context.

Estimating limits to the spatial extent and suitability of sole ( Solea solea) nursery grounds in the Dover Strait

There is a growing need for accurate and interpretable maps that describe the spatial extent and suitability of flatfish habitats. A common approach to developing such maps is to construct spatially explicit habitat models from fisheries-independent survey data. As the entire range of factors that define fish habitats can never be fully quantified, habitat models are invariably built from a small subset of factors, which typically consist of physical seabed and water column characteristics. If important physical and biological habitat features have not been measured, conventional modelling techniques may underestimate habitat use and quality. We present a spatial modelling technique capable of estimating the maximum extent and suitability of flatfish habitats, i.e. the potential or upper limits of the habitat, using juvenile sole ( Solea solea L.) in the Dover Strait as an example. To develop the models, juvenile sole catch densities and environmental habitat data were first acquired and assembled within a Geographical Information System (GIS). Regression quantiles were then estimated for models of change in juvenile sole catch density according to changes in a number of habitat variables. Finally, spatial models were constructed within a GIS by combining the quantile regression models with digital maps of the environmental variables. The use of regression quantiles allowed linear model parameters to be estimated near to the upper bounds of the sole-habitat relationships, thereby providing estimates of the limiting effects of the habitat. In turn, the habitat map built from the upper regression quantiles provided robust estimates of the maximum spatial extent and suitability of sole nursery grounds in the Dover Strait region, as confirmed by model tests using independent data. Habitat maps developed using this approach may be desirable from a species conservation perspective, as the likelihood of underestimating the extent and quality of the habitat is reduced.

Wind speed‐up in the Dover Straits with the Met Office New Dynamics Model

AbstractIt is part of British sailing and forecasting folklore that the wind speed increases in the Dover Straits when there is an established wind‐flow –westerly/south‐westerly or easterly/north‐easterly –along the English Channel. However the underlying mechanism of the phenomenon is unclear. We have used the Met Office ‘New Dynamics’ mesoscale model to perform a case study on an occasion when this phenomenon was observed in the Channel but not forecast well by the operational model, UM 4.5. Results are presented showing the sensitivity of forecasts to horizontal resolution (down to 2 km) and to vertical resolution. We probe the physical mechanism of the Channel jet by altering the surrounding orography and the land or sea surface roughness. Both the orography and the surface roughness are shown to influence the jet formation. Copyright © 2003 Royal Meteorological Society

The Hazards of Navigating The Dover Strait (Pas-de-Calais) Traffic Separation Scheme

The Chairman of the Sea Safety Group has most kindly agreed to the publication of this definitive paper on the hazards to be encountered by mariners when transiting the Dover Strait. The paper brings together the deliberations of the SSG Navigation Panel and the best information available to them sent from all quarters of the sharp end of the marine industry to produce a paper which provides a centre for discussion on this difficult and controversial issue. The Sea Safety Group retains the copyright.

The mud deposits and the high turbidity in the Belgian–Dutch coastal zone, southern bight of the North Sea

The suspended sediment processes and the mudfields found in the Belgian/Dutch coastal area (Southern North Sea) are discussed by presenting an integrated data-modelling approach of the suspended sediment transport along the Belgian–Dutch coast, using a fine-grid coupled 2D hydrodynamic and sediment transport model and existing field and literature data. These mudfields and turbidity maxima are situated in a well-mixed, highly energetic hydrodynamic environment. In the past the occurrence of this high turbidity zone (more than a few hundreds mg/l of suspended matter) was ascribed to a closed hydrodynamic system (gyre) in front of the coast. This study shows that the SPM input through the Strait of Dover, the shallowness of the considered area, the decreasing magnitude of the residual transport vectors from the French/Belgian border towards Zeebrugge and the specific hydrodynamic features are the main processes responsible for the presence of the turbidity maximum. The origin and the formation of these mud deposits in front of the coast are explained by the neap-spring tidal cycles and the presence of SPM sources (import of SPM through the Strait of Dover and through erosion of clay layers).

Le détroit du Pas-de-Calais : un espace frontalier terraqué ? (The Strait of Dover : a terraqué trans-border area ?)

Abstract. - We propose to study the Strait of Dover as a "terraqué" transborder area and not as a separated border or a crossing zone. After having justified this research position, we particularly analyse transborder cooperation documents between Kent and Nord-Pas-de-Calais because they are creating new spatial networks.

Derivation of sediment resuspension rates from acoustic backscatter time-series in tidal waters

Extending oceanographic forecasting models beyond dynamics to ecological parameters involves simulation of concentrations of suspended particulate matter (SPM). The latter will require assimilation of both in situ and remote sensing observations. Assimilation will need to reconcile both types of observations with modelling responses for a variety of both resuspension and settling velocity parameters. This study develops a systematic approach to this problem. Time series of suspended sediment particulate matter (SPM) concentration are routinely obtained via indirect optical, acoustic and satellite instrumentation. However, translating such measurements into components contributed by localised sediment resuspension and horizontal advection is severely complicated by uncertainties concerning the specific SPM characteristics which cannot easily be measured in situ. Since some estimate of synoptic tidal currents is generally available, resuspension-transport-deposition models can be used to interpret these SPM concentration time series. Here, a novel methodology, incorporating an optimisation procedure and a 1-D Lagrangian particle tracking model, is developed to automate this interpretation and indicate the nature of the associated SPM. Utilising calibrated acoustic backscatter measurements from Acoustic Doppler Current Profilers, a downhill simplex optimisation method minimises the least squares coefficient of determination ( R 2) between model and observed SPM concentration time series. Advection of a linear “background” concentration gradient is incorporated into the SPM model, and the optimisation procedure decouples observed SPM concentration time series into background and resuspension components. The model has been validated in three independent ways and good agreement between derived model parameters and independent observations has been found for settling velocity, background concentration gradients and erosion rates. Using data from two contrasting sites in the Mersey estuary and Dover Straits, agreement for concentrations involved 0.61 < R 2 < 0.83. A modular design provides scope for more complex formulations and improvements of 20% in R 2 occurred when a time varying eddy diffusivity was employed.

Morphodynamique d'une dune sous-marine du détroit du Pas de Calais. Morphodynamics of an undersea sandwave of the Dover Straits

This paper investigates the dynamics of sandwaves in relationship with tidal currents and weather conditions. The studied sandwaves are located in the Dover Straits and are covered by megaripples. These megaripples have migration speeds of and slopes of 34°, suggesting the potential for avalanches to occur along the flanks of the sandwave. Tidal cycles without reversing currents were observed during stormy weather. Wind-induced currents lead to a unidirectional migration of megaripples and sandwaves. Well-defined areas without megaripples were observed and correlated with an increase in sandwave height. We propose interpretations for understanding sandwave saturation and migration

Morphodynamique d'une dune sous-marine du détroit du pas de Calais

This paper investigates the dynamics of sandwaves in relationship with tidal currents and weather conditions. The studied sandwaves are located in the Dover Straits and are covered by megaripples. These megaripples have migration speeds of and slopes of 34°, suggesting the potential for avalanches to occur along the flanks of the sandwave. Tidal cycles without reversing currents were observed during stormy weather. Wind-induced currents lead to a unidirectional migration of megaripples and sandwaves. Well-defined areas without megaripples were observed and correlated with an increase in sandwave height. We propose interpretations for understanding sandwave saturation and migration. To cite this article: D. Idier et al., C. R. Geoscience 334 (2002) 1079–1085.

Channel's fate : terraqué ?

This paper suggests that today we should try to think of the English Channel as a territory in a state of dynamic mergence. A sort of new virtual territory in the process of being transformed into a site of experimentation in here to for unimagined European relations. Thus a site of fresh mental attitudes no longer divided into three separate entities but a whole made up of its components namely the English hinterland (Kent) the sea and the French hinterland (Flanders). The paper describes these phenomena and demonstrates that the Dover Straits are no longer just an empty space, once an obstacle to be crossed or conquered, but now a part of our respective heritage easily overcome by ferry or tunnel opening up new lands for greater business or pleasure opportunities.

Diversity of benthic macrofauna in the eastern English Channel: comparison among and within communities

The diversity of benthic macrofaunal assemblages in the eastern English Channel is described from 707 samples collected with a Rallier-du-Baty dredge during 1971-1975. Four assemblages were primarily defined by means of multivariate data analyses and clustering methods: the 'Abra alba com- munity', the 'Ophelia borealis community', the 'pebbles community' and a 'mixed assemblage' of the first three communities. Spatial heterogeneity of these communities is significantly correlated with sedi- mentary characteristics, although local variability appears to be controlled by both physical and biological processes. Ecological diversity of these communities was analysed considering species richness (S), the Shannon diversity index (H � ), and rank-frequency diagrammes (RFD). These analyses were performed at two spatial scales: for a single sample, and for a 'site' of 10 pooled samples. Thus, several sites were chosen in order to compare diversity patterns and species quantitative structure among and within the communities. The greatest species richness was recorded for the pebbles (57-69) and the A. alba (63- 79) communities. In the former, high values may be due to the complexity of microhabitats and the large flux of food related to strong currents. In the latter, both organic matter and terrestrial inputs associated with the mud favour the presence of deposit-feeder organisms. No clear trend was observed among and within the community sites in terms of the species quantitative structure. Thus, convex RFD shapes were observed in three assemblages: the 'mixed assemblage' (offshore site), the A. alba (North Sea), and the pebbles (Normandy coast). 'Sigmoid' shapes were observed in the pebbles (Dover Strait) and A. alba (English coast) communities. Presumably, these shapes can be caused by the combined action of phys- ical (strong currents, substrate stability, mud content in the sediments) and biological factors (co-occur- rence of species from different communities, strong species recruitment, relative dominance of carnivorous species).

Field and Seismic Images of Sharp-Based Shoreface Deposits: Implications for Sequence Stratigraphic Analysis

ABSTRACT Sharp-based shoreface sandstones are of considerable interest because of their potential as hydrocarbon reservoirs and because they play an important role in the stratigraphic analysis of basin fills. The sharp-based shoreface sandstones studied herein are Upper Jurassic (Kimmeridgian-Tithonian) and exposed along the coastal cliffs of the Dover Strait in northwestern France. These series consist of tens of meter-thick alternations of sandstones bodies and organic-rich shales that can be correlated for over 30 km along coastal cliff exposures and tied to high-resolution (ca. 1 m of sediment) marine-seismic profiles obtained several hundred meters offshore. The units described here comprise two sharp-based sandstone bodies. Each is composed of a basal progradational set of shoreface parasequences overlain by a progradational-aggradational shoreface succession. Each sharp-based sand body lies on a marine regressive surface of erosion and is truncated by a marine transgressive surface of erosion, which in turn is overlain by a thin retrogradational ravinement lag or coarse-grained, planar-laminated bedset. The two progradational packages are separated by a third surface, a subaerial exposure surface that is interpreted as a sequence boundary. Two distinct types of seismic units, referred to as type A and type B, have been identified in the study area. Seismic unit A has conformable upper and lower boundaries and parallel (aggradational) configurations; seismic unit B is characterized by downlap and toplap boundaries and simple or compound, sigmoid and oblique-tangential (progradational) configurations. A single sharp-based shoreface sandstone body makes up the type B unit and typically consists of two compound superimposed progradational sets (B1, B2). The lowermost set, B1, corresponds in the field to the progradational set sensu stricto, whereas B2 corresponds to a progradational-aggradational set. B1 and B2 are separated in outcrop by a sequence boundary. These observations led us to reevaluate the sequence stratigraphic interpretation of sharp-based shoreface sandstones. It is proposed here that complete, single, sharp-based shoreface sandstones bodies can be separated into two different systems tracts: (1) a progradational set (B1 seismic body) at the base, which corresponds to the forced regressive wedge systems tracts (FRWST) of Hunt and Tucker (1992), and (2) a progradational-aggradational set (B2) at the top, above the sequence boundary, which corresponds to the lowstand systems tract (LST) of Posamentier et al. (1992). A complete sharp-based shoreface sandstone body is bounded below the FRWST by a regressive surface of marine erosion caused by the downward shift of wave base, and by a transgressive surface of marine erosion, or ravinement surface, at the top of the LST.

An s coordinate density evolving model of the northwest European continental shelf: 2. Seasonal currents and tides

The barotropic tides and the residual currents from a year long run of a three‐dimensional baroclinic model (the Proudman Oceanographic Laboratory Three‐Dimensional Baroclinic B grid model) applied to the northwest European shelf are investigated. M2 currents and elevations differ from observations by typically 0.114 m s−1 and 0.143 m; these errors are dominated by a number of large values at the coast. The density component of the residual currents is derived from the difference between the full model and wind and tide only model runs. This demonstrates the importance of density‐driven currents in a number of regions, particularly in the Norwegian Trench, around the St. George's Channel, to the east of the Shetland Isles, and in the river plumes. However, volume fluxes show the mass budget of the North Sea is primarily determined by the wind‐driven circulation. Calculations of the dynamic balance in the model show the significance of friction and/or advective effects, on a timescale of days, at a number of locations (e.g., the Dover Strait and in the central North Sea). However, the monthly mean currents are in geostrophic balance over virtually the whole domain; ageostrophic components adjust the surface and isopycnal slopes to restore this balance on comparatively short timescales. Particular attention is given to the western boundary, and we demonstrate that variations in the imposed temperature and salinity here have only a limited effect on the shelf. Current meters on the Hebrides shelf show that the model produces reasonably accurate residual currents but also that this agreement is degraded by the boundary condition on Porcupine Bank.

Population dynamics and stage structure in a haploid‐diploid red seaweed, Gracilaria gracilis

Summary Many red seaweeds are characterized by a haploid‐diploid life cycle in which populations consist of dioecious haploid (gametophyte) and diploid (tetrasporophyte) individuals as well as an additional diploid zygote‐derived sporangium (carposporophyte) stage. A demographic analysis of Gracilaria gracilis populations was carried out to explore and evaluate the population dynamics and stage structure of a typical haploid‐diploid red seaweed. Four G. gracilis populations were studied at two sites on the French coast of the Strait of Dover. Survival, reproduction and recruitment rates were measured in each population for up to 4 years. Eight two‐sex stage‐based population projection matrices were built to describe their demography. All four populations were characterized by high survival and low recruitment rates. Population growth rates (λ) were similar between populations and between years and ranged from 1.03 to 1.17. In addition, generation times were found to be as long as 42 years. Sex and ploidy ratios were variable across populations and over time. Female frequencies ranged from 0.31 to 0.59 and tetrasporophyte frequencies from 0.44 to 0.63. However, in most cases, the observed population structures were not significantly different from the calculated stage distributions. Eigenvalue elasticity analysis showed that λ was most sensitive to changes in matrix transitions that corresponded to survival of the gametophyte and tetrasporophyte stages. In contrast, the contribution of the fertility elements to λ was small. Eigenvector elasticity analysis also showed that survival elements had the greatest impact on sex and ploidy ratios.

Holocene tidal conditions and tide‐induced sand transport in the southern North Sea

A numerical model of Holocene tides and sand transport in the North Sea was used to establish potential tidal sand transport patterns in the Southern Bight and sand budgets for the Dutch and Belgian coast. The sand transport formulation yields magnitude and direction in addition to erosion/deposition values, in contrast to previous studies. All palaeobathymetries were obtained using the present bathymetry and sea level change results from an isostatic rebound model. The sea first invaded the Southern Bight through the Strait of Dover, and the microtidal range increased rapidly to mesotidal. The amphidromic system developed when the land bridge between Britain and the continent flooded and the northern tidal influence increased. Simultaneously, the current ellipses rotated from shore normal to shore parallel, while the flow velocities increased. The net tidal sand transport direction changed from toward the Dutch and Belgian shore to northward alongshore in the north and southward in the south. Until 7000 B.P. erosion dominated at sea, and deposition dominated near shore. Subsequently, erosion occurred in the south, and sedimentation occurred in the north. To the north of the Southern Bight, transport rates were low. Since 7500 B.P., sand has been transported mainly in suspension. Dominant transport by tidal asymmetry changed to transport by tidal residual currents and back in large areas. Comparison with previous studies illustrates that isostatic rebound is important for constructing palaeobathymetries. Most sediment was supplied to the Dutch and Belgian coast before 6000 BP. Substantial tidally induced mean sea level changes occurred in the early Holocene.

Suspended particulate matter fluxes through the Straits of Dover, English Channel: observations and modelling

Suspended Particulate Matter (SPM) concentrations at various levels within the water column, together with salinity and temperature, were measured using water samples collected from six stations across the Straits of Dover. The sampling programme covered a 16-month period, undertaken during 23 cruises. On the basis of the spatial variability in the concentrations, the water bodies are divided by several boundaries, controlled by tidal and wind conditions. Within the water column, SPM concentrations were higher near the sea bed than in the surface waters. Throughout the cross-section, maximum concentrations occurred adjacent to the coastlines. Temporal variability in the SPM concentration exists on daily and seasonal scales within the coastal waters (4.2 to 74.5 mg·L −1): resuspension processes, in response to semi-diurnal tidal cycles (with a period of around 12.4 h) and spring-neap cycles (with a period of 15 days) make significant contributions. Distinctive seasonal/annual concentration changes have also been observed. In the offshore waters, such variability is much less significant (0.9 to 6.0 mg·L −1). In the summer the English Coastal Zone is associated with relatively high SPM concentrations: the Central Zone has a low and stable SPM concentration between these zones, there is a Transitional Zone, where there is a rapid response of SPM concentration to wind forcing. Finally, the French Coastal Zone is characterized by variable (sometimes high) SPM concentrations. Because of the zonation, SPM fluxes within the Dover Strait are controlled by different transport mechanisms. Within the Central Zone, the flux can be represented by the product of mean water discharges and SPM concentrations. However, within the coastal zones fluctuations in SPM concentrations on various time-scales must be considered. In order to calculate the maximum and minimum SPM fluxes, 10 cells were divided in the strait. A simple modelling calculation has been proposed for this complex area. The effect of spring-neap tidal cycles and seasonal changes can contribute significantly to the overall flux, which is of the order of 20×10 6 t·yr −1 (through the Dover Strait, towards the North Sea). Such an estimate is higher than most obtained previously. © 2000 Ifremer/CNRS/IRD/Éditions scientifiques et médicales Elsevier SAS suspended particulate matter / flux / transport mechanisms / straits / English Channel