Mechanisms controlling seaward escape of suspended sediment from the Gironde: A macrotidal estuary in France

doi:10.1016/0025-3227(81)90045-1

Marine Geology

Volume 40, Issues 1–2, March 1981, Pages 101-118

https://doi.org/10.1016/0025-3227(81)90045-1 Get rights and content

Abstract

The main parameters controlling suspended-sediment transport in and out of the Gironde estuary are river flow and tides. These combine to control water mixing, density circulation and the trapping of suspended sediment in the turbidity maximum. Seaward escape of sediment is related to the position of the maximum in the estuary, which is a function of river flow; and the amount of sediment in suspension as controlled by tide range. Seaward escape of sediment appears to follow two cycles: (1) a 14-day neap—spring tidal cycle, and (2) a seasonal river flow cycle. Maximum escape occurs during spring tides and high river flow. During these periods, the turbidity maximum is located downstream in the estuary and the increased seaward surface density flow supplies to the shelf large quantities of suspended sediment. At this time, net seaward flux is more than 100 times that measured during conditions of low river flow.

Thermal imagery and aerial photography in the inlet, repeated during a spring tide cycle, show an initial seaward drift of the surface estuarine water and suspensions, followed by a northward transport and mixing with water from the adjacent inlet. In succeeding tides, the turbid plume is dispersed, fragmented and transported seaward and to the north in the coastal drift system. Most of the suspended sediment expelled from the estuary is deposited on the shelf between 30 and 70 m depth, where wave resuspension is low and where suspended-sediment concentrations are high enough to supply and maintain a permanent mud deposit.

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Estuary — Shelf interrelationshipsMechanisms controlling seaward escape of suspended sediment from the Gironde: A macrotidal estuary in France

Abstract

Sediment. Geol.

Estuarine Coastal Mar. Sci.

Neth. J. Sea Res.

Etude des processus sédimentaires dans l'estuarie de la Gironde

Suspended-sediment transport from the Gironde estuary (France) onto the adjacent continental shelf

Mar. Geol.

Contribution à l'étude de la circulation des masses d'eau à l'embouchure de la Gironde

C.R. Acad. Sci.

Etude de l'aménagement de l'estuaire de la Gironde

Etude synthétique du régime hydraulique

Rapp. E.D.F., Chatou

Remarques sur les écoulements moyens à l'aval de la Gironde

Bull. Inst. Géol. Bassin Aquitaine

Paléogéographie de l'Holocène sur le plateau continental au large de l'embouchure de la Gironde

C.R. Somm. Soc. Géol. Fr.

Etude par télédétection de la dispersion en mer des eaux estuariennes issues de la Gironde et du Pertuis de Maumusson

Oceanol. Acta

On the residual transport of suspended matter by an alternating tidal current

Neth. J. Sea Res.

The regimen of the Thames estuary as affected by currents, salinities and river flow

Estuary — Shelf interrelationships
Mechanisms controlling seaward escape of suspended sediment from the Gironde: A macrotidal estuary in France