Elsevier

Marine Pollution Bulletin

Volume 37, Issues 3–7, March–July 1999, Pages 190-205
Marine Pollution Bulletin

Dynamics of the Turbidity Maxima in the Upper Humber Estuary System, UK

https://doi.org/10.1016/S0025-326X(98)00178-7Get rights and content

Abstract

Turbidity maxima in estuaries are important due to their influence on primary production, pollutant flushing, fish migration and dredging. There is a need for a better understanding of the dynamics of turbidity maxima. Results are given for the response of turbidity maxima and salinity in the tidal Trent and (Yorkshire) Ouse over time scales of a semidiurnal tide to an annual cycle with respect to tidal and fluvial influences. Under low fresh water flow conditions sediment moves landward and the turbidity maximum is observed upstream of the fresh–salt water interface. Longitudinal dispersion processes governing salinity appear to be dominated by transverse shear induced effects. Suspended solids concentrations within the turbidity maximum are strongly influenced by tidal asymmetry and suspended solids vertical concentration gradient effects and their associated influences. It is proposed that the higher concentrations of suspended solids in the Ouse estuary, compared with the tidal Trent, are due to the influence of the lower fluvial discharge in the appropriate reaches.

Section snippets

Previous Work

The transport of solute and sediment in a tidal channel may be given by the one dimensional, intra-tidal, time-dependent form of the advective dispersion equation(AcA)t+(AuAcA)x=xA(Dt+DvA)cAx+S,where cA is area mean concentration, uA is area mean longitudinal component of velocity, A is cross sectional area, Dt is the longitudinal dispersion coefficient due to transverse shear effects, DvA is an area mean vertical shear dispersion coefficient and S is a source/sink term. The second term

The Humber Systems

A location map for the Humber estuary system shows (Fig. 1) distances given from Trent Falls, the confluence of the tidal Ouse, tidal Trent and the Humber estuary. The catchment area is approximately 24240 km2 with a population of about 11 million people. The tidal Trent is a canalised estuary approximately 80 km in length, stretching from Cromwell Weir in the south to the Humber confluence at Trent Falls in the north. The summer flows are strongly influenced by inter-catchment transfers of

Data sources

The data on which this paper is based have been collected by the authors or kindly supplied by a number or organisations and members of the LOIS programme, as indicated in Table 2. The authors very gratefully acknowledge the provision of these data. The Environment Agency data in unedited form consist of readings of turbidity, conductivity, temperature and other variables at 15 min intervals at Burton Stather, Keadby Bridge and Gainsborough on the tidal Trent. Where necessary conductivity can

Discussion of Results

This section considers some of the characteristics of the hydraulics and salinity intrusion into Humber estuary system before describing the suspended solids concentration distributions, their relationship with the hydrodynamics and salinity, and likely sediment transport mechanisms.

Conclusions

1. The hydraulics of the upper Humber system of estuaries show a complex temporal and spatial variation of area mean velocity in response to channel topography, tidal range and fluvial discharge distributions.

2. Solute transport processes, as indicated by salinity fluctuations, are a complex function of time and space. Salinity shows strong tidal advective effects which are evidence of strong vertical mixing and a fairly rapid response to fluvial flow variations in the region of Trent Falls.

Acknowledgements

The authors gratefully acknowledge the provision of data by the Environment Agency, National Power and the LOIS community. The support of Ray Hodson in managing fieldwork programmes and of the crew of Sea Vigil is also gratefully recognised. This is LOIS Publication Number 353.

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