COMPARISON BETWEEN TURBIDITY MEASURED IN AN ESTUARY AND TURBIDITY CALCULATED FROM LABORATORY TESTS

Andre Wallet

Abstract


The study of navigation conditions in the Seine estuary has led to scale model tests which are now being carried out by the NEYBPIC Laboratory, Grenoble; for the Port of Rouen Authority.

In order to calibrate the model correctly, that is to say to ensure that the natural conditions would be reproduced on the model, it was necessary to carry out laboratory studies on the sand from the estuary bed to determine the solid discharge of this material for definite hydraulic conditions.

This was necessary because, while at some distance above the bed direct measurements of the solid transport are relatively easy to make in nature by means of samples, they are practically impossible in the immediate neighborhood of the bottom when the sand is fine, as is the case in the Seine estuary.

On the other hand, by taking certain precautions it is possible to measure the solid discharge in the immediate neighborhood of the bottom when.the transport of sand is studied in the laboratory. The two methods, direct measurements of the suspended load in nature and measurements of solid discharge near the bottom in the laboratory therefore complement one another.

However, it seemed interesting to justify this method by comparing the results where nature and the laboratory coincide, i.e. for material in suspension.

This paper gives details on the procedure followed for these laboratory tests on an experimental canal. The main results of these tests will be reviewed by examining the relationship between the concentration in the neighbourhood of the bottom and the solid discharge on the one hand, and the bottom shear stress on the other.

Keywords


turbidity; Seine Estuary; sediment transport

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