Description of the turbulence measurements conducted in the tidal channel "Groote Gat" (Ems/Dollard) in 1995 and 1996

Abstract

In 1993 an interdisciplinary research programme on the behaviour of mud in tidal waters was initiated by the Board of NWO-BOA. The programme aims at obtaining more detailed insight in the dominant processes that govern the transport behaviour of mud. These processes have strong time variability and therefore the general approach is to obtain long-term in situ measurements on a number of key parameters in a tidal channel and on a tidal flat. One of the surplus values of this research programme is that it contributes to an interdisciplinary perception of the behaviour of intertidal areas, in which the relevance of biological, physical and chemical processes and human activities is represented in a well-balanced way. This report provides a description of the field measurements of flow velocities and suspended sediment concentrations carried out in the tidal channel "Groote Gat" in the Ems/Dollard estuary in 1995 and 1996. It is addressed in the first place to those who want to make use of the turbulence data recorded in the tidal channel which is stored on CD Recordables which can be made available by the Hydromechanics Section of the Department of Civil Engineering of the Delft University of Technology. SOME CONCLUSIONS - The test measurements in June and August 1995 showed that the FOSLIM is a useful high-frequency device for measuring SSC. - It was found that the accuracy of the FOSLIM depends to a large extent on the in-situ calibration procedure. - It has been shown that by combining a FOSLIM and an EMF it is possible to measure vertical turbulent fluxes of fine sediments. - The data sets obtained from the field measurements in 1996 showed large quality differences. In April 1996 SSCs were extremely low so that suspended sediment induced stratification effects were fully absent. These low SSCs were ascribed to biogenic stabilisation of the sediment beds.