|Experimental determination of salt intrusion mechanisms in the Volkerak estuary|
Dronkers, J.; van de Kreeke, J. (1986). Experimental determination of salt intrusion mechanisms in the Volkerak estuary. Neth. J. Sea Res. 20(1): 1-19
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579, more
|Authors|| || Top |
- Dronkers, J., more
- van de Kreeke, J.
Salt transport mechanisms in the Volkerak estuary, The Netherlands, are analysed by use of the results of simultaneous measurements of current and salt concentrations in 32 verticals distributed over six cross-sections. Longitudinal salt fluxes in each cross-section are evaluated by interpolating measured values of current speed and salt concentration over the cross-section and in time. Salt fluxes are decomposed in an advective flux, a local salt flux (covariance of the deviations of velocity and salt concentration from the cross-sectional mean) and a non-local salt flux (covariance of the tidal variation in current speed and salt concentration). From a theoretical analysis it follows that the non-local flux in a cross-section equals the difference between the local salt flux in that cross-section and the local salt flux in a cross-section moving with the tidal velocity. Because of the relatively large tidal amplitude to depth ratio the existing decomposition techniques are expanded to include cross-sections with time-varying water levels. The field data and subsequent analysis reveal that in the seaward part of the estuary the advective salt flux is balanced by the non-local dispersive flux. Salt intrusion in this region is caused by large scale exchanges of water bodies between the Volkerak estuary and Eastern Scheldt estuary, between different tidal channels at channel junctions and between tidal channels and tidal flats. In the landward part of the estuary gravitational circulation is the dominant salt intrusion process, reflected most strongly in the local salt flux component associated with steady vertical variations in velocity and salt concentration.