Sponsor
This work was funded by LOICZ project 014.27.013 (Land Ocean Interaction in the Coastal Zone), and administered by NWO-ALW, the Netherlands Organization for Scientific Research.
Document Type
Post-Print
Publication Date
2009
Subjects
Turbidity currents, Marine sediments, Ems River Estuary (Germany and Netherlands)
Abstract
Motivated by field studies of the Ems estuary which show longitudinal gradients in bottom sediment concentration as high as O(0.01 kg/m4), we develop an analytical model for estuarine residual circulation based on currents from salinity gradients, turbidity gradients, and freshwater discharge. Salinity is assumed to be vertically well mixed, while the vertical concentration profile is assumed to result from a balance between a constant settling velocity and turbulent diffusive flux. Width and depth of the model estuary are held constant. Model results show that turbidity gradients enhance tidally averaged circulation upstream of the estuarine turbidity maximum (ETM), but significantly reduce residual circulation downstream, where salinity and turbidity gradients oppose each other. We apply the condition of morphodynamic equilibrium (vanishing sediment transport) and develop an analytical solution for the position of the turbidity maximum and the distribution of suspended sediment concentration (SSC) along a longitudinal axis. A sensitivity study shows great variability in the longitudinal distribution of suspended sediment with the applied salinity gradient and six model parameters: settling velocity, vertical mixing, horizontal dispersion, total sediment supply, fresh water flow, and water depth. Increasing depth and settling velocity move the ETM upstream, while increasing freshwater discharge and vertical mixing move the ETM downstream. Moreover, the longitudinal distribution of SSC is inherently asymmetric around the ETM, and depends on spatial variations in the residual current structure and the vertical profile of SSC.
DOI
10.1016/j.csr.2007.09.002
Persistent Identifier
http://archives.pdx.edu/ds/psu/11191
Citation Details
Talke, Stefan A.; de Swart, Huib E.; and Schuttelaars, H. M., "Feedback Between Residual Circulations and Sediment Distribution in Highly Turbid Estuaries: An Analytical Model" (2009). Civil and Environmental Engineering Faculty Publications and Presentations. 85.
http://archives.pdx.edu/ds/psu/11191
Description
NOTICE: this is the author’s version of a work that was accepted for publication in Continental Shelf Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Continental Shelf Research, Volume 29, Issue 1, (2009), Pages 119–135. http://dx.doi.org/10.1016/j.csr.2007.09.002