Sediment pumping by tidal asymmetry in a partially mixed estuary
Scully, Malcolm E.
Friedrichs, Carl T.
MetadataShow full item record
Observations collected at two laterally adjacent locations are used to examine the processes driving sediment transport in the partially mixed York River Estuary. Estimates of sediment flux are decomposed into advective and pumping components, to evaluate the importance of tidal asymmetries in turbulent mixing. At the instrumented location in the estuarine channel, a strong asymmetry in internal mixing due to tidal straining is documented, with higher values of eddy viscosity occurring during the less-stratified flood tide. As a result of this asymmetry, more sediment is resuspended during the flood phase of the tide resulting in up-estuary pumping of sediment despite a net down-estuary advective flux. At the instrumented location on the adjacent shoal, where no pronounced tidal asymmetry in internal mixing was found, both the pumping flux and advective flux were directed down-estuary. The down-estuary pumping of sediment on the shoal appears to be driven by asymmetries in bed stress. The impact of tidal asymmetries in bed stress at the channel location was negated because the amount of sediment available for resuspension was limited. As a result, the pumping flux was dominated by the overlying asymmetries in internal mixing. The asymmetries in stratification appear to exert an important control on the vertical distribution of sediment by both impacting the eddy diffusivity as well as the fall velocity. During the more turbulent flood tide, the fall velocities are smaller suggesting the Kolmogorov microscale is setting the upper bound on floc diameter.
Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 112 (2007): C07028, doi:10.1029/2006JC003784.
Showing items related by title, author, creator and subject.
Tidal asymmetry and residual circulation over linear sandbanks and their implication on sediment transport : a process-oriented numerical study Sanay, Rosario; Voulgaris, George; Warner, John C. (American Geophysical Union, 2007-12-22)A series of process-oriented numerical simulations is carried out in order to evaluate the relative role of locally generated residual flow and overtides on net sediment transport over linear sandbanks. The idealized ...
Nidzieko, Nicholas J. (American Geophysical Union, 2010-08-05)Tidal asymmetry in estuaries with mixed, mainly semidiurnal tides arises from both the interaction of principal tides and the higher harmonics generated by distortions within the estuary. The duration asymmetry in rise and ...
The importance of tidal and lateral asymmetries in stratification to residual circulation in partially mixed estuaries Scully, Malcolm E.; Friedrichs, Carl T. (American Meteorological Society, 2007-06)Measurements collected in the York River estuary, Virginia, demonstrate the important impact that tidal and lateral asymmetries in turbulent mixing have on the tidally averaged residual circulation. A reduction in turbulent ...