Oceanography The Official Magazine of
The Oceanography Society
Volume 32 Issue 01

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Volume 32, No. 1
Pages 231 - 236


HANDS-ON OCEANOGRAPHY • Forces in an Estuary: Tides, Freshwater, and Friction

By David Fugate  and Felix Jose 
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PURPOSE OF ACTIVITY. The goal of this activity is to help environmental science students understand and compare hydrodynamic forces in an actual estuary. The interplay of physical forces in an estuary determines the currents and the amounts of mixing and stratification within the water column. The currents, in turn, are an important control on the distribution of phytoplankton, which form the base of the food web, and suspended sediments, which contain nutrients and pollutants. During this activity, students estimate the relative strengths of the key forces in an estuary, the barotropic and baroclinic pressure gradients, and friction. In addition, students estimate how these values change during flood and ebb and spring and neap tidal phases. Another purpose of this activity is to provide students with experience in analyzing data using spreadsheets, in organizing and collaborating within a fieldwork team, and in producing a scientific report.


Fugate, D., and F. Jose. 2019. Forces in an estuary: Tides, freshwater, and friction. Oceanography 32(1):231–236, https://doi.org/10.5670/oceanog.2019.105.


Dyer, K.R. 1986. Coastal and Estuarine Sediment Dynamics. Chichester, John Wiley & Sons, 358 pp.

Friedrichs, C.T., and D.G. Aubrey. 1988. Non-linear tidal distortion in shallow well-mixed estuaries: A synthesis. Estuarine,Coastal and Shelf Science 27:521–545, https://doi.org/10.1016/0272-7714(88)90082-0.

Geyer, W.R., J.H. Trowbridge, and M.M. Bowen. 2000. The dynamics of a partially mixed estuary. Journal of Physical Oceanography 20:2,035–2,048, https://doi.org/10.1175/1520-0485(2000)030<2035:TDOAPM>2.0.CO;2.

Li, C., A. Valle-Levinson, L.P. Atkinson, K.-C. Wong, and K.M.M. Lwiza. 2004. Estimation of drag coefficient in James River Estuary using tidal velocity data from a vessel-towed ADCP. Journal of Geophysical Research 109(C3), https://doi.org/10.1029/2003JC001991.

North, E.W., and E.D. Houde. 2003. Linking ETM physics, zooplankton prey, and fish early life histories to striped bass Morone saxatilis and white perch M. americana recruitment. Marine Ecology Progress Series 260:219–236, https://doi.org/10.3354/meps260219.

Scully, M.E., C. Friedrichs, and J. Brubaker. 2005. Control of estuarine stratification and mixing by wind-induced straining of the estuarine density field. Estuaries 28:321–326, https://doi.org/10.1007/BF02693915.

Traynum, S., and R. Styles. 2007. Flow, stress and sediment resuspension in a shallow tidal channel. Estuaries and Coasts 30:94–101, https://doi.org/10.1007/BF02782970.

Trowbridge, J.H., W.R. Geyer, M.M. Bowen, and A.J. Williams III. 1999. Near-bottom turbulence measurements in a partially mixed estuary: Turbulent energy balance, velocity structure, and along-channel momentum balance. Journal of Physical Oceanography 29:3,056–3,072, https://doi.org/10.1175/1520-0485(1999)029​<3056:NBTMIA>2.0.CO;2.

US EPA. 1992. Protecting Coastal and Wetlands Resources: A Guide for Local Governments. Report to the Office of Water, Office of Wetlands, Ocean and Watersheds and Office of Policy, Planning and Evaluation, 185 pp.

Winterwerp, J.C., and Z.B. Wang. 2013. Man-induced regime shifts in small estuaries, Part I. Theory. Ocean Dynamics 63:1,279–1,292, https://doi.org/10.1007/s10236-013-0662-9.

Wong, K.-C., and J.E. Moses-Hall. 1998. On the relative importance of the remote and local wind effects to the subtidal variability in a coastal plain estuary. Journal of Geophysical Research 103:1,8393–18,404, https://doi.org/10.1029/98JC01476.

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