Ocean Dynamics

, Volume 61, Issue 2–3, pp 203–215 | Cite as

Fine sediment transport by tidal asymmetry in the high-concentrated Ems River: indications for a regime shift in response to channel deepening

Article

Abstract

This paper describes an analysis of the observed up-river transport of fine sediments in the Ems River, Germany/Netherlands, using a 1DV POINT MODEL, accounting for turbulence-induced flocculation and sediment-induced buoyancy destruction. From this analysis, it is inferred that the net up-river transport is mainly due to an asymmetry in vertical mixing, often referred to as internal tidal asymmetry. It is argued that the large stratification observed during ebb should be attributed to a profound interaction between turbulence-induced flocculation and sediment-induced buoyancy destruction, as a result of which the river became an efficient trap for fine suspended sediment. Moreover, an asymmetry in flocculation processes was found, such that during flood relative large flocs are transported at relative large flow velocity high in the water column, whereas during ebb, the larger flocs are transported at smaller velocities close to the bed—this asymmetry contributes to the large trapping mentioned above. The internal tidal asymmetry and asymmetry in flocculation processes are both driven by the pronounced asymmetry in flow velocities, with flood velocities almost twice the ebb values. It is further argued that this efficient trapping is the result of a continuous deepening of the river, and occurs when concentrations in the river become typically a few hundred mg/l; this was the case during the 1990 survey analyzed in this paper. We also speculate that a second regime shift did occur in the river when fluid mud layers become so thick that net transport rates are directly related to the asymmetry in flow velocity itself, probably still in conjunction with internal asymmetry as well. This would yield an efficient mechanism to transport large amounts of fine sediment far up-river, as currently observed.

Keywords

Tidal asymmetry Fine suspended sediment Turbulence-induced flocculation Sediment-induced buoyancy destruction High concentrations Ems River 

Notes

Acknowledgements

I would like to acknowledge my colleague Dr. Bas Van Maren for his valuable comments on an earlier draft of the manuscript. I also like to thank Dr. Stefan Talke for making available Fig. 3.

References

  1. Allen GP, Salmon JC, Bassoullet P, Du Penhoat Y, De Grandpre C (1980) Effects of tides on mixing and suspended sediment transport in macrotidal estuaries. Sed Geol 26:69–90CrossRefGoogle Scholar
  2. Cleveringa J (2008) Evolution of sediment volume Ems-Dollard and eastern Dutch Wadden Sea—summary of knowledge and data. Alkyon, report A2274, Emmeloord, The Netherlands (in Dutch)Google Scholar
  3. De Deckere EMGT, Kornman BA, Staats N, Termaat GR, De Winder B, Stal LJ, Heip CHR (2002) The seasonal dynamics of benthic (micro)organisms and extracellular carbohydrates in an intertidal mudflat and their effect on the concentration of suspended sediment. In: Winterwerp JC, Kranenburg C (eds) Fine sediment dynamics in the marine environment, Proceedings in Marine Science, vol 5. Elsevier, Amsterdam, pp 429–440CrossRefGoogle Scholar
  4. De Jonge VN (2007) Biological processes in the Ems estuary. Presentation at the LOICZ workshop on the Ems River, February, 2007, Emden, Germany (paper in preparation)Google Scholar
  5. Dickhudt PJ, Friedrichs CT, Schaffner LC, Sanford LP (2009) Spatial and temporal variation in cohesive sediment erodibility in the York River estuary: a biologically-influenced equilibrium modified by seasonal deposition. Mar Geol 267:128–140CrossRefGoogle Scholar
  6. Dronkers J (2005) Dynamics of coastal systems. World Scientific, Advanced Series on Ocean Engineering – Volume 25Google Scholar
  7. Dyer KR (1997) Estuaries: a physical introduction. Wiley, ChichesterGoogle Scholar
  8. Friedrichs CT, Armbrust BA, de Swart HE (1998) Hydrodynamics and equilibrium sediment dynamics of shallow, funnel-shaped tidal estuaries. In: Dronkers J, Scheffers M (eds) Physics of estuaries and coastal seas. Balkema, Rotterdam, pp 315–328Google Scholar
  9. Jay DA, Musiak JD (1996) Internal tide asymmetry in channels: origins and consequences. In: Pattiaratchi C (ed) Mixing processes in estuaries and coastal seas. American and Geophysical Union Coastal and Estuarine Sciences Monograph, pp 219-258Google Scholar
  10. Le Hir P (1997) Fluid and sediment ‘integrated’ modeling application to fluid mud flows in estuaries. Cohesive Sediments. 4th Nearshore and Estuarine Cohesive Sediment Transport Conference INTERCOH ’94Google Scholar
  11. Loose M (2008) Morphodynamics Suriname River: study of mud transport and impact due to lowering the fairway channel. Delft University of Technology, Civil Engineering and Geosciences, MSc-thesis 2008-09-04Google Scholar
  12. Nichols M, Poor G (1967) Sediment transport in a coastal plain estuary. ASCE J Waterways Harbors WW4(93):83–95Google Scholar
  13. Postma H (1961) Sediment transport and sedimentation of suspended matter in the Dutch Wadden Sea. Neth J Sea Res 1:148–190CrossRefGoogle Scholar
  14. Pritchard DW (1952) Salinity distribution and circulation in the Chesapeake Bay Estuarine System. J Mar Res 11:106–123Google Scholar
  15. Schrottke K, Bartholomä A (2008) Detaillierte Einblicke in die ästuarine Schwebstoffdynamik mittels hochauflösender Hydroakustik. Tagungsband zum Seminar Ultraschall in der Hydrometrie: neue Technik; neuer Nutzen; FgHW/DWA, Koblenz, June 2008, 75-82Google Scholar
  16. Scully ME, Friedrichs CT (2003) The influence of asymmetries in overlying stratification on near-bed turbulence and sediment suspension in a partially mixed estuary. Ocean Dyn 53:208–219CrossRefGoogle Scholar
  17. Scully ME, Friedrichs CT (2007) Sediment pumping by tidal asymmetry in a partially-mixed estuary. J Geophys Res 112:C07028. doi: 10.1029/2006JC003784 Google Scholar
  18. Stelling GS (1995) Compact differencing for stratified surface flow. In: Advances in Hydro-Science and –Engineering, II (A) 378-386, Tsinghua University Press, Beijing, ChinaGoogle Scholar
  19. Talke SA, De Swart HE, Schuttelaars HM (2009) Feedback between residual circulation and sediment distribution in highly turbid estuaries: an analytical model. Continental Shelf Research. doi: 10.1016/j.csr.2007.09.002
  20. Van Leussen W (1994) Estuarine macroflocs – their role in fine-grained sediment transport. PhD-thesis, Utrecht University, The NetherlandsGoogle Scholar
  21. Van Leussen W (2009) Macroflocs, fine-grained sediment transports and their longitudinal variations in the Ems estuary. Ocean Dynamics, in pressGoogle Scholar
  22. Van Rijn LC (1993) Principles of sediment transport in rivers, estuaries and coastal seas. AQUA, The NetherlandsGoogle Scholar
  23. Winterwerp JC (1998) A simple model for turbulence induced flocculation of cohesive sediment. IAHR, J Hydraul Eng 36(3):309–326CrossRefGoogle Scholar
  24. Winterwerp JC (2001) Stratification of mud suspensions by buoyancy and flocculation effects. J Geophys Res 106(10):22,559–22,574CrossRefGoogle Scholar
  25. Winterwerp JC (2002) On the flocculation and settling velocity of estuarine mud. Cont Shelf Res 22:1339–1360CrossRefGoogle Scholar
  26. Winterwerp JC (2006) Stratification effects by fine suspended sediment at low, medium and very high concentrations. Geophysical Research 111(C05012):1–11Google Scholar
  27. Winterwerp JC, Van Kesteren WGM (2004) Introduction to the physics of cohesive sediment in the marine environment. Elsevier, Developments in Sedimentology, 56Google Scholar
  28. Winterwerp JC, Wang ZB, Van der Kaaij T, Verelst K, Bijlsma A, Meersschaut Y, Sas M (2006) Flow velocity profiles in the Lower Scheldt estuary. Ocean Dyn 56:284–294CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  1. 1.Delft University of Technology, Environmental Fluid MechanicsDelftThe Netherlands
  2. 2.Deltares-WL|Delft HydraulicsDelftThe Netherlands

Personalised recommendations