Variability of the Mixing Zones and Estuarine Turbidity Maxima in the Elbe and Weser Estuaries

Kappenberg, J.; Grabemann, Iris

doi:10.2307/1352878

Cited by 47 publications

(28 citation statements)

References 11 publications

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“…In the Dutch and German part of the Wadden Sea, for example, an Tables 2 and 3 increase of 5 % in tidal marsh area was observed between two periods : /2001: /2007: (Bakker et al 1993Esselink et al 2009). Here, sediment deposition and accretion rates are often higher than the current sea-level rise (e.g.…”

Section: Changes In Tidal Marshes-differences Between Elevational Andmentioning

confidence: 99%

“…In tidal freshwater marshes, regressive succession of low marshes seems to be weakly related to decreases in MLW. This relationship might be explained by an increase in flow velocity, especially in the salinity zone of tidal freshwater marshes (Kappenberg and Grabemann 2001), which promotes erosional processes in marshes and tidal flats. Contrasting patterns in development from low to high marshes were found in anabranches of the tidal freshwater zone.…”

Section: Factors Influencing Succession Of Tidal Low Marshesmentioning

confidence: 99%

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Vegetation succession of low estuarine marshes is affected by distance to navigation channel and changes in water level

et al. 2016

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Climate change and engineering activities have modified the hydrology and morphology of estuaries. However, the potential effects of these modifications on vegetation succession in estuarine marshes are still poorly understood. Therefore, we studied temporal changes in tidal habitats of the Elbe estuary over a period of 30 years. We compared vegetation maps from 1980 to 2010 and calculated the change in area of habitats with respect to three salinity and three elevational zones. To analyze the direction of the temporal change, we differentiated between progressive and regressive succession. By using regression tree models (conditional inference trees), we identified the most influential factors determining progressive or regressive succession of low marshes. The total area of the estuarine tidal marshes at the Elbe increased by 2 % from 1980 to 2010, but changes were unequal among the salinity zones. In the salt and brackish zones, the area covered by high marshes increased substantially but decreased in the tidal freshwater zone, while that covered by low marshes decreased in all the salinity zones. Additionally, we determined high persistence of tidal flats and high marshes, whereas only 19 to 28 % of the low marshes found in 1980 remained in 2010. In salt and brackish marshes, more than two-thirds of the area that had been identified as low marshes in 1980 had progressively developed into high marshes. In contrast, 44 % of the area of low marshes in tidal freshwater marshes showed regressive succession back into tidal flats. The distance to the navigation channel was the main factor determining successional direction in salt and brackish marshes. Here, greater proximity to the channel was correlated with higher risk of regressive succession. In tidal freshwater marshes, we identified both the distance to the navigation channel and the situation on the river shore (i.e. inner bank, outer bank or straight bank) as the main factors for marsh succession. Here, considerable engineering activities in the channel had simultaneously decreased the mean low water level and increased the mean high water level between 1980 and 2010, which led to an increase in tidal amplitude. It is quite likely that these changes negatively modified marsh distribution, increased regressive succession and, thus, lowered the quality of tidal freshwater marshes.

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Section: Changes In Tidal Marshes-differences Between Elevational Andmentioning

confidence: 99%

Section: Factors Influencing Succession Of Tidal Low Marshesmentioning

confidence: 99%

Vegetation succession of low estuarine marshes is affected by distance to navigation channel and changes in water level

et al. 2016

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“…Field data collected in partially mixed and wellmixed estuaries reveal the presence of pronounced local maxima in SSC, when moving in both the longitudinal direction (Kappenberg and Grabemann 2001;Blake et al 2001;Lin and Kuo 2001;North et al 2004; Uncles et al 2006) and the lateral direction (Nichols 1972;Geyer et al 1998;Fugate et al 2007). Various models have been developed to explain the entrapment of sediments in specific areas.…”

Section: Introductionmentioning

confidence: 99%

Effect of bottom stress formulation on modelled flow and turbidity maxima in cross-sections of tide-dominated estuaries

2009

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A three-dimensional numerical model with a prognostic salinity field is used to investigate the effect of a partial slip bottom boundary condition on lateral flow and sediment distribution in a transect of a tidally dominated channel. The transect has a symmetrical Gaussian cross-channel bottom profile. For a deep, well-mixed, tidally dominated channel, partial slip decreases the relative importance of Coriolis deflection on the generation of cross-channel flow patterns. This has profound implications for the lateral distribution of residual salinity that drives the cross-channel residual circulation pattern. Transverse sediment transport, however, is always found to be governed by a balance between advection of residual sediment concentration by residual lateral flow on the one hand and cross-channel diffusion on the other hand. Hence, the changes in the cross-channel distribution of residual salinity modify the lateral sediment distribution. For no slip, a single turbidity maximum occurs. In contrast, partial slip gives a gradual transition to a symmetrical density distribution with a turbidity maximum near each bank. For a more shallow, partially mixed tidal channel that represents the James River, a single turbidity maximum at the left bank is found irrespective of the near-bed slip condition. In this case, semi-diurnal contributions to sediment distribution and lateral flow play an important role in cross-channel sediment transport. As vertical viscosity and diffusivity are increased, a second maximum at the right bank again exists for partial slip.

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“…In consequence, the transport and entrapment processes in the fresh-saltwater mixing region have been the subject of many studies for almost a century. The ETM is a well-documented feature and its widespread occurrence has been confirmed by studies in many estuaries: Chesapeake Bay (Schubel 1968), Columbia River (Gelfenbaum 1983;Jay and Musiak 1994), Demerara River (Postma 1967), Ems River (Postma 1967), Elbe River (Grabemann et al 1995(Grabemann et al , 1996Kappenberg and Grabemann 2001), Fly River (Wolanski et al 1995), Gironde Estuary (Allen et al 1980), Hudson River (Geyer et al 1998(Geyer et al , 2001Orton and Kineke 2001), Humber-Ouse-Trent (Uncles et al 2006), Kennebec Bay (Kistner and Pettigrew 2001), Mekong River (Wolanski et al 1996), Seine River (Avoine et al 1981;Brennon and Le Hir 1998), Tamar Estuary (Uncles et al 1985(Uncles et al , 1994Stephens 1989, 1993a,b), Tay River (Weir and McManus 1987), Weser River (Wellershaus 1981;Grabemann et al 1997), Winyah Bay (Patchineelam and Kjerfve 2004), and York River (Lin and Kuo 2001).…”

Section: Introductionmentioning

confidence: 80%

“…Furthermore, during certain tidal periods the entrainment-erosion capacity is too low to deplete the bed of mud. Examples of such cases are the Columbia River (Gelfenbaum 1983), Elbe River (Grabemann et al 1995;Kappenberg and Grabemann 2001), Fly River (Wolanski et al 1995), Gironde River (Allen et al 1980), Hudson River (Geyer 1993;Geyer et al 1998;Orton and Kineke 2001), Humber-Ouse-Trent (Uncles et al 2006), Mekong River (Wolanski 1996), Weser River (Wellershaus 1981;Schrottke et al 2006), Seine River (Brennon andLe Hir 1998, 1999;Le Hir et al 2001), Tamar River Stephens 1989, 1993a,b;Grabemann et al 1997), and York River (Lin and Kuo 2001).…”

Section: Introductionmentioning

confidence: 99%

The Effects of the Internal Flow Structure on SPM Entrapment in the Rotterdam Waterway

Nijs

Winterwerp

Pietrzak

2010

Journal of Physical Oceanography

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Field measurements are presented, which are the first to quantify the processes influencing the entrapment of suspended particulate matter (SPM) at the limit of saltwater intrusion in the Rotterdam Waterway. The estuarine turbidity maximum (ETM) is shown to be maintained by the trapping of fluvial SPM at the head of the salt wedge. The trapping process is associated with the raining out of fluvial SPM from the upper, fresher part of the water column, into the layer below the pycnocline. The dominant mechanisms responsible are baroclinic shear flows and the abrupt change in turbulent mixing characteristics due to damping of turbulence at the pycnocline. This view contrasts with the assumption of landward transport of marine SPM by asymmetries in bed stress. The SPM transport capacity of the tidal flow is not fully utilized in the ETM, and the ETM is independent of a bed-based supply of mud. This is explained by regular exchange of part of the ETM with harbor basins, which act as efficient sinks, and that the Rotterdam Waterway is not a complete fluvial SPM trap. The supply of SPM by the freshwater discharge ensures that the ETM is maintained over time. Hence, the ETM is an advective phenomenon. Relative motion between SPM and saltwater occurs because of lags introduced by resuspension. Moreover, SPM that lags behind the salt wedge after high water slack (HWS) is eventually recollected at the head. Hence, SPM follows complex transport pathways and the mechanisms involved in trapping and transport of SPM are inherently three-dimensional.

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Variability of the Mixing Zones and Estuarine Turbidity Maxima in the Elbe and Weser Estuaries

Cited by 47 publications

References 11 publications

Vegetation succession of low estuarine marshes is affected by distance to navigation channel and changes in water level

Vegetation succession of low estuarine marshes is affected by distance to navigation channel and changes in water level

Effect of bottom stress formulation on modelled flow and turbidity maxima in cross-sections of tide-dominated estuaries

The Effects of the Internal Flow Structure on SPM Entrapment in the Rotterdam Waterway

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