OMES Research on the environmental effects of the SIGMA plan
Multidisciplinary study on the estuarine environment of the Sea Scheldt


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  • Due to the latest problems with water nuisance, the interest in the possible role of flooding areas along the Scheldt to protect the land against floods, has increased.
    A salt marsh is a flooding area. These lowlands can locally 'absorb' a big volume of water when waterlevels rise extremely. As a consequence of the flooding of these salt marshes, the waterlevel drops locally and even upstream. This way, the risks of flooding for adjacent plots is diminished.

      Kruibeke-Bazel-Rupelmonde will be the thirteenth Flood Controlled Area or FCA whitin the framework of the SIGMA-plan. In april 2001 already 12 FCA's covering a total surface of 533 ha, were in use. The flood controlled area Kruibeke-Bazel-Rupelmonde covers a surface of at least 600ha. The salt marshes of Kruibeke, Bazel and Rupelmonde developped a more diverse environment then the other flooding areas. Instead of muddy planes without trees, used as farmland, Kruibeke has creeks, lower lained tree rows, marshland with Birches, grasslands, and higher lain, forrested, sandy hills. The FCA's are only flooded at extreme high waterlevels. (cfr.Scheldeinformatiecentrum)

    schets van GOG Kruibeke-Basel-Rupelmonde, vloed

    Flood controlled area of Kruibeke-Basel-Rupelmonde at High tide
    (Bron:Vlaamse gemeenschap)

    schets van GOG Kruibeke-Basel-Rupelmonde, springtij

    Flood controlled area of Kruibeke-Basel-Rupelmonde at Leap tide
    (Bron: Vlaamse gemeenschap)

    Flooding areas are not only interesting to control high waterlevels, they also contribute to the total surface of nature reserve. Due to the controlled sluice-system, creating a reduced tide in the flooding area, a typical vegetation of marshland with reed, willows and pioneers can develop. In this way the tested reduced tide-system will contribute to an increase in natural value of the flooding area. Within OMES a reduced flooding area is monitored:
    Experiments were set up to monitor the effects of a reduced tide on the Flood controlled areas.

    MESOCOSM experiments_________________________________________________________________

    click to enlarge
    reed growth Wilrijk mesocosm Wilrijk mesocosm mesososm Kruibeke sedimentpatch Kruibeke

    On the Wilrijk Campus, two experimental set-ups were exposed to a different tide-system: 'reduced tide' en 'natural tide'. The difference between the development of reed (Phragmatis australis) in the two set-ups was investigated by monitoring the development of the rootsystem, the length, width and leaf development of shoots. The evolution of sediment texture and the flooding frequency were registered as well.

    At Kruibeke an experimental set-up was positioned in the Scheldt river. The uptake of heavy metals at this mesocosm and the evolution of sediment texture were the main investigated variables.


    ...Lippenbroek is a pilot project focusing on safety, ecology and the development of a new ecosystem...

    More information on Lippenbroek:

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    The area is developped as a FCA-CRT area. Lippenbroek is surrounded by ringdykes, has a FCA-dyke or Flood Control Area and a CRT-sluice or Controlled Reduced Tide connecting the Scheldt river.

      De FCA-dyke is a lowered dyke allowing flooding of an area when waterlevels reach extreme high levels. In this way, other plots are protected against the flood.

    click for detail

      The in-and outflow of Scheldt water into the flooding area is controlled by a CRT-sluice(Controled Reduced Tide). The CRT-sluice has an in-and outflow positioned at different hights, this enhances a controlled reduced tide from up to 10 centimeters: the area floods at high tide and empties at low tide. The sluice controls the amount of water that flows into Lippenbroek at high tide. Grafiek

      click to enlarge


    Lippenbroek was sampled intensively in 2006 and 2007.

      Temporal variation= 4 seasons
      Spatial variation= between stations (horizontal)& between different depth layers in the sediment(vertical)


    The different components sampled within the OMES project are a good representation of the Lippenbroek ecosystem.


    The waterquality at Lippenbroek is monitored by the University of Antwerp, Research group Ecosystem managment (ECOBE).

    Basic waterquality parameters such as PH, Nitrates,Nitrites, Ammonium, BOD, Oxygen, Turbidity,...are measured in tidal lakes, from bridges and at the sluice. Current velocity is also measured at the in- and outflow of the sluice.

    In the tidal lakes the Université libre de Bruxelles, ULB monitors the light parameters, turbidity and suspended matter.

    monitoring at bridges monitoring at sluice monitoring of tidal lakes


    The benthic species are monitored by the University of Antwerp, Research group Ecosystem managment (ECOBE).

    For a period of two years , the benthos will be sampled seasonally at different stations in Lippenbroek, as well as at different depths in the bottom. The benthos species composition will be compared between Lippenbroek stations and adjacent reference sites at the Scheldt estuary.
    Different environmental variables are taken. Details

    sampling Lippenbroek sites Scheldt estuary reference sites


    The University of Ghent, Protistology and Aquatic Ecology (PAE) monitors the phytoplankton and phytobenthos at tidal lakes and developped swales.

    The phytoplankton is samples in four 13 hours-campaigns. Watersamples are taken from a central bridge. Pigments are filtered in the field and analysed with High Performance Liquid Chromatography. In summer the sampling of four extra sites is foreseen.
    In April, May, July, September and October the phytobenthos is sampled using contact cores with fluid nitrogen. The Phytobenthos is analysed using microscopes or by field observation.

    A first striking observation is the fast colonisation of Vaucheria, filamentous cyanobacteria and both planktonic and benthic diatoms.

    sampling cores with frozen nitrogen Phytobenthos

    FISH FAUNA___________________________________________________________________________________________________________

    Monitoring of the fish fauna is organized by the University of Antwerp, Research group Ecosystem managment(ECOBE). The fish fauna is sampled using fish traps at creeks and swales.  catching fish sample analysis


    The university of Antwerp, Research group Ecosystem managment (ECOBE) is is responsible for the monitoring of the sedimentation processes.

    Sedimentation processes are common at Lippenbroek because of its reduced tide system.
    The monitoring is executed at 50 sites within the Lippenbroek area and at eight adjacent sites at the Scheldt estuary.

    Sedimentation Sampling sites Creek development

    Three methods are used to monitor sedimentation:

    • Sediment Elevation Table(SET): 13 set-ups, measurement every two months Details
    • Horizon Markers (HM): 33 set-ups, measurement every two months ; using a perforated plate and kaoline clay. Details
    • Sediment Traps (ST): 58 set-ups , 13-hours measurement Details

    Next to these parameters the morfological development of the creek system is monitored every six months by:

    • Planimetric position of creeks
    • Length profiles of creeks
    • cross section profiles of creeks


    The influence of bioturbation by benthic species on the bottom structure is estimated by experimental research by the University of Antwerp, Research group Ecosystem managment (ECOBE) & Université Paul Sabatier, Laboratoire d'Ecologie des Hydrosystèmes.

    The activities of benthos varies from sediment reworking to building of tubes and burrows creating a bio-irrigation in the sediment.

    perspective bioturbation processes experiment
    Bioturbation can be divided into tree groups:

    • Biodiffusion: material on the surface is transported to the deeper bottom layers.
    • Conveyer belt feeding: material in the sediment is transported to the surface.
    • Downward non local transport: material is transported by the water that flows into the burrows and tubes.

    For a period of two years, experiments are executed on three sites at Lippenbroek.
    Cores are pushed into the sediment. On the surface of each core a frozen fluorescent microsphere cake is laid.
    After 15 days the cores are extracted, divided into nine depth layers. The Laboratoire d'Ecologie des Hydrosystèmes, Université Paul Sabatier registers the amount of microsperes at each layer. The benthic species of each layer is identified and counted by the University of Antwerp, ECOBE.

    SUSPENDED MATTER____________________________________________________________________________________________________

    The transport of sediment and suspended matter is monitored by the University of Brussels, Faculty Hydrology and Water engineering. flocs transport

    OMES is a project funded by the Flemish Government Waterwegen en zeekanaal NV; Afdeling Zeeschelde
    Web contact: Annelies Goffin
    Hosted by the Flanders Marine Institute (VLIZ)