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

BACKGROUND

English |  Nederlands | 

SIGMA plan_______________________________________________________________________

Overtroming in 1953, Bornem beukende golven in storm van 1953 Overstroming in 1976,Ruisbroek dijkbreuk in 1953 dijkbreuk in 1976, Ruisbroek

In 1953 the biggest flooding of the 20th century occurred. The combination of springtide and a strong Northwestern wind created big breaking waves and a rise of the waterlevel. These waves broke through the dykes and flooded the land.
The Netherlands responded with the Delta-plan. The Belgian government repaired the damage, but took no further steps to protect the land against floods. It was after a second big flooding in 1976, that the Sigma plan was constructed to protect the local residents, living on the banks of the Sea Scheldt, and its tributaries against floods. In this way three basic principles are linked to the river: Safety, Nature and Accessibility.

The original plan describes three solutions:

  • elevation of dykes along the Scheldt, Durme, Nete, Zenne and Rupel
  • construction of flood controlled areas or FCA's
  • storm barriers at Oosterweel and Over-Scheldt
"Space for the river" seemed the best assessment and a combination of dyke construction and flooding areas was accepted.

The Sigma plan was obliged to give attention to the effects of the plan on the environment. The loss of biotopes and diversity is a fact. Therefore, several nature conservation projects have been launched. New protected areas are created and existing nature reserves managed. Nature protecting programs are established such as the extension of the ZWIN area, the habitat and bird Directives are respected,…

Due to the water nuisance in 1993-94, the Flemish government approved an urgent program to control the water. This plan needed to follow an integrated vision on the management of river systems and therefore an AMIS note was constructed (General Environmental Impact study). This study did not only gave attention to possible environmental risks, it also formulated advice on how a positive approach can decrease the negative effects and enhance a positive environmental evolution. It emphasised the importance of ecosystem modelling and monitoring.

This AMIS note was the start of a multidisciplinary approach on the understanding of the Scheldt ecosystem and the possible role of flooding areas in the protection of the land against floods cfr OMES project. This research project, that resulted in a data system, an ecosystem model of the Scheldt and different habitat models, was a firm scientific base for an initial program on the recovery of the Seascheldt. The water quality of the Scheldt already was a hot topic. In spite of the bad reputation as a heavy polluted river, it was only recent that the water quality of the Scheldt became an issue. In 1971 physico-chemical measurements were started. Different institutes started their own campaigns, but no coherent data system as for the Dutch data on the Westerscheldt was constructed. The need for an integrated en coordinated research and monitoring program seemed to be launched and the Sigma plan needed ecological and scientific support. The OMES project brought together the experience of scientist with different background to create one integrated vision on the estuarine ecosystem of the Scheldt.

OMES project______________________________________________________________________

First phase : 1995-1998

  • Biogeochemical cycles of C, N and water balances details
  • Denitrification of the intertidal sediments and water quality parameters details
  • Ecology of macrozoöbenthos at the Sea Scheldt details
  • Ecology of fish populations at the Sea Scheldt details
  • Ecological modelling of the Sea Scheldt estuary and biogeochemistry of the rhizosphere details
  • Geomorphology en logistic support details
  • Hydrodynamica details
  • Characterisation of organic matter and plankton of the Sea Scheldt details
  • Pedologic characteristics of salt marches and alluvial plains details
  • Sediment transport en sedimentation processes of the Scheldt, between Zandvliet and Ghent details
  • Study on microplankton and the microbial "loop" of the Sea Scheldt details
  • Ecology of vegetation on alluvial plains and salt marches details
  • Water balance details
  • Water quantity and logistic support details

Second phase: Integration, 1999

    The knowledge of the different processes within the biogeochemical cycles of C and N, the role of vegetation and benthos, the pedology and sedimentology,... knew an important increase due to the first phase of OMES. Nevertheless an integrated vision of these aspects was lacking. A first step to integrate the data, concerned the knowledge of the water quality and it's evolution. A datasonde at Kruibeke registered since 1996 the water quality and these data were compiled with all the existing data available from other sources!

Thirth phase: Effects of dredgings and harbour expansion on the environment, 2002-2003

  • The basic water quality in the Flemish part of the Scheldt estuary details
  • Study on the effects of water quality and tide on the flooding areas of the Flemish part of the Scheldt estuary: two mesocosmos experiments details
  • The C cycle of the Flemish part of the Scheldt estuary details
  • Primary production in the Flemish part of the Scheldt estuary details
  • Sedimentology of the Flemish part of the Scheldt estuary details
  • Study on the lateral input of the Flemish part of the Scheldt estuary details
  • The phytoplankton of the Flemish part of the Scheldt estuary details
  • The zooplankton of the Flemish part of the Scheldt estuary details

Fourth phase: Effects of dredgings and harbour expansion on the environment, 2004-2007 and prolonged until 2009

  • The basic water quality in the Flemish part of the Scheldt estuary details
  • The C cycle of the Flemish part of the Scheldt estuary details
  • Primary production in the Flemish part of the Scheldt estuary details
  • Sedimentology of the Flemish part of the Scheldt estuary details
  • The phytoplankton of the Flemish part of the Scheldt estuary details
  • The zooplankton of the Flemish part of the Scheldt estuary details
  • Study on the vegetation under tidal range in the Flemish part of the Scheldt estuary: 2 mesocosmos experiments and experimental area Lippenbroek 'details'
  • Evaluation and update of the OMES database, concerning the data of the Flemish part of the Scheldt estuary details

MOSES ecosystem model____________________________________________________________

details

In previous years, different ecosystem models for the Scheldt estuary were designed. Within this research the MOSES-model (Model of the Scheldt ecosytem) (Soetaert & Herman, 1993) will be further developped. This model originates from the Dutch Institute for Ecological research- Centre for Estuarine and Marine Ecology (NIOO-CEMO) at Yerseke. The model formulates:
submodel structure of MOSES
  • transport of water
  • dissolved and suspended matter
  • primary production
  • pelagic and benthic algae
  • autotrophic bacteria
  • bacterial mineralisation(aerob and anaerob)
  • grazing by zooplanktonic and benthic filterfeeders
  • bottom mineralisation
  • decomposition by benthic deposit feeders
The model describes the important cycles of carbon, nitrogen and silicium of the estuary. The geographic range is limited to zone between the estuary mouth (Vlissingen-Breskens) and Rupelmonde. Within the OMES project the geographic range of the ecosystem model will be expanded up to the whole tidal zone of the Scheldt.


  • Soetaert, K.; Herman, P.M.J. (1995). Nitrogen dynamics in the Westerschelde estuary (SW Netherlands) estimated by means of the ecosystem model MOSES. Hydrobiologia 311: 225-246 details

  • Soetaert, K.; Herman, P.M.J. (1995). Carbon flows in the Westerschelde estuary (The Netherlands) evaluated by means of an ecosystem model (MOSES). Hydrobiologia 311: 247-266 details

  • Soetaert, K. et al. (1992). MOSES: model of the Scheldt estuary: ecosystem model development under SENECA. NIOO-CEMO: Yerseke, The Netherlands. 67 pp details

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)