Areas close to the Scheldt are high-risk zones for flooding. In 1976 the dyke of Ruisbroek broke resulting in the flooding of one third of the Province of Antwerp. Following these events, a new plan arose to protect the basin of the Zeeschelde against flooding: the Sigmaplan. In the plan the same safety measurements are taken into account as those on the Western Scheldt (Deltaplan), which essentially means a chance of storm tide in 1/100 year, a water level of 9.05m TAW in Antwerp.
After a new storm in 1994, causing the highest water levels ever measured on the Zeeschelde, a disaster and emergency program was accepted. Its implementation had to fit within a full vision on the management of watercourses. This led to an environmental impact study (AMIS – Algemene Milieu Impact Studie) for the Sigmaplan and was followed by Research on the environmental effects of the Sigmaplan (OMES – Onderzoek Milieu – Effecten Sigmaplan).
The OMES project aims to actualize the biogeochemical knowledge of the Zeeschelde and to extend it where possible. In continuation of these studies a large monitoring program was set up: Research on the impact of the Sigma plan, dredging activities and harbor expansion in the Zeeschelde on the environment (named OMES). An estuary is a very complex system, influenced by different (human) factors. In the new vision, in which safety, accessability an naturality is handled together, extensive knowledge of the estuarine ecosystem is necessary.
OMES has become an important instrument for scientific research in the estuary. Monitoring can only be really valuable when measurements are systematic, and taken over long periods, in order for long term effects to be distinguishable from short term effects. This also meant the dataset could not contain any gaps. OMES has had a consistent dataset since december 1995, for which monthly samples were taken on fixed stations and by a fixed schedule. Some (station) adaptations were made, but no interruptions were made in the measurement pattern.
Early 2008, MONEOS was presented: a program for integrated monitoring of the Scheldt Estuary in The Netherlands and Flanders. The program defines the the desirable monitoring to describe the evolutions in the Scheldt and to identify causal relationships. This is essential to manage the estuary in a scientific manner. The monitoring contains several aspects of the ecosystem: hydro- and morphodynamics, diversity of habitats, physico-chemistry, ecological functioning and diversity of species. OMES monitors several of the physico-chemical and ecological monitoring of the Zeeschelde. In 2009, OMES and MONEOS were matched.
Since then, monitoring campaigns of OMES have 3 sampling days (on Monday, Tuesday and Wednesday).
In the first 3 phases of OMES an attempt to understand and model the role of the intertidal zone on the functioning of the ecosystem was undertaken. Modelling and data gathering were the main activities and a detailed dataset on chemical, biological and ecological data of the Scheldt is since then available. With this multidisciplinary knowledge of the Scheldt estuary, it would be possible to visualize possible alternatives of the Sigma dykes that are still under construction and to develop a suitable water management protocol. The 4th phase of OMES started in 2006 and continued the monitoring of the third fase. This phase specifically focused on the possible role of controlled flooding areas to secure the land of flooding and protect the functioning of the estuarine environment.
A 5th phase continues the monitoring of the Scheldt. The project is integrated in the new monitoringprogram MONEOS from O&M, a collaboration between the Dutch and Flemish government aimed at a coördinated and integrated monitoring of the Scheldt. More information about OMES is in MONEOS.
The different phases within OMES:
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 expertise on the different processes within the biogeochemical cycles of C and N, the role of vegetation and benthos, the pedology and sedimentology,... largely increased as a result of the first phase of OMES. Nevertheless an integrated vision of these aspects was lacking. A first step in integrating the data was concerned with the water quality and its evolution. Data from a datasonde at Kruibeke, which registered the water quality from 1996 on, was therefore compiled with the existing data available from other sources.
Thirth phase: Effects of sigmaplan, 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 sigmaplan, 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
- Evaluation and update of the OMES database, concerning the data of the Flemish part of the Scheldt estuary details
Fifth phase within MONEOS, 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
- Evaluation and update of the OMES database, concerning the data of the Flemish part of the Scheldt estuary details