Table of contents

1. A synthesis onthe assessment of an alternative disposal strategy to serve sustainability in the Scheldt estuary ir. Frederik RooseFlemish Government, Mobility and Public Works Department, Maritime Access Division, Belgium ir. Yves Plancke, ir. Stefaan IdesFlemish Government, Mobility and Public Works Department, Flanders Hydraulics Research, Belgium Departement Mobiliteit en Openbare Werken Maritieme Toegang

2. Table of contents • Long Term Vision (2001) • Alternative disposal strategy (2001) • Feasibility study (2002-2003) • First pilot study (2004-2006) • Second pilot study (2006-2008) • Large-scale application • Conclusion Departement Mobiliteit en Openbare Werken Maritieme Toegang

3. 1. Long Term Vision (2001) = a framework for sustainability Focusses on 3 utility functions: • Safety against flooding • Navigable access to harbours Morphology • Naturalness • Conservation of multiple channel system • Contribution by well-considered dredging/disposal strategy } Departement Mobiliteit en Openbare Werken Maritieme Toegang

4. 2. Alternative disposal strategy (2001) • Morphological dredging (PAET): dredging as a tool to preserve morphological diversity • Pilot project: reshaping Walsoorden sandbar Departement Mobiliteit en Openbare Werken Maritieme Toegang

5. 3. Feasibility study (2002 – 2003) • Field measurements (dGPS-floats, sediment transport) • Physical scale model (hydrodynamics and sediment transport): • most suitable location for disposal test • a large amount of sediment can be stored • Numerical model (hydrodynamics): • Increase of flow velocity in channels with reshaped sandbar => Promising results Departement Mobiliteit en Openbare Werken Maritieme Toegang

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7. 4 First pilot study (2004 – 2006) Departement Mobiliteit en Openbare Werken Maritieme Toegang

8. 500.000 m³ • Diffuser • Evaluation criteria • Monitoring program of 1 year 4.1 Setup of the 1st pilot study Departement Mobiliteit en Openbare Werken Maritieme Toegang

9. Rapid detection of possible negative evolutions, by • Repeated multibeam echo sounding surveys • Occasional LiDAR-flights • Volume calculations in control zone 4.2 Morphological monitoring program Departement Mobiliteit en Openbare Werken Maritieme Toegang

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11. Rapid detection of possible negative evolutions, by • Repeated multibeam echo sounding surveys • Occasional LiDAR-flights • Volume calculations in control zone 4.2 Morphological monitoring program Departement Mobiliteit en Openbare Werken Maritieme Toegang

12. => 1 year after disposal test: more than 80% of disposed sediment remains within control zone Departement Mobiliteit en Openbare Werken Maritieme Toegang

13. Detect changes in macrobenthos community • essential role in estuarine ecology • sensitive to environmental changes • Subtidal: BACI-design (Before – After – Control – Impact) • Intertidal: changes in particle size distribution, silt content and macrobenthos community • => None of the observed effects are significant or can be distinguished from long term trends 4.3 Ecological monitoring program Departement Mobiliteit en Openbare Werken Maritieme Toegang

14. A well-considered disposal management may contribute to a sustainable morphological management • The disposed sediment is stable enough to allow the usual disposal technique 4.4 Conclusions from 1st pilot study Departement Mobiliteit en Openbare Werken Maritieme Toegang

15. 5 Second pilot study (2006 – 2008) Departement Mobiliteit en Openbare Werken Maritieme Toegang

16. phase 1: 500.000 m³ • phase 2: 770.000 m³ • Direct release from dredger • Long-term monitoring program • Succes when disposed sediment remains or moves towards sandbar 5.1 Setup of the 2nd pilot study Departement Mobiliteit en Openbare Werken Maritieme Toegang

17. Rapid detection of possible negative evolutions, by • Repeated multibeam echo sounding surveys • Occasional LiDAR-flights • Volume calculations in control zone 5.2 Morphological monitoring program Departement Mobiliteit en Openbare Werken Maritieme Toegang

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20. Rapid detection of possible negative evolutions, by • Repeatedly multibeam echo sounding surveys • Occasional LiDAR-flights • Volume calculations in control zone 5.2 Morphological monitoring program Departement Mobiliteit en Openbare Werken Maritieme Toegang

21. => Sediment transport towards Walsoorden sandbar Departement Mobiliteit en Openbare Werken Maritieme Toegang

22. => After 2.5 years no significant negative effects have been related to the pilot projects 5.3 Ecological monitoring program Departement Mobiliteit en Openbare Werken Maritieme Toegang

23. Current disposal strategy handles maintenance dredging material • Application of alternative disposal strategy is necessary for handling sediment from enlargement • => 3 additional disposal locations near sandbars 6 Large scale application Departement Mobiliteit en Openbare Werken Maritieme Toegang

24. Long Term Vision: acknowledges human impact, further interventions should not endanger preservation of estuary • Morphological diversity can be attained by a well-considered morphological management • Combination of study tools is necessary for a decent assessment: a feasibility study and two pilot projects confirm alternative disposal strategy • Large-scale application • Other tools towards morphological diversity in the Scheldt estuary ?? 7 Conclusion Departement Mobiliteit en Openbare Werken Maritieme Toegang