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The authors are solely responsible for the content of this report. Material included herein does not represent the opinion of the European Community, and the European Community is not responsible for any use that might be made of it.
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The relocation test as executed at the Walsoorden sandbar in 2004 showed the feasibility of morphological relocation at sandbars. This strategy could become part of a global approach of morphological management. Morphological relocation at sandbars is a creative solution to use dredged material to create positive effects (instead of the actual “get rid of the sediments”-principle). In addition, the sediment is relocated at a permanent location so it will less circulate throughout the system and possibly reduce the need for maintenance dredging.
An important critique on the relocation strategy is that it only tackles the effect of erosion, not the cause. However, this is crucial for a proper morphological management. The cause of the erosion (orientation of the flood currents towards the tip of the sandbar) should be investigated and solved within the philosophy of morphological management of the estuary (which would also have to include morphological dredging and modifying the hard bordering at some locations).
Other commonly known knowledge gaps are on the understanding of sediment transport pathways and resulting sedimentation and erosion patterns and on the inhabitation of benthic macrofauna of new shallow areas.
The successful results of the in situ test of 2004 formed a base for a new in situ test in 2006. With this test another relocation methodology was analysed: traditional “clapping” technique (Plancke and Ides 2007). This test will be discussed as a separate measure: Walsoorden pilot test part B 2006.
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Walsoorden pilot part A (2004): relocation of dredged sediment to a shallow water area at the edge of the Walsoorden sandbar
Table of content
- 1. Description of measure
- 1a. Measure description
- 1b. Monitoring
- 1c. Monitoring results
- 2. Execution of main effectiveness criteria
- 2a. Effectiveness according to development targets of measure
- 2b. Impact on ecosystem services
- 2c. Degree of synergistic effects and conflicts according to uses
- 3. Additional evaluation criteria in view of EU environmental law
- 3a. Degree of synergistic effects and conflicts according to WFD aims
- 3b. Degree of synergistic effects and conflicts according to Natura 2000 aims
- 4. Crux of the matter
- 5. References
Additional information
for this measure:
No further information available.
for this measure:
No further information available.
Crux of the matter
This first relocation test proved that the new relocation strategy is feasible. When relocating sediment near the Walsoorden sandbar, the sediment is stable. The planning phase was not an issue because it was integrated in the regular maintenance dredging activities. Also the implementation was not an issue because it was executed in an area that was already licenced for relocation of dredged material. Only for the use of the diffuser pontoon an extra licence had to be requested.The relocation test as executed at the Walsoorden sandbar in 2004 showed the feasibility of morphological relocation at sandbars. This strategy could become part of a global approach of morphological management. Morphological relocation at sandbars is a creative solution to use dredged material to create positive effects (instead of the actual “get rid of the sediments”-principle). In addition, the sediment is relocated at a permanent location so it will less circulate throughout the system and possibly reduce the need for maintenance dredging.
An important critique on the relocation strategy is that it only tackles the effect of erosion, not the cause. However, this is crucial for a proper morphological management. The cause of the erosion (orientation of the flood currents towards the tip of the sandbar) should be investigated and solved within the philosophy of morphological management of the estuary (which would also have to include morphological dredging and modifying the hard bordering at some locations).
Other commonly known knowledge gaps are on the understanding of sediment transport pathways and resulting sedimentation and erosion patterns and on the inhabitation of benthic macrofauna of new shallow areas.
The successful results of the in situ test of 2004 formed a base for a new in situ test in 2006. With this test another relocation methodology was analysed: traditional “clapping” technique (Plancke and Ides 2007). This test will be discussed as a separate measure: Walsoorden pilot test part B 2006.