Disclaimer:
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.
Back to overview measures
This measure fits in with "The Long Term Vision 2030 for the Scheldt estuary" which presents a view on the preferred functioning of the system, accepted by both the Dutch and the Flemish government. The LTV states that further interventions should not endanger the preservation of the existing dynamic evolution of the multiple-channel estuary. One of the projects within the first action plan of the LTV is a further deepening of the navigation channel to guarantee optimal port accessibility. Based on the experiences at Walsoorden (2004-2006), one of the alternatives in the environmental impact assessment was to relocate sediment near several sandbars in the Western Scheldt. The main target of the project was to enable the deepening of the navigation channel, while conserving the multiple channel system, and creating new valuable areas (low dynamic areas, i.e. subtidal and intertidal areas with low currents). The initial goal of this measure is to ensure that the additional volumes produced by the capital dredging works could be kept within the estuary instead of exporting it out of the estuary, into the sea (Plancke et al. 2010) or storing it on land.
The study area is located in the Western Scheldt (the Netherlands), more specifically on the sandbars Walsoorden, Rug van Baarland, Hooge Platen Noord, and Hooge platen West. The cumulated area amounts 1,513 hectares. An extensive research program was executed to determine more into detail the relocation strategy at these new locations, using field measurements (both GPS-floats and sediment transport) and hydrodynamic numerical models. An extra model validation was performed for the flow velocities on the intertidal area of the sandbars, to improve the correspondence of the patterns of ecological valuable ecotopes. Also different disposal techniques were studied: traditional disposal technique and diffuser technique. Based on this research, a site specific relocation strategy was proposed for each location (Figure 2).
Beside the new relocation sites near sandbars, the current (2010) disposal license will include larger relocation zones in the secondary channels and in the deeper parts of the navigation channel (Plancke et al. 2010). This will allow the Maritime Access Division (Flemish government), responsible for executing the dredging and relocation works, to anticipate to morphological evolutions in the estuary and adapt the relocation strategy within the limitations of the disposal license.
DETAILS per sandbar
1) For the Walsoorden sandbar, the relocation strategy aims at creating a subtidal macro-dune which will migrate towards the sandbar under influence of the flood-dominated currents (Plancke et al. 2010). This macro-dune will be created using both the traditional disposal technique and the diffuser technique. A total amount of 6.5 million cubic metres of sandy sediments will be relocated at this location over a period of 5 years. This measure would increase the conservation of the multiple channel system by improving the separation between the current between ebb- (Zuidergat “2”) and flood channel (Schaar van Waarde “3”) (Figure 3). Additionally, the self-eroding capacity of the current upstream the “drempel van Hansweert” will increase, so that the dredging effort at this spot will decrease. The third and last effect would be the decreasing current velocity in shallow water round and above the sandbar, which will increase the ecological value of the area.
2) Near Rug van Baarland the relocation strategy aims at constructing a sand spit near the southern tip of the sandbar. This new sand spit, in combination with the existing sand spit in the northern part, aims for the creation of an underwater barrier reducing the currents between the barrier and the sandbar, creating a low dynamic shallow water area (Plancke et al. 2010). In a second stage, the intertidal area will be expanded at the Western side of the sandbar, creating a low dynamic intertidal mudflat on the sandbar. A total amount of 5 million cubic metres of sandy sediments will be relocated here over a period of 5 years, mostly with the diffuser technique (Plancke et al. 2008).
3&4) For the Hooge Platen North the relocation strategy is similar to the Rug van Baarland and aims at constructing a sand spit. For the Hooge Platen West the relocation strategy is similar to the Walsoorden sandbar and aims at constructing a subtidal macro-dune. For both locations near the Hooge Platen, a total amount of 8,2 million cubic metres of sandy sediments will be relocated over a period of 5 years, both with the traditional disposal technique and with the diffuser technique (Plancke et al. 2010).
Starting situation (2010) of ecological valuable ecotopes at the four relocation areas (Table 1).
Table 1. Ecological valuable ecotopes at the four relocation areas, starting situation in 2010 (IMDC 2012)
Back to top
TIDE pilot 1: large scale execution “plaatrandstortingen” (2010), relocation of dredged sediment to shallow water areas near sandbars
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.
Measure description
GENERALThis measure fits in with "The Long Term Vision 2030 for the Scheldt estuary" which presents a view on the preferred functioning of the system, accepted by both the Dutch and the Flemish government. The LTV states that further interventions should not endanger the preservation of the existing dynamic evolution of the multiple-channel estuary. One of the projects within the first action plan of the LTV is a further deepening of the navigation channel to guarantee optimal port accessibility. Based on the experiences at Walsoorden (2004-2006), one of the alternatives in the environmental impact assessment was to relocate sediment near several sandbars in the Western Scheldt. The main target of the project was to enable the deepening of the navigation channel, while conserving the multiple channel system, and creating new valuable areas (low dynamic areas, i.e. subtidal and intertidal areas with low currents). The initial goal of this measure is to ensure that the additional volumes produced by the capital dredging works could be kept within the estuary instead of exporting it out of the estuary, into the sea (Plancke et al. 2010) or storing it on land.
The study area is located in the Western Scheldt (the Netherlands), more specifically on the sandbars Walsoorden, Rug van Baarland, Hooge Platen Noord, and Hooge platen West. The cumulated area amounts 1,513 hectares. An extensive research program was executed to determine more into detail the relocation strategy at these new locations, using field measurements (both GPS-floats and sediment transport) and hydrodynamic numerical models. An extra model validation was performed for the flow velocities on the intertidal area of the sandbars, to improve the correspondence of the patterns of ecological valuable ecotopes. Also different disposal techniques were studied: traditional disposal technique and diffuser technique. Based on this research, a site specific relocation strategy was proposed for each location (Figure 2).
Beside the new relocation sites near sandbars, the current (2010) disposal license will include larger relocation zones in the secondary channels and in the deeper parts of the navigation channel (Plancke et al. 2010). This will allow the Maritime Access Division (Flemish government), responsible for executing the dredging and relocation works, to anticipate to morphological evolutions in the estuary and adapt the relocation strategy within the limitations of the disposal license.
DETAILS per sandbar
1) For the Walsoorden sandbar, the relocation strategy aims at creating a subtidal macro-dune which will migrate towards the sandbar under influence of the flood-dominated currents (Plancke et al. 2010). This macro-dune will be created using both the traditional disposal technique and the diffuser technique. A total amount of 6.5 million cubic metres of sandy sediments will be relocated at this location over a period of 5 years. This measure would increase the conservation of the multiple channel system by improving the separation between the current between ebb- (Zuidergat “2”) and flood channel (Schaar van Waarde “3”) (Figure 3). Additionally, the self-eroding capacity of the current upstream the “drempel van Hansweert” will increase, so that the dredging effort at this spot will decrease. The third and last effect would be the decreasing current velocity in shallow water round and above the sandbar, which will increase the ecological value of the area.
2) Near Rug van Baarland the relocation strategy aims at constructing a sand spit near the southern tip of the sandbar. This new sand spit, in combination with the existing sand spit in the northern part, aims for the creation of an underwater barrier reducing the currents between the barrier and the sandbar, creating a low dynamic shallow water area (Plancke et al. 2010). In a second stage, the intertidal area will be expanded at the Western side of the sandbar, creating a low dynamic intertidal mudflat on the sandbar. A total amount of 5 million cubic metres of sandy sediments will be relocated here over a period of 5 years, mostly with the diffuser technique (Plancke et al. 2008).
3&4) For the Hooge Platen North the relocation strategy is similar to the Rug van Baarland and aims at constructing a sand spit. For the Hooge Platen West the relocation strategy is similar to the Walsoorden sandbar and aims at constructing a subtidal macro-dune. For both locations near the Hooge Platen, a total amount of 8,2 million cubic metres of sandy sediments will be relocated over a period of 5 years, both with the traditional disposal technique and with the diffuser technique (Plancke et al. 2010).
Starting situation (2010) of ecological valuable ecotopes at the four relocation areas (Table 1).
Table 1. Ecological valuable ecotopes at the four relocation areas, starting situation in 2010 (IMDC 2012)
| Ecotopes (2010) | Hooge Platen West | Hooge Platen Noord | Plaat van Walsoorden | Rug van Baarland |
| Low dynamic shallow habitat | 11.8 | 35.4 | 46.5 | 205.3 |
| Low dynamic low marsh | 6.5 | 32.1 | / | 2.8 |
| Low dynamic medium marsh | 27.4 | 224.2 | 30.6 | 36.0 |
| Low dynamic high marsh | / | 21.7 | 32.0 | 0.8 |
| Total | 45.7 | 313.4 | 109.1 | 244.9 |