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
The Walsoorden small-scale in-situ relocation test 2006 was a follow-up of the first, and successful, small-scale in-situ relocation test of 2004. The 2006 test was different in that way that another relocation technique was studied: traditional “clapping” technique (instead of the diffuser). The diffuser has the advantage to allow a very precise relocation, the clapping technique on the other hand can realise a higher time-efficiency in execution, using the flood current to transport the material towards the sandbar.
The traditional dumping or “clapping” technique involves the hopper of the dredging vessel being opened so that the material can sink to the bottom (Figure 3). Compared to the 2004 test with the diffuser technique, another relocation location had to be chosen further away from the sandbar because the draught of the dredging vessel is greater than that of the pontoon. The new area was not only much deeper but also characterised by higher dynamics, both hydrodynamic (currents) as morphodynamic (sediment transports).
The 2006 relocation test occurred in two phases: relocation of 500,000 m³ in the first phase (phase A: January – March 2006) and another 900,000 m³ in the second phase (phase B: September 2006 – March 2007). These relocations were carried out within continuous maintenance dredging works in the Western Scheldt. Therefore a larger spreading in time is found for this test compared to the test of 2004, where the relocations were concentrated in time.
The morphological target was again to test the stability of the relocated material (including the wanted transportation of the relocated material towards the sandbar). The relocation test was however again small-scale (1,400,000 m³) and set-up as a research project. The ecological monitoring was executed in order to detect possible effects of the relocation test on the local ecology.
Back to top
Walsoorden pilot part B (2006): 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.
Measure description
This project fits in with "The Long Term Vision 2030 (LTV) for the Scheldt estuary" which presents a view on the preferred functioning of the system, accepted by both the Dutch and the Flemish government. One of the main questions considered in the LTV was where to relocate the large volumes needed for further deepening and widening of the navigation route, respecting the preservation of the estuary’s physical system characteristics. An international expert team proposed that strategic relocation of dredged sediment could fit in a proactive morphological management strategy as an instrument to improve the morphology of the Western Scheldt, for instance by steering the development of channels and shoals. As a pilot project to test this strategy, the expert team proposed to relocate sediment at the eroded tip of the Walsoorden sandbar.The Walsoorden small-scale in-situ relocation test 2006 was a follow-up of the first, and successful, small-scale in-situ relocation test of 2004. The 2006 test was different in that way that another relocation technique was studied: traditional “clapping” technique (instead of the diffuser). The diffuser has the advantage to allow a very precise relocation, the clapping technique on the other hand can realise a higher time-efficiency in execution, using the flood current to transport the material towards the sandbar.
The traditional dumping or “clapping” technique involves the hopper of the dredging vessel being opened so that the material can sink to the bottom (Figure 3). Compared to the 2004 test with the diffuser technique, another relocation location had to be chosen further away from the sandbar because the draught of the dredging vessel is greater than that of the pontoon. The new area was not only much deeper but also characterised by higher dynamics, both hydrodynamic (currents) as morphodynamic (sediment transports).
The 2006 relocation test occurred in two phases: relocation of 500,000 m³ in the first phase (phase A: January – March 2006) and another 900,000 m³ in the second phase (phase B: September 2006 – March 2007). These relocations were carried out within continuous maintenance dredging works in the Western Scheldt. Therefore a larger spreading in time is found for this test compared to the test of 2004, where the relocations were concentrated in time.
The morphological target was again to test the stability of the relocated material (including the wanted transportation of the relocated material towards the sandbar). The relocation test was however again small-scale (1,400,000 m³) and set-up as a research project. The ecological monitoring was executed in order to detect possible effects of the relocation test on the local ecology.
