Presentation by Filip Schuurman, Royal HaskoningDHV, Netherlands, at the Delft3D - User Days (Day 2: Sediment transport and morphology), during Delft Software Days - Edition 2017. Tuesday, 31 October 2017, Delft.

1. Dynamics of dredged sediment upon
discharge in the North Sea
Modelling in Delft3D and DELWAQ
Filip Schuurman, Erik Hendriks,
Thijs van Kessel, Petra Dankers
31 October 2017

2. 31 October 2017
Port of Rotterdam
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3. 31 October 2017
Fine sediment in the port and North Sea
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4. 31 October 2017
Annual maintenance dredging
(only clean fine sediment)
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5. 31 October 2017
Release of the clean fine sediment part
 Sand is used for coastal
protection
 Poluted fine sediment to special
pit (Slufter)
 Clean fine sediment to
deepened pit in North Sea
(‘Verdiepte Loswal’)
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6. 31 October 2017
Releasing of fine sediment in ‘Verdiepte Loswal’
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10 m deep
5 million m³

7. 31 October 2017
Problems
 The ‘Verdiepte Loswal’ pit is nearly full
 Return of dredged+ released fine sediment:
1. Released fine sediment remains in suspension
2. Suspended sediment is transported back to the Port of Rotterdam by tidal flow
3. Returned fine sediment deposits in the port and needs to be dredged again
4. Re-dredging of sediment increases the dredging volume
Research questions:
1. What is the return percentage of fine sediment in the present situation?
2. How does release location affect the return percentage?
3. How does river discharge affect the return percentage?
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8. 31 October 2017
Approach for modellling
 Hydrodynamics in Delft3D:
 Tidal currents
 Waves
 River discharge
 Salinity, temperature, wind
 Representative year 2007
 Fine sediment dynamics in DELWAQ (offline):
 Advection and diffusion
 Sedimentation and erosion
 River discharge
 Automatic dredging in Port of Rotterdam + release in pit
 10 years, analysis for years 9+10
 Equilibrium sediment concentration, independency for initial conditions
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9. 31 October 2017
ZUNO-DD model schematisation
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10. 31 October 2017
ZUNO-DD model schematisation
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11. 31 October 2017
Fine sediment modelling
 Offline DELWAQ modelling
 Aggragation of finest grid
 3 fine sediment fractions:
 0.001 mm/s
 0.125 mm/s
 1 mm/s
 Automatic dredging of all
deposition in the Port of Rotterdam
 Automatic release of dredged
sediment at one of the release
locations
 Released sediment is labelled
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12. 31 October 2017
Sediment release locations
 Distance from Port of Rotterdam
 Flow conditions
 Salinity
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13. 31 October 2017
Spatial variation in salinity
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14. 31 October 2017
Effect of release location
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15. 31 October 2017
Effect of release location
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16. 31 October 2017
Return percentage and dredging volume
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17. 31 October 2017
Return percentage for sediment fractions
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0.125 mm/s
1 mm/s
0.001 mm/s

18. 31 October 201718
Release at Verdiepte
Loswal
Mean annual sediment
concentration in
bottom layer [mg/l]
0.125 mm/s
background
0.125 mm/s
Dredged + released
1 mm/s
background
1 mm/s
Dredged + released

19. 31 October 2017
Effect of cross-shore distance
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LW2 LW3 LW West
Difference in sediment concentration compared to releasing in Verdiepte Loswal
+0.1 is 10% higher sediment concentration

20. 31 October 2017
Effect of alongshore distance
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LW NW
Difference in sediment
concentration compared to
releasing in Verdiepte Loswal
+0.1 is 10% higher sediment
concentration

21. 31 October 2017
Effect of river discharge
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22. 31 October 2017
Effect of river discharge
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-25% river
discharge
+25% river
discharge

23. 31 October 2017
Variation between years
 Variation in sediment in- and outflow
 Variation in dredging volumes
 Return flow is stable (34 - 39%)
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24. 31 October 2017
Summary
 Present retour percentage is about 36% with dredging of 3.1 Mton/year. This
consists of 1.1 Mton/year of dredged+released fine sediment. Retour
percentage is relatively stable in the years.
 Higher river discharge increases the dredging volume AND the return
percentage. The increase in dredging equals an increase in river discharge.
 Fine sediment concentration, sedimentation in Port of Rotterdam and return
percentage are sensitive to release location, in particular to distance to the
port. Balance between transport costs and dredging volume.
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