Presentation by Filip Schuurman (Royal Haskoning DHV) at the Delft3D User Days, during Delft Software Days 2016. Wednesday 2 November 2016, Delft.

1. Stochastic Dredge Plume Modelling
in the Great Barrier Reef
Filip Schuurman, Andrew Symonds &
Marcela Busnelli

2. Abbot Point
port

3. Abbot Point port
• Australia’s most
northerly and largest
bulk port
• Started in 1984
• Capacity 50 Mton/year
• Area 5350 ha
• Operated by Abbot
Point Bulkcoal Pty Ltd.

5. Location of Abbot Point within
Great Barrier Reef Marine Park

6. 2.8 km jetty
Existing coal
terminal T1
Berthing and
loading of ships

7. Existing and proposed terminals

8. Existing and proposed terminals
Dredging for deepening
of berthing place
(1.1 million m³)
Onshore dumping of
dredged sediment

9. Main question:
Will the dredged and dumped sediment affect
the Great Barrier Reef?

10. Scope of work
• Data collection and analysis
• Hydrodynamics around the Abbot Point port
• Dredged sediment dispersal and deposition
• Modelling approach:
– 3D hydrodynamic modelling using Delft3D 4
– Sediment dynamics using DelWaq offline
– Assess dredging and onshore dumping strategies
– Account for large variation in meteorological conditions
(incl. tides, wind, El Niño, cyclones and regional scale
circulations)

11.  110 km by 60 km
 Nested grids (3x)
 Outer grid = 350 – 550 m
 Inner Grid = 30– 60 m
 3x water level boundaries

13. Driving Forces
• Astronomical Tides – water level boundaries derived
using DHI Global Tidal Model, KMS.
• Wind and wave data – from regional scale hindcast
wave model (resolution 0.05 degrees).
• Wave modelling online with hydrodynamics
• Uniform wind field
• Regional scale circulation processes……

14. Calibration Water level
WL at location A2:
WL at location B1:

15. Wind
• Wind-induced currents from South-East

16. Calibration regional flow circulation
Flow speed:
Flow direction:

17. Dominant flow at peak ebb

18. Wave
Calibration
0
0.5
1
1.5
2
2.5
3
3.5
4
24/12/2013 31/12/2013 7/01/2014 14/01/2014 21/01/2014 28/01/2014 4/02/2014 11/02/2014
SignificantWaveHeight(m)
Date
Measured
Modelled
0
90
180
270
360
24/12/2013 31/12/2013 7/01/2014 14/01/2014 21/01/2014 28/01/2014 4/02/2014 11/02/2014
MeanWaveDirection(degs)
Date
Measured
Modelled
0
2
4
6
8
10
12
14
24/12/2013 31/12/2013 7/01/2014 14/01/2014 21/01/2014 28/01/2014 4/02/2014 11/02/2014
PeakWavePeriod(S)
Date
Measured
Modelled

19. Sediment properties
• 3 fractions
• Sediment concentrations based on measurements

20. Stochastic Modelling
• Modelled 3 years:
– El Nino (1997)
– La Nina (2011)
– Neutral year (2007)
• 10 months dredging period
• 13 scenarios with 21 days
difference in starting date

21. Result: sediment concentration
95th percentile of sediment concentration
in a neutral year

22. 95th percentile of sediment deposition
in a neutral year

23. 95th percentile of sediment concentration
in a neutral year

24. El Niño, La Niña and neutral year
La Niña El Niño
Neutral year

25. Wet vs dry season
Wet season Dry season

26. Summary
• Undertook a numerical modelling comparative
assessment for offshore disposal sites at Abbot Point
• Extensive modelling required to meet approval
requirements
• Study showed that impact to Great Barrier Reef is
insignificant
• Study helped identify most suitable dredging
conditions

28. QUESTIONS?