Workshop Quest4DMay 14 2009

LTV-slib: Modelling of mud dynamics

Joris Vanlede (WL)

Thijs van Kessel (Deltares)

Marieke Eleveld (IVM)

Daphne van der Wal (NIOO)

Workshop Quest4D –May 14 2009 – WL Borgerhout 2

Managerial Questions

LTV slib (Long Term Vision – Mud transport)

• Effects of maintenance dredging– Harbour maintenance: mostly mud– Maintenance dredging of fairway and sills: mostly sand

• Effects of capital dredging– Harbour extension (e.g. Deurgancdok)– Fairway deepening and widening– …

• Effects on mud dynamics– Turbidity – Siltation rates– Sediment composition of tidal mud flats– Mud balance– …

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Model vs. Measurements

• Measurements:– Knowledge of present condition– System knowledge

• Process-based model:– Based on a physical description of processes (e.g. 3D mixing)– Quantify effects (e.g. fairway deepening, sea level rise,…)– Model output available “always” and “everywhere”

(<-> monitoring)

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Past activities

• 2006: – Literature survey

– Data-analysis

– Calculation of 14 days

• 2007: – Model improvements

– Calculation of 3 months

• 2008: – Improvements in 3D hydrodynamics

– Calculation of 1 year (seasonal dynamics)

– Model application : 2nd fairway deepening

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Hydrodynamics

• Year 2006• BC from ZUNO 2006 model• Resolution

– WS: 100m

– Upstream: 30m

• 1 million cells in 5 layers• 27 days CPU time for 1 yr. (x13)• 2 TB of HD results

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Hydrodynamics: conclusions

• Calculation of 1 year of 3D hydrodynamics with measurements as boundary conditions.

• Seasonal influence is modeled explicitly.• Most important difference model - measurement is

M4 phase in boundary condition (action 2009).

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Remote sensing data

• SPM in upper part water column (IVM)• Silt content of mud flats (NIOO)

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IVM: SPM in de waterkolom

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NIOO: Mud content mud flats

0

10

20

30

16Jan06 1Feb06 1May06 17May06 26Jul06 14Aug06 30Aug06 8Nov06 27Nov06

Slib

(%

) .

PlatenSlikkenIntertidaal totaal

►Mud content from radar images (SAR)►Seasonal variation in mud content

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Seasonal dynamics

• Seasonal dynamics is present, but not sufficiently– Seasonal variation of settling velocity ws or erosion parameter crit

– Boundary conditions are already seasonally variable

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Import/export at Vlissingen

Gross kton/day Net

• Model: Net export of 2 MT/yr• Van Alphen (1990): 0.6 MT/yr net import• Van Maldegem & Vroom (1995): 0.1 +/- 0.2

MT/yr net import

• Gross export of 37 MT/yr• Gross import of 35 MT/yr

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Validation at Antwerp

Boei 84 Boerenschans

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Validation at Antwerp (2)

Bottom concentration too low

Peak missing

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ETM: Estuarine Turbidity Maximum

Neap tide Spring tide

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Validation Remote Sensing Data

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Validation Remote Sensing Data

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Application: 2nd fairway deepening

1997 – 19987.5 m³ capital dredging worksDeepening of naturally occuring sills

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Application: 2nd fairway deepening

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Conclusions

• Mud transport model is operational and is compared to measurements (in-situ & remote sensing)

• Points of attention:– Seasonal dynamics– Estuarine circulation– M4 phase

• 2nd fairway deepening had little effect on SPM concentrations

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Plans 2009

• Further application of the model– Effect opening of DGD on SPM and siltation rates around

Antwerp.– Effect of dumping of dredged material around Terneuzen

harbor

• Development of a Zeebrugge detail model• Inter-comparison between mud transport models of

BMM and WL• Analysis of effects 2nd fairway deepening on siltation

in harbors