2 juli 2015
Human versus natural mud fluxes in
the Scheldt estuary
Are they significant and if so, how can they best
be optimised?
Thijs van Kessel (Deltares)
Joris Vanlede (Flanders Hydraulics)
Gijsbert van Holland (IMDC)
IAHR conference, 29 June, 2015
Mud balance
Some ballpark numbers:
• Cmud = 50-100 mg/l, Vtide = 109 m3, Atidal = 45 Mm 2
• Gross import = 50 MT/year, net import = 0.5 MT/year
• Smarsh = 1 cm/year (0.5 MT), Sharb = 1 cm/day (1 + 1 = 2 MT)
• K = Sharb/Smarsh = 4 > 1 (human impact on mud balance expected)
Source: Arcadis (2013)
29 jJune, 2015
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2 juli 2015
Process-based numerical model
Wal D. van der, T. van
Kessel, M.A. Eleveld, J.
Vanlede (2010).
Spatial heterogeneity in
estuarine mud dynamics. .
Ocean Dynamics
doi:10.1007/s10236-0100271-9.
Kessel, T. van, J. Vanlede,
J.M. de Kok (2011).
Development of a mud
transport model for the
Scheldt estuary.
Continental Shelf Research
31 S165–S181 DOI:
10.1016/j.csr.2010.12.006.
29 jJune, 2015
Process-based numerical model
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2 juli 2015
Effect of Sloe harbour (1)
29 jJune, 2015
Effect of Sloe harbour (2)
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2 juli 2015
Mud origins near Vlissingen
29 jJune, 2015
Mud origins near Antwerp
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2 juli 2015
Explanation of issues at Antwerp
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Narrower estuary
ETM formation, location dependent on freshwater discharge
Construction of DGD
Deepening
Possibly increasing trend SPM
High maintenance volumes and cost
29 jJune, 2015
Shift of release location
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2 juli 2015
Conclusions
• ‘Human’ fluxes small compared to gross natural mud fluxes
• But significant compared to net fluxes
• Siltation in harbours and access channels >> accretion tidal flats
and saltmarshes
• A large part of the mud in the Scheldt is ‘second hand’
• This percentage increases from the mouth to Antwerp
• Both concentration in water column and siltation rate can be
influenced significantly by adapting the maintenance strategy
• A down-estuary shift of release locations reduces both mud
concentration and siltation
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