Iahr2015 human versus natural mud fluxes in the scheldt estuary, kessel, deltares, 29062015
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Transcript of Iahr2015 human versus natural mud fluxes in the scheldt estuary, kessel, deltares, 29062015
IAHR conference, 29 June, 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)
29 jJune, 2015
Mud balance
Some ballpark numbers: • Cmud = 50-100 mg/l, Vtide = 109 m3, Atidal = 45 Mm2 • 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)
Process-based numerical model
29 jJune, 2015
Wal D. van der, T. van Kessel, M.A. Eleveld, J. Vanlede (2010). Spatial heterogeneity in estuarine mud dynamics. . Ocean Dynamics doi:10.1007/s10236-010-0271-9.
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.
Process-based numerical model
29 jJune, 2015
29 jJune, 2015
Effect of Sloe harbour (1)
29 jJune, 2015
Effect of Sloe harbour (2)
29 jJune, 2015
Mud origins near Vlissingen
29 jJune, 2015
Mud origins near Antwerp
29 jJune, 2015
Explanation of issues at Antwerp
• 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
29 jJune, 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