Entrapment of SPM in the

1
Entrapment of SPM in the Rotterdam Waterway
PhD student Michel A.J. de Nijs Supervisors
Johan C. Winterwerp, Julie D. Pietrzak and
G.S. Stelling
m.a.j.denijs_at_tudelft.nl
2
Harbor mouth
Exchange of SPM
April 2005
New Meuse
Old Meuse
3
Harbor mouth
Exchange of SPM
Velocity ms-1
SPM transport kgm-2s-1
Depth below surface
Dredging Botlek (2005) 0.40 Mton/year Exchange
Botlek (2005) 0.66 Mton/year (160 of yearly
dredging) exchange Botlek MKO (1989) 35
of yearly dredging
4
Idealized models

• Turbulence damping by salinity stratification
  (Munk Anderson, 1948)
• Time dependent entrapment processes Near slack
  tide front formation turbulence damping (Geyer,
  1993) T1L/u, T2 H1/ws

along channel
5
Idealized models

• Internal tide asymmetry (Jay and Musiak, 1994)

? ?(z)dz 0
A
U(z,t) u(z,t)?(z,t)
?(z,t) ?(z)-0.636 0.424 cos 2(?t-F) 0.085
cos 4(?t-F).....
6
Rotterdam Waterway

• Entrapment of SPM
• Salt intrusion (Chatwin, 1976)

Lagrangian measuring style
Eulerian measuring style
April 2006
New Meuse
Old Meuse
7
Rotterdam Waterway

• Front formation and turbulence damping

Depth below surfacde m
Front formation
Turbulence damping
ebb
Distance from Hook of Holland km
8
Rotterdam Waterway
Near-surface
up-estuary
z
down-estuary
?S 10 PSU
Distance from Hook of Holland
Near-bed
PSU
up-estuary
down-estuary
9
Rotterdam Waterway
z
Near-surface
seaward directed
U m/s
landward
U m/s
HWS
HWS
Distance from Hook of Holland
LWS
z
seaward
U m/s
landward
Near-bed
10
Rotterdam Waterway
HWS
LWS
HWS
Hook of Holland
New Meuse
Botlek
New Meuse
HWS
Rotterdam
Old Meuse
rkm 1012
11
Rotterdam Waterway
Near-surface
up-estuary
down-estuary
Distance from Hook of Holland
Near-bed
ebb
flood
up-estuary
SPM clouds
SPM cloud
down-estuary
Time
12
Rotterdam Waterway
Relative motion
Patch lags salt water
ETM
ETM
Rotterdam Waterway
13
Entrapment
Box model
Dyer, 1997
Depth and tidally averaged
New Meuse
D
Old Meuse
14
Long-term data
Port of Rotterdam
Rotterdam
New Meuse
Old Meuse
15
Excursions of salt water
Dynamic estuary!

• Fresh-water discharge
• Surges
• Spring to neap
• transitions

Surge-tide induced filling and emptying of the
estuary
Hook of Holland (rkm 1030)
Botlek (rkm 1014)
Rotterdam (rkm 1005)
16
Pilot survey
New Meuse (Rotterdam)
Rotterdam Waterway
ETM 2
ETM 1
17
Conclusions

• The salt induced baroclinic and buoyancy
  structure keep fluvial sediment in the estuary
  through their effects on currents and turbulence
  damping
• A proper reproduction of the siltation rates
  requires a proper quantification of the along
  channel distribution of salinity and sediment
  (three-dimensional modeling)
• The length of the salt water limit controls the
  trapping probability of fluvial SPM (see also
  Geyer, 1993)
• The amount of SPM in the ETM is determined by the
  length of the salinity intrusion not by the
  strength of the gravitational flow and tidal
  pumping importing marine SPM

18
Sediment transport
Numerical results
19
Sediment transport
Numerical results
20
Sediment transport
Numerical results