TIDE-INTEGRATED SEDIMENT TRANSPORT IN TIDAL CHANNELS AND EFFECT OF CHANNEL DEEPENING

Effect of deepening the Rotterdam Waterway on turbidity maximum

2 November 2016

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Outline Study area

Results Delft3D model

Conclusions

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Rotterdam Waterway Ship canal from Rotterdam to North Sea

Artificial mouth of river Rhine

Length of 20 km

Width 480-675 m

Depth 14.5-16 m below NAP

Started in 1866 (150 years!), opened in 1872

Stairway line (trapjeslijn) 1970

Closing off Haringvliet 1970

Flood protection system Maeslantkering (1997)

Mean tidal range 1.7 m

Discharge 500-4500 m3/s

Sand D50 = 200-350 µm

Mud 10-35%

Botlek

Hoek van Holland

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Bed level Hoek van Holland NAP-16 m

Botlek NAP-14.5 m

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Dredging volumes in Rotterdam Waterway 1970’s: ~2x106 m3 per year

2010’s: ~0.5x106 m3 per year

Change in dredging and disposal strategy

Staircase line (trapjeslijn)

Haringvliet closed off

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Residual current

Hoek van Holland Botlek

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Computed mud concentrations

Van Rijn (2007)

transport module

in Delft3D

(mud and sand)

Agrees with

measurements

50% discharge

1 mud fraction

1 sand fraction

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Deepening

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Peak flood velocities

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Extra siltation

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Effect on mud concentrations

However:

Import increases

slightly

Effect on long

term?

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Mud transport along Rotterdam Waterway is non-saturated transport over a mainly sandy bed

Mud concentrations in ETM are supplied by the river and from sea

Deepening increases salinity intrusion and causes larger peak flood velocities at seaward side of deepened stretch

Initially, deepening Nieuwe Waterweg around Botlek results in small landward shift of turbidity maximum but not in increase of maximum

Deepening results in larger sedimentation rates in harbour basins

However, deepening also results in slightly more mud import

Start MSc research: effects on bed composition and turbidity on long term (years)

Conclusions

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Arcadis. Improving quality of life.

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Staircase line

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Discharge as function of Rhine discharge

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 2000 4000 6000 8000 10000 12000 14000

Lo

kale

afv

oer

[m

3/s

]

Bovenrijnafvoer [m3/s]

Nieuwe Waterweg Nieuwe Maas Oude Maas

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Suspended sediment concentrations

Source: De Nijs (2012)

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Depth-averaged concentrations

Source: Snippen et al. (2005)