Fettweis, M.

Van den Eynde, D.

Open Marine Archive

 Management Unit of the North Sea Mathematical Models
MUMM | BMM | UGMM
Towards the application of an operational sediment transport model 
for the optimisation of dredging works in the Belgian coastal zone 
Dries Van den Eynde and Michael Fettweis
Management Unit of the North Sea Mathematical Models (MUMM) 
Royal Belgian Institute of Natural Sciences, Brussels, Belgium
D.VandenEynde@mumm.ac.be
http://www.mumm.ac.be
Tide-dependent dumping
Abstract
This research was executed in the framework of the MOMO project, funded by the Maritime Access Division, Ministry of the Flemish Community. 
Dredging works 
Numerical models
Currents and water elevations are calculated by 
the operational hydrodynamic models, based on 
the COHERENS software. The models comprise a 
2D model for the North-West European 
Continental Shelf, a 3D model for the southern 
North Sea and a 3D model for the Belgian 
Continental Shelf. The models were extensively 
validated using ADCP measurements. 
The sediment transport model MU-STM is a semi-
Lagrangian model, calculating the advection and 
diffusion of the material in suspension. The model 
calculates deposition and resuspension and includes a 
consolidation model. The model has been validated 
using radio-active tracer experiments, executed by 
HAECON NV. The model has been used also to calculate 
the sediment balance for the Belgian Continental Shelf. 
In the  Belgian Part of the North Sea, high concentration of fine-grained suspended particulate matter occurs, which is responsible for significant siltation of the ports 
and navigation channels. Every year, about 11 million to of dry material is dredged and dumped back inot sea. A non negligible part recirculates back to the dredging 
places. To study the process, numerical models are developed, validated and used in an attempt to help the authorities in the choice of an optimum dredging 
methodology. Different model simulations are carried out to investigate the influence of the position of the dumping sites and the meteorological conditions on the 
recirculation process. A first step is made in the operational implementation of a tool that can help the authorities to make the best choice for the dumping site.
The wave model MU-WAVE is based on the 2nd 
generation HYPA-S wave model. A coarse grid model is 
implemented for the entire North Sea, a finer 
resultaion model is used for the southern Bight of the 
North Sea. The model is validated using buoy 
measurements of the Meetnet Vlaamse banken, 
Vlaamse Gemeenschap, Afdeling Kust en by 
comparison with results of the WAM model. 
Numerical simulations are executed to 
evaluate the recirculation of dumped 
material from the dumping sites to the 
zone around the harbour (see above) 
and the zone of the fair channels. Two 
dumping sites are evaluated, the 
dumping site ZBO and a new site, west 
of Zeebrugge harbour (ZBW). Also the 
tide-dependent dumping (dumping on 
ZBO at flood, dumping at ZBW at ebb) is 
evaluated. The simulations are done 
over a period of 5 days 5 hours. 
Left: Amount of material on the bottom, averaged 
over the last day of the simulation for dumping at 
ZBO, ZBW and tide-dependent dumping (TDD). 
Right: Amount of material on the bottom, averaged 
over the last day of the simulation, as a function of 
the starting date and for different meteorological 
conditions. Results clearly show the influence of the 
dumping strategy, dumping time and meteorological 
conditions on the recirculation. Depending on 
meteorological conditions and tide, better dumping 
strategies can be selected, resulting in less 
recirculation to the harbour and to the fair channels.
Conclusions
Numerical  models 
(hydrodynamical models, 
w a v e  m o d e l s  a n d  
s e d i m e n t  t r a n s p o r t  
models) can be used to 
calculate the recirculation 
of dumped material.
Recirculation is a 
function of dumping site, 
d u m p i n g  s t r a t e g y,  
meteorological conditions. 
Operational forecasts 
could help the decision 
takers in their decision to 
s e l e c t  t h e  o p t i m a l  
dumping site, for the 
present situation.
More validation and 
calibration of the model is 
n e c e s s a r y.  A  f i e l d  
experiment is planned for 
2012-2013. 
Dredging Total Mud Sed. Rate
Mton dry material/year m/year
Harbour Zeebrugge 7.00 6.96 2.9
Harbour Oostende 0.45 0.45 0.3
Pas van het Zand 1.17 0.97 0.6
Scheur Oost 1.08 0.82 0.1
Scheur West 1.38 0.99 0.1
Channel Oostende 0.15 0.13 0.1
Dumping
Mton dry material/year
S1 7.54 5.26
S2 0.82 0.68
Zeebrugge 4.35 4.31
Oostende 0.60 0.57
 
  
Operational forecasts are being 
prepared of the recirculation to the 
zones of interest, using the three 
different dumping strategies and 
using the actual meteorological 
conditions. A table is prepared 
with the calculated recirculation. 
This could be used by the decision 
takers to decide which dumping 
strategy to follow during the 
following days, to minimise 
rercirculation. 


Towards the application of an operational sediment transport model for the optimisation of dredging works in the Belgian coastal zone [POSTER]

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