Decrop, B.

Depreiter, D.

Jespers, N.

Leyssen, G.

Vanlede, J.

Viaene, P.

Open Marine Archive

Storm surge prediction in the Belgian coastal zone 
Leyssen Gert1, Joris Vanlede2, Davy Depreiter1, Niels Jespers1, Peter Viaene2 and Boudewijn Decrop1 
1 IMDC, International Marine and Dredging Consultants, Coveliersstraat 15, B-2600 Berchem, 
Belgium 
E-mail: Gert.Leyssen@imdc.be  
2 Flanders Hydraulics Research, Berchemlei 115, B-2140 Antwerp, Belgium 
 
The water level in the southern part of the North Sea and in the Scheldt Estuary are composed of the 
astronomical tide and an atmospherically induced surge. These water levels can be accurately 
simulated with a combination of hydrodynamic shallow water models and atmospheric data. The 
hydrodynamic modeling train of CSMv5 (Continental Shelf Model) and ZUNOv3 (ZUidelijke 
NOordzeemodel) (RWS-Waterdienst & Deltares)  translates the astronomic water levels at the 
boundaries of the continental shelf to the Belgian coast while calculating the surge generated by 
meteorological conditions. 
Flanders Hydraulics has a hindcast modeling train installed for research purposes and a forecast 
modeling train coupled with inland river models for prediction purposes. Both modeling trains run 
on the parallelized SIMONA WAQUA shallow water software (SIMONA 2009). CSMv5 has a Cartesian 
grid in spherical coordinates with a resolution of 1/8° longitude (9.3-6.5km) and 1/12° latitude 
(9.25km). The astronomical boundary conditions consist of the 11 main tidal components. ZUNO 
has a curvilinear grid  with a resolution of 1-4km in the Belgian coastal zone. The models are linked 
with water level boundaries.  
A hindcast validation analysis is performed to investigate the performance of the models, compared 
to one year of water level measurements (Belgium, France, Netherlands, UK) (Leyssen, 2011a). The 
influence of the wind on the surge level is investigated during a sensitivity analysis (Leyssen, 
2011b). 
Wind speed, wind direction and fetch length and atmospheric pressure are the three main causes 
for a surge in front of the Belgian coast. Theoretically a static windspeed of 30ms-1 (11beaufort) can 
create a surge level of over 2.5m if it has a fetch length of 200km (Leyssen, 2011b). So an 
atmospheric depression above the North Sea can create a substantial increase in water level in front 
of the Belgian coast. This water level rise does not include the waves associated with such an event. 
The propagation of the tidal waves from the continental shelf to the Belgian coast is investigated 
using harmonic analysis of simulation results and measurements. A good agreement is obtained for 
both amplitude and phase of the major tidal components. 
The hindcast shows that water levels can be predicted with an accuracy between 0.1m and 0.2m in 
the Belgian coastal zone, both for calm and stormy periods. 
The relevance of this work is reflected in the operational hydrodynamic forecasting system that runs 
at Flanders Hydraulics. This system consists of a nested train of SIMONA models, starting with the 
CSMv5 and ZUNOv3 models and further refining into Kuststrook and Kustzuid models (RWS-
Waterdienst & Deltares). The predictions use atmospheric forecasts from HIRLAM and ECMWF.  Data 
assimilation techniques are applied to ameliorate prediction quality based on observations. 
Forecasts are produced every six hours. 
From the most detailed models, water and surge levels and current data for the Belgian and Dutch 
coastal zone and the Scheldt River are extracted and forwarded to the Hydrologic Information 
Center (Flanders Hydraulics) and Oceanographic Meteorological Station (Coastal Division) to be used 
in e.g. flood and storm warning systems.  
 
References 
SIMONA. 2009. Waqua/Triwaq- two- and three dimensional shallow water flow model: Technical 
documentation. Simona report number 99-01. 
Leyssen G., J. Vanlede, B. Decrop, and F. Mostaert. 2011a. Modellentrein CSM-ZUNO, Deelrapport 2: 
Validatie. (in preparation) 
Leyssen G., J. Vanlede and F. Mostaert. 2011b. Modellentrein CSM-ZUNO, Deelrapport 1: Opzet en 
gevoeligheidsanalyse. WL2011R753_12rev2_0, I/RA/11313/11.087/GLE. 
 
 - 47 -


Storm surge prediction in the Belgian coastal zone

www.watlab.be
Gert Leyssen2 , Joris Vanlede1 , Davy Depreiter2
Niels Jespers2, Peter Viaene1 , Boudewijn Decrop2
1Flanders Hydraulics Research (Waterbouwkundig Laboratorium), 
 Berchemlei 115, 2140 Antwerp, Belgium 
2IMDC, International Marine and Dredging Consultants,
 Coveliersstraat 15, 2600 Antwerp, Belgium
Storm surge prediction 
in the Belgian Coastal zone
Project objectives:
Deploying the Continental shelf model (CSM)- Zuidelijke Noordezee (ZUNO) modeling train  to 
translate astronomic water level boundary conditions from the continental shelf to the Belgian 
coastal zone. The  wind generated surge is taken into account by  imposing  wind and pressure 
fields.  An extensive validation procedure and sensitivity analysis is performed with 19 measurement 
stations  in front of the Belgian, the French and  the English coast.
CSM
ZUNO
NEVLA
Modeling train Results
Wind and pressure fields
Model Quality
Water level
Surge
Operational prediction systems
A hydrodynamic modeling train is running in 
operational mode at the Hydrologic Information 
Center (Flanders Hydraulics Research). 
• Water level expectations and storm tide warnings
• Data-assimilation (Kalman filtering) of water 
level observations in the North Sea 
• Downstream boundary conditions for hydrological 
models of inland river systems. 
    Combined prediction of surge and discharge with 
  separate modeling systems is especially useful 
   in estuaries.
Applications
•	Hindcast
 - Generation of boundary conditions
  Hydrodynamic models
  Sediment transport
 - Scenario analysis
•	Operational prediction system
 - Kalman filtering
 - Surge levels > 3 m possible
Reports
• Leyssen ,G.; Vanlede, J.; Mostaert. F.; (2011) 
Modellentrein CSM-ZUNO, Deelrapport 1: 
Opzet en gevoeligheidsanalyse, 
WL2011R753_12rev2_0, I/RA/11313/11.087/GLE.
• Leyssen ,G.; Vanlede, J.; Decrop B.; Mostaert. F.; 
(2011) Modellentrein CSM-ZUNO, Deelrapport 2: 
Validatie, in preparation.
Bias [m] RMSE [m] Bias M2
amplitude [m]
Bias M2
phase [m]
Belgian coast 0,10 0,18 0,05 3,5


Storm surge prediction in the Belgian coastal zone [POSTER]

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