Gruwez, Vincent

Kortenhaus, Andreas

Troch, Peter

English

Gruwez, V.

Kortenhaus, A.

Troch, P.

Open Marine Archive

- 40 - 
 
 
Advanced modelling of wave overtopping for climate resilient 
coastal defence systems 
Gruwez Vincent
1
, Kortenhaus Andreas
1
 and Troch Peter
1
 
1 
Department of Civil Engineering, Ghent University, Technologiepark 904, 9052 Zwijnaarde (Ghent), 
Belgium 
E-mail: Vincent.Gruwez@UGent.be 
 
Only 67 km long, the Belgian coast represents a significant touristic, socio-economic and cultural value 
for the densely populated country. Historically, the coastal land-use planning was much less restrictive 
than that of the neighbouring countries. This caused a very high degree of local coastal development 
from the end of the 19th century on and increased considerably after the Second World War, with the 
rise of middle-class mass-tourism and apartment buildings on the sea dike. In addition, since the 
1970’s, beach nourishment was adopted as a complementary coastal protection scheme: millions of 
cubic meters of sand were artificially added to the beach and foreshore and pushed the sea further 
away from the sea dikes. This resulted in the typical Belgian coastal appearance as it is known today: 
an almost continuous row of high rise apartment buildings fronted by a sea dike with promenade and a 
mildly sloped beach. 
 
The typical Belgian coastal defence system, in the urbanised coastal areas, is a nourished beach 
providing a long and (very) shallow foreshore in front of a sloped sea dike with promenade and 
buildings and/or storm wall(s) close to the dike crest. Climate change is expected to keep causing sea 
level rise and an increase in storm occurrence and intensity. The Belgian coastal defence system 
against flooding is therefore being adapted, according to the masterplan for coastal safety [1], by a 
combination of a beach nourishment and dike crest level increase by a storm wall. 
 
In the functional design of these storm walls, the height of the storm wall is calculated by determining 
the wave overtopping, which is limited to a specific safety criterion. The wave impact forces need to be 
resolved for the design of the structural stability of the storm wall. Current state of the art 
methodologies to calculate the wave overtopping still contain simplifications that are too conservative 
for this kind of cross-section. For example, they do not take into account some important physical 
processes resulting from the complex geometry of the typical Belgian coastal profile. In addition, the 
design criterion for wave overtopping has focussed on the mean overtopping discharge. Individual 
wave overtopping volumes have not been investigated into much detail yet. 
 
The present research focusses on advanced numerical modelling of wave overtopping over and wave 
forces on this typical Belgian coastal defence system, resolving the hydrodynamic flow in full 3D (or 
2DV, disregarding the alongshore horizontal dimension). This should allow for a much more accurate 
prediction of the mean overtopping discharge and individual overtopping volumes. Furthermore, 
hydrodynamic experiments in both a wave flume (2D) and wave basin (3D) in addition to field 
measurements will be performed to provide data with which the numerical method can be verified. 
Field tests do not suffer from scale effects nor from model effects and are a crucial source of 
information to be integrated in the overall validation of the methodology. The field measurements will 
include an artificial dike constructed on the beach, close to the high water line, to allow measurement 
of wave overtopping and wave impact on the short term. 
 
This research is part of the fundamental strategic research project ‘‘CREST ‐ Climate REsilient coast 
(www.crestproject.be): wave action in a changing climate: effects on the dynamics of the coast and 
implications for future safety strategies’’, funded by the Flemish Agency for Innovation by Science and 
Technology (formerly known as IWT, now part of VLAIO, Flanders Innovation & Entrepreneurship). 
 
Keywords: wave overtopping; wave impact; storm wall; very shallow foreshore; numerical wave 
modelling; hydrodynamic experiments; field measurements 
 
Reference 
- MDK - Afdeling Kust, Flanders Hydraulics Research, 2011. Masterplan Kustveiligheid – Kustveilig-
heidsplan. MDK - Afdeling Kust & Flanders Hydraulics Research. 
  


Advanced modelling of wave overtopping for climate resilient coastal defence systems

Ghent University Academic Bibliography

https://biblio.ugent.be/publication/8515896/file/8515897.pdf

Advanced modelling of wave overtopping for climate resilient coastal defence systems

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Ghent University Academic Bibliography