Dupont, Y.

Papili, S.

Wever, T.

Open Marine Archive

Dealing with storms is always a fascinating matter. They are uncontrollable and 
destructive. It is not always possible to get real data measurements during a storm 
due to large magnitudes involved. Having recording instruments deployed on the 
seafloor and properly working, gave the rare opportunity to observe and analyze 
the storm impact directly on the sea-floor.  
(1)Belgian Navy-RCMG: VSW-MWU, Marinebasis Zeebrugge, Graaf Jansdijk 1, 8380 Zeebrugge, Belgium. Sonia.Papili@ugent.be 
(2) Wehrtechnische Dienststelle für Schiffe, Marinewaffen, Maritime Technologie und Forschung, WTD 71 Berliner Str. 115, D-24340 Eckernförde, Germany. Thomas Waver@bwb.org 
(3) Belgian Navy: Marinebasis Zeebrugge, Graaf Jansdijk 1, 8380 Zeebrugge, Belgium. Yves.Dupont@mil.be 
Conclusion 
Introduction 
Storm  1 
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STORMS: A CHALLENGE OF KNOWLEDGE 
Papili Sonia1, Thomas Wever2, Yves Dupont3 
Acknowledgements 
I would like to thank The Belgian Navy, founder of this research, Prof. Dr. M. De Batist and Dr. Vera Van Lancker, promotor and co-promotor of 
the related PhD research; Ralf Ludher, from the German Navy; all my colleagues from the Belgian Navy and from Ghent University. 
References 
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Ashley, G.M. (1990). Classification of large-scale subacqueous bedforms: a new look at an old problem. J. Sedim.Petrol., 60, 1,p. 160-172 
Verfaillie E., Van Lancker V;, Van Meirvenne M. (2006). Multivariate geostatistics for the predictive modelling of the surficial sand distribution in 
shelf seas. Continental Shelf Research, 26, p. 2454-2468 
Current data by Ministery of the Flemish Community, Maritime Services, Coastal Division/Hydrography  
Hydro-meteo data by 'IVA MDK - afdeling Kust - Meetnet Vlaamse Banken'  
This paper presents the effects of two storms on a measuring object deployed on 
the seafloor in shallow water. The experimental area has a water depth range 
between 7 to 12 meters, depending on tides. Two storms passed the experiment 
site during a three months experiment directed towards a better understanding 
of the sand mobility in a highly dynamic environment. 
Storm  2 
The experimental area named Wandelaar 
(blue circle in figure 1) is located at 12 km 
distance from the port of Zeebrugge in the 
vicinity of the main navigation channel on 
the Belgian part of the North Sea. It is a 
sandy shallow water area characterized by 
the presence of small to large dunes (sensu 
Ashley, 1990), of up to 2 m in height. 
The Burial Recording Mine (BRM) is an 
experimental instrument recording 
presence or absense of sediment at 
programmed time recording. With its 3 rings 
of 24 led bridges (sensors) equally spaced 
on its sides and its centre detects the 
sediment height surrounding itself once is  
deployed on the sea-floor. It has a lenght of 
1.70 m, diameter of 0.47m and weight in air 
of 500 Kg. Accelerometers inside the object 
monitor the pitch and the roll and their 
variation in time. 
The hydrological and meteorological data were analyzed to evaluate the two storms affecting the 
area during the experiment. The threshold necessary to initiate movement of sand grains on the 
seafloor was calculated. The threshold orbital velocity for sediment motion is used to calculate the 
corresponding required critical wave height. 
The calculated curves were compared with the measured wave height, percentage of sediment 
volume around the object, and current measurements.  
During both storms wave affecting the 
seafloor caused reduced burial (i.e., 
sediment coverage) of the BRM. After the 
storms increased burial of 60% (October) 
and 80% (November) was observed. The 
high storm waves eroded sediment in the 
vicinity of the BRM and created scour 
holes at both ends. Once the scour holes 
merged to form one, the BRM rests on a 
small sediment cone. Upon collapse of the 
cone the BRM rolls into the bigger scour 
hole. During the sedimentation phase this 
new deeper hole is filled and causes a 
higher percentage of buried volume.  
Area of investigation 
Measuring instrument 
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Fig. 3: storm in October 2008. (a): comparison between measured curve of real wave height (red) and calculated 
curves of critical wave height (different tone of grey); (b): curve of burial volume; (c): curve of wave energy. 
Fig. 6: storm in November  2008. (a): comparison between measured curve of real wave height (red) and calculated 
curves of critical wave height (different tone of grey); (b): curve of burial volume; (c): curve of wave energy. 
Fig. 4: storm in October 2008: comparison 
between measured curves of current speed  (l 
and n) and calculated curve of wave energy 
(m). Curve l represents current speed measured 
for superficial layer of water depth, curve n for 
deep water. 
Fig. 5: storm in November 2008: comparison 
between measured curves of current speed  (l 
and n) and calculated curve of wave energy 
(m). Curve l represents current speed measured 
for superficial layer of water depth, curve n for 
deep water. 
Fig. 1: extract from a grain size map on the BCS. (Verfaillie et 
al., 2006) 
Fig. 2: BRM: experimental instrument 
l 
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