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IN F R A STR UCTUUR I N H E T LEEFMILIEU
513
RELATIVE SEA LEVEL RISE ALONG
THE BELGIAN COAST:
ANALYSES AND CONCLUSIONS W I T H
RESPECT TO
THE HIGH WATER, THE MEAN SEA AND
THE LOW WATER LEVELS
by Ing. C. Van C auw enberghe
C oastal H y d ro g raphic Service, O stend, Belgium.
1. IN T R O D U C T IO N
1.1. Tide gauges stations only measure locally the
Relative Sea Level (RSL)-oscillations.
These variations, m easured relative to the land, are
originated by periodic (tidal effects), random (m eteo­
rological and hydrological influences), isostatic {redis­
tribution o f the mass o f the earth, due to geological
processes), tectonic (crustal movements) and eustatic
(changes o f the capacity o f the water-volumes o f the
seas and the oceans) ajjeuts1/ / ^ 4.
The so called uplift o f Scotland and Scandinavia is
isostatic; it is the result o f the glacial melting o f the
former ice-sheets, by which the shape o f the geoid
gradually changed (geological process, due to the
post glacial rebound).
Local earthquakes (crustal movements) are tectonic
and also can modify the geoid.
1.2. The world today is consuming its resources at a
relatively high speed and is producing large amounts
o f waste. Some o f these products, the so called green­
house gases, such as carbon dioxide (C 02), nitrous
oxide (N 20 ) , m ethane (C H 4), chlorofluorocarbons
(CFC's), etc., are concentrated in the atmosphere;
mostoften they are generated by industry, but also by
other hum an activities.
The “Intergovernm ental Panel on Clim ate
Change” or IPCC assumed already in 1990 that a
doubling o f the C02-content in the atmosphere will
cause an increase in global mean tem perature from
1,5° to 4,5° CL
This may lead, probably in the second half o f the
next century, to irreversible global changes in sea
level, i.e. this phenom enon may produce the so called
“greenhouse effect” .
Eustacy will produce changes in the capacity o f the
water-volumes o f the seas and the oceans and is due
to the melting o f large am ounts o f glaciers and polar
ice-sheets (glacio- eustacy), to tectonic movements
(tectono-eustacy) and to the sedimentation, origina­
ted by the erosion o f the continents on the long run
(sedimentation eustacy).
For the low-lying areas, like the D utch and the
Flemish coastal plains, being nearly situated at about
mean sea level and only being protected from the sea
by dikes and dunes, it thus looks very opportune to
m onitor and to investigate this evolution.
We may consider the periodic and random effects as
being short term influences, while the isostatic, tec­
tonic and eustatic changes have m ostoften a long­
term character.
1.3. The present paper is in an updating o f two ear­
lier studies6’7, both being contributions o f the
Coastal Waterways Division-Hydrographic Service,
Oostende, to former EC-contracts.
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INFRASTRU CTU U R I N H E T LEEFMILIEU
The Annexes 1, 2 and 3 give a synopsis o f the
periods o f these observations along the Belgian coast
(Oostende, Zeebrugge and N ieuw poort); here the
periods, for which a harmonic analysis occurred, are
also indicated8 to 19.
If we compare also the yearly values o f these periods
with those ofVlissingen (the Netherlands), we some­
times found differences o f more than 10 cm , where­
as only 3 or 4 mm are the normal values for years with
reliable observations...
From 1925 till now (1998), the records o f the years
1925, 1926 and o f m ost part o f World War II ( 1940,
1941, 1942 and 1944) are very discontinuous; so we
decided not to use them in this study, except when
using the technique o f moving averages (see further
sub 3.3).
From the Rijksinstituut voor Kust en Zee (RIKZ) of
the Dutch Rijkswaterstaat in The H ague, we kindly
received the analogous information for Vlissingen,
related to a reliable and continuous period o f 109
years (1890-1998).
For Zeebrugge and N ieuw poort, the observations
started in the early thirties, but the data for 19321940 and 1941-1943 were also very discontinuous.
Continuous data are only available respectively from
1964 and 1967 onwards, as indicated in the Annexes
2 and 3.
We want to stress that the tidal observations needed
to be reliable and to be obtained over extented and
uninterrupted periods.
3. LOCAL T R E N D S FO R HW, MSL A N D LW
2. CH O ICE A N D QUALITY OF T H E DATA
The analyses o f the relevant tidal elevation data
along the Belgian coast in the past, such as the annu­
al levels o f H igh W ater (HW ), Mean Sea Level (MSI.)
and Low Water (LW) for O ostende, Zeebrugge and
Niem vpoort, can yield information both about the
short and about the long term trends.
At the same tim e wc found it interesting to make a
comparison with the same levels, calculated for
Vlissingen (the Netherlands).
Before attem pting to analyse the tidal data, we
must consider its value and usefulness.
As the history o f the tidal observations for the 3
locations, m entionned above, has been
given alre­
ady in an earlier paper 6, we found it useful to repeat
and to update all o f it once more.
As can be noticed from the tables, for some years,
there are significant gaps in these series, mainly for
the earlier periods.
It can be noticed that O ostende has the longest
records (see A n n ex I); so, this location can be consi­
dered as the main tide gauge station for the Belgian
coast.
Reasonably good observations (readings o f HW
and LW on a tide pole) began already in 1820, but,
unfortunately, these data have been lost.
All the other earlier records, mainly predating
World War I and II, were also carefully examined:
(1) For the period 1835-1852, the m onthly values o f
H W /L W are based on continuous
H W /L W
records, read from a tide-pole, close to a lock in the
harbour o f O ostende (Reference 3) and near to a
reliable benchmark, to which the gauge was referred.
This benchmark was incorporated in a quay wall.
Because only m onthly mean values o f H W /L W were
available, mean tide levels (i. e. the mean o f HW and
LW) could be calculated. The difference between this
level and MSL along the Belgian coastline is nearly
constant; e. g. for the period 1949-1988 the diffe­
rence is +0,063 m. So, knowing the mean tide levels,
we were able to determ ine the MSL-value for each
year o f the period concerned.
(2) For many reasons the period 1878-1914 was not
useful for this study: some data have been lost, there
are too many gaps in the data and the reference
datum is uncertain.
For the EC-project E P O C 6, only the tidal elevation
data for Oostende and Vlissingen have been taken
into consideration, i.e. those for H igh Water (HW ),
for Mean Sea Level (MSL) and for Low W ater (LW).
In the later study7, besides the data o f Oostende
and Vlissingen, we also made use o f the data o f
Zeebrugge and o f Nieuwpoort.
For the determ ination o f the local trends, we used,
so far, the following methods:
- linear curve fittings 6 and y,
- cyclic curve fittin g s 6,
- moving averages 6,
- singular spectrum analysis1.
The first three m ethods will be applied again for
this publication: see further sub 3.1., 3.2. and 3.3.
As the last m ethod, applied in our second paper
(Reference 7), did no t supply so much added value,
we did not use it in the present paper any more.
A nother additional m ethod is to make an investi­
gation on the values o f the main harmonic components
for our main tide gauge station (Oostende): this has
been carried ou t in 3.4.
3 .1 . Linear curve fittings
The A nnex 4 represents the yearly values or scatter
diagrams o f HW, MSL and LW for Oostende. These
data are referred to TAW (Tweede Algemeene
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INFRASTR UCTUUR I N H E T LEEFM ILI E U
Waterpassing) , being the Belgian National Reference
Level.
Further on, the linear best fit calculations through
these 3 diagrams values have been carried out by
means o f the m ethod o f least squares; the outcome of
these curve fittings have been represented on the
same Annex; the linear correlation coefficient
(Pearson r) and the 95% confidence limits are deter­
mined as well.
For the 3 annual values we see a linear increase
o f nearly 0,01 m /decade, if the two periods, i.e.
1835-1852 and 1927-1998 (less 4 years o f the World
War II), are taken into account.
On the other hand, if only the last period, less the
years as m entionned above, is considered, the 3
regression lines for HW, MSL and LW indicate a rise
o f 0,0217 m /decade, o f 0,0144 m /decade and of
0,0084 m /decade.
In all cases, the correlation coefficients are rather
high, except for LW (period 1927-1998). This is nor­
mal because the HW- and LW-configuration is sub­
ject to the same nodal fluctuations (see further sub
3.2.); as a m atter o f fact, a linear best fit will be bet­
ter at HW than at LW.
Anyway, all correlation coefficients are high
enough: for a severe one-tailed test o f 0,5%, r has to
be at least 0,3076 if n or the num ber o f the pairs o f
observation equals 68.
Also for LW, the significance o f the regression line
is thus n o t compromised at all.
The A n n ex 5 shows the yearly values o f HW, MSL
and LW for Vlissingen, being referred to TAW as
well; on the left o f this Annex, the regression lines for
the period 1890-1998 have been indicated, m entio­
ning at the same time increases o f 0,0329 m /decade,
0,0206 m /decade and 0, 0174 m /decade for the
3 main levels.
In the same Annex, on the right, we only, for reas­
ons o f making a comparison with Oostende, took the
more recent period 1927-1998 into account; this
period indicates nearly the same value for HW
(a rise o f 0,0339 m /d e c a d e ), b u t differs for
MSL (0,0162 m /d e c a d e ) and even m ore for
LW (0,0099 m /decade).
In all cases, the correlation coefficients are rather
high, except at LW for the period 1927-1998, where
we obtain r = 0,49648; nevertheless, as the n pairs of
observation equal 72, the test o f significance causes
no problem (e.g. for the same one-tailed test o f
0,5%, r is due to be 0,2988).
In our former report, we considered the results o f
the linear trends for Zeebrugge (31 years available:
1964-1994) and for N ieuw poort (with a period o f
continuous records o f 28 years: 1967-1994) as being
515
rather disappointing, because they did not follow the
same trendsetting, as found for O ostende and
Vlissingen.
Meanwhile we re-examined the data o f Zeebrugge
(1964-1998) and we discovered a serious offset for
the period 1964-1970...
In the A nnex 6, after having made the necessary
corrections and after adding 4 more years (thus the
period 1964-1998), we now can notice for
Zeebrugge an increase o f 0,0170 m /d eca d e for
HW , o f 0,0150 m /d e c a d e for MSL and o f
0,0086 m /decade for LW.
These values are a bit lower than the ones for
O ostende, but nevertheless they have nearly the same
order o f magnitude.
For the same one-tailed test o f 0,5%, r has to be
0,418 (with n = 35).
The correlation coefficient for MSL (0,46138) is
thus the only one, being high enough.
The other two r-values are too small and, as a m at­
ter o f fact, the significance o f the 2 regression lines
for HW and for LW are thus compromised.
At N ieuw poort, for the period 1967-1998, we
found: 0,0412 m /decade for HW, 0,0277 m /d ecad e
for MSL and 0,0188 m /decade for LW. See also
A nnex 7.
These higher values are due to a local subsidence o f
the quay wall, on which the tide gauge has been
installed. Earlier, we already corrected for this pheno­
m enon, but probably we did not do it as com prehen­
sive as it should be...
For the same one-tailed test o f 0,5%, r has to be
0,454 for n = 32.
The r-values for H W and MSL (0.77146 and
0.69848) are high enough, but this is not the case for
the r o f LW, being only 0.36152.
We can notice that the periods, taken into account
for N ieuw poort and Z eebrugge, represent only
1,72 and 1,88 nodal cycles, while the periods, used
tor the curve fitting for Oostende (1927-1998) and
Vlissingen (1890-1998), are 3,87 and 5,86 nodal
cycles.
H ere we thus have to consider that - due to the
nodal ondulations, as m entionned before - some
m isinterpretations may occur, if we cannot use m ul­
tiples o f a nodal cycle.
3.2. Cyclic curve fittings
In order to understand why this m ethod o f curve
fitting is used, it looks useful to explain briefly the
basic theories behind the so called “nodal cycle” .
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F IG U U R 1
IN F RA STR UCTUUR IN H ET LEEFMILIE U
F IG U U R 2
Equinox
w
W inter
Solstice
Vernal
Equinox
E.d'PliS---—
—
s'*
■*-'-----Aseending
kfnrfoc
s
First we will have a look on the movements o f the
sun and the m oon, relative to the earth; since
N ew ton's time (1642-1727) we know that the attrac­
tion o f one mass upon another in general and the gra­
vitational forces o f the sun and mainly the m oon par­
ticularly are responsible for the tidal movements o f
the oceans and o f the seas...
Relatively we can consider the sun and the m oon as
moving eastwards around the earth on the celestial
ecliptic and on the m oon's orbit. The Figures 1 and 2
below’ show the move- ments o f the sun and the
moon round the earth, supposed to be in the middle
o f the circles.
As the moon is m uch nearer to the earth than the
sun, its m ovem ent, relative to an observer on the
earth, is much faster than the relative m ovem ent o f
the sun around the earth.
The sun completes its orbit in about one year
(365,25 mean solar days [AWKlJdavs), while one
revolution o f the m oon needs less time: it amounts,
relative to the sun, to 29,5306 mean solar days
(or one lunar m onth or one lunation or 1 synodic
period).
The plane o f the sun is inclined to the celestial
equator at an angle o f about 23°27', being the obli­
quity’ o f the ecliptic.
The m oon's path has an inclination o f about
05°09', relative to the plane o f the ecliptic.
The points, where the m oon's orbit crosses the
ecliptic, are called nodes; the point, where the
m oon's orbit crosses the ecliptic from the south to
the n o rth /th e n o rth to the south is called the ascen­
ding node (at G in Fig. 2) / the descending node
(at I in Fig. 2).
The length o f the ascending node or L has the ver­
nal equinox (first point o f Aries - at B in Fig. 1 ) as
reference. Point D in Fig. 2 is the ascending node on
one lunar orbit, while point K is the next ascending
node for the following m oon's path. The regression
o f the ascending node is just the m ovem ent west­
wards along the ecliptic; one single regression o f the
nodes on the ecliptic is completed after 18,61 years,
being one nodai cycle.
Due to the regression o f the 2 nodes, the obliquity
o f the lunar orbit to the celestial equator (m oon's
declination) will change gradually with each orbit
between a variable maximum (23°27'+ 05°09' =
28°36') and a variable minimum value (23°27'05°09'= 18°18').
As the length o f the ascending node am ounts to
90° and 270°, the yearly tidal range has a mean value,
while, with values o f 0° and 180°, the yearly tidal
range has a m inim um /m axim um value; the last valu­
es o f L coincides with a m axim um /m inim um decli­
nation o f the moon.
The Royal Observatory o f Belgium (Brussels) kind­
ly provided us the dates o f the relevant values o f L,
m entioned before, and this for more than a century,.
See also A nnex 8.
The motions o f the m oon and the sun, relative to
the rotating earth, produce thus different tidal pat­
terns on the so called “equilibrium tide”, being the
hypothetical tide, which would be produced if the
earth should be fully covered with a global deep
ocean.
The cyclic fluctuations, due to the nodal cycle, only
can be noticed on the configuration of the yearly
values o f H W /L W o f a certain tidal station.
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IN F RA STR U C TU U R I N H E T LEEFMILIEU
The Annexes 9 and 10 show' these values for
O ostende with the fittings o f a cyclic trend. The rat­
her irregular shape o f the yearly data is random and is
originated by meteorological influences; as a matter
o f fact, the |i-value is very small , but the a-value can
be more than 10 cm, due to these random influen­
ces...
In the equations o f this cyclic curve fitting we
found (with the A-coefficient) an increase o f
0,01758 m /d ecad e for HW and 0,01149 m /decade
for LW; the first is slightly less than the similar value
o f the Annex 4, but for the second we just come to
the opposite conclusion.
Any way, here also we noticed the same global
increase o f 2 and 1 m m /y ear for H W and LW.
Also for reasons o f comparison, the similar curves
for Vlissingen have been given in the Annexes 11 and
12. The cyclic equations provide now A-coefficients
o f 0,03166 m /d eca d e and 0,0123 m /decade; these
values too are comparable with the ones o f Annex 5.
The annual increase o f nearly 3 m m /year for H W
and 1 m m /y ear for LW is thus confirmed.
We did not carry out the analog exercises for
Zeebrugge and N ieuw poort, because there we con­
sidered the time series as being too short for this sort
o f exercise.
3.3. M oving averages
Further we th o u ght that the use o f moving avera­
ges could be interesting, in order to eliminate the
oscillations, due to the nodal cycle and to m eteorolo­
gical influences.
Bv applying this sort o f filtering, w'e are able to
detect accelerations in the increase o f HW, MSL and
LW levels o f O ostende, if any; also the similar values
o f Vlissingen have been added in the Annexes 13, 14,
15, 16, 17 and 18, where successively groups o f obser­
vations o f 1, 7, 13, and 19 years have been taken into
consideration for the period 1925-1998 (included
the 4 years during World War II).
In none o f the pictures o f both places we see up to
now any significant indication o f an acceleration in
the increase o f the concerned values.
3.4. H arm onic analysis
From the Annexes 1, 2 and 3 we can learn that
O ostende has the longest series o f harmonic analysis;
the first occured already for the period 1882-1888
and for the period 1894-1912 13.
However, as there were big gaps in the records of
the periods, last m entioned, we were w ondering if the
analysed data would form a good basis for a possible
reference.
517
The A nnex 19 represents a spreadsheet, where for
2 periods o f 19 years (nearly 1 nodal cycle), the vec­
tor averages o f the 12 main com ponents for
Oostende have been given.
These are in the order o f magnitude o f the ampli­
tude: M 2, S2, N 2 , K2, 2M N 2, M 4, M U 2 , O l ,
N U 2 , 2M S6, M S4 and M 6.
The first period is related to 1944-196416 and the
second period concerns 1980-199819; in between the
last years o f the 2 periods, there is a difference in time
o f 34 years.
Although we can consider a period o f 34 years as
being not so long (nearly 1,83 nodal cycles), we
found it w orth while to compare the Hi and Gi-values o f the 12 com ponents, m entioned before, between
the first and the second period.
Concerning the H i-values, we directly can notice
that the amplitude o f M2, being from far the biggest
in the row, increases with 15,16 m m /3 4 years or
0,4511 n u u /o n e year or 0,84% /34 years; from these
figures we can calculate that the yearly increase o f the
range o f M2 (being twice the amplitude) am ounts to
nearly 1 mm.
The last figure already explains partly the increase
o f the rise we found before.
Apart from N U 2, all the amplitudes o f the 10 other
harmonic constants were subject to an increase. If we
look at column (6), we can see that, from far, the
shallow water com ponents M4, 2MS6, MS4 and M 6
underw ent the biggest increase; here MS4 (with
12,75% /34 years), M 4 (with 7,44% /34 years) and
2MS6 (with 5,17% /34 years) are the biggest in the
row; no doubt, these increases are due to changes in
the configuration o f the bathymetry.
As a m atter o f fact, the amplitudes o f these consti­
tuents are smaller than the one o f M2; nevertheless
also these, together with the others, will contribute to
the increase o f RSL.
The Gi-values also change slightly; M2 and N2
advances with more than 1 m in u te /3 4 years, but for
S2, K2 and 2MN2 a certain retardation occurs.
M ostoften, the smaller ones (from M 4 on), advan­
ce also; only the diurnal O l and the shallow water
constituent MS4 are delayed.
O l and K2 indicate the biggest delay, being
3,33 minutes and 2,41 minutes for 34 years.
As expected already with the findings, m entioned
sub 3.1. and 3.2., we can confirm that the amplitudes
o f the main harmonic constituents increased; also the
phases o f those constants were subject to some chan­
ges.
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518
4 . C O N C L U SIO N S
After the application o f the different techniques on
the configuration o f the annual values o f HW, MSL
and LW for O ostende, Vlissingen, Zeebrugge and
Nieuw poort and on the evaluation o f the harmonic
tidal analysis for O ostende, we come to the following
general conclusions:
4.1. During the last 70 years, a Relative Sea Level rise
occured for the main Belgian coastal tide gauge,
O ostende, being 2 m m /o n e year at HW, 1,5
m m /o n e year for M SL and 1 m m / one year for LW;
as this rise is higher at H W than at LW, an increase o f
the range o f the tide is happening as well
These findings have been evidenced by linear and by
cyclic trends.
O n the one side, Belgian geologists have good reas­
ons to believe th at Oostende has had a rather high
degree o f stability o f the substratum since the quater­
nary period; on the other hand we still consider this
sea level rise as “relative” , because we do not know
for sure how stable the benchmarks near the tide
gauge are and how the stability o f the area, surroun­
ding the tidal stations, is, as the time is passing by.
I f we also take the data o f 1835-1853 into considera­
tion, we only come to a global increase o f 1 m m /year
for all three levels; however, here we are less sure
about the vertical references.
4.2. The stability o f the area, neighbouring the tide
gauge in V lissingen is probably no t so high as for
O ostende 20. The phenom enon o f subsidence o f the
substratum in Zeeland (the Netherlands) may cause
the bigger increases o f the RSL's for HW
(3,3 m m /o n e year), MSL (2,1 m m /o n e year) and
for LW (1,7 m m /o n e year), as can be noticed in the
Annex 5 for the period 1890-1998.
O n the other hand, if we just consider the period
1927-1998 in the same Annex, this higher increase is
just valid for H W (3,3 m m /o n e year), bu t not for
MSL (1,6 m m /o n e year) or for LW (1,0 m m /o n e
year). The last tw o figures are thus very similar to
those for Oostende...
4.3. A lthough th e continuous time series
N ieuw poort and Zeebrugge are not very long so
we nearly come to similar conclusions as
Oostende, as far as the linear trend calculations
concerned.
for
far,
for
are
4.4. So far, the m ethod o f moving averages (see 3.3. )
did not depict any acceleration in the relative sea level
rises o f Oostende and Vlissingen.
4.5. As we expected before, the comparisons o f two
vector averaging results o f tidal harmonic analysis also
show increases for the amplitudes o f 11 o f the 12
most im portant harm onic components.
The impact o f the amplitude o f M2 in the RSL-rise
amounts already to nearly 1 m m /o n e year; expressed
I X I R A STR UCTUUR IN H E T LEEFMILIEU
in percentages, the amplitudes o f the m ost im portant
shallow water constants increased mostly.
The phases o f these components were subject to
advancements or to retardations.
4.6. Similar am ounts o f RSL-rise for comparable
areas in the UK and the Netherlands also can be
found in some recent papers21-22-23 and 24
4.7. Will the Relative Sea Level rise go on in the next
century in the same way?
Is there a chance that, from a certain m om ent, an
acceleration o f RSL will occur?
A prognosis o f coming developments in this field is
extremely difficult to set up and should be based on
a wide range o f international climatic research, lea­
ding to the establishment o f reliable climatic models.
So far, the models o f the Intergovernm ental Panel on
Climate Change (IPCC) only provided inform ation,
which was related to different possible scenarios,
going from a lower increase to a higher increase o f
the RSL.
4.8. Any way, as time passes by, it will be further a
must to pay great attention to the measurements of
the sea levels all over the world in general and o f our
coastal areas particularly.
A thorough quality controll on the tidal records in
the field never should be forgotten; once again, I
want to repeat that, for this sort o f studies, conti­
nuous data are indispensable.
A better m onitoring o f the benchmarks, nearby the
gauges, with m odern techniques as Differential
Global Positioning System (DGPS) - On The Fly, will
allottr the hydrographers to be still more sure about
the absolute referencing for the future.
For this discipline an international cooperation
between specialists is also a need.
Since many years the Coastal Waterways DivisionHydrographic Service, Oostende, provides informa­
tion (hourly values on a yearly basis) to the
Perm anent Service for Mean Sea Level (PSMSL) at
the Proudm an Oceanographic Laboratory (POL),
Bidston Observatory, Birkenhead (UK), which is
wordwide a source o f maregraphical data.
The Global Sea Level Observing System (GLOSS) is
an Intergovernm ental Oceanographic Commission
(IO C ) project, which is aimed to improve the quality
and quantity, supplied to the PSMSL; this is a p ro ­
gram for the establisment o f nearly 300 scientific,
quality controlled tide gauges for global climate
change and oceanographic sea level monitoring.
In this context, Euro-GLOSS is m ore meant as a local
densified network o f GLOSS.
Finally we may m ention a recent European program
for the observation o f sea level, called “European sea
level Observing System” (EOSS) - COST Action 40.
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IN FRASTRU C TU U R I N H E T LEEFMILIEU
In its m em orandum o f understanding for EOSS, it is
stated that “the m ost im portant outcom e o f it is
expected to be an organism, that guarantees and
coordinates the long-term m onitoring activities and
data exchange along the European coastline” . Since
the very start o f this project (Novem ber 1996), the
Coastal Waterways Division-Hydrographic Service,
Oostende, participates in this program.
5. ACK NO W LEDG EM ENTS
Once again, I wish to thank the personnel o f the
Coastal Hydrographic Service, Oostende, involved in
tidal and software matters for their very valuable and
useful contributions.
Many thanks also to the Royal Observatory o f
Belgium, Brussels, for providing the most detailed
information concerning the nodal cycles.
Finally, we are grateful to Koos Doekes o f the
“ Rijksinstituut voor K ust en Zee (R IK Z ) Rijkswaterstaat” , The H ague, The Netherlands, for
putting the relevant data o f Vlissingen regularly at
our disposal and for giving us some interesting com ­
ments on our findings.
REFERENTIES
[1] CU C H LA IN E A. M. KING. Oceanography fo r
Geographers.
Edward Arnold Publishers Ltd. London, 1962.
[2] D. T. PU G H . Tides, Surges and Mean Sea level.
A Handbook fo r Engineers and Scientists. John
Wiley & Sons LTD. Chichester-New YorkBrisbane-Toronto-Singapore. B ath,1987.
[3] P. A. PIR A ZZO LI. Secular trends o f Relative
Sea-Level (R SL ) Changes by Tide-Gauge
Records. Journal o f Coastal Research, SI,
No. 1, 1986.
[4] P. A. PIR A ZZO LI. Recent Sea-Level Changes in
the North A tlantic. Late Q uaternary Sea-Level
Correlation and Applications, 153-167. Kluwer
Academic Publishers. 1989.
[5] U N IT E D
N A T IO N S
E N V IR O N M E N T
PRO G R A M M E-G O V ERN M EN T OF T H E
NETH ERLA NDS. Impact o f Sen Level Rise on
Society.A case study fo r the Netherlands.
Delft Hydraulics, Rijkswaterstaat and Resource
Analysis. Final report. March 1991.
[6] C. VAN CAUW ENBERGHE. Synopsis o f the
tidal observations along the Belgian coast
Conclusions with respect to the high water, the
mean sea and the low water levels.
Final report o f the EC-contract EPOC-CP900015-Volume 4. March 1993.
519
[7] C. VAN CAUW ENBERGHE. Relative sea level
rise: further analyses and conclusions with respect
to the high water, the mean sea and the Ios water
levels along the Belgian coast. Final report o f the
EC-contract EV5V CT 93 0266. August 1995.
[8] J. LAUWERS. Les marées du port d'Ostende.
Annales des Travaux Publics de Belgique. A oût
1930.
[9] L. JONES et R. H EID ER SC H EID T. Surfaces
de niveau zéro belges et zéro hydrographique H.
Annales des Travaux Publics de Belgique. Juin
1952.
[10] J. H EN R IO N ET. Notice sur les travaux topo­
graphiques exécutés au Dépot de la Guerre de
Belgique. Archives de l'In stitu t Géographique
Militaire. Bruxelles. 1876.
[ 11] A. STESSELS. Discussion des observations de la
marée et ses effects dans l 'Escaut. Annales des
Travaux Publics de Belgique. Tom e XXX,
Deuxième Cahier. 1872.
[12] M. BOVIE. Etude sur la régime de la marée
au port d'Ostende. Annales des Travaux
Publics de Belgique. Tome XLIV. 1887.
[13] P. M E L C H IO R et P. PAQUET. Les constantes
des marées océaniques au port d'Ostende de
1882 à 1964. Koninklijke Academie van
België. M ededelingen van de Klasse der
W etenschappen-5e Reeks-Boek LIV -1968,
10.
[14] J. LAUWERS. Les marées des ports d'Ostende,
de Zeebrugge et de Nieuwpoort. Annales des
Travaux Publics de Belgique. Avril Juin 1949.
[15] C. VAN CAUW ENBERGHE. Overzicht van
de tijwaarnemingen langs de Belgische kust.
Periode: 1941-1970 voor Oostende, 1959-1970
voor Zeebrugge en Nieuwpoort. Tijdschrift der
Openbare Werken van België. Nr.4, 1977.
[16] P. M ELC H IO R , P. PAQUET et C. VAN
CAUW ENBERGHE. Analyse harmonique de
vingt années océaniques à Ostende. Koninklijke
Academie van Belgie. M ededelingen van de
Klasse der W etenschappen-5e Reeks-Boek
LIII-1967,2.
[17] C. VAN CAUW ENBERGHE. Overzicht van
de tijwaarnemingen langs de Belgische kust.
Periode: 197T l 980 voor Nieuwpoort, Oostende
en Zeebrugge.
Tijdschrift der Openbare Werken van Belgie.
Nr.5, 1985.
[18] C. VAN CAUW ENBERGHE. Overzicht van
de tijwaarnemingen langs de Belgische kust.
Periode: 1981-1990 voor Nieuwpoort, Oostende
en Zeebrugge.
Infrastructuur in het Leefmilieu - 6 /9 3 .
520
[19] C. VAN C A U W EN B ER G H E. Harmonie
Tidal Predictions along the Belgian coast History and present Situation. Infrastructuur
in het Leefmilieu - 1 /9 9 .
[20] D. D IL L IN G H EN P. F. H E IN E N .
Zeespiegelrijzing, getijveranderingen en deltaveiligheid. R apport RIKZ - RWS - 94.026 Juni 1994.
[21] P. L. W O O D W O R T H , S. M. SHAW and D.
L. BLACKMAN. Secular trends in mean tidal
range around the British Isles and along the
adjacent European coastline.
Gcophys. Journal Int. (1991) 104, 593-609.
3/99
IN F RA STR UCTUUR I N H ET LEEFMILIEU
[23] C O M M ISSIO N OF T H E E U R O PE A N
C O M M U N IT IE S -D IR E C T O R A T E FOR
SCIENCE, RESEARCH AND D E V E L O P­
M ENT, CLIM ATOLOGY AND NATURAL
HAZARDS. Climate Change, Sea Level Rise
and associated Impacts in Europe.
Final reports o f the E C -contract EPOCC P 90-0015-Volume 1 to 4. M arch 1993.
[24] P L . W O O D W O R T H , M .N .T SIM PL IS,
R.A.FLATHER and I. SH EN N A N . A review
o f the trends observed in British Isles mean sea
level data measured by tide gatiges. Geophys.
Journal Int. (1999) 136, 651-670.
[22] I. SH EN N A N and P. L. W O O D W O RTH .
A comparison o f late Holocene and twentiethcentury sea-level trends from the U K and North
Sea region. Geophys. Journal Int. (1992) 109,
96-105.
RESUME:
SAMENVATTING:
M ontée relative d u niveau de la m et le long de la
côte Belge - analyses et conclusions pour les
niveaux de la marée haute, du niveau moyen et
de la marée basse.
Relatieve zeespiegelrijzing langs de Belgische
kust: analyses en conclusies m et betrekking tot
de niveaus van hoogwater, van gem iddeld zeeni­
veau en van laag water.
Les gaz à effet de serre dans l'atm osphère de notre
planète seraient à l'origine de la m ontée relative du
niveau de mer en général et de celle le long de la côte
Belge en particulier.
De broeikasgassen in de atmosfeer van onze planeet
zouden aan de basis liggen van de relatieve zeespie­
gelrijzing (RSL) in het algemeen en van deze langs de
Belgische kust in het bijzonder.
Les données m arégraphiques de longue durée pour
notre côte, ayant u n caractère continu et étant d'une
haute qualité, ont permis au Service Hydrographique
de la Côte, O stende, à m ettre au point quelques
m éthodes pour étudier cette phénom ène plus prof­
ondém ent.
Aan de hand van langdurige, continue en betrouw ­
bare gegevens van de 3 kustmaregrafen kon men in
de Hydrografische Dienst van de Kust te Oostende
enkele m ethoden vooropstellen om de genoemde
stijging van het zeeniveau na te trekken.
Line comparaison avec les données de Flessingue
(Pays Bas) était aussi très valable.
A l'aide des calculs des m oindres carrés, on a
dém ontré qii' au courant de ce siècle, une montée du
RSL à la côte Belge est différent selon le niveau de la
mer concerné: marée haute, niveau moyen ou marée
basse.
Hierbij was een vergelijking m et de gegevens van
het nabije Vlissingen (Nederland) zeer waardevol.
M et lineaire en cyclische best-fit berekeningen kon
m en aantonen dat een stijging van RSL aan de
Belgische kust in de loop van deze eeuw verschillend
is naargelang men de jaarlijkse niveaus van hoog
water, van m iddenstand o f van laag water beschouwt.
3/99
IN F RA STR UCTUUR I N H E T LEEFMILIEU
521
A fdeling W aterw egen K ust
H y d ro g rafie
O ostende
A n n ex 1
SYNOPSIS OF THE TIDAL OBSERVATIONS FOR OOSTENDE (Belgium)
Periods
Tid e pole (a) or
auto m atic tide
gauge (b)
Harm onic Tidal
Analysis
R eferences
Rem arks
1820-1834
(a)
No
Ref. 8 & 9
Data are lost
1835-1853
(a)
No
Ref. 10
Only m onthly m ean values available
1866-1871
(a)
No
Ref. 11
Data are lost
1878-1914
(b)
Yes for 1882-1888
and for 1894-1912
Ref. 12 & 13
Big gaps In the records
Reference level not well known
(b)
No
Ref. 8 & 14
Big gaps in the records
for 1925, 1926 & 1940
1941-1970
(b)
Yes fo r 1943-1968
Ref. 14, 15 & 16
Big gaps in the records
fo r 1941, 1942 & 1944
1971-1980
(b)
Yes fo r 1976-1980
Ref. 17
C ontinuous records
1981-1990
(b)
Yes fo r 1981-1990
Ref. 18
C ontinuous records
1991-1998
(b)
Yes fo r 1991-1998
C ontinuous records
1925-1940
522
3/99
IN F RA STR U C TU U R IN H E T LEEFMILIEU
A fdeling Waterwegen Kust
Hydrografie
Oostende
Annex 2
SYNOPSIS OF THE TIDAL OBSERVATIONS FOR ZEEBRUGGE (Belgium )
Periods
Tid e pole (a) or
autom atic tide
g a u g e (b )
Harm onic Tidal
Analysis
R eferences
Remarks
1932-1940
(b)
No
Ref. 14
Big gaps in the records for 1932 and 1940
1941-1943
(b)
Yes for 1943
Ref. 14
Big gaps in the records from 1941 to 1943
1959-1970
(b)
Yes for 1963-1969
Ref. 15
Big gaps in the records from 1959 to 1961
1971-1980
(b)
No
Ref. 17
C ontinuous records
1981-1990
(b)
Yes for 1981-1990
Ref. 18
Continuous records
1991-1998
(b)
Yes fo r 1991-1998
Continuous records
3/99
IN F RA STR UCTUUR IN H E T LEEFMILIEU
523
Afdeling Waterwegen Kust
Hydrografie
O ostende
A nnex 3
S Y N O P S IS OF TH E TID A L O B S E R V A T IO N S FOR N IE U W P O O R T (B elg iu m )
T id e p o le (a) or
H a rm o n ic T id al
R e fe re n c e s
A n a ly s is
R e m a rk s
(b)
No
Big g a p s in th e re co rd s fo r 1933, 1 9 3 7 &
1938
1 94 1-19 43
(b)
Yes fo r 1943
1 95 9-19 70
(b)
Y e s fo r 1 96 7-19 69
P e rio d s
a u to m a tic tid e
g a u g e (b)
1 93 3-19 38
Ref. 14
Ref. 14
Big g a p s in th e re co rd s fo r 1942 & 1943
Ref. 15
Big g ap s in th e reco rd s from 195 9 to
1961 & fro m 1964 to 1965
1 97 1-19 80
(b)
Y e s fo r 1980
Ref. 17
C o n tin u o u s reco rd s
1 98 1-19 90
(b)
Y e s fo r 1 98 1-19 90
Ref. 18
C o n tin u o u s reco rd s
1 99 1-19 98
(b)
Y e s fo r 1 99 1-19 98
C o n tin u o u s reco rd s
3/99
IN F RA STR UCTUUR I N H E T LEEFMILIEU
A fdeling W aterwegen Kust
Hydrografie
O ostende
Annex 4
LINEAR TRENDS,
calculated on
the ANNUAL VALUES of HW, MSL and LW
for OOSTENDE (Belgium)
Period: 1927-1998
(-1940, 1941, 1942, 1944)
Period: 1835-1852
1927-1998
(-1940, 1941, 1942, 1944)
JAAR vs. HW
JAAR vs. HW
HW = 2.1819 + .00105 'JA A R
O ostende HW 1835-1852 / 1927 -1 9 9 8 Correlation: r = .79230
HW = -.0106 + .00217 * JAAR
O ostende HW 1927-1998 Correlation: r =
4.5
4.46
4.42
4.38
4.34
I
?
>
d
~
55
a>
E
.E
£
5° 4.22
426
8
«
4.18
4.14
■- 4.06
X 402
3.98
3.94
3.9
1820
X
1840
1860
1880
1900
1920
JAAR [
1940
1960
Regression
1980
2 000
95% confid.
4.58
4.54
4.5
4.46
4.42
4.38
4.34
4.3
4.26
4.22
4.18
4.14
4.1
4.06
4.02
3.98
3.94
3.9
1920
JAAR vs. MSL
MSL = -.5811 + .00144 * JAAR
O ostende MSL 1927-1998 Correlation: r = .76372
2.48
2.4
............... i ...................
...
m
£
£, O
....O....
o
2.24
2.2
2.16
2.12
2.08
2.04
o
0
-
o
....... i . . .
..................
1860
1880
1900
1920
jáár
1940
°
1960
R egression
1980
2000
1960
95% confid. I
JAAR
JAAR vs. LW
JAAR vs. LW
LW = -1.278 + .00084 * JAAR
O ostende LW 1927-1998 Correlation: r = .38247
0.7
0.66
0.66
-
..................... i ...................
> 0.46
5 0.42
0.38
cu 0.34
E 0.3
0.26
0.62 ................... i .............
...................
0.58
0.54
0.5
0.46
Ö .................
..............,°oS
0.42
0.38 .................
0.34
o
-u0.3
L
....
0.26
3 0.22
0.22
0.18
0.14
0.18
0.14
0.1
0.62
0.58
0.54
1860
:
1980
Regression
LW = -1.604 + .00101 * JAAR
O ostende LW 1835-1852 /1 9 2 7 -1 9 9 8 Correlation: r =
1840
...
o
? 1
0.7
1820
-oo—o...... '•
................
:
1840
........ ¿
2.18
1880
1900
1920
JAAR I ^
1940
1960
R egression
1980
2000
confid.
o
°
0
...
1820
•
:
.......
..................
1990
2000
95% confid.
1970
1980
Regression
1960
JAAR vs. MSL
2.32
c
1950
JAAR
O ostende MSL 1835-1852 /1927-1998 Correlation: r = .90585
1
1940
1930
MSL = .25183 + .00102 * JAAR
26
5
f>
o°öö
............:...................
2000
-
-
................:................... : ................
:
Oo
o ~ °— -<r~
0
°
o°
” 0
'
.................i _________
1960
JAAR
Regression
95% confidTj
3/99
525
IN F RA STR UCTUUR I N H E T LEEFMILIEU
A nnex 5
Afdeling Waterwegen Kust
Hydrografie
Oostende
LINEAR TRENDS,
calculated on
the ANNUAL VALUES of HW, MSL and LW
for VLISSINGEN (The Netherlands).
Period: 1927-1998
Period: 1890-1998
JAAR vs. HW
JAAR vs. HW
HW = -2.396 + .00339 * JAAR
V 1927-1998 Correlation: r = .86208
HW = -2.194 + .00329 * JAAR
Vlissingen HW 1890-1998 Correlation: r = .93334
4.5
4.45
4.4 ...........
4.35
4.3
4.25
4.2
i
i
i
î
i
i...........
i
o °
.......... i .......... j
i
........ i
: oô
? ...
..
o
¿a
"
4.15
4.1
o' o
...O 0
......
i
i
¡
i
fo
.......... r i i ; ; ; ; : ;
'« °
:
.
i
!
i
°°n
o
°>
.........
4.05
4
s
3.95
3.9
1880 1890
:
; ...........i...........
:
..............i ............
1900 1910
i
1920
i
1930
....... i . .. .
197Q. 198Q_
R egression
1940
JAAR
JAAR
JAAR vs. MSL
JAAR vs. MSL
MSL = -1.814 + .00206 * JAAR
MSL = -.9338 + .00162 * JAAR
Vlissingen MSL 1927-1998 Correlation: r = .77693
Vlissingen MSL 1890-1998 Correlation: r = .90030
2.6
2.55
2.5
2.45
2.4
i
........ :........
:
•
’•
i
;
....... i........I........
. ....
CO
“ vLaSfto
2.3
2.25
2.2
2.15
2.1
2.05
■ÆT.
°o-^
o
........
°n
1900 1910
1920
O
0
.....
1930 1940
1950 1960
o
1990 2000
1950
95%confid7]
1960
JAA R I
Regression
JAAR vs. LW
...
.........
.........
b°
.......
...0% ,
c i" "
..... t r i .......-
0.35
..... „
.E
J 0.25
-i
0.2
........ :....... .?....... i.......
........ :. ....... £ ..... i.......
: ■
P
<3°.
95% confid. |
zr
........ I ......
C
'0®-— 0 "
Ö o
.........
LW = -1.482 + .00099 * JAAR
Vlissingen LW 1927-1998 Correlation: r = .49648
0.45
0.15
0.1
o
JAAR vs. LW
........ i........ i....;;;
........ ;............... i .......
........ :........ i .......
° '4
0
o o0
° o.
0
2
1970 1980
0.7
5
......¿ 0 "
LW = -2.948 + .00174 * JAAR
Vlissingen LW 1890-1998 Correlation: r = .79069
0.65
t
.........
2.16
2.12
2.08
2.04
i
R egression
2.56
2.52
2.48
2.44
2.4
2.36
2.32
2.28
2.24
2.2
...
i
....... !.......
JAAR I ^
5
-cP O
o o
o ' '°? i
95% confia
2.6
i
i
;;:;;:i;::i
:
;
ioo °<
....... i ....... i .......
....... i ....... i.........
2.35
Regression
-i
0 °oô5 ..........
a
°
o
........
.
!
;
........ i. .......
;
1950
JA A R
I
Regression
95% confid. |
1960
JAAR
Regression
95% confid
526
3/99
IN FRASTRU C TU U R IN H E T LEEFMILIEU
Afdeling W aterwegen Kust
Hydrografie
Oostende
Annex 6
LINEAR TRENDS,
calculated on
the ANNUAL VALUES of HW, MSL and LW
for ZEEBRUGGE (Belgium).
Period: 1964-1998
JAAR VS. HW
HW = .82499 + .00170 ' JAAR
Zeebrugge HW 1964-1998 Correlation: r = .35134
.5
4.46
4.42
4.38
4.34
4.3
4.26
4.22
4.18
4.14
4.1
4.06
4.02
3.94
3.9
1920
1930
1940
1950
1960
já á r
I
1970
1980
R egression
1990
2000
95% confid. |
JAAR vs. MSL
MSL = -.6937 + .00150 * JAAR
Zeebrugge MSL 1964-1998 Correlation: r = .46138
2.6
2.56
2.52
2.48
2.44
2.4
2.36
2.32
2.28
2.24
2.2
2.16
2.12
2.08
2.04
12920
d z z z b :
1930
1940
1950
1960
1970
1980
R egression
1990
2000
95% confid. [
JAAR vs. LW
LW = -1.169 + .00086 * JAAR
Zeebrugge LW 1964-1998 Correlation: r = .21145
0.78
0.74
0.7
0.66
0.62
0.58
0.54
0.5
0.46
0.42
0.38
0.34
0.3
0.26
0.22
0.18
0.14
0.1
1920
:h:
1930
1940
1950
1960
JA A R
1970
I
1980
Regression
1990
2000
95% confid. |
3/99
IN F RA STR U C TU U R I N H E T LEEFMILIEU
Afdeling Waterwegen Kust
Hydrografie
O ostende
Annex 7
LINEAR TRENDS,
calculated on
the ANNUAL VALUES of HW, MSL and LW
for NIEUWPOORT (Belgium).
Period: 1967-1998
JAAR vs. HW
HW = -3.772 + .00412 * JAAR
Nieuwpoort HW 1967-1998 Correlation: r = .77146
4.58
4.54
4.5
4.46
4.42
4.38
„ 4.34
0
4.3
Z 4.26
S 4.22
E 4.18
c 4.14
4.1
> 4.06
1 4.02
'<D
3.94
3.9
1920
1930
1940
1950
1970
1980
R egression
1960
JAA R I
1990
2000
95% confid. |
JAAR v s. MSL
MSL = -3.205 + .00277 * JAAR
Nieuwpoort MSL 1967-1998 Correlation: r = .69848
2.56
2.52
2.48
2.44
2.4
5
<
2 2 36
~ 2.32
&
- 2.28
at
£ 2.24
c
2.2
z
2.16
gj
2.12
o no
2.04
1920
1930
1940
1950
1970
1980
R egression
1960
JAAR
1990
2000
95% confid.
JAAR vs. LW
LW = -3.428 + .00188 * JAAR
Nieuwpoort LW 1967-1998 Correlation: r = .36152
0.7
0.66
0.62
0.58
0.54
. 0.5
£<
d o-46
■ 0.42
0.38
0.34
c
0.3
~ 0.26
B
5j
OíM_
0.22
0.18
0.14
0.1
1920
1930
1940
1950
1960
JA A R
1970
I
1980
Regression
1990
2000
95% confid. |
52S
3 /M
IN F RA STR UCTUUR I N H E T LEEFMILIEU
A fdeling Waterwegen Kust
Hydrografie
O ostende
Annex 8
N O D A L C Y C LE S FROM 1913 TO 2025
L or the Lenght
of the
Ascending Node
0° = 360°°
Date and
Time in GMT
Time
Difference
in days
Range
of the
Tide
Remarks
Minimum
27/05/1913 0:09:14
1699,59140
2 7 0 '°
20/01/1918 14:20:51
Mean
1699,59156
CO
o
o
180'°
16/09/1922 4:32:42
Maximum
1699,59174
12/05/1927 18:44:48
Mean
1699,59190
0° = 3 6 0 '°
6/01/1932 8:57:08
Minimum
1699,59207
2 7 0 '°
31/08/1936 23:09:43
Mean
1699,59225
CO
o
o
180” °
27/04/1941 13:22:33
Maximum
1699,59242
22/12/1945 3:35:38
Mean
1699,59258
0° = 360“ °
17/08/1950 17:48:57
Minimum
1699,59275
2 7 0 '°
13/04/1955 8:02:31
Mean
1699,59292
CO
o
o
180'°
7/12/1959 22:16:19
Maximum
1699,59310
2/08/1964 12:30:23
Mean
1699,59326
0 ' = 3 6 0 '°
29/03/1969 2:44:41
Minimum
1699,59343
2 7 0 '°
Mean
22/11/1973 16:59:13
1699,59361
CO
o
o
180"°
19/07/1978 7:14:01
Maximum
1699,59377
14/03/1983 21:29:03
Mean
1699,59395
0' = 3 6 0 '°
8/11/1987 11:44:20
Minimum
1699,59412
2 7 0 '°
4/07/1992 1:59:52
Mean
1699,59428
o
0
CO
180'°
27/02/1997 16:15:38
Maximum
1699,59446
24/10/2001 6:31:39
Mean
1699,59463
0° = 3 6 0 '°
19/06/2006 20:47:55
Minimum
1699,59480
2 7 0 '°
13/02/2011 11:04:26
Mean
1699,59497
CO
o
0
1 8 0 '°
10/10/2015 1:21:11
Maximum
1699,59514
4/06/2020 15:38:11
Mean
1699,59531
0' = 3 6 0 “
29/01/2025 5:55:26
Minimum
Mean year in the nodal cycle
3/99
IN F RA STR U C TU U R I N H ET LEEFMILIEU
529
Afdeling Waterwegen Kust
Hydrografie
O ostende
Ul,
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10
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Annex 9
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530
INFRASTR UCTUUR I N H E T LEEFMILIEU
A nnex 10
Afdeling Waterwegen Kust
Hydrografie
O ostende
C"'
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3/99
IN F RA STR UCTUUR I N H ET LEEFMILIEU
531
Afdeling Waterwegen Kust
Hydrografie
O ostende
in.
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A nnex 11
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3/99
532
IN F R A STR UCTUUR I N H E T LEEFMILIE U
A nnex 12
o».
<n
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1SS0.5
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Afdeling Waterwegen Kust
Hydrografie
Oostende
09.
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3/99
IN F R A STR UCTU U R IN H E T LEEFMILIEU
333
Afdeling W aterwegen Kust
Hydrografie
Oostende
A nnex 13
MOVING AVERAGES,
calculated on
the ANNUAL VALUES o f HW
for OOSTENDE (Belgium) AND FOR VLISSINGEN (The Netherlands).
Period: 1925-1998
Oat
4.5
m
1 4 aa
V. G.
X
X :
X
!
Oostende
per
Î
J aapx
* * *
X
X
...............V y y y ^
X
X
* * \
:
*
V
xx x x
*x
X*
x xx
x*
X
x
*
xv
X
X „
XX
X*X v
V
X
x
Moving averages, calculated
on the annual values
o f HW for Oostende
*
x
XX
X
X
x
x
H. W.
1935
-
1990
ONE YEAR
VI
4.5
m
V. G.
T .R .M .
Vlissingen
per-
Ost
4
m
I J a en
1 * 0«
x
X
X
AV
V
A
- ...................... V
X
/
X
X X X
_
v
X x
vX
V
X
X
X
X
X
*
x
*
/
X
XX
x
X*
X
*
*
Moving averages, calculated
on the annual values
of HW for Vlissingen
X
X
X
N'x
X X xXX X xAX
x
X
ex
*xx
*
A
y*
x
Xx
X
'
*
*
x *
X
X
tatea
33^5
3 9)35
VI
'
IS Ë 5
lates
3 a ‘75
3 SÖ5
19Ö5
4 rr.
Ost
4,5
m
M «
V.G.
Oostende
per
xx
? Jaar
X
. x « 1* * *
x
x
a x x * * x XX v
XXX, ,
Xx * *
X
X
X
**x
x x
*xv
x*
Xx x x x
xx
* x*
*XxX
H. W.
VI
4.5
V.G,
m
Os t 4
T. f l . W,
VI l a a l n g e n
pe r -
1935
-
1990
SEVEN YEARS
m
7 Jaar
) * ob
X
XX Y
YX
*XÄ
y XY
X
XXX
VX**
X
x XxXx
xX*XvXY
.
vXX
XX
V
X
Moving averages, calculated
on the annual values
o f HW for Vlissingen
„
» X * ’ X X X X>
x*X
ï * l i X x * 1‘ X X ï
xXx
xk
xXxxx
X
Y X*
Xv
*
A XX
13Ï5
Moving averages, calculated
on the annual values
o f HW for Oostende
Ä * * X XX K
Xx
x
/
XX X X x X X
i aàs
V1 4
ia'4S
m
196s
lates
i a.7s
-
.
lates
lates
534
3/99
IN F RA STR U C TU U R IN H E T LEEFMILIEU
A fdeling Waterwegen Kust
H ydrografie
O ostende
Annex 14
MOVING AVERAGES,
calculated on
the ANNUAL VALUES of HW
for OOSTENDE (Belgium) AND FOR VLISSINGEN (The Netherlands).
Period: 1925-1998
Ost
4.S m
) -4 no
V.G.
Oùstande
pep
13 J a a r
Moving averages, calculated
on the annual values
of HW for Oostende
ïX ) ( X * m ï ïx x l(xxx*
---------------------------------- ---------------------------------------------X*x*
X XX
**xx*xx
H. W.
1925
-
1338
THIRTEEN YEARS
VI
4.5
V.G.
m
T.fl.H .
Vlls&lngen
pa r -
Oat
4
m
13 J a a r
1
fl
yxxxx * x x x x x xxxx
*xx
Moving averages, calculated
on the annual values
of HW for Vlissingen
) [ XXXx x X Xx X x x x x x X 1<xxX
..V
XX * *
jgfes
• • X* *
y x X x x x x X x x Xx A
„ XX*
V.X
i aH5
tais
i s 55
tafes
,V1 A m
is?s
Ost
4,5
'Hastende
per
XXXXXXXXXXXXX.XXXXXXXXX
19 Ja ar -
V. G .
m
Moving averages, calculated
on the annual values
of HW for Oostende
xx
H. W.
4.5
am
yïïXXXXXXX
V , ^ X X X X X X X X X X X X XXXXXX.
....................................... ..........................................
VI
1395
rn
1A
V.G.
Ja' as
. .. .
T.fl.W.
Vil »singeri
par
Oat
4
1925
-
1998
NINETEEN YEARS
m
13 J a a r 1 a a.
v
VXx X X
X XX X X
xxxxxx*.<1
-
X*
„
x
Xï
x x X: x x X x
Moving averages, calculated
on the annual values
o f HW for Vlissingen
Xx
,*«X X **
x*x***>
xxxxxxxxx
L3Ö5
1339
V1 4 m
1945
1353
3303
•
_
.
.
.
.
Lá?9
L385
3/99
IN F RA STR UCTUUR I N H E T LEEFMILIEU
A fdeling W aterwegen Kust
Hydrografie
O ostende
A nnex 15
MOVING AVERAGES,
calculated on
the ANNUAL VALUES of MSL
for OOSTENDE (Belgium) AND FOR VLISSINGEN (The Netherlands).
Period: 1925-1998
Ost
2.5
m
I -4 d a
V. G.
Oostende
per
1 Jaar*
X* y
y X^
x
**x
XX *v
X %
x*
x
x
y
ï
w
*
VX
Ï
X
X
X
XX
y V .,
*
*
Moving averages, calculated
on the annual values
o f MSL for Oostende
V
a
*
/
y
X
X
M- S . L .
VI a .5 m
V.G.
T.ñ.Wn
VI 1 b s 1 n g a n p e r
1 3 2 5 - 1QQÖ
ONE YEAR
Oat £ m
I J a &r
) -1 via
*
X
x*
•«■\
X
--------------------------------------- vMv --- X*--- ..---------u-- *v x
XX
XX
V*
X
x
X XX
**
**
X
x
x
„
X
*
X
ï
» v.
xx
x
V
*
*
X
*
x*
X
Moving averages, calculated
on the annual values
o f MSL for Vlissingen
**
y' i ■
■ X x * xx * x *
--------------------------*
X
*
*
*
X
aaäs
3asa
ie * g
tasa
lafcs
iais
...................... vi a m
Ost
V. G.
ta a s
Oostende
per
?
2.5
m
jaar
xi
VI 2 . 5 m
T.F I.W .
Vlissingen
per
O st 2
Moving averages, calculated
on the annual values
o f MSL for Oostende
Xxxxxxxxxx***xxx
M . S . i.
V.G.
taas
_ ._________________
is a s
-
1B3Ö
SEVEN YEARS
m
? Jaar
I 0
Moving averages, calculated
on the annual values
o f MSL for Vlissingen
Xx X X x x x x x x x * * x x *
xx.-xxxx
X X X X ^X x****
XX Xy X
ta 'S S
1335
.......
vi a m
L3Ü5
1355
19Ü S
L S ^S
ta'B S
1995
.............................................. ................... _______________________________
3/99
IN F RA STR UCTUUR I N H ET LEEFMILIEU
A fdeling W aterwegen Kust
Hydrografie
O ostende
A nnex 16
MOVING AVERAGES,
calculated on
the ANNUAL VALUES of MSL
for OOSTENDE (Belgium) AND FOR VLISSINGEN (The Netherlands).
Period: 1925-1998
Ost
2.5
m
1 A o.
V.G.
Oüstendß
per
13 J a a r
Moving averages, calculate
on the annual values
of MSL for Oostende
..< x x X * x X X x x x x x
x 7 x x * x x x * * v * * * K X * » x x X « K * ' * x .................- ........ ...........................
..................... .... " " ...............m
K X K X X * * * * 10™
* * *
X
M .S.L.
1325
-
1999
THIRTEEN YEARS
VI
2.5
m
V.G.
T.fl.W.
VI l a s l n g t t n
per
Ost
2
m
13 J a a r
1 A -JH
Moving averages, calculate
on the annual values
of MSL for Vlissingen
vxXxXxxXxxx
..............................................
........................................
XXXXXXXXXXKXX****
3Säg
lâ'35
.............................. VI a
13*5
39135
.......................................................
m
lâ’BS
. '
Ost
J3?S
lâ'B5
la s s
..
2.5
m
J 4 ÜB
V.G.
Oostende
per
19 j a a r
Moving averages, calculate
on the annual values
of MSL for Oostende
^ v x x x x x x x x x x x x x x x
'
x x x * x ; x X X X X X x x XX XXX V X ... M . U « X
x x x x x XX AA
* - .......
M .S.L.
1325 -
1999
NINETEEN YEARS
VI
2.5
V.G.
m
T.fl.W.
VilaeIngen
per
Ost
2
m
13 J a a r
1A
IB
Moving averages, calculate
on the annual values
o f MSL for Vlissingen
V* V VXX XXX
. „ V V x y. x x x x x x * • • *
........................... " ........... ... " "
X x x x x * x * x :•< x * » x x x x :« * x * •' ............................... -..........
,.x xxxX X xxxxxX
xxxxx***
193s
...................... V I a m
lääs
1345
1355
.......................................................
.
.
190S
.
ia?s
i s es
3/99
537
IN F RA STR U C TU U R I N H E T LEEFMILIEU
Afdeling Waterwegen Kust
Hydrografie
Oostende
A nnex 17
MOVING AVERAGES,
calculated on
the ANNUAL VALUES of LW
for OOSTENDE (Belgium) AND FOR VLISSINGEN (The Netherlands)
Period: 1925-1998
Qs-fc . B75 m
I «
V .G .
ô û s te n dc
per
1 Jaar
Moving averages, calculated
on the annual values
of LW for Oostende
V
X
*" x
X
X
X
Xx X*
x* *
X
\
X
*
y
* X
XX VX X
x X
*
**
X
X X ***
3
L .W .
1325
-
1330
ONE YEAR
VI
. B75 m
V.G.
T .fl.W .
VI 1 asst n g e n
psr
Oat .1 7 5
m
..........................
I Jisr
I A IB
*
*
xX*X X
*•’ *>.* <x>
:
X
X-
-J.
XX
x *
vX
v
19S5
^
~
ï
„
* * \ x* x
\\* x
* * X*XX
XV * *
x„ xX xXX*
x /x
Moving averages, calculated
on the annual values
of LW for Vlissingen
*
; ---------------- *------X---------------------------------------3
X x
19^5
VI
19Ë5
ISiJ-S
. 37 5
13ÉS
.
m
-
Oat
1375
.
lâ'05
1335
_______________________
.5 7 5
m
I AdB
V.G.
per
?
Jaar
XxX
*
v X x X Xv
xxx*
ö ü a te n d e
-X
X* x x x * x x
V
vXX
***
x * xxx x*
X
X
X
. B75 m
V .G .
T .fl.W .
V I 1 Bia I n g e n
per
O at . 175
1925
» X*
Ü2
lâï5
jf*
xXx*x*
19)15
............................. VI
I 34S
. 375
rr>
SEVEN YEARS
A 'JB
XX
V*X X XX
XXXXXX*
Í3SS
1330
7 Ja ar-
x*xXx„
* v.*■
-
m...............................
I
, A*
*
X* x X x * X
L .W .
VI
Moving averages, calculated
on the annual values
of LW for Oostende
x x X X * X!<* * X
X X x vAy
X>¡XXx*
19Ï5
. ■
X
L9 7 5
XXXXXX
Moving averages, calculated
on the annual values
o f LW for Vlissingen
***
t â f iS
..................................................
3/99
538
IN FRASTRU C TU U R I N H E T LEEFMILIEU
Afdeling W aterwegen Kust
Hydrografie
Oostende
Annex 18
MOVING AVERAGES,
calculated on
the ANNUAL VALUES of LW
for OOSTENDE (Belgium) AND FOR VLISSINGEN (The Netherlands).
Period: 1925-1998
Os t
«E75
m
\ 4 MM
V .fi.
ô û a t e n d ft
per
13
ja a r
X V«
xXxX xxxx
Moving averages, calculated
on the annual values
of LW for Oostende
M* X X
-X
.,* * *
„ « X X X X O X ÏÏJ ,
><Xx X X X
XXxxxXXXXXx
xX !< v
L .W .
1335
-
133B
THIRTEEN YEARS
VI
.6 7 5 m
V I 1» & 1n g e n
V .G .
Oat
T .fl.W .
per
13
m
.1 7 5
J aa.r
1 4 <3«
x x X * x x X X X X X XX X X X X X XX XX
^
x
X
^
x x x x
^
^
x
Xx x x k x x ^
^
x x
*
Moving averages, calculated
on the annual values
of LW for Vlissingen
X X X X v x w v ï v X**
19äS
iâ35
....................................
VI
1945
.1 7 3
w
1955
lâBS
..................................................................
1SÍS
L3â5
13Ï5
.
O st
. E75
m
M a.
V .G .
Où s t e n d e
per
19
Jaar
Moving averages, calculated
on the annual values
of LW for Oostende
.J X X X X X K X X *
x X X X X X X X xX *X X *X xX X X xX X X x x x x X x x x x x xXXXXXXX
X XX * x
L .W .
1335
-
L33B
NINETEEN YEARS
VI
,B ? 5
V .G .
rn
T .fl.W .
V M a a ln g tn
per
O st
13
.1 7 5
m
J aar
1 4 aa
xxxxxxxxxxxxxxxxx
Moving averages, calculated
on the annual values
o f LW for Vlissingen
............, x x x « « * x x x « « x
13ÖS
....................................
1935
VI
. 1?5
1345
m
............................................
1 35 S
1335
13'7 5
193 S
3/99
IN F RA STR U C TU U R I N H E T LEEFMILIEU
539
A fdeling Waterwegen Kust
Hydrografie
Oostende
A nnex 19
EVOLUTION OF THE MAIN HARMONIC COMPONENTS FOR OOSTENDE
1944-1964
1980-1998
A Hi
A Hi
in cm
(5) =(3)-(1)
in %
(34 years)
(6)=((3)(1 ))*100/(1 )
4,68
1,52
52,62
57,95
341,19
30,80
15,22
56,90
2MN2
12,18
M4
A Hi
AGi
in cm
in 0
(yearly)
(7)=(5)/34)
(34 years)
(8)=(4)-(2)
in minutes
(34 years)
(9)
0,84
0,045
-0,57
-1,18
0,20
0,38
0,006
0,27
0,54
340,44
0,25
0,83
0,007
-0,75
-1,58
15,34
58,10
0,12
0,79
0,004
1,21
2,41
200,41
12,38
200,58
0,20
1,66
0,006
0,16
0,34
10,48
335,32
11,26
332,55
0,78
7,44
0,023
-2,77
-2,87
MU2
9,94
113,64
10,05
111,26
0,11
1,11
0,003
-2,38
-5,11
01
9,48
167,54
9,69
168,31
0,21
2,22
0,006
0,77
3,33
NU2
9,07
335,58
8,97
334,02
-0,10
-1,10
-0,003
-1,56
-3,27
2MS6
6,96
345,44
7,32
343,76
0,36
5,17
0,011
-1,68
-1,15
MS4
6,43
37,35
7,25
38,22
0,82
12,75
0,024
0,87
0,88
M6
6,79
298,68
7,01
295,25
0,22
3,24
0,006
-3,43
-2,36
HARMONIC
COMPONENT
OOSTENDE
Hi
Gi (GMT)
Hi
Gi (GMT)
in cm
in °
in cm
in °
(1)
(2)
(3)
(4)
M2
179,56
5,26
181,08
S2
52,42
57,68
N2
30,55
K2
(34 years)
AGi