- Rapport nr. 37bis van de Hydrografische .Dienst ·der .·Kust.
- Final report of the contract EPOC - CP - '0015 .. Participant 23 - Dienst
der Kusthavens - Hydrografie - Oostende.
DIENST DER KUSTHAVENS
HYDROGRAFIE
OOSTENDE.
SYNOPSIS OF THE TIDAL OBSERVATIONS ALONG THE BELGIAN COAST CONCLUSIONS WITH RESPECT TO
THE HIGH WATER,THE MEAN SEA LEVEL AND THE LOW WATER LEVELS.
by Ing.C.Van cauwenberghe.
* * *
* *
*
1.INTRODUCTION.
Many scientists accept that the increase in carbon dioxide (C02)
and other gases, concentrated in the atmosphere, which are
generated by industry, may, in a not too distant future, lead
to irreversible global changes in sea level, i.e. may produce the
so called "greenhouse effect".
The analysis of reliable past, and more recent, tidal elevation
data, such as those of High Water (HW), Mean Sea Level (MSL) and
Low Water (LW), can yield information about this development.
The prognosis of future events should be based on a wide range of
climatic research and applied to the production of climatic
models.
2.THE QUALITY OF THE DATA.
Before attempting to analyse the data, we must consider its value
and usefulness. The observations need to have been reliable and
to have been obtained over extended and uninterrupted periods.
The Annexes 1, 2 and 3 give a synopsis of the periods of the
tidal observations along the Belgian coast, i.e. for Oostende,
Zeebrugge and Nieuwpoort; here the periods, for which a harmonic
analysis occurred, are also indicated.
As can be seen from these, there are significant gaps in these
series, particularly for Oostende.
In the case of Oostende (see Annex 1), reasonably good observations began as long ago as 1820, but unfortunately the data are
lost; all the other earlier records, predating World War I, were
carefully examined.
The usefulness of those records were judged to be:
(1)For the period 1835-1852, the monthly values of HW/LW are
based on continuous records, read from a tide-gauge, close to
a lock in the harbour of Oostende (Ref 3) and near to a
reliable benchmark, to which the gauge was referred. This
benchmark was incorporated in a quay wall.
Because only monthly mean values of HW/LW were available, mean
tide levels (i.e.the mean of 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
difference is +0,063 m.
-
2 -
So, knowing the correct mean tide levels, we were also able to
determine the MSL-value for each year of the period concerned.
(2)The period 1878-1914 is NOT useful for this study, because
there are too many interruptions in the data and because the
reference datum is uncertain.
There are some data for the periods 1878-1885 and 1902-1914,
which are unfortunately frequently interrupted.
Comparing the yearly values for these periods with those of
Vlissingen (The Netherlands), we found sometimes differences
of more than 10 cm, whereas only 3 or 4 mm are the normal
values for years with reliable observations.
(3)From 1925 till now, the records of the years 1925, 1926 and
most of the years during 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 of moving
averages (see 3.2).
For Nieuwpoort and Zeebrugge continuous data are only
available respectively from 1967 and 1962 onwards.
3. LOCAL TRENDS FOR HW, MSL AND LW.
As periods of 25 and 30 years for Nieuwpoort and Zeebrugge are
rather short, we decided not to use this information for the
time being. Only the records of Oostende were considered for
further examination.
3.1.Linear curve fittings.
Annex 4 represents the values of HW, MSL and LW.
These data are referred to TAW (Tweede Algemeene
Waterpassing), being the Belgian National Reference Level.
Best fit calculations through these 3 annual values
(linear, exponential, logarithmic, binomial) are also
available, but only the equation of the least squares
linear fit, is indicated in the same Annex.
For the 3 values a linear increase of 0,01 m/decade can be
noted, if the two periods are taken into account: 18351852 and 1927-1991 (less the 4 years of the World Warii).
on the other hand, if only the last period, less the
years as mentionned, is considered, we find for HW, MSL
and LW a rise of 0,02 m - 0,015 m and 0,01 m/decade.
From the Dutch Rijkswaterstaat we kindly received the
corresponding information for Vlissingen, for a reliable
period of 102 years {1890-1991). We transformed the data
by referring these to TAW as well.
In the Annex 5 we see some increases of 0,03 m - 0,02 m
and 0,015 m/decade for the 3 levels, as mentionned before.
3.2.Cyclic curve fittings.
To understand why this method of curve fitting is used, it
is necessary to explain the movement of the moon's node on
the ecliptic (solar orbit).
-
3 -
The point, where the moon crosses the ecliptic from the
south to the north/the north to the south is called the
ascending node/the descending node. The length of the
ascending node has the vernal equinox (first point of
Aries) as reference; with values of 90° and 270° as length
of the ascending node, the tidal range has a mean value,
while with 0° and 180° the tidal range has a minimum 1
maximum value.
The regression of the ascending node is just the movement
westwards along the ecliptic. Due to the regression of
both of the nodes, the obliquity of the lunar orbit to the
celestial equator will change progressivily with each
orbit between a variable maximum and a minimum value (i.e.
23°27'+ 05°09'= 28°36' or 23°27'- 05°09'= 18°18') with a
periodicity of 18,61 years.
In other words, the declination of the moon is
characterised generally by 2 periodicities, first the
lunation-period of 29,53 mean solar days (synodic period),
due to the rotation of the moon around the earth (which,
on its turn, moves around the sun), and secondly the
period of 18,61 years, which is called the nodal cycle.
The Annexes 6 and 7 show the values of HW and LW for
Oostende with the fittings of a cyclic trend; for reasons
of comparison the similar curves for Vlissingen also have
been given in the Annexes 8 and 9.
For Oostende nearly the same increase of 2 mmjyear for HW
and 1 mmjyear can be noted, while for Vlissingen again the
annual increase amounts to nearly 3 mmjyear for HW and to
1 mmjyear for LW.
3.3.Moving averages.
Further i t was considered that the use of moving averages
could be interesting in order to eliminate the oscillations and afterwards to detect any acceleration in the
increase of HW, MSL and LW levels; also the similar values
of Vlissingen have been added in the Annexes 10, 11,.12,
13, 14 and 15, where successively groups of observations
of 1, 7, 13, and 19 years have been taken into
consideration for the period 1927-1991.
In none of the pictures of both places we see up to now
any significant indication of an acceleration in the
increase of the values concerned.
* * *
These conclusions on the rise of the 3 levels only are valid
if the land is not subject to crustal movements from isostatic
or eustatic origin.
However, geologists in our country have good reasons to
believe that Oostende has had a rather high degree of
stability of the substratum since the quaternary period.
Probably this statement is not valid for Vlissingen, where
indeed we see a greater increase in the levels, due to the
subsidence of land.
- 4 As time passes by, it will be highly desirable to pay attention to
the evolution of the sea levels very closely.
REFERENCES
1. J.LAUWERS. Les marees du port d'Ostende. Annales des Travaux
Publics de Belgique. Aout 1930.
2. L.JONES et R.HEIDERSCHEIDT. surfaces de niveau zero belges et
zero hydrographique H. Annales des Travaux Publics de Belgique.
Juin 1952.
3. J.HENRIONET. Notice sur les travaux topographiques executes au
Depot de la Guerre de Belgique. Archives de l'Institut
Geographique Militaire. Bruxelles, 1876.
4. A.STESSELS. Discussion des observations de la maree et ses
effects dans l'Escaut. Annales des Travaux Publics de Belgique.
Tome XXX, Deuxieme Cahier. 1872.
5. M.BOVIE. Etude sur la regime de la maree au port d'Ostende.
Annales des Travaux Publics de Belgique. Tome XLIV, 1887.
6. P.MELCHIOR et P.PAQUET. Les constantes des marees oceaniques au
port d'Ostende de 1882 a 1964. Koninklijke Academie van BelgieMededelingen van de Klasse der Wetenschappen-5e Reeks-Boek LIV1968, 10.
7. J.LAUWERS. Les marees des ports d'Ostende, de Zeebrugge et de
Nieuwpoort. Annales des Travaux Publics de Belgique. Avril Juin 1949.
8. C.VAN CAUWENBERGHE. Overzicht van de tijwaarnemingen langs de
Belgische kust. Periode:1941-1970 voor Oostende, 1959-1970 voor
Zeebrugge en Nieuwpoort. Tijdschrift der Openbare Werken van
Belgie. Nr.4, 1977.
9. P.MELCHIOR, P.PAQUET et C.VAN CAUWENBERGHE. Analyse harmonique
de vingt annees oceaniques a ostende. Koninklijke Academie van
Belgie. Mededelingen van de Klasse der Wetenschappen-5e ReeksBoek LIII-1967,2.
10.C.VAN CAUWENBERGHE. overzicht van de tijwaarnemingen langs de
Belgische kust. Periode: 1972-1980 voor Nieuwpoort, Oostende en
Zeebrugge. Tijdschrift der Openbare Werken van Belgie. Nr.5,
1985.
11.C.VAN CAUWENBERGHE. Overzicht van de tijwaarnemingen langs de
Belgische kust. Periode: 1981-1990 voor Nieuwpoort, Oostende en
Zeebrugge. Will be published later on in "Infrastructuur in het
Leefmilieu" of the "Ministerie van de Vlaamse Gemeenschap".
ostend, 04 March 1993
Ing.C.Van Cauwenberghe
Head of the Coastal Hydrographic Service
DIENST DER KUSTHAVENS
HYDROGRAFIE
OOSTENDE
Annex 1
PERIODS OF
THE TIDAL OBSERVATIONS
for OOSTENDE (Belgium).
Period
Tide pole(a)
or automatic
tide gauge(b)
Harmonic analysis
References/Remarks
1820-1834
(a)
No
Ref 1 & 2
Data are lost
1835-1853
(a)
No
Ref 3
Only monthly mean
values available
1866-1871
(a)
No
Ref 4
Data are lost
1878-1914
(b)
Yes for 1882-1888
and for 1894-1912 ·
Ref 5 & 6
Many interruptions
Reference level
not well known
1925-1940
(b)
No
Ref 1 & 7
Interruptions for
1925, 1926 & 1940
1941-1970
(b)
Yes for 1943-1968
Ref 7, 8 & 9
Interruptions for
1941, 1942 & 1944
1971-1980
(b)
Yes for 1976-1980
Ref 10
Continuous records
1981-1991
(b)
Yes for 1981-1991
Ref 11
Continuous records
DIENST DER KUSTHAVENS
HYDROGRAFIE
OOSTENDE
Annex 2
PERIODS OF
THE TIDAL OBSERVATIONS
for ZEEBRUGGE (Belgium).
Period
Tide pole(a)
or automatic
tide gauge(b)
Harmonic Analysis
References/Remarks
1932-1939
(b)
No
Ref 7
Interruptions for
1932
1941-1943
(b)
Yes for 1943
1959-1970
(b)
1971-1980
(b)
1981-1991
(b)
Yes for 1963-1966
No
Yes for 1983
Ref 7
Interruptions from
1940 to 1943
Ref 8
Interruptions from
1959 to 1961
Ref 10
Continuous records
Ref 11
Continuous records
DIENST DER KUSTHAVENS
HYDROGRAFIE
OOSTENDE
Annex 3
PERIODS OF
THE TIDAL OBSERVATIONS
for NIEUWPOORT (Belgium).
Period
Tide pole(a)
or automatic
tide gauge(b)
Harmonic Analysis
References/Remarks
1933-1938
(b)
No
Ref 7
Interruptions for
1933, 1937 & 1938
1941-1943
(b)
Yes for 1943
Ref 7
Interruptions for
1942 & 1943
1959-1970
(b)
Yes for 1967-1969
1971-1980
(b)
No
Ref 10
continuous records
1981-1991
(b)
Yes for 1983
Ref 11
Continuous records
Ref 8
Interruptions for
1959, 1961 & from
1963 to 1966
DIENST DER KUSTHAVENS
HYDROGRAFIE
OOSTENDE
Annex 4
LINEAR TRENDS
calculated on
the Annual Values of HW, MSL and LW
for OOSTENDE (Belgium).
y
*****
0
<D
1/)
Periods:1835-1852
1927-1991
(-1940,1941,1942,1944)
TAW
C)
(""
Period:1927-1991
(-1940,1941,1942,1944)
L')
Y=A+B. X
0
00
A = 4,0874
B = 0,0010
Error = 0,0412 m
""
....
0
A= 3,9195
B = 0,0020
Error = 0,0390 m
A ~
.....
+$ ,t,...,}h-#-ffl,J#+
~~~-!f+
0
0
.,.
*
Error =
2:_ (yi - Y)
~
n -
+
2
2
with yi = HW, MSL or LW-value of a year
Y = A + B . X
n = number of events
* Standard error of estimate of Y on X
w
:z:....,
00
i..i._;
\I
"4 .._
HW
•
f-1'>
(f)
0
0
:;;:o
I"'?
"'
--'
(f)O
L:"":
3
---'
A= 2,0846
B = 0,0010
Error = 0,0245 m
A = 2,0151
B = 0,0014
Error = 0,0253 m
A = 0,2043
B = 0,0010
Error = 0,0418 m
A = 0,2139
B = 0,0010
Error= 0,0439 m
;*t
#"¥+
~
#W
"'
0
0
"'
0
<D
0
N
0
(0
0
~~+ -+
0
4-#'$:¥
LW
+
g
1850
1900
1950
2000
o;---.---.---.--.---.---.-=~=-.---.---.---.-~~-----.---.---.--~~.--.x
30-00
so.oo
70.00
30. CO
., 1 0. 00
JAAR 1800
l30-0C
=0
170.00
190-00
210.00
DIENST DER KUSTHAVENS
HYDROGRAFIE
OOSTENDE
Annex 5
LINEAR TRENDS
calculated on
the Annual Values of HW, MSL and LW
for VLISSINGEN (The Netherlands).
0
oL•
*****
y''l
Period:1890-1991
TAWo
N
L')
Y=A+B.X
0
00
A= 3,7255
B = 0,0033
Error = 0,0402
m
HW
0
0
I
0
<1J
Error
*
I
L
2
(yi - Y)
\1 -----------
=
:z:
n -
V
w
:zo
~N
(f)
2
with yi ~ HW, MSL or LW-value of a year
Y ~ A + B • X
n ~ number of events
* Standard error of estimate of Y on X
•
U)l">
>
:z:
A = 1,8919
B = 0,0021
Error = 0,0312 m
i.J~
MSL
3
___J
0
0
N
0
<D
0
N
A = 0,1603
B = 0,0019
Error = o , o4 2 3 m
0
<0
0
-~,
0
...,.
•*'tj'f+
rr -'¥!' '"
*
(.)
g
1850
-lt+-
/ ~ J~ l:t= :l¥fttr+
~~~:fAA+~cq_w
LW
+1j..*1-
1900
1950
2000
01---.-~~~--~--~----~~~----.---.---r-~~-----.---.---.~~~---.x
JO.OC
50.00
?C.OO
)0.00
110.00
JAAR 1800
130.00
=0
150.00
170.00
190.00
21::1.00
------------------------·-··----·-·------Oostende HW van 1925 tot 1991
H = A*Yr + B*SINCCYR-ORIG)*2*pi/period) + c
PERIOD 18.512 ORIG 1992.5 R= .001?87 m B= .0408 m C= 4.3
mu= ?.025E-15 m sigma= 0895 m
1925.5
1930.5
1935.5
1940.5
1945.5
195,0.5
195_5.5
1960.5
1965.5
1970.5
1975.5
1980.5
1985.5
---------·-------.O::t:t:1
OJoo<:H
mt:1ttj
8::0Z
ttjQm
m
ZQI-3
g~t:1
l-%jtlj
H!=O
1990.5
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m
8
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4.4
4.4
--·~-------·~
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192.5.5
193.0.5
193S.5
194.0.5
194.5.5
195'0.5
195.5.5
L ____. ·-----~--------------- ---~- --------~-----~--------
196-0.5
196.5. 5
197.0.5
197.5. 5
198·0. 5
198.5.5
199.0.5
-··-···----.---------·--------------'
0\
--~-~--------------·--------·-'
Oostende LW van 1925 tot 1991
H = A*Yr + B*SINCCYR-ORIG)*2*pi/period) + c
PERIOD 18.512 ORIG 1992.5 R= .001055 m B=-.04527 m
mu=-8.451E-17 m sigma=
124 m
1925.5
193.0.5
193_5.5
194_13.5
194_5.5
195_13.5
195_5.5
196_13.5
196_5.5
197_13.5
1975.5
1980.5
o::r::o
O~H
C= .3989
t.llOt:r::!
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t:r::!Ot.ll
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m
g~o
t-.:jt:r::!
1985.5
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1990.5
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193'5. 5
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194.13.5
.. ---·
-- -
194.5.5
1950.5
195.5.5
1960.5
l96·s.s
19i0.5
197.5.5
198·0.5
198's.s
19!:f0.5
-..J
r---·---------------------···-···-o-·-··--1
Vl issingen HN van 1925 tot 1991
H = A*Yr + B*SINCCYR-ORIG)*2*pi/period) + c
PERIOD 18.512 ORIG 1992.5 R= .003309 m B= .03418 m
mu= 3.049E-15 m sigma= .0?301 m
192S.S
1930.5
1935.5
194_B.S
1945.5
1950.5
1955.5
1960.5
1965.5
1970.5
1975.S
1980.5
l
C= 4.355 m
0~0
O~H
(I)Otr:l
trjQ(I)
:ZGJt-3
l-3!:t'Z
~~0
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198S.5
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1990.5
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~
c::::
(I)
t-3
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tr:l
·····------- 4. 4
z
rt
Hl::T
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(1)
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1-'·
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(I)
(1)
li >
t$::::10('}
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192S.5
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1935.5
194.0.5
194.5.5
195·0.5
195.5.5
196.0.5
19s·s.5
197.0.5
1975.5
198.0.5
198·5.5
1990.5
---- --- -------
-~--
~
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(1)
X
CO
-------------------------·------Vl issingen LW van
H
1925 tot
o::x::o
Ot<H
= R*Yr + B*SINCCYR-ORIG)*2*pi/period) + c
PERIOD
18.512 ORIG
1992.5 A=
mu=-2. 519E-15 m si gma=
1925.5
1991
193_0.5
193_5.5
194_0.5
194_5.5
195_0.5
.001192 m
B=-.03502 m
UlOt<:l
r-3::0Z
t<:lOW
C= .4992 m
Z
1
195_5.5
196_0.5
G)
8
~~0
1-tjt:l:j
. 1049 m
196_5.5
197.0.5
197_5.5
198_0.5
198_5.5
199_0.5
H::O
t<j
~
Cl)
8
• 6 --------------
~
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t<j
z
·------------~--------------------·-----------------------------------------------------------·---------------~~------
-------------------·------·--·-··----·------------···---·-·------------·-----··----
rt
1-cJ
Cl)
Hl::t
0 (I)
>
(I)
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ts::SOCJ
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:z:~O.t<:l
z
(I)
.-.,(1)00
r-3
::tO
(I) Hl
::s
~~
rt
::t
(1)
.3
li
1-'
-------------------------- --------
~
---·-···
::s
a.
(/)
.._.,.
--------·-------- ____________________._.,
. 2 --------·---·--· .......
I
192.5.5
L__ _
193.0.5
----------- ---------·····
193.5.5
194·0.5
- - - - - . ---.. . ...... .......
______________
~_
----------·-··-·-. ·------· ----------------------·---- -- ------ ------- ... - ---------
-----~----~---------------"·---------------------------·-···
194.5.5
....
195.0.5
195'5.5
1960.5
------------ ---------------------
t9s·s. 5
t97·e. 5
------ -------------· .-..
!97's. 5
1ss'e. 5
.2
198.5.5
199'0.5
------
-------------
J
~
::s(I)
:><
1.0
DIENST DER KUSTHAVENS
HYDROGRAFIE
OOSTENDE
Annex 10
MOVING AVERAGES
calculated on
the Annual Values of HW
for OOSTENDE (Belgium) and for VLISSINGEN (The Netherlands).
****
Period:1925-1991
O'!'t
5 m
'•/1
4,5 m
I•
~
:-::.:
:( ,&,
X
l
_1._
.E...'-.
'i. :-:
.X
:!: .•:
:;: :s:
)::..: -,.:
)(
~- ·-·
_li._ :··):
-~- ~-
:.-:
:.-.xi x
I-LIA ..
1
year
(1st 4
199l
m
:'1!:
)(
_ _ _ _ _ _ _ _ _ _ J.__ _____;{,
;.:
i"l25 -
··:a:
X
:rl.
L9~5
LS4.5
'·/1 4
fll
\'1 5
m
o~t
I
4 .. 5 m
i
V.G.
Oo~tende
per
~
-1-c.n
jaar
I
. :~:
. ).':(X.-·.
I
!-LM.
7 years
\.'l 4. 5 m
I
L-
LS35
','1
1925- 1Q!H
I
T.R.l·L
tS£5
1---"m,______________t:~=s""·t,----'3'-'_'-=S'--'-'m,__ _ _ _ __
l!::IBS
J
Annex 11
DIENST DER KUSTHAVENS
HYDROGRAFIE
OOSTENDE
MOVING AVERAGES
calculated on
the Annual Values of HW
for OOSTENDE (Belgium) and for VLISSINGEN {The Netherlands).
****
Period:1925-1991
'./1
5
O::::t 4.5 m
m
!'····························
•._.I_(J.
l
I
Ocd;:-t.~nde.
per
13 ja.a.r-
:!: X'!'~
X J. :-: -,· X ;(
.···.X).:
:a·:.::!: X;;.:)(~)():;-::
:r:
X.:)(
:r:. :«: J.: :S: :"':
i X ·• .. , :&: ,: .._ :=:: ·t X X i
.s:
I
I
13 years
I
II
I-LW.
\1! 4.5 m
1925 -
1!l9l
T.A.~L
p-er·
l3
jb.~P
l
I
\
I
!
I
!
!
tS45
••..•1
4 m
'•/1
5 m
i.!l'5S
:1585
L_•;..:~.-
3.5 m
I+~
H-14 _ 1g25 -
19!ll
19 years
I •
i
L
~
. . '""····· . . . . . ··=···=•'~
DIENST DER KUSTHAVENS
HYDROGRAFIE
OOSTENDE
Annex 12
MOVING AVERAGES
calculated on
the Annual Values of MSL
for OOSTENDE (Belgium) and for VLISSINGEN (The Netherlands).
r-
****
Period:1925-1991
'o/1
3
O=!=t 2.5 m
m
..
1
I
)()(.
i ..
!
i
l
1
year
iI
M.9 L.
(Jst
2
1925 -
m
I •
~
I
I
1991
)(
)(
:-:
...
ts3s:
\·'1
t.S45
3
tsSs
t·.:J£5
m
l.SiB5
O:;:t
1 .. 5 m
o~t
2.5 m
;:-:: )()(X X
... _:-:_ )( .'( )(.-
l'
t-1_ 9. L.
7 years
O.st:: 2
1925 -
1991
m
I•
~
: :~.:
-------------(c:::•:cc:::-::'J..-. -• :.: X:•: )( .'( .•. -x-)_ .t.
_v::e:X
. : )( ::< ): :t.: X :fo: )( ~ ::-::J: X
1
:r: :1 .· -. :~:
. ·•· '( :!.
-··a·A
.".!(_'(X;.:~.-}-:.' :1(
....... )(:,g:_"i.. ~~:···)('
·,·. -...·
...fl.
X .a. ·~~~---
:e.: X:<(:':.'(
tsts
l~IGS
DIENST DER KUSTHAVENS
HYDROGRAFIE
OOSTENDE
Annex 13
MOVING AVERAGES
calculated on
the Annual Values of MSL
for OOSTENDE (Belgium) and for VLISSINGEN (The Netherlands).
****
Period:l925-1991
'•/1
3
(l~i:;
m
Z
~5
m
Ii
I
I
M.G.L.
13 years
\·'1 2 ..1 m
(1:•::=t
2
1925- 1991
I
m
I
I
I
L555
1565
:1 :1'?5
.E:IH~
________-_--·_--·_···_····_···_··-_--~c~_:~~-t~l~-~5~m____
·--_--·_····_---_
..._..._.. _____________ ____j
t:i35
Vl
3
l94S
m
J
V_G.
Qo~t~nd~
per 19
+r.r:.
I
!
I
Jaa~
1
I
Il
M.~.L-
19 years
'·/1 2.5 m
1925- 1991
T.R.H.
I
!
.1::125
j
\11
~:
ffr
9'BS -- ................. --- ....... B'75
I
I
_ _ _ _ _j
DIENST DER KUSTHAVENS
HYDROGRAFIE
OOSTENDE
Annex 14
MOVING AVERAGES
calculated on
the Annual Values of LW
for OOSTENDE (Belgium) and for VLISSINGEN (The Netherlands).
****
Period:1925-1991
!····················
'•/l
l. 175 m
~575
(l;::t
m
I
V.~-
I
On~tende
per 1
J~ar
I
II
!
.•.
.•.
I
X
L_ >!.
1
year
Vl
.675 m
.175
(!;::.t
1925 -
II
1!Hll
m
l
I
I
:i:
·•';;'
:e..-~.
~:-.
:!: ):
:•:
:~~.:
:S:)(
...
I
l9it-5
I
l955
________________________ _ 1.'
L-------------~'~11~.~~~7~5-~~·----------------------'~J~~-t~-~-~s~·~~·s~m
'•/1
t. 175 m
. ·,: s: >-:X
( ..
·... X
L.W.
7 years
'•,•'1
.675
V.G.
m
V11~~1ng~n
0:3t "l?5
1925- 19!ll
m
per 7 Jaar
I•~
:s:
-
-~
x~
xxx xxxx
xx
.•. x~
Xxxx .•_-xx
"""--""'*--.:L_X_ _ _ _ _ _ _ _ _ _ _x~.•.·.~.·_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
··x:.::•:::-:··
~~
.......~x_:t:_x_·-·_··_>-':-•-'-:·._·
.....................
l::ia5
·.n . L75
rr,
C:~t-.
32S m
-··-·····----
I
I
------------'
DIENST DER KUSTHAVENS
HYDROGRAFIE
OOSTENDE
Annex 15
MOVING AVERAGES
calculated on
the Annual Values of LW
for OOSTENDE (Belgium) and for VLISSINGEN (The Netherlands).
****
Period:1925-1991
'o/1
1, 175 m
•.}_\-3.
i')o.~Lende
per
o~t
.. 575
(1st
• 175
m
13 Ja.ar-
13 years
m
l ..
~-.
I
I
I
•,_,'1
. l75
Vl
L.l75 m
V.G.
O!O::t-_ 325
fr•
Oo~t~nd~
:j
L955
l945
o~t
per l9
1Sc-·S_ _ _ _ _
Ill
-575 m
J~ar·
L-~-
1g2s -
1991
19 years
'•/1
I
675
ITi
T.R.l·L
(i=:::t
• 175
m
I • "'
19}"5
' - - - - - _ _ __,·,••
. l75
tic_•- - -