S jmmaries
Owing to the difference in the water-level
across the barrier, the water running through
the cross-section will significantly gain in
speed. Further landinward we not only observe
a phase-difference still with the tidal action at
the sea-side of the barrier, but also a reduced
amplitude in the tide. The velocities of the water
are lower, however, than at the mouth of the
Oosterschelde, in fact they will even be lower
than to-day, especially in the northern flow
channel.
It is remarkable that under stormy
conditions the absorbing effect of the open
storm-surge barrier on the tidal motion
diminishes according as the water-level rises.
This is only of theoretical interest however, as in
practice the storm-surge barrier will be closed
during stormy weather.
Th probabilistic concept of the design of the
st< rm-surge barrier. Ill: Natural boundary
co ditions and loads
Th loads exerted on the storm-surge barrier
ar due to the stormflood level at sea, the inner
w; er-level and the significant wave height. By
mt ans of the probabilistic method one seeks to
de ermine statistically the
pr bability-distribution of these three natural
bo ndary conditions. The possibly occurring
stc mflood levels are determined by
ex apolation of the curve of observed high
Wf er-levels. There also appears to exist an
int rrelationship between the water-levels and
the significant height of the waves which
pe etrate from the North Sea into the
Oc terschelde; another part of the waves are
ge erated at the mouth of the Oosterschelde.
Ot ervated data are available for the inner
wa ar-levels, which data can be worked out
ste stically. A computation model translates
the natural boundary conditions and their
ch ice of occurence into the probability of
sp' :ific loads. By calculating many
co binations of the natural boundary
co: ditions and their chance of occurence the
pre lability-distribution of the loads will finally
be etermined.
Fu ire changes in the tidal motion on the
Oc erschelde-basin
Th construction of the storm-surge barrier and
of :e compartment-dams will effect the tidal
m ion on the Oosterschelde. At the inner side
of ie barrier a phase difference will occur as
co ipared to the tidal motion at the seaward
sit 9. The tidal amplitude will become less at
th inner side of the barrier.
Storm-surge barrier in the Oosterschelde
Settlement of sand during the construction of
the sill
During construction of the foundation bed of the
storm-surge barrier and during the time the
piers are being positioned, troublesome
settlement of sand may occur in the channel
that has been dredged in the alignment of the
closure gap. Computation models were used to
provisionally determine how sedimentation will
proceed. In order to compare the result of the
calculations, two test-channels were dug in
which the development was observed by
means of measurements and soundings.
In the Roompot the settlement of sand proves to
be caused by bed-load transport. The
flow-pattern there is three-dimensional. In the
Schaar van Roggenplaatthe pattern is much
quieter.
The sand deposits amount to an average of
several centimeters a day. The sediments form
mostly ridges up to 1 meter.
The wet cross-section of the storm-surge
barrier
In this paper an explanation is given about the
interrelationship of an average tidal range in the
Oosterschelde-basin and the size of the wet
cross-section of the barrier across the mouth of
the Oosterschelde. The discharge-coefficient of
the cross-section - an important factor in this
matter- improves according as the streamlines
are gradually compressed. The scourings
behind the barrier can be reduced by a properly
calculated position of the upper sill-beam per
section.
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