Si mmaries
Th origin of the Delta Scheme
Tv nty five years ago, on February 1 rst, 1953,
ttv Netherlands were struck by a flood-
di; ister, in which nearly 2000 people were
kil 3d. Soon thereafter, the closure of the
se -arms of the Delta-area, which had been
un er study for some time already, became
a I aw.
Th 3 article describes the pre-history of the
Ds a Scheme and especially the significant
ro* that was played therein by one of
He and's most prominent hydraulic autho-
riti s, Dr. Ir. Johan van Veen.
Th Oosterschelde: from conflict to
co promise
Th original scheme to completely close
off he mouth of the Oosterschelde has
fre uently been opposed by action groups
for he environment and advocates for the
int ests of the fishing industry. The history
of >eir extra-parliamentary action is
de ribed as well as the way in which the
ch ged insights permeated into the
ide ogy of the political parties.
Eve tually the compromise of a movable
sto i-surge barrier was reached.
Th' oundation of the piers or columns
Fo. ie stability of the piers of the storm-
sur barrier a soil mechanical research was
nec sary, both in the field and in the models,
Tes have been made in a centrifuge at the
Unii sity of Manchester. Tests have equally
bee; made on a large scale in the Delta-area
itsel n order to ascertain the friction factor
betw en the base of the pier and the
foun. ng bed.
On b ralf of the foundation the bottom of the
Oosterschelde will partly be consolidated;
moreover, over the major part of the align
ment a trench will be dredged for the
foundation-bed.
Design and construction aspects of the sill
The sill of the storm-surge dam is a very
important component of the barrier; it not only
serves as a protection of the foundation-bed,
but it also lends support to the column-
construction.
The junction of the sill with the columns must
be infallible at all times. Two alternative
designs have been outlined meeting all
conditions. While executing the works special
attention will be given to the finishing of the
flatness of the sill and the eventual excessive
sanding thereof during its construction.
Piers, superstructure and abutments
This article gives a description of the design
of the piers of the storm-surge barrier and
the manner in which these piers will be
positioned. Further information is also
given about the superstructure and the
junction with the abutments.
Gates and operating mechanisms
The 40 meter wide cross sections in the
barrier will be closed with (vertical) sliding
gates; its profile is turned towards the
Oosterscheide-side.
The gates can retain a tidal range of 7 meter
and an incoming wave with a significant
height of 4.50 meter.
The dynamic action of the gates is still being
tested in the models.
A hydraulic system has been selected for the
operating mechanism which can be handled
either centrally or per unit.
Aspects of construction of the works
The columns will be built in a construction
pit. Jobwise it would be preferable to con
struct a pit near the Philipsdam.
The supply-route towards the mouth of the
Oosterschelde carries too many risks,
however. The construction pit will therefore
be situated right behind the Oosterschelde-
dam.
Between the construction pit and the isle of
Schouwen a permanent bridge, three
kilometers long, will be built.
Positioning of one pier alone will probably
take as long as 70 hours.
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