The objectives, tasks and equipment of the
Delta fleet
A large number of ships are used in the delta
works, not only for the execution of the
Oosterschelde barrier, but also for all kinds of
technical and hydraulic relief, for research and
for keeping guard. These ships are owned
partly by the Rijkswaterstaat and partly by the
contractors and a further part is hired from a
third party. Several separate articles have been
written on the large specific service vessels,
but not on the smaller ones. However the
development of the measuring fleet in particular
is remarkable for its continual enlargement and
modernisation. Thus data gathering has been
automised and its assimilation computorised at
a high pace, which has made no mean demands
upon the electrical installations and
accomodation arrangements on board.
An acoustic sand-conveyance gauger
In order to become aquainted with and to
follow the morphology of the Oosterschelde
bed it is necessary to keep a constant check on
sand conveyance in the estuary. A new instru
ment has recently become available for this
ourpose: the acoustic sand-conveyance
gauger. The sand concentration in a given
volume of water can be determined by the
detraction and dispersal of an acoustic signal
rassing through that same volume of water. At
he same time the time, speed and direction of
he current can be registered. This instrument
/vill work under any circumstances and is
herefore a great asset to the extensive measu-
ing programs at present being carried out in
he Oosterschelde.
V new computation centre at the Measuring
ind Study Department in Zierikzee
X new computation centre came into use at the
vleasuring and Study Department in Zierikzee
i mid 1983. It has taken a whole year to
>uild this up. An important improvement has
>een achieved in the effectivity of the centre,
he possibilities for carrying out extensive and
omplex research have been considerably
nlarged.
"his was indeed badly needed as in 1980 an
xtensive measuring net came into operation
n the mouth of the Oosterschelde. Amongst
ither things it was intended for the setting up
if short-term forecasts on the wave, tide and
urrent conditions in the working area of the
torm-surge barrier.
The remaining study services of the
Rijkswaterstaat will mondernise their
computation centres in a similar fashion.
Drainage of the construction pits at the Bathse
Spuikanaal
Four hydraulic structures had to be installed in
construction pits at the laying of the Bathse
Spuikanaal, between the Zoommeer and the
Westerschelde. The most important of these is
the Bathse sluice in the Westerschelde dike.
The groundwater level should be maintained at
half a metre below the lowest part of the
structures in the construction pits, which
explains the need for drainage. Firstly an
advice on drainage is presented in which the
water-load in the pit is calculated and lay-out
plans for drainage are suggested.
The article describes the progress of some of
the aspects in this specific case. An important
characteristic of the ground-profile in this case
was that a consistent peat/clay layer lay in
between the surface layer and the deep sand
layer intended for drainage, which presents a
hindrance to vertical water currents.
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