HEADING PAGE - port of ploce authority * welcome

ENVIRONMENTAL IMPACT STUDY
Rn: 03-033 CONTAINER TERMINAL PLOCE PAGE: 22
In order to get a better insight into the deep-sea spatial circulation, the figure 18 shows
currents at 5 m depth, separately for flood tide and ebb tide. In the very location of the
project, ebb and tide currents alternate and amount to about 8 to 10 cm/s (about 0.35 km/h).
With the estimate in the first approximation through the continuity equation and considering
two-beat mean sea tide for the volume of the Ploèe Port aquatorium, we arrive at these
speeds exactly as the maximum ones in the channel near the cape G.Višnjica, at mean
oscillations of the sea. This leads to the conclusion that the currents in the neighbourhood of
this project are under the distinct impact of ebb and tide and have regular periodic alternating
flow. The Crna rijeka river confluence in the aquatorium of the port of Ploèe which is
minimum in the summer season was not taken into consideration here.
As far as the execution of the project and its impact on the sea current is concerned, it is
necessary to conclude immediately that this impact practically does not exist or if it exists
then it is positive.
Namely, the project is executed laterally, by preserving the existing coastline and deepening
the basin, thus enabling better spatial circulation and eddying motion around the vertical
edges of the basin.
Besides, with the execution and maintenance of an appropriate access waterway of the
constant depth, hydrodynamic resistances to current will be reduced, which will contribute to
the safety of the waterway.
Sea waves
Surface sea waves, as oscillatory periodic occurrences of sea fluctuation are divided into
short and long waves.
Among long waves, which by their definition are those with period of more than about thirty
seconds, the sea tides and atmospheric (baric) waves were processed because of the
passage of front or gusts of wind.
With a simple calculation for the own frequency of semiopen rectangular basin, it can be
seen that the first tone has a period of about 160 seconds. Therefore, there is the possibility
of resonant effect of long waves of mentioned period, but according to above mentioned
measurements of seiches, which could cause this resonance effect, they have a much
greater period (about 30 minutes).
As the own periods of ship movements which will be berthed in this port basin are also
significantly lower, for rolling motion between 25 and 35 seconds, for pitching motion
between 10 to 15 seconds and for heaving motion about 10 seconds, these long waves
cannot cause resonance effects neither of the basin or of the ship, significant for safety resp.
operational level.
The short waves which are wind-related can have an effect if they should penetrate the basin
in which they are also analyzed.
RIJEKAPROJEKT d.o.o.