1$ JUN 1979
ARCHIEF
SYMPOSIUM ON ASPECTS OF NAVIGABILITY
DEVELOPMENT AND CRITERIA FOR THE DESIGN AND CONSTRUCTION
OF THE PORT-APPROACH AND HARBOUR ARA ENThANCE OF ROTTERDAI4-EUROPOORT
y.
J. van Dixhoorn, J.F. Agema2, L.A. Koe13' and W.A. Roose4,
Rijkswaterstaat, Ministry of Transport and Public Works,
the Netherlands
1.. The problem .
In 1958 the decision was taken to adapt the existing navigation facilities at the head of the river Rhine in the coastal area near Hook of Holland to modern ship-ping. In working out the original formulated, general plan, special attention had to be paid to the accessibility for deep draught tankers with as destination the
harbour basins of Rotterdam-Europoort The decision involves the requirement that
during the construction time forthe new facilities, the traffic flow to tha exis-ting harbours in the Rotterdam area had to be. assured as well as p.ssible.
In the initial stage of the project the development of the increasing size of
oil-tankers had recently started. Also eveloprnents.inother types of vessels were in
the cours.e of preparation; according to announcements the new ships would be faster and in so cases bigger than existing ones; among the new types of seagoing ves-sels expected were those for the transportation of containers, chemicals, liquified
gas etc In addition the amount of shipping was still growing, resulting in a
high-er traffic density in the local navigation area.
Lab.
v. ScheepsbouwJçud.
Technische Hogeschoofr
Deift
Head of Project Bureau, Department of Harbour Entrances,
Principal officer for preparation of design, Project Bureau, Department of Harbour Entrances,
Principal officer for hydronautic research and research coordi.nation, Project Bureau, Department of Harbour Entrances,
-2-With regard to the preparation and the execution of the project the question arose as to which data of future traffic and the different elements, the design concepts would have to be based on. Also how general formulated requirements, such as safe
expeditions navigation for an as yet non-existing type of shipping, could be trans-lated and expressed in layout, dimensions and construction of new facilities to be realized in the coming years taking into account besides the requirement that
unfavourable situations like beach erosion, sàltation etc., which may occur in the surrounding coastal- and river areas as a consequence of the realized facilities, had tO be avoided as much as possible.
Finally how could unfavourable situations in the navigation of ships and in the traffic flow (resulting in congestion, delays, collisions, groundings) be avoided both during the construction time, as well as after project realization in a more
or less fixed configuration of maritime provisions in the local area, while devel-opment in type of shipping and in traffic would stil continue.
This paper considers aspects of the layout and will discuss aspects of the methods to realize the new facilities in relation to the navigation Of arriving and depar-ting ships Particular attention is paid to the alignment, the dimensions of the approach channels and port entrance, including the definite entrance to Europoort basins, and further to aids to navigation from a point of view of design and
eval-uation of criteria applied in the different stages in project realization and exe-cuted via a sequence of four significant stages.
In a study of this process one can say that activities in creasing such a navigable waterway with constraints in depth and width in weather and sea conditions, in ships in traffic conditiOns (in brief in the functioning of a maritime wätèrway) can be looked upon as the development, the choice and the application of boundary values the latter related to-channel dimensions and the availability of aids and
other provisions which are both contributing as well as limiting factors within
which the human tasks for the navigation of ships have to be carried out
In this way the chosen characteristics of the more or less fixed part of the area configuration can be considered as criteria with the expectation that the real paths of especially the very large carriers (VLC's) sailing under human cotrol will lie within the boundaries set bi thee criteria under all relevant conditions.
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2. The procedure
.2.1. A starting point
The increase in transport after World War II needed an increase in harbour
facili-ties - especially for large and deep draught tankers - in the area of Rotterdarn.
The local harbour basins branch out. in the coastal region of central Holland along
the borders of the Rotterdam Waterway. The area forms a part of the northern area
of a delta region where the rivers Rhine, Waal, Maas and Schelde flow into the North Sea (Fig. l.a.)
A. multi disciplinary study led in 1.958 to an overall plan, taking into account dif-ferent aspects and functions of .the area. With regard to shipping this plan contains
a first concept of a new harbour area close to and extending into the sea with an
own entrance, situated south of the existing port entrance near Hook of Holland (Fig. l.b.)
A feasibility study of this concept learned - mostly based on hydraulic research
and comparisons with nautical Situations elsewhere - that suitable tidal current
patterns in the harbour entrance could better be realized with a combined port
en-trance (Fig. l.c.) giving way to:
I. shipping to respectively the new complex of harbour basins - indicated by the name "Europoort" - and to the more inland situated Rotterdam harbour
area;
2. that part. of natural water discharge of the rivers Rhine, Waal and Maas which flows via the Rotterdam Waterway (R.W.W.) into the North Sea.
With the assumption in 1961 of this indicative plan - the "general plan" - a start-ing point was formulated which can be looked upon as the beginnstart-ing of the Europoort project.
2.2. State of affairs in 1961
In principle the existing navigation area is .bounded by two zones: (Fig. 2a) - the port entrance zone A, located on the seaward side,
- the harbour entrance zone B, located on the inland side.
The two zones are connected by the Rotterdam Waterway. In zone A one of the new Europoort harbour basins is already in operation since this basin was connected with the R.W.W. via a temporary entrance in 1960. The bottom profile in the navi-gation areais schematically indicated in Figure 2b.
Also taking into account tidal water-level variations the area is accessible in 1961 to schips with draughts. up to 43 ft to harbour basins in zone B and to the Europoort basin in zone A.
More or less irregularly shaped patterns of currents,. waves, visibility and wind,
distributed in time and place occur in the whole confined area Pilot assistance in
navigation is recommended for all ships to prevent dangerous situations
in zone A the main approach direction to the coastal inlet marked by two moles -is. indicated by an 108° leading line of lights; the whole navigation area is cover-ed by a System of shore bascover-ed radar - and radio sensors, in use for operations in the field of assistance to shi.p traffic and administration. Special pilot service, tug service etc are in operation for ship handling in the harbour basins
Coming from the sea, ships enter the area from directions within the range
indicat-ed in Figure 2c A rough picture of progress directions of single ships shows the
main lines in the .flow of traffic (Fig. 2c) in which the position of the two pilot service vessels play a dominant role.
During the foregoing period the number of ships still increased; in 1961 about 30,000 incoiing ships passed zone A, which resulted in about 60,000 ship movements a year in both directions; an average of 300 per day with peaks up to 600 per day. The types of vessel vary from coasters to supertanke.rs carrying a variety of types
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Figure
1 :The plans
4
DISTANCE. IN km
1.1 19
NAP -22 m
MEGA RIPPLES BOTTOM PROFILE.
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Oostvoorne oek n HLIcnd BreCI tsr Heijd. TRAFIC FLOWS 1960 ARRIVING SHIPS DEPARTING SHIPS RANGE OF RADARFigure 2 : Port entrance zone and harbour entrance zone
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of cargo and in different loading conditions. Constraints in the infrastructure of the area occur in zone A in the transition zone near the entrance moles; during high tide strong local cross currents force passing ships to drift towards the northern mole; especially under conditions of high traffic density and bad weather with reduced visibility, marginal situations occur. In addition the asymmetrical incoming flow pattern causes a remarkable sedimentation in this zone - the mainte-nance of water depths requires intensive dredging works..
2.3. The project
The future navigation area as indicated in the general plan had to be access:ible for incoming fully loaded carriers of 80 - 100,000 dwt with draughts up to 50 ft; the existing development of larger ships has to be taken into account. Also a fur-ther growth in the total amount of ship movements and developments in. the types of vessel has to be taken into account.
In addition during the construction phase both the "water discharge and cOast pro-tection function" as well as the "navigation transport function" of the local area had to be maintained.
A comparison of the generaiplan and the state of affairs in 1961 reveals that the project to be realized consists in headline o.f two components:
a local modification in the riverbed and in the configuration of the beach; a modification (including, extension) in zone A of the navigation area.
The two modifications can be considered as a transformation of the local coastal area; in principle such a transformation will influence the two components mentioned before.
In this way the project range can be formulated as follows: to make a new navigation area zone A, via a transformation of the existing local area with the condition that in all transition states during the transformation period the operations in the field of navigation are maintained as well as possible; in addition an analogous formulation holds for the second component.
2.4. The course of action
The design and realization of the Europoort project did exist in phases within the framework of the general plan. The project has also been put into use in phases; the experience obtained from a former phase, together with the analyzed results of mea-surements in situ, in hydraulic and ship models and in simulator tests, is taken into account to modify and define the following phase.
This procedure, an iteration process of theory and practice, made it possible to head a ships demand continuously in alteration during the 10 years transformation period (1966-1976) positioned in a period of preparation and research ranging from
about 1961-1976. . .
The increase in the size of ships and inherent changes in manoeuvrability in conf in-ed waters on the one hand and the development in navigation systems and research. facilities on the other, did modify and define the design more and more in a quan-titative sense, supported by recent experience.
The project starte4 up for ships up to 80-100,000 dwt (50 ft) developed in 1966 to
a facility for ships up to 150-170,000 dwt (57 ft), in 1969 up to 200,000 dwt (62
ft), in 1971 up to 250,000 dwt (65 ft), in 1975 300,000 dwt and larger loaded up to 68 ft; the most recent tanker navigation regards two way traffic in the approach channels.
Furthermore a perspective is developed for a facility for ships up to 425,000 dwt (72 ft) in the so-called "restricted draught class of supertankers". In different
stages of realization still more attention has to be given to the criteria given by
the human operators both on board as well as on shore based stations (in brief
"users" of the navigation area) and finally to the additional information the
users need to operate the ships in accordance with the actual project stage.
-6-3. The preparation of the design
3.:1 Main aspects
The devices formulated within the framework of the general plan are translated in starting points for the design. With regard to the formulation of the starting points, the foll9wing main aspects are taken into account:
- the fixed position of the already realized 4th oil harbour in the Europoort area and of a part of the Calandkanaal' (see Fig. 1);
- the future availability of an area of at least 1500 ha, the seaward side of the EuropOort area;
- a future growth - initially not specified - in the size of loading tankers start-ing with carriers of 80 - 100.000 dwt;
- a future growth in the amount of ship movements up till 140.000 a year in both directions equally distributed over respectively the trajects R.W.W. and Europoort; - a protection of the navigation area by means of dams at such a distance from the
beach that the expected amount of maintenance for undesired sedimentation and erosion satisfy an economical propositiOn;
- an adaption of the foundation level of the seaward protection on the dimensions of the approach channel in such a sense that the total amount of initial invest-ment for dams and approach channel and of maintenance costs will be a minimum.
3.2 Starting points
The choice of the shape and the dimensions and further characteristics of the pro-visions to be made in the navigation zone A are mainly based on the requirements to secure safe and expeditions navigation of ships in this area and tc an important extent to safe and expeditions navigation of large deep draught carriers to Europoort,
both during construction phases as well asin the. completed stage of the project. As a consequence of these starting points the following requirements are formulated with regard to the infrastructural parts of the provisions to be made:
- to create optimum current and wave patterns for ships in the navigation area, es-pecially for VLC-channel navigation;
- to improve existing geometric constraints for shipping bounds for the harbours in zone B via R.W.W;
- to create sufficient available space in the area protected by dams for the exe-cution of safe and expeditions stopping manoeuvres of incoming VLC's;
- to create a shifting zone in the protected area in such a way that in- and out-going ships bound for Europoort as well as for zone B have sufficient available navigation space to adapt the course of progress on the different points of
des-tination;
to create a rate of accessibility for incoming deep draught tankers which is res-tricted as little as possible by sea and weather conditions;
- to create a proposition in which the availability of aids to the navigation of
deep draught tankers (situated in the navigation area) can be adapted to the di-mensions of the approach channel.
3.3 Design of the harbour enit:rance
3.3.1 Main outlines
Taking into account the foregoing, particularly where this concerns the tendency to achieve the most favourable current pat-terns for shipping, a so-called combined en-trance for Europoort and the Rotterdam Waterway has been chosen. In all tidal phases these optimally favourable current patterns can be achieved under the influence of the storage basin area and the upper water runoff of the Rotterdam Waterway., situ-ated farther inland.
To this end two breakwaters are required, viz. (see Fig. Ic): a South Mole A-B, which meets the coastline at Z,
a North-Mole C-N, which is an extension of the presently existing North Pier.
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Besides separating the entrances to Europoort and Rotterdam Waterway required c) a Dividing Mole.
For the rapid and safe handling of áhipping to and from various directions, a shifting zone is required and the necessary guidance should be given, taking into account the degree of wave penetration.
Preference has. been given to a system in which incoming traffic is diverted into two main directiOns: Rotterdam and Europoort. The divertion is made before the harbour entrance (P) is reached, consequently before the physical division (Q) between the Rotterdam Waterway and the access to Europoort.
The joining of the traffic flows coming from Rotterdam and Europoort in principle takes place in the outer harbour, where these flows cross those of incoming traffic. The shifting zone thus extends to the outer harbour and this also contributes to dictating the dimensions of the outer harbour. In view of the stopping distance
and time required for large tankers, a relatively great length is essential In
principle tankers in the Caland canal, must be stopped abeam the fourth oil harbour. The procedure for entering harbour then is as follows:
- the tanker approaches the harbour entrance with as little headway as current
and wind will allow (8 10 knots);
- as the entrance is negotiated, speed is further reduced (to 6 - 7 knots), at which stage tugs can make fast (still in the outer harbour),
- with steering assistance from the tugs the Europoort entrance is negotiated and the tanker proceeds towards its destination, while the speed is constantly being further reduced. At a short distatce from its berth, when the speed is down to 2 - 5 knots, the ship will go full astern. During this manoeuvre the
tanker completely depends on the tugs for its steering.
The distance covered by this stopping manoeuvre is 6 8 kilometers for tankers
of 100,000 - 250,000 tons dw.
3.3.2. The seaward extension of the entrance
When weighing the variously considered criteria it was found that the distance and
time to stop of tankers was the decisive factor. To this end the new entrance has
to be extended by an additional three kilometers into the sea, taken from the 1961 entrance to the Rotterdam Waterway, a total of around five kilometers from the
coastline. For the shifting zone, which coincides with the outer harbour and also
for hydraulic engineering reasons a given distance is required between the entrance
and the dividing point. With the aforementioned seaward extension a distance of
three kilometers remains for this purpose, which is sufficient to meet demands.
3.3.3. Location and'width
of
the entranceThe location of the entrance, measured at approximately right angles to the coast, was determined in the foregoing. Parallel to the coastline the location of the
en-trance was projected in such a way, that the current will maintain an even depth
as much as possible. In other words, the choice of location was dictated by the
ebb-tide being directed at the southern side of the entrance and the flood tide striking the northern end. Pnother consideration was that shipping will have to continue to follow the existing route during construction. In determining the width of the entrance the nautical demand had to be taken into consideration that two loaded and two large ships in ballast have to be able to negotiate the entrance approximately simultaneously, without being subjected tO trouble some heading changes. In addition the width is of importance in relation to current and tidal velocities, which for shipping should not be too high, while these on the other hand should not be too low either in terms of maintaining the necessary depth. The
(usable) width for the present has been determinded at 850 meters - from an hy-draulic engineering point of view a greater width is decidedly undesirable with a view to the maintaining of the required depth.
-8-3.3.4 The positioning of the breakwaters
The positioning of these moles is a function of their current deflecting properties and is determinded principally by the tidal currents. These, immediately outside the harbour entrance, deviate from the main current at sea, influenced by the sto-rage basin capacity of the Rotterdam Waterway and Europoort.
The ebb flow presents a favourable pattern, as the outflow from the storage basin, to which is added the surface water outflow, flows into the sea in a virtually un-changed direction until some dinstance from the entrance..
A smooth ingress of the flood tide can in the first instance only be achieved by the deflection of the curved section of the South Mole., by it being guided in the
direction of the main current at sea and additionally by the current deflection
of the straight North Mole in the stretch of the northern shOre of the Rotterdam Waterway. Favourable patterns in all stages of the construction of the moles can only be obtained if the curved part of the South Mole will be linked to the Voorne coast. .This creates an opportunity for the reclaiming and construction of a 2500
hectare harbour complex on the Maasvlakte, outside the shoreline Construction
takes place from the coast outwards, in a seaward direction. Attention is drawn to the fact that the coastal connection in no way makes a current deflection, in
ap-proximately the direction Of the South Mole, superfluous.
This
socalled South Wallis designed as a dam with fairly shallow slopes, next to the outer harbour, and has the additional function of reducing wave action.
3.3.5 The division point
Hydraulic engineering and nautical considerations play their part in the design of the head of the Dividing Male between the entrances to the Rotterdam Waterway and Europoort (Caland canal) and the Beer canal, which immediately afterwards turns to
the South, giving access to the harbours at West-Rozenburg and the future harbour complex on the Maasvlakte.
For brief periods during the falling tide the horizontal tides of Europoort and the Rotterdam Waterway are out of phase, i.e. at that stage there is a current from Europoort around and in front of the head of the Dividing Mole and the Rotterd Waterway or, in a later period, a current circulating from the Waterway towards Europoort. These currents may prove troublesome to shipping,.
This
phenomenon may befurther complicated by interchanging currents caused by differences in density. During another part of the tidal cycle, currents are phased, be it that they have
differing velocities In this case a junction of flows resp a division of flows,
will gave a favourable current pattern. The question whether, in view of these cir-culating currents, the division should be in the shape of a pointed mole, or in the shape of a dam with a rounded head, is answered by the first-mentioned solution.
3.4 4ccess to Europoort an4 the Rotterdam Waterway
The entrance width is suited to simultaneously arriving and departing traffic. The maximum width of 500 meters is intended for the passage of the largest ships. The channel to and in the definitive entrance and the Caland canal which forms its continuation to the Europoort harbour complex, is marked by a leading line of lights
of 1120, which at sea, just outside the harbour entrance, separates from the central line of lights.
The second main channel, the Beer canal to Europoort (Maasvlakte), makes a curve
of approximately 100 from the definitive entrance towards the South. The radius of
the curve of this channel is 1800 m.
In order to accommodate the intensive traffic on the Rotterdam Waterway a useful width of 350 m. is available. Along a "red" leading line of lights (108°), which also links up with the central (white) line of lights outside the harbour entrance, the Rotterdam Waterway is approached.
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3.5 Approach Channel
3.5.1
Agime
The design of the alignment of the approach channel is dictated by a nuthber of
fac-tors In terms of cost the intention is to achieve minimal initial and maintenance
dredging activities In this respect the configuration of the bottom is of prime
importatice.
A straight channel offers the best possibities for safe navigation, patiçularly for large ships. It is clear that the direction of the channels is also determined
b the prevailing ëurrent and wind conditions. The latter is not Only of importance
to ship handling, but also to shipping movements In this context the direction,
particularly of that part of the chatnel Maas channet), which connects directly
with the harbour entrance, should form a straight line, both to the entrance of Europoort as to the mouth-of the Roiterdain Waterway. As the location of the harbour
entrance and the secondary approaches have been fixed earlier (see Fig ic), the
axis (112 ) has in principle been determined The topography of the bottom, also
in relation to' the heading of the channel, have determined the seaward axis of the channel (EurO channel) at 82°31'.
The transition (angle) of the Euro channel to the Maas channel is situated approx-imately 15 km. outside the harbour entrance and has a curve with a radius Of 10 km.
3.5.2 Wi4h ad Depth
These are determined for a, given vessel by the following factors: - ship handling
- shipping movements - ship's speed
- possibility of passing or overtaking
- navigation aids ashore or at sea (leading lines of lights, radio beacons, radar buoys)
navigation equipment on board - human influence on navigation - wave and wind condit-ions
- tidal conditions (curtents and water levels)
Extensive reserch with hydraulic models, current measuring in situ,
ships'
ma-noeuvring, shipping movements and ship's simulator have provided dimensions which were achieved itt three phases.
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4. Research for realization of accessibility
4.1. Introductory remarks; interaction between operational experience and research
Different types of studies, investigations and measurements have been made for the realization of the accessibility for deep draught tankers with destination Europoort The decision to perform this research has been made because of the limited knowledge available in 1961 and to answer questions arosed in the preparatory stage and during execution of different parts of the project.
In the course of the project the harbour area had to be made accessible - and con-sequently the shallow coastal area had to be made navigable - for tankers in the class of 100,000-170,000 dwt with full loaden draughts of 53-57 ft; 200,000-250,000 dwt, draughts 62-65 ft and 270,000 dwt and more with draughts up to 68 ft, taking into account a future increase up to 7.2 ft.
In 1961 the harbour area was accessible for ships up to 30-40,000 dwt with draughts
up to 43 ft The then existing knowledge on and experience with the behaviour of
deep draught tankers sailing in an approach channel through a shallow entrance zone was restricted to ships of this size. The behaviour of the anticipated larger tan-kers was known to be different ftom that of the existing smaller ships with respect to their reactions to variations in 1) the ambient conditions (weather conditions and sea conditions) and in 2) the position of the controls (position of rudder and propellor revolutions). The reactions of the larger ships were known to be more slow than the reactions of the smaller ships. In principle this implies that the larger ships would require relatively more space (in time and distance) for the execution of manoeuvres such as acceleration, deceleration and changing course. In particular with regard to navigation in confined waterways it was uncertain how this type of vessels had to be controlled on the ships bridge, how the ship would response to wave and current patterns under way and which type of aids to navigation had to be available on the ship as well as in the navigation area to realize safe and expedi-tions channel t-ransits. Consequently there was uncertainty about the space require-ments (channel alignment, width and depth) and in related procedures for the tanker-channel operations. Within the above context insight was needed to create conditions allowing the big ships to sail through the approach channel, the ship being con-trolled by its crew from the bridge with pilot assistance using the navigation equip-ment available on board as well as in the navigation area,; this leaded to the neces-sity of performing research throughout the construction of the project. Performing this research the results and the experience obtained in the early stages of the project were used as input for the research performed in connection with the later stages of the project. In this respect their was a continuous interaction between operational experience obtained after completion of the one stage of the project and the research being performed for the following stages.
In broad lines the research activities were concentrated on navigability aspects also taking into account aspects of constrUction and maintenance.
Describingthe navigability studies distinction will be made between the area out-side the harbour entrance, i.e. the. approach channel as indicated in Section 3.5 and the area inside of the port entrance, reaching from the entrance to the terminals in the harbour basins.
4.2. Investigations on behavipur and movement of a VLC naiigating in a constraint
channel
Aspects of the behaviour and movement of a self propelled tanker navigating under hUman control in a constraint channel have beem studied both in nature and in labo-ratories. The effect of the following factors has been considered:
a) the weather- and sea-condition pertaining in the navigation area and their effect on the tanker movements;
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the shape, the dimensions and the size of the vessel, the type of rudder and propellers; the method of control by the pilot and the helmsman; the navigation instruments available on board;
the shape, the dimensions of the cross-section and the alignment of the channel; the presence of fixed objects or other vessels and obstacles in the channel or its vicinity;
some types of navigation aids installed in the navigation area and the way of marking of a humber oUfixed Objects in the navigation area.
Studying the movement of a tanker sailing in a waterway whose bOttom has a deepened channel and whose dimensions are restricted in width and depth the following con-ditions were deemed essential to be satisfied.
I The tanker needs a certain range of speeds which make it possible to navigate the
ship to be manoeuvred through the channel by its crew from the bridge.
2. The crew needs a certain number of data to make it possible to adapt the progress direction of the navigating tanket aoñg other things to the invisible submerged
banks of the channel and to avoid contacts with shallows, other ships and, fixed
obstacles.
Data on the behaviour and movement of VLC's during channel navigation are derived in two ways.
by means of field measurements and observations in the different stages of the
project, =
by means of measurements on laboratory scale for not yet existing stages of the project as prepared in the design.
In the study of non-existing situations'5 design tankers were selected respec:tively of 100,000, 200,000, 300,000, 500,000 and 425,000 dwt, each tanker being represen-tative as well as possible for the tanker classes the harbour area had to be made accessible for (see under 4.1). The design ships are tabulated in Table 1.
4.2.1. Investigations for area outside harbour entrance
Recordings of the movement of tankers sailing along, a' prescribe track (such as the approach channel) were an element of essential interest., in the investigations made. These recordings were made on a routine basis from 1965 until 1976.. In the initial period the movement of almost each tanker entering Europoort has been recorded in situ. In a later stage this number has been some what reduced.
In these field measurements the following quantities have been recorded
- actual course of ship, its position as a function of time while sailing along the prescribed track,
- speed of the ship,
- keel clearance, .
- position of rudder, propeller revolutions.
Further, observations were made to characterize the weather- and sea-conditions (currents, waves, swell, available depth) pertaining in the navigation. Samples of the recordings made are shown in Figure 3. The measurements covered both the area outside and inside the existing port entrance.
The field-recordings were made during different stages of the project. In the initial period the recordings were made for tankers with a small draught navigating in a
channel whose bottom is deepened only over a small vertical distance.. In the later stage the size of the tankers and the depth of the deepened channel increased grad-ually. Results of these field measUrements were used for differentpurposes.
mong other things, the real time data have been used tO analyze I) the reactions of
the helmsman to actual deviations in the ship's coursewith reference to the courses ordered by the pilot, in combination with 2) the reactions of the moving vessel to
-Table I Dimensions of design tankers MOLE RUDDER ANGIE 6 sea 400 sea 400 .500 m A -*, dJ.tonc. s-.-.
D
flION IN APPSOACI4 Poe h.,,,,.I U A--! r'
i'.-Figure 3 Recordings on two tankers sailing the same track in the outer channel
L
!1
.414
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r ----- -
...:'-
-
,-
--Figure 4 : Model ship (scale 1.:82)
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tcnnage 100,000 dwt 200,000 dwt 300,000 dvt 500,000 dvt 425 000 dwt length, L 264 rn. 310 rn 330 m 398m 399 m beam, B fuUy loaden. draught, .T 37.7 m 15.36 in(52. ft) 47,17 m 18.96m (62 ft) 53,3 m 24.10 m(79..ft) 64 m 26 m(86 ft) 66,54 m 21.95 m(72 ft)7
the position of the control devices as
a
result of helmsman performances. Doing soa servo mechanism could be developed to reproduce the behaviour of the helmsman approximately in tests performed with free-sailing ship models (scale 1:82)(FIg.4).
In laboratory tests with free-sailing ships, which were prepared along the. ab9ve procedure the factors mentioned in items a, b and c of Section 4.2 were varied over a certain range. The results of the tests were a set of conditions deemed to be
"safe" and a set of conditions deemed to be "unsafe" A condition was deemed to be safe when the following restrictions were satisfied
- constant pre set propeller revolutions; no necessity to increase rpm's of propel-ler suddenly to re-enforce the effect of the rudder
- rudder angle remaining below some critical value.
Application of this criterion was though to make sense for conditions as pertaining in the Europoort area. It was established consulting the pilots working in the area.
The results of the tests with free-sailing model ships were found to be reliable in the following sense. Trends found in the predictions made for a situation not exist-ing while the model test were made were gradually also found in the field measure-ments and the experience of the pilot once this situation was established in the
field. Situations deemed to be. safe in the free-sailing ship experiments were also evaluated
as
such in the operation experience. Situations deeed to be unsafe often turned out to be the ones avoided by the pilots.The preceeding investigations dealt with the behaviour of the helmsman, the courses being given by the navigator. To incorporate the effect of the method Of bridge con-trol, including performances of the pilot, investigation were made using a shiphán-dung simulator. In this context a mathematical model has been developed to reproduc especially the frequency dependant reactions of the ship to chances in the position
of the control devices and to external forces over a wider range than the range
covered in the field recordings and in the free-sailing ship model tests. This math-ematical modelling of tanker behaviour in a channel acted in the shiphandling simu-lator as the subject to be controlled by human operators on the bridge.
By means of the shiphandling simulator, among other things, studies were made on some functional effects of navigation aids on I) the behaviour of the controlled
ship expressed in tetm Of for instance the way the naigator makes use of: the
presented data during his several task performances, and 2) the path covered by the ship. (see Figs. 5 and 6). In these studies the following quantities were varied - the type of navigation aid (decca, radar etc.,) and the way of presenting the data
to the pilot.on thetanker bridge
the accuracy and the available amount of position data. given by these navigation aids and the sensitivity of the received data for atmospheric disturbances
- the type of inanoeuvres to be performed e.g. covering special channel trajects and passing an other tanker.
The studies made showed that the required channel alignment and width may not be selected without regard of the type of navigation aids being selected, and vice
versa. Further the organization of the bridge tasks to be performed and the way the
actual control proces is and can be performed are to be taken into account. In the studies these items were incorporated schematically and restricted to the pilot's and helmsman's performances.
The effect of the optical appearance of the waterway on the behaviour of the
naviga-tor has been studied using a model of the waterway and its surroundings (scale 1:500). In this model the movements of the ship were introduced by the movements of a television camera mounted on a carriage. Among other things, studies were made of the effect of the waterway being symmetrical (width of entrance to Rotterdam Water-way equal to width of entrance to Europoort). Pilots also participated in this
investigations.
-Figure 5 Influence of ship speed to the average of the maximum values Y max Simulator tests manoeuvre and guiding line ..) sitioii of 150.. 100. decca system
centre line of lane Vmj
0
radar system 50.
5
ship speed
cross distances Yin cross section I_I (siip center of gravity)
mean value r. ms. value
0 1Gm
cross distances Y (ships bridge)
mean value r m.s. value
.) the given values refer to the
statistical distribution of
cross distances Y measured
in section 1
-172m 64m ..) the actual X and Y -values
are presented on the bridge desk in a digital way
-) for bridge display see fig. 10
Figure 6 : Influence of different types of guiding lines on the path of a 200.000 dwt tanker
4.2.2. Investigations for area inside harbour entrance
10 75k,,ots
The field measurement described in the previous section also covered the area inside the harbour entrance. Data were collected on stopping manoeuvres, on the navigation through different current patterns occurring in different tidal stages, and on traffic situations. 15
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,49m 54m track lenght 600Cm Europoort prototype recordings of 22 tankers + 12Gm _120 m7
For the designed area inside the harbour entrance tests with free-sailing model schips (scale 1:82k) were made using the techniques and the criterion describe4 in the previous section to distinguish "safe" and "unsafe" conditions. The schematized background patterns of currents and wind through which the model ship was made to sail were derived as well as possible from field measurements; additional data being provided by the hydraulic model (horizontal scale 1:640, vertical scale 1:64) which
is described in further detail in Section 4.3. Th tests made were concerned with
the questions referred to in Section 3.3.5, such as the shape óf.the head of the Dividing Mole,the depth and the width of the entrance to. Europoort and the radius of curvature of. the waterways leading to the terminals. In a later stage of the project
these items were also studied in the hydraulic model as mentioned above.
4.3. Investigations for selection of channel characteristics and additoial
provi-sions " . .. : . '
4.3.1. Necessity of verifying results
The requirement to create a rate of accessibility for incoming deep draught tankers which is restricted as little as possible by sea and weather conditions had
impor-tant consequences when selecting the channel characteristics. Among other things this requirement made it necessary to obtain insight in the frequency of accurance of flow, wave, swell and wind conditions and the correlation between these condition and water depth, which varies with time within a tidal period on the one hand and controls the keel clearance available, in the iertical plane on the other. This in-formation was essential to determine how often the "safe" and "unsafe" conditions referred to in Section 4.2.1 would occur, depending on the. type of ship and the dimensions of the channel.
Further the formulated requirement on the rat,e of accessibility (also. during con-struction) made it necessary tO verify thé accuracy and tli'eigtiificance of the results of the investigations as often as possible before entering a new stage' of
the project. This verification was made consulting the pilots and authorities,
charged with the operational aspects of the navigation': in the 'considered area. For the area outside .the harbour entrance this verification has been el'aborated upon in Section 4.2.1.
4.3.2. Transition from, temporary entrance of Europoort harbours to new entrance
The above verification was in particular importance for the studies on navigability
during a critical construction phase involving the making of a new entrance to the Europoort harbours and the closing of the temporary one. Small chajiges in the
geom-etry of these entrances could be associated with significant,ëh'ange's in flow
pat-terns, the flow pattern in the vicinity of the one entrance depending upon the geom-etry of the other, and vice versa. To satisfy the requirement of accessibility it
was impossible to close the temporary entrance before opening 'the new one. Hence in
a given construction stage the connection between the new entrance and the temporary one could operate as a shunt to the Rotterdam Waterway to modify the stream pattern in the temporary entrance and in the 'harbour basin, during the flood period as: well
as the ebb period. As a consequence of pertaining density currents the magnitude anc
direction of the stream velocities varied considerably with depth.
The problems 'associated with the transition from the temporary entrance to the new one have been studied. by the following procedure. Field measurements were made
during each stage realized during construction, showing the magnitude and direction
of stream velocities as a function of time and (three-dimensional) space. These field data were used fora continuous' verification of 'a hydraulic model of' the problemarea, reproducing both tidal and density cur-rents. This hydraulic model
(horizontal scale 1:640, vertical scale 1:64) was' found to satisfactorily reproduce the variations of the stream pattern associated with the variations of the entrance
geometries as realized in the project. Accordingly it was necessary and justified
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to derive the consequences for .ngvigat ion of variations in the stream pattern depending on the channel geometries still to be made from the hydraulic model. In
the hydraulic model stream patterns have been photographed for floats of various lengths. For .the temporary entrance with the Rotterdam Waterway and for the main shipping routes, forces perpendicular to the shipping routes as some representation of flow forces acting on a tanker supposed to be present have been computed based on velocity data from photographs (see Fig. 7).
For each situation realized during construction the relation between prevailing current patterns and comments of pilots guiding tankers through these current
pat-terns were analyzed. A great part of this work consisted of comparisons of mutual situations or comparison of situations with reference situations. In these compar-isons the forces (perpendicular to the route) and the moments, and also the gra-dients of these quantities along the route of the ships as computed fron the stream patterns were used as a quantitative basis. There is an obvious lack of know-how to judge this information in absolute sense; yet this problem could be solved in most cases by referring to known situations. The data on, for example, forces and gra-dients were tabulated as a function of place and time and were compared with similar data from reference situations. Some well-selected codes helped to visualise the relative improvement or worsening, so that a final judgement could be made in co-operation with a Nautical Committee in which the various disciplines involved were represented. This procedure was found to have worked satisfactorily. The effect of new situations was smoothed by informing the pilots before hand through stream atlasses about new situations, predicted from stream patterns measured in the hy-draulic model.
4.4. Dimensiojis and further provisions selected for appoach channel
The level of the bottom of the approach channel should be such that for a. VCL navigating in the channel the available keel clearance D/T is sufficiently large
taking into account reductions underway by combined effects as trim, squat, (as a result of ship speed) rolling, heave and pitching (as a result of swell), where D represents the actual available water depth in a channel position on the moment the VCL passes this. point and where T is the draught of the VCL in a position that the
ship is dead in the .water.
From studies on ship behaviour it was learned that the keel clearance influences the manoeuvring capabilities of the shipin the following sense, taking into account
actual ship draught under given conditions of speed. For the
navigation area under
consi4eratwn
a decrease in the available keel clearance averaged over some time and distance could be associated with an decrease in the ranges of ship speed available for the pilot to choose from for the execution of the required manoeuvres during channel navigation. Accordingly the .choise of a minimum keel clearance to be. aimed at has been an important factor in channel dimensioning, as the possibility to perform eventually required manoeuvres increases when the afore mentioned range is greater.Considering the type. of manoeuvres which had to be expected this coücept implies the keel clearance to be a factor which governs the space for navigation in terms of alignment, width and depth required for the approach channel. It further implies
that the actually available keel clearance is a factor influencing the channel tran-sit strategy, as during channel navigation the actual keel clearance varies with the changing of water-levels caused by the tidal wave progressing in the channel area. The mean tidal amplitude is in the order of magnitude of 1.5 metres.
Figure 8 shows three channel configurations which were realized in respectively the project stages 1966-1969, 1970-1973 and 1974-1976, giving access to VCL's with
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Figure 7 Flow pattern before making new entrance at 11W +3 hrs (length of floats 5 m prototype). Forces perpendicular to route of ship computed from velocity data
-18-VLCC ANCHORAGE
1970-1974 1974 TODAY
Figure 8 : Channel configurations
19
as a. perspective
- 20
draughts up to respectively 53-57 ft, .62-65 ft and 68-72' ft. The associated charac-teristic channel dimensions are given in Table 2.
Table 2 Channel dimensions
The channel dimensions listed in Table 2 were selected in combination with a. certain
availability of navigation aids, on which they depend In this context the following
remarks are made..
4.4.1. Navigation aids in connectioti with channel depth and alignment
The depth (bq.ttom leve.l). of the channel is still such that the largest tankers enter
during a sufficiently long period of time around the time of high water Then in the
outer Euro channel the minimum available water depth is equal to 1 2 times the
draught, in the inner Maas channel it is 1 15 times the draught and in the area
in-side the port entrance 1.1 times the draught.
In the sea .area under consideration waves which induce relatively large vertical
-motions of VLC's can be expectedto occur a number of times a year. These waves which are of low frequency arise from severe local storms with wind from the West
and North or as swell coming from distant storm centres in the Northern part of the North Sea, Northern Icesea or the Eastern part of the Atlantic Ocean entering from
a northerly direction. If not forseen in the preparation of the VLC chantiel transit
operation especially in the Euro channel they can attack the tanker underway Then
bottom contact is likely to occur because of the induced vertical motions of the
ship. . . . . maximum tanker draft 53-57 ft 62-65 ft 68 ft Maas channel Euro channel Maas channel Euro channel Maas channel Euro channel direction 108° - 112° 82°30' 112° - - 82°30' - --length on sea-side of port entrance
.5km
-15km
29.5 km 15 km 29.5 km width of chan-nel bottom - seaside end before port-entrance 1000 m 400 m . 1000-600 m 400-600 m 1800 m 600 m 600 m . 1200 m - in port en-trance - in harbour entrance 350 m 175 rn . .. 350 m 17.5-350 m 350 rn 350 m effective chan-nel bottom 1ev-el;position with respect to mean sea level-19.5 m . . -22 m (62'.) -23 m (65') 23 m (62') -24 m (65') . . -23.5 m . resp. -24.5-25.00 m over 600 m width and -23.5 rn over the remaining width
As found in ship model tests this effect of waves increases about linearly with keel clearance over the range of keel clearance which was of interest. Hence a deepening of the bottom of the channel did not seem an adequate solution. To avoid dangerous situations of this type a proposition of a so called hydro meteo system was developed, which is operational since 1970 in a provisional stage. This system contains two components: 1) a numerical technique for swell prediction, input data being derived from discrete points in the North Sea and northern area, 2) a measur-ing system in the channel area collectmeasur-ing data on wave energy density in the rele-vant frequency range. Based on the data provided by these components information on swell conditions is produced by the Dutch Ministry of Transport and "Waterstaat" at Hook of Holland for shipping and other interested parties by the central control station at the Hook of Holland and issued by the Governmental Harbour master of Rotterdam-Europoort.
The length of the Euro channel is approximately 30 kin, the length of the inner Maas channel approximately 14 km. The average time taken by a VCL to travel the total length of the approach channels is approximately 2.6 hours with a maximum of approx-iniately 4 hours and a minimum of approximately 1.8 hour dependent on ship speed. Because of this reason information on anticipated water-levels being included in the information issued by the Harbour master is of importance, especially for the planning of VCL channel transit operations in time for the deepest tankers which only enter around the time of high water. For these ships at each location along the channel there is a period of limited duration during which the ratio between the available water depth and the draught exceeds the afore mentioned numbers of respectively 1.2, 1.15 and 1.1. Plotted in a distance versus time space these periods form a time gate within which the channel transit has to be accomplished
(see the shaded area represented in Fig. 9).
H
;
trocklerqth in km
Figure 9 : Time gate Europoort channels for 65 ft tankers
(mean tide) 21 -Hock of HIand
7
H III 10 20 30 40 50km I--de .___p oCatOn!flU-,.
euro - cha,neI maas_chanreI
7
4.4.2. Navigation aids in connection with channel width, depth and alignment
From the navigation aids we can mention light buoys which mark the0channel alignment and boundaries, the leading lines of lights (a leading line of 112. marking the main direction of the Maas channel both for VLC's and other traffic, the red line of 1080 leading to Rotterdain Waterway, the green line leading to Europoort), a shore based radar chain in combination with a VHF radio communication system for shore based
pilot assistance and a similar system used for authorisation of VLC channel transit
operations by the Governmental Harbour master in the navigation area.
The pilot on board having accurate and reliable information for positioning and for adopting the progress of the ship to the course of the channel is still a factor governing the required channel width to an important extent To provide this
informa-tion under all condiinforma-tions a special radio posiinforma-tioning system has been developed based on the existing Decca Navigator chain. The system. is simple in use and the pilot, arriving on the ship by helicopter or pilot cutter equipped with the same
positioning system, brings a relatively small box on board with him This box
corn-menly known as the "Brown Box" is connected with the Decca receiver on the bridge providing the pilot with conveniently displayed information on position Averaged over the length of the channel the position is given within .15 rn.
In a functional sense the afore mentioned set of nautical equipment has been found essential both with regard to the chosen effective channel dimensions and for the preparation and execution of the channel transit operations.
Figure 8 shows the routes to be followed by the other trafic. The separations be-tween the routes for ingoing and outgoing trafic are indicated. These routes are located outside the area of the VLC channel. Nevertheless VLC's navigating in the channel occasionally meet other traffic. The VLC's, carrying two red lights to in-dicate restricted tnanoeuvrability, have the right of way. Yet the VLC pilot still has to take care of emergency manoevres to avoid collision when the right of way is not given. How this influences channel dimensions can be illustrated by the
dimen-sions selected for the 68 ft channel. This channel with a width of 600 m has been Obtained by deepening only the middle part of the then existing 65 ft channel with a width of 1200 m, leaving a. 300 m wide navigation space for emergency manoeuvring on both sides of the channel.
Technical failures on board such as deficiencies of the steeri.ng machine and/or the propulsion unit may lead to groundings. The slopes of, the submerged sandy banks of
the channel have been made small as to limit the possible damage for the ship by such an event. Besides in the area within the port entrance tugs make fast as early as possible. By doing so they can assist if failures of the above occur.
4.4.3. Development in channel dimensions
Table 2 illustrates how the width of the channel decreases in the course of time from a width of 1800m in 1969 to a width of 600-1200 m at present. This reduction has to be looked upon taking into account the combined effect of the following developments
- developments in the method of control of VCL's and the organization of the control tasks on the bridge
- increasing knowledge available for dimensionering navigation channel and naviga-tion aids in the area under consideranaviga-tion
- developments in the use of the navigation aids by the pilots
- developments in the procedures and the execution of the assistance of the channel transit operations provided from shore stations
- developments in the training of pilots
- the assistance by two pilots on board each VCL instead of. one as common for other
traffic.
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From the experience obtained in the realization of the project we have learned that
all above mentioned elements play an important role both in the process of making
the coastal area navigable for the considered type of navigation as well as in the
execution of the VCL channel transits. In connection with the human elements
involv-ed we wish to make the following remark.
Many uncertainties affected the initial stage of the project which were reflected in the dimensions of and the type of provisions for the early channel. Research performed during the realization of the project in combination with increasing operational experience made the afore mentioned development possible. It was also
felt, however, that more knowledge is needed on the following subjects
- how to characterize and possibly measure the degree of complexity of tasks to be performand among other things in bridge control under pertaining conditions - how to determine the conditions to be satisfied to make a performance demanded
executable under pertaining conditions.
Indepent of the state of the art on the above subjects, in any case it must be en-deavoured to include criteria for the executability of the human control performan-ces in the weighting properforman-cess for decision taking on the choice of channel dimensions and availability of furthernavigation provisions.
-5. Ongoing traffic studies
Data needed for statistical, analyses of. the traffic pattern in the port entrance. zone A (see Fig 2) are being collected For this purpose shipping movements are to
be recorded The recording system recently developed for this purpose is being
in-stalled. Furthera mathematical model has been developed so that. eventually alter-native traffic modes can be analysed and alteralter-native traffic recommendations
possi-bly can be made. . .
Within the. above framework also the rnoiOns in the. h6rizontai plane of VCL'.s s'ailing
through the appraoch channel are recorded Equipment to measure the motions in the
vertical plane is being developed.
